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Supercontinents in Earth History
Abstract
Understanding the formation of cratons and orogenic belts is critical to the modelling of supercontinental assemblies. Continental cratons began to assemble by 3000 Ma or possibly earlier. The oldest assembly, Ur, was followed by Arctica at ∼2500 Ma and Atlantica at ∼2000 Ma. These three continental blocks apparently remained coherent until the breakup of Pangea. Nearly all of earth's continental blocks were assembled into one large landmass during at least three times in earth history. The oldest assembly comparable in size to Pangea was probably Columbia, which formed at ∼1800 Ma and began to rift at ∼1500 Ma. Columbia was followed by Rodinia, which lasted from ∼1100 Ma to 700 Ma. East and West Gondwana combined to form Gondwana at ∼500 Ma, and it joined with Laurasia to form Pangea at ∼250 Ma.
... Much of the Earth's ancient oceanic lithosphere is preserved in 'intercontinental' orogenic belts (Rogers and Santosh, 2003) as 'Ophiolites' accreted and obducted during ocean basin closure and continent-continent collisions. Precambrian and Phanerozoic ophiolite sequences representing vestiges of subducted oceanic lithosphere that experienced a transitional thermo-tectonic evolu-tion marked by generation at oceanic spreading centres e.g. ...
... The geochemical study on ophiolitic mantle peridotites has restructured our conception of the complex mechanisms of depletion and enrichment processes within the upper mantle through geological time. After the breakup of Rodinia and opening of the first phase of Tethyan ocean in Late Proterozoic to the last phase of basin closure in Eocene, the Tethyan mantle has been subjugated to diverse tectono-magmatic processes controlled by the motion of the bounding supercontinent-derived continental blocks (Rogers and Santosh, 2003;Metcalfe, 2021). The resultant geochemical character of these mantle rocks is thus subjective to variable episodes and degrees of partial melting and melt extraction, and multiple geodynamic components that refertilze the refractory mantle. ...
... Re-Os isotopic plots reflect the role of ancient depleted SCLM and the large variations in ɣ Os values attest to involvement of both SCLM and depleted MORB component thereby contributing to pronounced Os isotopic heterogeneities in the upper mantle that in turn manifest inputs of discrete depleted and enriched mantle components during opening and closure of ocean basins synchronized with assembly and dispersal of continental blocks (Tsuru et al., 2000). The 720 to 549 Ma melt extraction ages for the studied samples correspond to multiple melt extraction and mantle depletion events preceding the opening of Neo-Tethyan seaway and SCLM delamination concurrent with subduction driven ocean basin closure and amalgamation of Gondwana Supercontinent (Fig. 9a) (Meert and Van der Voo, 1997;Rogers and Santosh, 2003;Meert, 2003). The model ages 1142 Ma and 466-250 Ma possibly indicate some melt extraction in the sub-continental lithospheric mantle of Rodinia and Pangea supercontinent respectively. ...
... The cratons of India preserve geological evidences from Archean to the recent evolutionary history of the Earth and are considered key crustal blocks in ancient supercontinents [18][19][20]. The Bundelkhand Craton in north-central India preserves continental crust that has formed and has been recycled in phases between ~3.6 and 2.5 Ga [21][22][23][24][25]. ...
... There is a general agreement that the supercontinent cycles govern the thermal evolution of different Archean blocks in the Earth [21,82,83]. The Ur is the oldest known supercontinent in the Archean, which stabilized by assembling the East Dharwar, West Dharwar, Bastar, and Singhbhum cratons of South India Block [19,30], Bundelkhand Craton of north-central India [21,23], the Kaapvaal Craton of South Africa, and the Pilbara Craton of Western Australia [18,19]. Rogers and Santosh [18] and Mohanty [84] suggest that the Yilgran Cratons and the Zimbabwe Craton assembled with the original Ur at 2500 Ma by forming extended Ur. ...
... The Ur is the oldest known supercontinent in the Archean, which stabilized by assembling the East Dharwar, West Dharwar, Bastar, and Singhbhum cratons of South India Block [19,30], Bundelkhand Craton of north-central India [21,23], the Kaapvaal Craton of South Africa, and the Pilbara Craton of Western Australia [18,19]. Rogers and Santosh [18] and Mohanty [84] suggest that the Yilgran Cratons and the Zimbabwe Craton assembled with the original Ur at 2500 Ma by forming extended Ur. Magmatism associated with high-temperature metamorphism at Limpopo Belt [85], Zimbabwe Craton [86], high-pressure low-temperature metamorphism followed by widespread granite magmatism along central Bundelkhand Craton [21,23], East and West Dharwar Cratons [87,88], and Bastar Craton [89] marked the stabilization of extended Ur. ...
... The cratons of India preserve geological evidences from Archean to the recent evolutionary history of the Earth and are considered key crustal blocks in ancient supercontinents [18][19][20]. The Bundelkhand Craton in north-central India preserves continental crust that has formed and has been recycled in phases between ~3.6 and 2.5 Ga [21][22][23][24][25]. ...
... There is a general agreement that the supercontinent cycles govern the thermal evolution of different Archean blocks in the Earth [21,82,83]. The Ur is the oldest known supercontinent in the Archean, which stabilized by assembling the East Dharwar, West Dharwar, Bastar, and Singhbhum cratons of South India Block [19,30], Bundelkhand Craton of north-central India [21,23], the Kaapvaal Craton of South Africa, and the Pilbara Craton of Western Australia [18,19]. Rogers and Santosh [18] and Mohanty [84] suggest that the Yilgran Cratons and the Zimbabwe Craton assembled with the original Ur at 2500 Ma by forming extended Ur. ...
... The Ur is the oldest known supercontinent in the Archean, which stabilized by assembling the East Dharwar, West Dharwar, Bastar, and Singhbhum cratons of South India Block [19,30], Bundelkhand Craton of north-central India [21,23], the Kaapvaal Craton of South Africa, and the Pilbara Craton of Western Australia [18,19]. Rogers and Santosh [18] and Mohanty [84] suggest that the Yilgran Cratons and the Zimbabwe Craton assembled with the original Ur at 2500 Ma by forming extended Ur. Magmatism associated with high-temperature metamorphism at Limpopo Belt [85], Zimbabwe Craton [86], high-pressure low-temperature metamorphism followed by widespread granite magmatism along central Bundelkhand Craton [21,23], East and West Dharwar Cratons [87,88], and Bastar Craton [89] marked the stabilization of extended Ur. ...
In this article, novel geochronological (U–Pb SHRIMP) and geochemical data are presented from the lowermost sandstone
unit (Par formation), basement granites of Gwalior Basin and sandstones from the Bhopal Basin, located along margins of the
Archaean Bundelkhand Craton. The geochemical variation diagrams imply that sandstone units in the Gwalior and Bhopal
Basins were deposited in rift-induced passive margin tectonic settings. In contrast to the magmatic features that are preserved
in the zircons of granite of the Gwalior Basins, detrital zircons from sandstones of both basins are fragmentary and polymodal
in size. The magmatic zircon grains from the basement granites yield a 207Pb/206Pb concordant age of 2538 ± 2 Ma. A group of
detrital zircons from the sandstone of the Gwalior Basin with concentric magmatic zonation yield a weighted mean average age
of 2564 ± 24 Ma. The detrital zircons from Gwalior Basin exhibit a patchy U-Th distribution overgrowing the magmatic zonation
yield average age of 2044 ± 2 Ma. The detrital zircons from the Bhopal basin yield three distinct concordant ages of 2511 ± 5,
1694 ± 6, and 1355±9 Ma. The presence of ~2540 Ma concordant zircon population with concentric zonation in the sandstone
of Bhopal Basin suggests their derivation from the granite of similar age. Therefore, an extension of Bundelkhand Craton granite
below the Bhopal Basin is suggested. The 2500 Ma ages from the Gwalior granites are linked to global magmatic activity leading
to the stabilization of extended Ur at ~2500 Ma. The 2048 and 1355 Ma ages from the Gwalior and Bhopal Basins, respectively,
are concluded as the maximum depositional age (MDA) of the lowermost stratigraphic units within the basins. The MDAs are
concluded to be the timings of passive margin basin formations along margins of the Bundelkhand Craton during extended Ur
and Nuna or Columbia disintegration, respectively, during plume-driven tectonics.
... There is a consensus that subduction zone tectonics in the Earth was initiated during the Mesoarchean time [1,2]. Subsequently, the Neoarchean and the Paleoproterozoic periods experienced extensive subduction and rift-related magmatism leading to the cratonization of Archean blocks [3][4][5]. Jayananda et al. [4,6], Condie and O'Neil [7], Condie [8], Condie et al. [9] correlate the late Archean-Paleoproterozoic transition with the extraction of continental crust from the mantle, with a significant increase in large-ion lithophile and high-field strength elements and a decrease in Sr in the continental crust that reflect in the change in magma chemistry from tonalite-trondhjemite-granodiorite to calcalkaline-alkaline granite. ...
... Ur is the oldest known Archean supercontinent, which sta-bilized~3000 Ma by assembling the Dharwar and the Singbhum cratons of the Indian subcontinent, the Kaapvaal craton of South Africa and the Pilbara cratons of western Australia [3,126]. Saha et al. [26] report~3400-3500 Ma zircon from the Bundelkhand craton and correlate the same with crust formation events in the Dharwar and the Singbhum craton as a part of the original Ur supercontinent. ...
... Saha et al. [26] report~3400-3500 Ma zircon from the Bundelkhand craton and correlate the same with crust formation events in the Dharwar and the Singbhum craton as a part of the original Ur supercontinent. Rogers and Santosh [3] also, suggest that the Yilgarn craton and the Zimbabwe craton accreted with the original Ur 2500 Ma to form the extended Ur (Figure 11(a)). It is generally agreed that the configuration of crustal blocks in extended Ur exists till the stabilization of Mesozoic supercontinent Pangea. ...
... Consequently, it is speculated that a mathematical equation prediction may fit the observations in Earth's supercontinent history. Nonetheless, Earth has evolved since − 4550 Myr and it is consequently very difficult to establish the exact timing of Earth's previous supercontinent assemblies because of several destructive cycles (such as possibly forming Kenorland, Columbia, Rodinia, Gondwana and Pangea) ( Fig. 1) 7,[13][14][15][16][17][18] . To fulfil this end, the Earth's metamorphic record is used as a proxy for supercontinental assemblies, considering that metamorphic events result mostly from collision and the closure of oceanic domains (Figs. 1, 3) [18][19][20] . ...
... Finally, the ε Hf (t) record could be considered a validating proxy for supercontinental assemblies because increased crustal reworking could occur during the assembly of a supercontinent (Fig. 3), e.g., 22 . These three potential proxies allow the establishment of the approximate assembly dates of the different supercontinents, at − 2700 to − 2500 Myr for Kenorland, − 2100 to − 1600 Myr for Columbia, at − 1300 to − 900 Myr for Rodinia, at − 660 to − 450 Myr for Gondwana, and at − 350 to − 230 Myr for Pangea (Figs. 1, 3) 4,9,10,[13][14][15][16][17][18][19][20][22][23][24][25] . Given all these elements and based on the assumption of the assembly of Columbia and ...
... 3; Fig. 2), where X(n) is still the supercontinent assembly and n is the position of the supercontinent in the sequence: Equation (3) considers the results from Eq. (1) with the addition of a supercontinent Kenorland at approximately − 2500 Myr, which could be argued as the potential first supercontinent (Table. 3; Fig. 2) 4,5,14,26 , where X(n) is still a supercontinent assembly and n is the position of the supercontinent in the sequence: Table 3. (Table. 3). ...
The supercontinent cycle has been the focus of researchers for many years, but the parameters of its cyclicity remain a central debate; thus, prediction of the occurrence of the next supercontinent remains elusive. In this research, a mathematical point of view is adopted, based on the assumption that the supercontinent Columbia assembled at – 2000 Myr $$\left( {X\left( { - 2} \right)} \right)$$ X - 2 and the supercontinent Rodinia assembled at – 1000 Myr $$\left( {X\left( { - 1} \right)} \right)$$ X - 1 . The younger supercontinents are calculated following this mathematical equation: $$X\left( n \right) = 2*X\left( {n - 1} \right) - X\left( {n - 2} \right) - \left( {\frac{540}{{3^{n} }}} \right)$$ X n = 2 ∗ X n - 1 - X n - 2 - 540 3 n , where $$X\left( n \right)$$ X n represents the assembly and n is the position of the supercontinent in the sequence. Therefore, Gondwana $$\left( {X\left( 0 \right)} \right)$$ X 0 amalgamated at -540 Myr, Pangea $$\left( {X\left( 1 \right)} \right)$$ X 1 at – 260 Myr, Eurasia $$\left( {X\left( 2 \right)} \right)$$ X 2 at – 40 Myr and Pangea Proxima $$\left( {X\left( 3 \right)} \right)$$ X 3 might form at + 160 Myr. Moreover, two logarithmic regressions give fairly similar results, confirming that a constant acceleration of the supercontinent cycle is probable. The detrital zircon, metamorphic and hafnium isotope records support the assemblies’ hypotheses that produce the mathematical equation. However, a recent supercontinent or “megacontinent” called Eurasia lacks strong geological evidence in the three datasets. These findings might reconcile the paradox brought about by the closer ages in time for the Earth’s more recent supercontinental assemblies and the assumed constant cyclicity of the cycle.
... 2.45-2.20 Ga based on the global distribution of zircon (magmatic and detrital) U-Pb ages, reflecting the reduction in global magmatic activity and plate tectonic shutdown, but the NCC has widespread early Paleoproterozoic magmatism, especially in the Xiaoqinling Terrane ( Fig. 1; Diwu et al., 2007;Diwu et al., 2014;Diwu et al., 2018;Jiang et al., 2011;Huang et al., 2012;Huang et al., 2013;Yu et al., 2013;Wang et al., 2014;Chen et al., 2015;Jia, 2016;Sun et al., 2017;Jia et al., 2020), although it used to be thought relatively stable during the tectonic quiescent period (Zhai and Santosh, 2011;Zhai and Santosh, 2013). The early Paleoproterozoic tectonic setting of the NCC is debated between magmatic arc (continental or island arc) (Diwu et al., 2014;Diwu et al., 2018) and extension associated with the initial breakup of the Kenorland supercontinent (Bekker et al., 2003;Rogers and Santosh, 2003;Jia, 2016;Jia et al., 2020). ...
... Diwu et al. (2014), Diwu et al. (2018) related it with the Andeantype continental arc or island arc setting. A group of researchers considered tectonic extension associated with the breakup of the Kenorland supercontinent (Bekker et al., 2003;Rogers and Santosh, 2003;Jia, 2016;Jia et al., 2020). Chen et al. (1988), Chen and Fu (1992) and Chen and Zhao (1997) addressed the intensive subduction-related magmatism at SNCC in the period of 2.55-2.3 ...
... Here we prefer an extensional setting to explain the A-type granite affinity and low pressure melting of the Xiaohe granite. The ca. 2.3 Ga Xiaohe A-type granite is consistent with the extension of SNCC during the breakup of the SNCC as a part of the Kenorland supercontinent (Rogers and Santosh, 2003;Zhai and Santosh, 2011;Jia et al., 2020), where associated lithosphere thinning and mantle upwelling. After ca. ...
The early Paleoproterozic is generally considered as a worldwide tectonic quiescent period. It is unusual that widespread early Paleoproterozoic magmatism has been identified in the North China Craton (NCC), especially in the Xiaoqinling Terrane at the southern NCC. The Xiaohe granite occurs along the southern margin of the Xiaoqinling Terrane and intrudes the lower portion of the Taihua Supergroup (gneisses). Previous data suggest the emplacement time of the Xiaohe granite ranging from the early to late Paleoproterozoic, leaving a controversy over 500 Ma. To accurately constrain the age, genesis and tectonic setting of the Xiao granite, we have carried out a comprehensive study and here present new petrographical, geochronological, and isotope and element geochemical data. It is confirmed that the Xiaohe granite is dominated by the ca. 2.3-Ga monzogranite and locally intruded by the Guijiayu granites at 1.82 ± 0.05 Ga. Three samples from the Xiaohe granite yield consistent zircon U − Pb ages of ca. 2.3 Ga, and ɛHf(t) values showing mixing of juvenile and recycled continental crust sources. The Xiaohe granite are characterized by high SiO2 (70.7–79.6 %) and high alkali (5.67–10.15 %), belong to calc-alkaline to shoshonite series and show weak peraluminous feature with A/CNK values around 1.1. Its geochemical characteristics are similar to those of A-type granites formed involcani arc or syn- to post-collision tectonic settings. Samples also display eastward decrease of Sr/Y, (La/Yb)N and δEu values, and weakening REE fractionation, indicating an eastward increase of plagioclase in residue during partial melting of the crust, and the magma sources become shallow eastwardly. Hence it is concluded that the Xiaohe granite was formed in a widespread granitic event associated with continental collision or terrane amalgamation.
... The crustal density inversion is considered as one of the dominant processes that caused the formation of granite-greenstone terranes (Nebel et al., 2018). The marginal zones of such terranes are characterized by Precambrian orogenic belts, along which Archean cratons, having distinct geological histories, were amalgamated (Rogers and Santosh, 2003). These orogenic belts are the product of tectonic events that occurred during two distinct stagesaccretionary and collisional orogensand mark the onset of plate tectonics ( Fig. 1; Cawood et al., 2009;Grenholm et al., 2019). ...
... Although temporally similar thermal events were reported from the Satpura mobile belt (i.e., 1.65 Ga age Gangpur granite; Chakraborty et al., 2019) and CGC (i.e., 1.69 Ga age of Bhagalpur porphyritic granitoid; Chatterjee and Ghose, 2011), the contrasting mesoscale structures, magmato-metamorphic histories and geochronological data suggest that the CGC and SMB Fig. 15. Simplified schematic diagrams showing the reconstruction and paleogeographic position of the Indian Plate within various Precambrian supercontinents, including (a-c) Columbia (Rogers and Santosh, 2003;Zhao et al., 2004;Zhang et al., 2009), (d-e) Rodina (Torsvik, 2003;Li et al., 2008) and (f) Gondwana (Collins and Pisarevsky, 2005) configurations. In all these configurations, the approximate position of the Aravalli-Delhi Fold Belt is indicated. ...
... However, the paleogeographic positions of proto-India in these supercontinents (Fig. 15a-e) remain enigmatic due to the lack of reliable paleomagnetic pole data (Meert, 2002;Ernst and Srivastava, 2008;Evans and Mitchell, 2011;Meert, 2012;Zhang et al., 2012;Belica et al., 2014). For example, Rogers and Santosh (2003) placed the position of India in the Columbia Supercontinent by correlating the geographical locations of multiple Mesoproterozoic rifts of the eastern margin of India and East Antarctica (i.e., Mahanadi-Lambert rift and Godavari rift) with those in western North America (i.e., Belt and Uinta rifts) (Fig. 15a). Zhao et al. (2002 and2004) proposed that proto-India occupied the western margin of Columbia assembly on the basis of available geochronological data from ~2.1-1.8 ...
The Aravalli Craton, representing the Precambrian nucleus of northwestern India, consists of the Archean Banded Gneissic Complex (BGC; 3.3–2.5 Ga) overlain by Paleoproterozoic (~2.2–1.7 Ga) and Paleo- to Neoproterozoic (~1.7–0.7 Ga) metasedimentary sequences of the Aravalli and Delhi supergroups, respectively. The extensively reworked Late Paleoproterozoic terrane located between the Aravalli and Delhi supracrustal sequences is known as the Sandmata Complex. The BGC, Sandmata Complex and supracrustal sequences, collectively known as Aravalli Craton, were developed by multiple accretionary-collisional processes from ~3.3 to 0.7 Ga and are regarded as classical terranes for understanding Precambrian crustal evolution. The previous multidisciplinary studies have invariably described the litho-tectonic relationships of the Aravalli Craton. Considering the voluminous literature and arguable interpretations, we present a holistic review addressing the Mesoarchean to Neoproterozoic tectonic evolution of the basement and the polydeformed supracrustal sequences of Aravalli and Delhi supergroups. We suggest that the Aravalli Craton evolved by the accretionary-collisional interactions between three major crustal domains, viz., the Mewar gneissic terrane and intrusive granitoids (~3.3–2.5 Ga), the Aravalli fold belt (~2.2–1.7 Ga) and the Delhi fold belt (~1.7–0.7 Ga). The Mewar gneissic terrane formed between 3.3 Ga and 2.7 Ga by partial melting of hydrated mafic crust, where the terrane evolved continuously and finally stabilized due to the collision between the Bundelkhand and Aravalli cratons, resulting in the emplacement of several granitoids between 2.6 and 2.4 Ga. The subsequent development of the Aravalli fold belt (~2.2–1.7 Ga) to the west of Mewar gneissic terrane was characterized by the ~2.2–2.1 Ga mafic-ultramafic volcanism and ~1.8–1.7 Ga felsic magmatism, marking the opening and closing of the Aravalli Basin, respectively. The final closure of this basin was contemporaneous with the exhumation of the Sandmata granulite terrane along the western margin of Aravalli fold belt. Although the Sandmata Complex was previously interpreted as a reworked equivalent of the basement gneisses, based on contrasting lithology, deformation styles and metamorphic grade, we infer that the Sandmata Complex possibly represents an independent terrane with a distinct tectonothermal history. The tectonic evolution of the Delhi Basin most likely took place in two stages from ~1.7 to 0.7 Ga. The initial stage (~1.7–1.4 Ga) led to the development of the north Delhi fold belt and emplacement of A-type granitoids (~1.5–1.4 Ga), whereas the high-grade metamorphism and I- and S-type granite magmatism in the southern part characterize the later stage (~1.3–0.7 Ga) of the Delhi Basin. Following the Delhi Basin closure, the areas to the west of the Aravalli Craton witnessed the emplacement of the Malani Igneous Suite and the development of the Sirohi and Marwar basins. Altogether, the available key information on structural patterns, magmatic-metamorphic histories and geochronology allows more detailed correlations with possible contiguous orogens of the Great Indian Proterozoic Fold Belt. Our synthesis and tectonic interpretations help us discuss and provide alternate explanations for some of the controversial issues from existing tectonic models. Further, we summarize important unresolved issues, which require special attention to improve our knowledge of the Archean to Proterozoic crustal evolution in northwestern India.
... Rogers and Santosh (2002 proposed that the oldest supercontinent 'Ur' in the Mesoarchean incorporated the cores of major Archean cratons including most of those in Peninsular India such as Dharwar, Bastar and Singhbhum, as well as those elsewhere on the globe such as Kalahari in South Africa, Pilbara in western Australia and the coastal domain of East Antarctica. The active subduction-accretion-collision process during the Paleoand Mesoarchean resulted in an expanded ''Ur" at around 3.0 Ga (Rogers and Santosh, 2003;Yang et al., 2022Yang et al., , 2023. Continental outbuilding and collisional amalgamation with final cratonization resulted in the construction of the Neoarchean supercontinent Kenorland, which incorporated the Ur assembly at its core. ...
... Several hypothetical reconstructions have been proposed for the late Archean supercontinent, with different terminologies. Here we follow the term Kenorland (e.g., Rogers and Santosh, 2003) and illustrate in Fig. 16 the configuration of this supercontinent as proposed by Lubnina and Slabunov (2011) based on paleomagnetic data. This reconstruction incorporates the Kaapvaal, Karelian, Pilbara, and Superia cratons within the supercontinent. ...
The Coorg Block in southern Peninsular India is one of the oldest crustal blocks on Earth that preserves
the evidence for continental crust formation during the Paleo-Mesoarchean through subduction related
arc magmatism, followed by granulite facies metamorphism in the Mesoarchean. In this study,
we report for the first time, the ‘bar codes’ of a major Paleoproterozoic Large Igneous Province in the
Coorg Block through the finding of mafic dyke swarms. The gabbroic dykes from the Coorg Block, dominantly
composed of plagioclase-pyroxene assemblage, show a restricted range in SiO2 values of 50.04–
51.27 wt.%, and exhibit a sub-alkaline tholeiitic nature. These rocks show relatively flat LREE and constant
HREE patterns and lack obvious Eu anomalies. Trace element modeling suggests that the dyke swarm was
fed from a melt that originated at a shallow mantle level in the spinel stability field. Zircon grains are rare
in the gabbro samples and those separated from two samples yielded 207Pb/206Pb weighted mean dates of
2214 ± 12 Ma and 2221 ± 7 Ma. The grains show magmatic features with depleted LREE and enriched
HREE and positive Ce and negative Eu anomalies. Baddeleyite grains were dated from five gabbro samples
which yielded 207Pb/206Pb weighted mean ages ranging between 2217 ± 7 Ma and 2228 ± 10 Ma. The
combined data show a clear age peak at ca. 2.2 Ga. The mafic dykes in the Coorg Block show geochemical
similarities with ca. 2.2 Ga mafic dyke swarms in different regions of the Dharwar and other cratons in
Peninsular India and elsewhere on the globe. The data also support the inference that the global mafic
magmatism at ca. 2.2 Ga was linked with intracontinental rifting of the Archean cratons through mantle
upwelling or plume activity. We correlate the mafic dyke swarms in the Coorg Block with attempted rifting
of the Neoarchean supercontinent Kenorland.
... The Proterozoic Eon extended from 2.5 billion years ago and ended 542.0 million years ago and is the second part of the Precambrian time. It is subdivided into three geologic eras, the Paleoproterozoic (2.5-1.6 Gya), Mesoproterozoic (1.6-1 Gya), and Neoproterozoic (1 billion to 542.0 Mya) (Rogers and Santosh 2003). One of the most well-known events of this period was the transition to an oxygen-rich atmosphere during the Mesoproterozoic period. ...
... One of the most well-known events of this period was the transition to an oxygen-rich atmosphere during the Mesoproterozoic period. Several glaciers, including the hypothetical snowball Earth of the age of the Neoproterozoic period, and the Ediacaran period (635-542 Mya) are characterized by the evolution of abundant soft-bodied multicellular organisms (Rogers and Santosh 2003). The first known glaciations in the history of the Geosphere occurred during the Proterozoic epoch, one shortly after the beginning of the eon, and at least four during the Neoproterozoic period, climaxing with the Snowball Earth of the Sturtian and Marinoan glaciations (Young 2013). ...
... The Proterozoic Eon extended from 2.5 billion years ago and ended 542.0 million years ago and is the second part of the Precambrian time. It is subdivided into three geologic eras, the Paleoproterozoic (2.5-1.6 Gya), Mesoproterozoic (1.6-1 Gya), and Neoproterozoic (1 billion to 542.0 Mya) (Rogers and Santosh 2003). One of the most well-known events of this period was the transition to an oxygen-rich atmosphere during the Mesoproterozoic period. ...
... One of the most well-known events of this period was the transition to an oxygen-rich atmosphere during the Mesoproterozoic period. Several glaciers, including the hypothetical snowball Earth of the age of the Neoproterozoic period, and the Ediacaran period (635-542 Mya) are characterized by the evolution of abundant soft-bodied multicellular organisms (Rogers and Santosh 2003). The first known glaciations in the history of the Geosphere occurred during the Proterozoic epoch, one shortly after the beginning of the eon, and at least four during the Neoproterozoic period, climaxing with the Snowball Earth of the Sturtian and Marinoan glaciations (Young 2013). ...
Biogeochemistry is a relatively new interdisciplinary field exploring the link between biotic and abiotic constituents. It investigates physical, chemical, geological, and biological reactions and processes that govern the biogeochemical cycles essential to sustain life on earth. Geosphere and biosphere are the two major components of the earth that play an imperative role in biogeochemical cycles, involving the transformation and fluxes of chemical elements and nutrients among different parts of the ecosystem. The geosphere on earth is around 4.54 billion years, and various indigenous and exogenous processes have resulted in the formation and evolution of the biosphere over 3.5 billion years. During the past few years, anthropogenic activities have significantly contributed to the biogeochemical processes, causing a cascade of changes to the earth's ecosystem. The current chapter focuses on important aspects of biogeochemistry concerning the geosphere, biosphere, natural and artificial biogeochemical cycles, different areas of biogeochemistry, and applications of biogeochemistry.
... The ca. 1.3 Ga magmatism was global in extent, suggesting the extensional/rifting event during this period was a global phenomenon. Mafic dyke swarms ranging in age from 1.3 to 1.2 Ga have been identified in the Mackenzie Mountains in Canada, the Săo Francisco craton in southeastern Brazil, and Australia [16,56,57]. In addition to mafic magmatism during the middle Mesoproterozoic along the northern margin of the NCC, granites were formed at this time in the study area and surrounding regions due to continental extension and rifting [8,[18][19][20]53]. ...
Mesoproterozoic (ca. 1.3 Ga) magmatism in the North China Craton (NCC) was dominated by mafic intrusions (dolerite sills) with lesser amounts of granitic magmatism, but our lack of knowledge of this magmatism hinders our understanding of the evolution of the NCC during this period. This study investigated porphyritic granites from the Huade–Kangbao area on the northern margin of the NCC. Zircon dating indicates the porphyritic granites were intruded during the Mesoproterozoic between 1285.4 ± 2.6 and 1278.6 ± 6.1 Ma. The granites have high silica contents (SiO2 = 63.10–73.73 wt.%), exhibit alkali enrichment (total alkalis = 7.71–8.79 wt.%), are peraluminous, and can be classified as weakly peraluminous A2-type granites. The granites have negative Eu anomalies (δEu = 0.14–0.44), enrichments in large-ion lithophile elements (LILEs; e.g., K, Rb, Th, and U), and depletions in high-field-strength elements (HFSEs; e.g., Nb, Ta, and Ti). εHf(t) values range from –6.43 to +2.41, with tDM2 ages of 1905–2462 Ma, suggesting the magmas were derived by partial melting of ancient crustal material. The geochronological and geochemical data, and regional geological features, indicate the Mesoproterozoic porphyritic granites from the northern margin of the NCC formed in an intraplate tectonic setting during continental extension and rifting, which represents the response of the NCC to the break-up of the Columbia supercontinent.
... An integrated palaeomagnetic and geochronological study of the basaltic dykes is a suitable approach to place constraints on the paleogeographic reconstructions and could establish various models for the breakup and assembly of paleo supercontinents (McFadden 1990(McFadden , 1998Butler 1992;Joseph 1994;McElhinny and McFadden 2000;Pradhan et al. 2010;Dash et al. 2013). Various crustal elements from the Indian subcontinent also contribute a significant role in paleogeographic reconstructions for every supercontinent (Rogers and Santosh 2003;Halls et al. 2007;Meert et al. 2010;Pradhan et al. 2010;Meert 2012Meert , 2014Dash et al. 2013;Pivarunas et al. 2018). ...
... Finally, it has long been recognized that super-continents assemble and break up episodically throughout Earth's history, and this cycle is intimately linked to whole-mantle convection (e.g., Mitchell et al., 2021;Nance et al., 1988Nance et al., , 2014Rogers & Santosh, 2003;Rolf et al., 2014). In particular, the assembly stage of super-continent cycles is heavily influenced by subduction. ...
Seismic tomography of Earth's mantle images abundant slab remnants, often located in close proximity to active subduction systems. The impact of such remnants on the dynamics of subduction remains underexplored. Here, we use simulations of multi‐material free subduction in a 3‐D spherical shell geometry to examine the interaction between visco‐plastic slabs and remnants that are positioned above, within and below the mantle transition zone. Depending on their size, negatively buoyant remnants can set up mantle flow of similar strength and length scales as that due to active subduction. As such, we find that remnants located within a few hundred km from a slab tip can locally enhance sinking by up to a factor 2. Remnant location influences trench motion: the trench advances toward a remnant positioned in the mantle wedge region, whereas remnants in the sub‐slab region enhance trench retreat. These motions aid in rotating the subducting slab and remnant toward each other, reducing the distance between them, and further enhancing the positive interaction of their mantle flow fields. In this process, the trench develops along‐strike variations in shape that are dependent on the remnant's location. Slab‐remnant interactions may explain the poor correlation between subducting plate velocities and subducting plate age found in recent plate tectonic reconstructions. Our results imply that slab‐remnant interactions affect the evolution of subducting slabs and trench geometry. Remnant‐induced downwelling may also anchor and sustain subduction systems, facilitate subduction initiation, and contribute to plate reorganization events.
... A subsequent major stage of tectonism that occurred throughout the Cretaceous Period (Scotese, 2004;Rogers and Santosh, 2003) was associated with the separation of Eastern Gondwana (Antarctica, Australia and India) from Western Gondwana (Africa and South America). During the Valanginian (~133 Ma), "Atlantica" (the 2.2 Ga ancient continent described by Rogers (1996), which encompasses the Archean Guyana/Brazilian, São Francisco, and Rio de la Plata cratons of South America, and West African, West Nile and Congo cratons of Africa) entered into a diachronous rifting phase propagating from south to north (Pletsch et al., 2001;Labails et al., 2010;Torsvik et al., 2008) resulting in the opening of the proto-South Atlantic Ocean and the eventual formation of the Equatorial Atlantic Gateway. ...
Climate change directly impacts the source, mode and volume of sediment generation which can be observed in the rock record. To accurately model source to sink systems, in addition to hinterland geology, tectonics and transport distance, a thorough comprehension of the climate is essential. In this study we evaluate the role of climate on Cretaceous sediment delivery into the Senegal Basin, NW Africa, using data recorded from extensive sampling of basinal sediments. This is achieved through the mineralogical characterisation by X-ray diffraction and 146Nd/144Nd and 86Sr/88Sr isotopic analyses, which are correlated against existing, climate, tectonic and oceanographic models.
Examples of climatic indicators include the change from predominantly smectitic deep marine basinal-clays recorded from the Cretaceous in DSDP wells 367 and 368 to clays with increased illite and kaolinite content, observed during the Albian and Cenomanian-Turonian, interpreted to be representative of higher humidity following the kaolinisation of hinterland source-rocks. Another climate indicator is the observation of palygorskite in deep-marine sediments, noted to be indicative of ocean anoxia related to the authigenesis of marine-smectite, a product of warm saline bottom waters and increased abundancy of silicon. The increase in salinity is interpreted to be a biproduct of elevated temperatures throughout the Cenomanian and increased denudation of the North Atlantic circumjacent continental evaporite-belts. Increase in silicon (biogenic) is related to a result of ocean-wide mass extinction of foraminifera during OAE2 triggered by the eruption of the Caribbean large igneous province.
The results suggest that Cretaceous climate evolution of Senegal can be divided into four stages: 1. Berriasian-Barremian; an arid-period with monsoonal weather producing modest fluvial systems restricted to coastal regions. 2. Aptian-Albian; the establishment of a paleo-Intertropical Convergence Zone began to increase global temperature and humidity as recognised by the increase in kaolinite content. 3. Cenomanian-Turonian; the Cretaceous Thermal Maximum hothouse period incurring exceptional temperatures and humidity. This is represented as an antithetical shift in clay mineralogy from chlorite-illite to smectite-kaolinite throughout most of the onshore and nearshore basinal sediments. 4. Coniacian-Maastrichtian; transitional from tropical-to-tropical swamp-like conditions evidenced by increased onshore basin sediment capture and a shift in vegetation to aquatic-fern species.
The impact of climate change throughout the Cretaceous produced dynamic shifts in both river size and source-catchment, witnessing exception rates of denudation during the hotter and more humid periods, which climaxed during the Cenomanian and Turonian as a result of the Cretaceous Thermal Maximum. This eroded sediment was deposited in both the onshore and offshore basins during the mid-late Cretaceous but became increasingly restricted to the onshore segment of the basin during the Late Cretaceous.
... (b) Histogram distribution of zircon ages. Times of supercraton/ supercontinent assembly highlighted by pink and green bars (Rogers and Santosh, 2003;Mitchell et al., 2021;. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ...
The enigmatic nature of the Precambrian era poses ongoing challenges for researchers seeking to uncover its secrets. With the exponential growth of scientific data, there exists a vast repository of information through which these mysteries can be explored. However, this data is often derived from fragmented investigations of geological phenomena within specific disciplinary domains and limited spatiotemporal boundaries, resulting in untapped potential for extracting undiscovered knowledge. To address this limitation, the field of big data science provides a foundation for multidisciplinary research on the geological evolution of the Precambrian. By harnessing the power of large-scale data integration and analysis, valuable insights into this pivotal era in Earth's history can be revealed. This paper offers a comprehensive overview of big data types in geoscience and elucidates common analysis methods. Through a case study focused on the North China Craton (NCC), we demonstrate the application of conjoint analysis to a dataset comprising rock and mineral geochemistry data. Employing local singularity analysis and wavelet analysis on zircon age frequency and Hf isotopic time series, we reveal a persistent long-term periodicity of 800–500 million years since 3.5 billion years ago. This finding indicates a co-evolution between the NCC and the global supercontinent cycle dating back to the Archean period. To investigate the formation of the NCC, we employ machine learning-based crustal thickness evolution reconstruction, which highlights arc formation during subduction as the primary factor, with regional mantle activities playing a secondary role in the convergence. Combining spatio-temporal evolution analysis of magmatic intensity and εHf(t) values, we infer that the development of the NCC primarily resulted from a prolonged process of accretion targeting the Eastern Block (the primary continent nuclei) through the incorporation of diverse arc massifs. This examination of the NCC serves as an example of how data collection, processing, and utilization can enhance our understanding of formational and evolutionary processes, signaling a paradigm shift in Precambrian research driven by the integration of big data.
... Being part of the Brst supercontinent 'Ur' (Rogers 1993), Singhbhum Craton in the Eastern Indian Shield has the evidence of the oldest developed continental crust cratonised C3 Ga (Rogers 1993(Rogers , 1996Rogers and Santosh 2003;Eriksson et al. 2009). It is marked by two distinct types of supracrustal sequences. ...
Bonai Granite Complex andthe volcanosedimentary sequence around it
... By contrast, using the relative age of oceanic crust, Murphy and Nance (2003) identified Gondwana (or Pannotia) to have formed by extroversion from Rodinia, that is, by preferential subduction of the Mirovoi Ocean exterior to Rodinia, with Pangaea forming by introversion, that is, by subduction of the oceans (Iapetus, Rheic) that formed due to the breakup of Pannotia. The ambiguity in the definition of interior and exterior oceans has led to Columbia, Rodinia and Gondwana being described as forming by extroversion and introversion by different workers (Hoffman 1991;Murphy and Nance 2003;Rogers and Santosh 2003;Rino et al. 2008;Oriolo et al. 2017;Li et al. 2019Li et al. , 2023. ...
Supercontinent amalgamation is described by the end-member kinematic processes of introversion - closure of interior oceans; extroversion - closure of exterior oceans; or orthoversion - amalgamation 90° from the centroid of the previous supercontinent. However, supercontinent formations are often ascribed to contradictory mechanisms; for example, Pangea has been argued to have formed by introversion from Pannotia/Gondwana, and extroversion from Rodinia. Conflicting interpretations arise partly from attempting to define oceans as interior or exterior based on paleogeography, or the age of the oceanic lithosphere relative to the time of supercontinent breakup. We define interior and exterior oceans relative to the external subduction ring, and associated accretionary orogens that surround amalgamated supercontinents. All oceans within the continental dominated cell and internal to the subduction ring are interior oceans. The exterior ocean is separated from the interior oceans by the subduction ring and bordered by external accretionary orogens. Wilson cycle tectonics dominate the interior continental cell, conversely, subduction of the exterior ocean is doubly vergent and lacks continent-continent collision. For the exterior ocean to close, the subduction ring must collapse upon itself, leading to the collision of external accretionary orogens. Employing this definition, Rodinia formed by extroversion, but all other supercontinents formed by introversion.
... Numerous studies have found that magma addition and crustal growth have been episodic throughout Earth's history, with prominent magmatic episodes at ca. 2100-1800 Ma, 1100-800 Ma, and 350-250 Ma, corresponding to the assembly of the Columbia, Rodinia, and Pangea supercontinents, respectively (Condie, 1998(Condie, , 2007Rogers and Santosh, 2003;Kröner and Stern, 2004;Cawood and Buchan, 2007;Linnemann et al., 2008;Cao et al., 2017b;Spencer et al., 2018). Recent studies have similarly demonstrated that the construction of Phanerozoic arc belts worldwide has also been episodic, with so-called magmatic flare-ups (voluminous magma additions) typically lasting ~10-30 m.y. and intermittent magmatic lulls (minor magma additions) (Ducea and Barton, 2007;Ducea et al., 2015;Paterson and Ducea, 2015;Cao et al., 2017b;Chapman et al., 2017;Ma et al., 2021bMa et al., , 2022. ...
The Gangdese belt of the southern Lhasa terrane (southern Tibet) records a Chilean-type accretionary orogeny driven by subduction of Neotethyan oceanic lithosphere, prior to Indo-Asian collision and formation of the Tibetan Plateau. We present detailed structural analysis of outcrops and a drill core in the Jiama copper ore district along with 40Ar-39Ar cooling ages from white mica, plagioclase, and potassium feldspar and zircon U-Pb geochronology of granitoids and sandstone. These data add new constraints to the formation of a major angular unconformity, deformation along and within the footwall of the Gangdese décollement, and the coupling between deformation and magmatism. Structural analysis indicates that top-to-the-south motion along the décollement produced south-vergent folding and thrusting of Upper Jurassic to Cretaceous strata in the Gangdese back-arc basin. A synthesis of new and compiled age data reveals that the décollement and associated south-vergent deformation occurred between ca. 90 and 65 Ma, contemporaneous with the formation of a major ca. 85–69 Ma angular unconformity between the overlying Paleocene–Eocene Linzizong Formation and the underlying Upper Cretaceous Shexing Formation. We posit that this deformation in the Gangdese belt resulted from flat-slab subduction of the Neotethyan oceanic slab beneath the southern margin of the Asian continent. A flat-slab subduction geometry is consistent with previously documented synchronous thrusting in the forearc and back-arc basins as well as the observed arc magmatic lull of the Gangdese belt between ca. 80 and 65 Ma.
... It is conspicuous that eclogites on five cratons have Neo-to Mesoarchean ages [plus probably xenolithic eclogites from the West African craton, the ages of which remain ill-constrained (Figure 4a)]. It is possible that these eclogites formed part of Earth's first supercontinent [Ur (Rogers & Santosh 2003)] and that they represent the first global, linked plate tectonic network. Orogenic eclogite suites become rather common by the Paleoproterozoic (Tamblyn et al. 2021), and these ages are matched by eclogite xenolith suites from the Slave craton and the East European Platform (Figure 4a), which plausibly formed part of the Nuna/Columbia supercontinent. ...
Kimberlite-borne xenolithic eclogites, typically occurring in or near cratons, have long been recognized as remnants of Precambrian subducted oceanic crust that have undergone partial melting to yield granitoids similar to the Archaean continental crust. While some eclogitized oceanic crust was emplaced into cratonic lithospheres, the majority was deeply subducted to form lithologic and geochemical heterogeneities in the convecting mantle. If we accept that most xenolithic eclogites originally formed at Earth's surface, then their geodynamic significance encompasses four tectonic environments: ( a) spreading ridges, where precursors formed by partial melting of convecting mantle and subsequent melt differentiation; ( b) subduction zones, where oceanic crust was metamorphosed and interacted with other slab lithologies; ( c) the cratonic mantle lithosphere, where the eclogite source was variably modified subsequent to emplacement in Mesoarchaean to Palaeoproterozoic time; and ( d) the convecting mantle, into which the vast majority of subduction-modified oceanic crust not captured in the cratonic lithosphere was recycled. ▪ Xenolithic eclogites are fragments of 3.0–1.8 Ga oceanic crust and signal robust subduction tectonics from the Mesoarchean. ▪ Multiple constraints indicate an origin as variably differentiated oceanic crust, subduction metamorphism, and prolonged mantle residence. ▪ Xenolithic eclogites thus permit investigation of deep geochemical cycles related to recycling of Precambrian oceanic crust. ▪ They help constrain asthenosphere thermal plus redox evolution and contribute to cratonic physical properties and mineral endowments.
Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 51 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... 2.1-1.3 Ga; Rogers and Santosh 2003) and Rodinia (ca. 1.2-0.8 ...
... Granitoids, compared with other igneous rocks, are more widespread in orogens and commonly better studied in geochronology and geochemistry. Thus, data of granitoids can provide much information about orogenic processes and continental assembly (e.g., Ş engör and Okurogullari, 1991;, 2018; for instance, age peaks of global granitoids are consistent with events of supercontinental assembly (e.g., Condie et al., 2009;Rogers and Santosh, 2003;Scotese, 2004;Condie and Aster, 2010). ...
The Asian continent consists of many continental blocks that assembled during the Phanerozoic, accompanied by widespread granitoids. By compiling a series of digital maps of igneous rocks with associated zircon U-Pb ages and petrological datasets, we illustrate the spatial-temporal evolution of the granitoids, which shed new light on the assembling process of the Asian continent.
Neoproterozoic granitoids in the Central China Orogenic System evolved from deformed S-type (1100–900 Ma) to weakly or undeformed I-, and A-type granites (850–700 Ma), displaying a transition from syncollisional to postcollisional environment along the northern margin of the South China Craton (or Block), corresponding to the assembly and breakup of Rodinia, respectively. Phanerozoic igneous rocks mainly occur in the Central Asian Orogenic Belt (CAOB) and the Tethyan orogenic system, and record the closure processes of ocean systems, i.e., the Paleo-Asian Ocean (PAO), the Mongol-Okhotsk Ocean, and the Tethyan Ocean, as well as marginal processes along the west Paleo-Pacific Ocean (PPO). The assembly of the Asian continent can be summarized into five major stages. (1) Initial formation of the Siberian-Mongol collage in the PAO domain and the East Asian continental assemblage in the Proto-Tethyan domain, which is evidenced by voluminous 550–500 Ma magmatic belts in the northern CAOB and 520–400 Ma belts in the Central China Orogenic System, respectively. (2) Formation of the North Asian continent through the amalgamation of the above two collages following the closure of the PAO (310–250 Ma). The closure occurred in a double scissor-like manner, as indicated by a westward younging trend of granitoids along the western segment (western Tianshan) of the southern CAOB and an eastward younging trend of granitoids along the central and eastern segment (the Solonker-Xilamulun suture zone) of the southern CAOB. (3) Formation of the East Asian continent by 230–210 Ma through the collision of continental blocks/terranes with the North Asian continent. The processes are recorded by several large (> 1500 km-long) Triassic magmatic belts that evolved from subduction (250–230 Ma) to collision (230–220 Ma). (4) Formation of the main Asian continent through the collision between the East Asian and Siberia-Europe continents, following the closure of the Mongol-Okhotsk Ocean by 150 Ma. This closure also occurred in a scissor-like fashion, as evidenced by an eastward younging trend of 230–150 Ma collision-related granitoids along the Mongol-Okhotsk Suture. (5) Final formation of the Asian continent by the terminal suturing of the Meso- and Neo-Tethys and the final collision between the Indian-Arabian continent and Eurasia, marked by a large 130–120 Ma magmatic belt and a 70–4 Ma leucogranite belt in the southern Tethyan Orogenic System. Continental assembly in north Asia (the PAO domain) was associated with oblique collision and terrene rotation, characterized by curved magmatic belts/oroclines and involved a large volume (ca. > 50%) of juvenile crust; whereas continental assembly in south Asia (the Tethyan domain) was characterized by direct collision, characterized by straight linear magmatic belts and involved a smaller (< 5 %) volume of juvenile crust.
... Laurasia is the northern of two large landmasses that formed the supercontinent Pangea, the southern being Gondwana. Laurasia separated from Gondwana approximately 138-160 million years ago (Ma) during the breakup of Pangea, subsequently drifting farther north and finally breaking apart with the opening of the North Atlantic Ocean, eventually giving rise to North America, Europe, and much of Asia (Scotese, 2001;Rogers and Santosh, 2003). This reorganization of the continents changed the flow of the oceanic currents and shaped heterogeneous temperature gradients along their longitudes. ...
The water boatmen of Corixoidea, a group of aquatic bugs with more than 600 extant species, is one of the largest superfamilies of Nepomorpha. Contrary to the other nepomorphan lineages, the Corixoidea are most diverse in the Laurasian remnant Holarctic region. To explicitly test whether the present-day Holarctic distribution of diverse corixids is associated with the arising of the Laurasian landmass that was separated from Gondwana, we investigated the phylogeny, divergence times and historical biogeography of Corixoidea based on morphological and molecular characters sampled from 122 taxa representing all families, subfamilies, tribes and approximately 54% of the genera. Our results were largely congruent with the phylogenetic relationships within the established nepomorphan phylogenetic context. The fossil calibrated chronogram, diversification analysis and ancestral ranges reconstruction indicated that Corixoidea began to diversify in Gondwana in the late Triassic approximately at 224 Ma and the arising of the most diverse subfamily Corixinae in Corixidae in the Holarctic region was largely congruent with the time of separation of Laurasia from Gondwana. The large-scale expansion of the temperate and cold zones on the northward-moving Laurasian landmass after the breakup of the Pangea provided new aquatic niches and ecological opportunities for promoting rapid diversification for the Holarctic corixid lineage.
... Geologists have good evidence that there were at least two major supercontinents on Earth, Rodinia (formed at 1 Ga), and Pangea (formed at 300 Ma), defining a complete supercontinent cycle (Rogers and Santosh, 2003;Meert, 2014). Some authors also consider that a short-lived supercontinent, Pannotia, might have existed between Rodinia and Pangea, at 660 Ma (Nance and Murphy, 2018). ...
Plate tectonics is the unifying theory of solid earth sciences. It describes that the surface of the Earth is divided into several lithospheric tectonic plates that move in relation to each other and over the less viscous asthenosphere. Many of the fundamental geological phenomena occur along the plate's boundaries, such as earthquakes and volcanoes, and the plates’ movement gives rise to a number of fundamental geological processes that include mountain building and the supercontinent cycle itself. The idea of surface mobility was first solidly proposed by Alfred Wegener in the start of the 20th century, but it took another 50 years for a unified theory of the solid earth to emerge. Plate tectonics dictates how the surface of the planet changes, how supercontinents break and come together, and how new oceans form and old ones close. As we will see in this book, plate tectonics is intertwined with ocean tides in unexpected ways. This chapter provides a brief introduction to the history and the workings of plate tectonics.
... The assembly and breakup of supercontinents have taken place over multiple tectonic episodes (Rogers and Santosh, 2003;Zhao et al., 2002). The fragmentation of the Paleo-Mesoproterozoic supercontinent Columbia resulted in continental rifting during the Mesoproterozoic (1.5-1.3 ...
The investigation of the rigid lithospheric mantle architecture floating over the weaker hotter asthenosphere is key to understanding the plate tectonic evolution of the Eastern Ghats Mobile Belt and the adjoining Archean Cratons. We present shear-wave velocity (VS) structure for the crust and upper-mantle below the Eastern Ghats Mobile Belt (EGMB) and adjacent Archean cratons. The lithospheric structure is constrained through 4–150 s fundamental-mode Rayleigh and Love-wave group velocity dispersion measurements, using regional (2–30◦) earthquakes recorded at 27 seismic stations installed along two distinct profiles. Velocity models are improved by joint inversion of resultant dispersion curves with receiver functions computed from the teleseismic P-waves. Observed variations in crustal and lithospheric architecture across the domains of the Eastern Ghats Province are implication of the deformations due to rifting and collision of India and East Antarctica in the context of assembly and breakup of Rodinia and Gondwana supercontinent. The cratons and the mobile belt are characterised by 34–38 km, ∼45 km thick heterogeneous crust and 120–160 km and 90–120 km thick lithospheres, respectively. The abrupt changes in the crustal thickness owes its origin to the collisional thrusting of the Eastern Ghats Province against the Archean Cratons. Significant variations in the nature of Moho are also noted. The flat sharp cratonic Moho is distinct from the gradational Moho below the Eastern Ghats Province, possibly a signature of magmatic underplating below the mobile belt. The nature of the Lithosphere-Asthenosphere Boundary (LAB) interpreted from the gradient change in velocity appears to be poorly-resolved. Therefore, we utilise radial anisotropy determined from the discrepancy between VSH and VSV based on Rayleigh and Love-wave velocities respectively as a proxy. Our findings confirm the LAB through positive radial anisotropy (VSH > VSV) prevalent in the asthenospheric-mantle that is likely explained by flow-induced shear. Overall, the lithospheric architecture below the study area has been shaped through several deformational episodes that distinguish the multiple litho-tectonic units within the mobile belt. The loss of cratonic lithospheric keel can be attributed to the mantle plume given the Gondwanan trajectory of the Indian subcontinent over Kerguelen and Crozet hotspots.
... 2010 Another abiotic factor comes from pure geological events, and, contrary to the previous one, may be damaging but also fruitful. As tectonic plates move, interact with earth's mantle and rub with one another (Wegener, 1912;Hess, 1954;Heezen et al., 1965;White et al., 1970), new territories, be they land, sea or lake, emerged or merged (Heezen et al., 1965;Rogers et al., 2003), mingling biology with geology into biogeography (Wallace, 2011(Wallace, -(1876 McIntyre et al., 2017). When continents merge, a burst of extinction may occur as organisms formerly isolated suddenly engage in a new competition. ...
Since Life was born, its Evolution has created an exceptional diversity of entities spanning an extravagant range of sizes from tiny microscopic molecules to the giant organisms that embody Megafauna. This broad variability, which exists both between and within classes of biological entities (eg. proteins), has often been theoretically explained by assuming the existence of biological trade-offs – impossibility to optimise many traits at once - and/or specific niches (eg. two different nutrients in the environment). However, how these trade-offs build up at the cellular level has mostly remained elusive because models of specialisation overlook the very mechanistic underpinnings of cells, that is to say how they actually work. Here, we develop a model where the fitness of cells emerges from a sequence of enzyme-substrate reactions that each produce a specific metabolite like ATP, and first show that accounting for physical, ecological and cellular constraints sheds light on the reasons why enzyme properties resemble a zoo although they seemingly evolve under a similar directional selective pressure – and should thus, at first glance, all look the same. Based on these landscapes of metabolic fitness and adaptive dynamics, we then simulate cell competition to demonstrate how the simple and intrinsic physical constraint of membrane permeability can explain the emergence of cross-feeding in an environment where only one ecological niche seems to exist, thus violating Gause's principle of competitive exclusion. This form of specialization sees one of the types specializing at the exploitation of a waste product released by the other, and it has generally been explained through considerations on the cost of processing metabolites, but this does not allow one to explain why certain metabolites seem more often associated with cross-feeding (acetate, glycerol). Our model specifically makes it possible to predict which intermediate metabolites should give rise to cross-feeding interactions and we emphasize that the available data seems to match our predictions. Yet, in this model, the enzymatic properties cannot evolve and the optimization simply concerns their levels of expression. If enzyme kinetics could be easily improved, cross-feeding would probably not emerge, but this not what the data shows. Hence, we then develop a quantitative genetic model intended to clarify the mechanistic underpinnings of metabolic epistasis and its consequences on the fitness reached at the mutation-selection-drift equilibrium. Because of these consequences, optimising enzymes above a given level may be compromised. Finally, we discuss the open perspectives whose vocation would be to combine these approaches in order to bring the fields of systems biology closer to those of quantitative genetics, and, thereby, to feed the field of quantitative evolution.
... The Southern Granulite Terrane (SGT), India, of Archean-Proterozoic age is one of such kind, which forms the southernmost tip of the Indian shield ( Figure 1a). The SGT is well studied for the last three to four decades (Drury et al. 1984;Harris et al. 1994;Raith et al. 1999;Rogers and Santosh 2003;Rajesh and Santosh 2004;Santosh et al. 2009;Chetty et al. 2016, Santosh 2020, Ganguli et al. 2021a for the pursuit of deciphering its evolutionary history. These studies conform to the idea that the SGT is a collage of crustal blocks weaved together by crustal-scale shear/suture zones. ...
We present a combined analysis of remote sensing, gravity and magnetic data across Moyar Bhavani Shear Zone (MBSZ), Southern Granulite Terrane (SGT), India to study crustal architecture and tectonics. The horizontal gradient of gravity data shows strong density inhomogeneity across the MBSZ. The magnetic data and residual gravity analysis shows corroboration of a NE–SW trending linear magnetic anomaly zone and residual gravity high strip along the MBSZ. The low magnetic anomalies dominate the northern part of the MBSZ, while the southern part is dominated by moderate to high anomalies. The integration of potential data and remote sensing data clearly reveals that ENE–WSW is the dominant structural trend that coincides with the Mettur Shear Zone (MeSZ) trend. The joint gravity and magnetic modelling suggest that the MBSZ, is characterized by the disposition of mélange of moderate to high-density rocks of diamagnetic nature.
... Since the Archean, there have been a number of supercontinent amalgamations and dispersal cycles (Murphy & Nance, 2008;Rogers & Santosh, 2003), among which Pangea was the last one. As per the current understanding based on geochemical studies, the amalgamation and formation of the Pangea supercontinent took place from 350 to 170 Ma (Cawood, Pisarevsky, & Leitch, 2011). ...
The paradigm of plate tectonics has aided in the identification of the journey of continents on the globe, their assembly into supercontinents, disruption, and re‐assembly. Here, we use meteorite impact craters as proxies for tracking the voyage of lithospheric plates. Employing the provisions in GPlates, an interactive geographic information system‐based plate tectonic reconstruction model, we were able to identify the palaeo‐position, and velocity of the 174 terrestrial impact craters, formed after 1,100 Ma, across the globe. These parameters of craters were evaluated for independent tectonic plates and were correlated with global tectonic events. For example, the similarity in the velocity of Beaverhead (900 Ma) and Holleford (550 Ma) craters since 550 Ma is traced to the connection between the Eastern Basin and North America Craton commencing 1,100 Ma, and through the South Basin and Range. Likewise, the drastic reduction in the velocity of Spider Crater (700 Ma) in Australia after 600 Ma can be attributed to the subduction between east and west Gondwana. The accelerated motion of the Indian Plate at 63 Ma, when the lithosphere was hovering over the Réunion hotspot, is also explained. With the advent of more improved plate tectonic models and the discovery of more impact craters, improvised interpretations will be possible. Voyage of Ramgarh Crater.
Since the Proterozoic, considerable expansion of the continental crust has taken place. A significant amount of granitic plutons were deposited on the earth’s crust during this time. The dynamic structure of the earth plays a close role in the genesis of granites and related rocks. Information about the formation and development of the continental crust can be understood from the study of these rocks. The emplacement of large scale anorthosite massif in shield areas was another process that contributed to the Proterozoic expansion of the continental (Mukherjee, et al.,, 2005). One of the primary sources of information regarding the formation and evolution of the continents over geological time is the genesis of granite. Enclaves of supracrustal meta-sediments intrude the Chotanagpur Gneissic Complex (CGC), which is primarily composed of granites, granitoid gneisses, and migmatites exhibiting a wide range of structure, texture, and mineralogy variations.The granitic plutons exposed in the northern fringe of the Chotanagpur Gneissic Complex, CGC, and the associated anorthosites of the Barabar Anorthosite Complex along the northen margin of Bihar holds information about the various magmatic episodes that have taken place in that area millions of years ago.
Seismic tomography of Earth’s mantle images abundant slab remnants, often located in close proximity to active subduction systems. The impact of such remnants on the dynamics of subduction remains under explored. Here, we use simulations of multi-material free subduction in a 3-D spherical shell geometry to examine the interaction between visco-plastic slabs and remnants that are positioned above, within and below the mantle transition zone. Depending on their size, negatively buoyant remnants can set up mantle flow of similar strength and length scales as that due to active subduction. As such, we find that remnants located within a few hundred km from a slab tip can locally enhance sinking by up to a factor 2. Remnant location influences trench motion: the trench advances towards a remnant positioned in the mantle wedge region, whereas remnants in the sub-slab region enhance trench retreat. These motions aid in rotating the subducting slab and remnant towards each other, reducing the distance between them, and further enhancing the positive interaction of their mantle flow fields. In this process, the trench develops along-strike variations in shape that are dependent on the remnant’s location. Slab-remnant interactions may explain the poor correlation between subducting plate velocities and subducting plate age found in recent plate tectonic reconstructions. Our results imply that slab-remnant interactions affect the evolution of subducting slabs and trench geometry. Remnant-induced downwelling may also anchor and sustain subduction systems, facilitate subduction initiation, and contribute to plate reorganisation events.
Heterogeneous nature, textural variation, and compositional diversity are reported from the north-western part of the Kanker Granites, exposed in parts of Kanker District, Chhattisgarh, India, where the possible petrogenesis and tectonic history of the same, with special emphasis on its REE mineralogy and genesis. The granites are ferroan, alkalic to sub-alkalic, per-aluminous and oxidized A-type in nature. An integrated field-petrography-whole rock analysis-mineral chemistry approach indicates injection of mafic magma into crystallizing felsic host with different stages of interaction through mixing, mingling and hybridization. Major oxides, trace elements and REE geochemistry suggest derivation from a predominant crustal source involving a variable degree of mantle input, with a key role of fractional crystallization from mafic magma and partial melting of quartzo-feldspathic igneous sources during petrogenesis. The evolution of the granites can be best explained in an accretionary post-orogenic (collision) phase in subduction setting (A2-type granites) during the Archean-Proterozoic transition. The granites are enriched in LREE, the REE bearing phases being monazite, xenotime, allanite, parisite, and zircon. Occurrence of the REEs in granites probably have occurred through magmatic processes, hydrothermal fluid mobilization and precipitation. The REE contents in granites can be a potential resource in terms of economic geology.
Mesoproterozoic orogenesis is well established on the western and southern flanks of Laurentia in the well-known Racklan-Forward and Mazatzal Orogens, but its significance within the previously assembled interior of the supercontinent Nuna has not been established. We examine regional isotopic and structural evidence for Mesoproterozoic deformation in the ca . 1.7-1.63 Ga Hornby Bay, Elu, Thelon and Athabasca intracontinental basins, and present evidence for Mesoproterozoic reactivation of Paleoproterozoic structures in Wopmay and Trans-Hudson orogens. Racklan-Forward Orogeny in the interior of north Laurentia comprises north-south trending, high angle, east-vergent folds and thrusts that occur across a region 1660 kilometers wide and over 1000 kilometers long, stretching from the Yukon to near Hudson Bay and from Banks Island to below the Western Canada Sedimentary Basin. The structures progress from ductile amphibolite and greenschist facies in the Racklan type area to subgreenschist facies and ultimately brittle or brittle-ductile in the far foreland, showing a predominant thick-skinned style typical of many intracontinental orogens. We present compiled low-temperature thermochronologic data, including ages of spatially associated uraninite mineralization, to characterize the scope of reactivation of basement structures in the Archean Rae craton in Nuna's interior. We compare the nature of widespread far-field reactivation in Racklan-Forward Orogen with other orogens of Nuna's assembly to show it is unusual for Nuna's peripheral margin. We suggest that ca. 1.6 Ga continent-continent collision of North Australia with northwest Laurentia propagated stresses far into the interior as a result of combined favourable pre-existing structural grain and a weak subcontinental lithosphere mantle in Rae craton due to repeated episodes of refertilization across 500 Ma of accretion and intrusion. Cratons that experience the complex, two-sided collision and protracted upper plate setting during supercontinent assembly noted herein may be particularly susceptible to extensive foreland propagation of peripheral orogens.
Coupled paleomagnetic and geochronologic data derived from mafic dykes provide valuable records of continental movement. To reconstruct the Proterozoic paleogeographic history of Peninsular India, we report paleomagnetic directions and U-Pb zircon ages from twenty-nine mafic dykes in the Eastern Dharwar Craton near Hyderabad. Paleomagnetic analysis yielded clusters of directional data that correspond to dyke swarms at 2.37 Ga, 2.22 Ga, 2.08 Ga, 1.89–1.86 Ga, 1.79 Ga, and a previously undated dual polarity magnetization. We report new positive baked contact tests for the 2.08 Ga swarm and the 1.89–1.86 Ga swarm(s), and a new inverse baked contact test for the 2.08 Ga swarm. Our results promote the 2.08 Ga Dharwar Craton paleomagnetic pole (43.1° N, 184.5° E; A95 = 4.3°) to a reliability score of R = 7 and suggest a position for the Dharwar Craton at 1.79 Ga based on a virtual geomagnetic pole (VGP) at 33.0° N, 347.5° E (a95 = 16.9°, k = 221, N = 2). The new VGP for the Dharwar Craton provides support for the union of the Dharwar, Singhbhum, and Bastar Cratons in the Southern India Block by at least 1.79 Ga. Combined new and published northeast-southwest moderate-steep dual polarity directions from Dharwar Craton dykes define a new paleomagnetic pole at 20.6° N, 233.1° E (A95 = 9.2°, N = 18; R = 5). Two dykes from this group yielded 1.05–1.01 Ga 207Pb/206Pb zircon ages and this range is taken as the age of the new paleomagnetic pole. A comparison of the previously published poles with our new 1.05–1.01 Ga pole shows India shifting from equatorial to higher (southerly) latitudes from 1.08 Ga to 1.01 Ga as a component of Rodinia.
Because of tectonics, oceans change shape, leading to changes in the tides. We know that past tides have gone through a series of short-lived maxima above a low-energy state, but what will happen in the future? Here we present four scenarios of how the future might tectonically develop. In all four scenarios the Atlantic will continue to grow and the Pacific will continue to shrink for the next 20 or so million years. This will eventually lead to loss of the tidal resonance in the Atlantic. After that, the scenarios diverge into a closing Atlantic (Pangea Ultima), closing Pacific (Novopangea), closing of both Atlantic and Pacific (Aurica), and closing the Arctic (Amasia). In all scenarios but Amasia, tidal dissipation rates peak and fall as growing and shrinking oceans go in and out of resonance as the next supercontinent assembles over the next 200–250 Myr (million years). Once each supercontinent has formed tidal dissipation rates drop to a fraction of the present-day rates, agreeing with previous work that tides during supercontinent tenure are weak because the large super ocean that surrounds each supercontinent is too large to be resonant. These results suggest that as long as there is plate tectonics and a supercontinent cycle on Earth, the tides will continue to vary on geological time scales.
Despite vast scientific inquiry, the evolution of Appalachian Mountain topography in eastern North America has yet to be robustly explained. After a century and a half of investigation, two end member visions have developed to explain its geomorphic origins. One view holds that topographic remnants of the Paleozoic orogen were eroded away and that the modern mountains are explained by Cenozoic topographic rejuvenation from crustal tectonics or mantle dynamics. The alternative vision is the mountains are supported by a lingering Paleozoic crustal root, but are actively shaped by erosional processes and their adjustment to changing boundary conditions. In this review, we first examine the observations and interpretations that comprise the vision of active Cenozoic rejuvenation. Although there is considerable evidence for tectonic deformation, mantle support, and topographic disequilibrium, the interpretations are non-unique and universal signals have yet to emerge. Next, we explore the alternative view by examining how the signals of topographic disequilibrium may be explained without invoking rejuvenation. We present evidence, including new examples, for landscape unsteadiness due to basin reorganization, climate change, and the three-dimensional complexity of exhuming bedrock of variable erodibility. These factors can force continual topographic and erosional adjustment. This complexity-driven disequilibrium yields geomorphic noise that can mimic signals of active uplift, but does not preclude Cenozoic rejuvenation. We conclude that is it not yet possible to quantify the effects of any one specific variable on the modern landscape, but stress the importance of a holistic investigative approach that accounts for the innate complexity of the system.
The Paleo-Mesoproterozoic Lesser Himalayan Crystalline Sequence (LHCS) of the Himalayan orogen are critical in the understanding of pre-Himalayan tectonics in relation to the supercontinent Columbia. The LHCS is considered as the Paleoproterozoic northern boundary of the Indian Continental Block (ICB). Geological and geochemical studies of the LHCS have provided contrasting interpretations for its tectonic evolution, leading to a lack of consensus. This contribution reviews all the existing hypotheses for the Columbia assembly focusing on the nature of the northern margin of the ICB and address the inconsistencies regarding tectonic evolution of the LHCS. Petrological, geochemical, and geochronological observations of the LHCS from NW, Central and Eastern segments of the Himalaya suggest that the rocks witnessed a tectonic cycle of Paleoproterozoic oceanic subduction, rifting, and syn-collisional events, which is similar to the tectonic cycle experienced by the Paleoproterozoic rocks of the Eastern Cathaysia Block of South China. Integrating the signatures of these two domains yields a divergent double sided subduction tectonic scenario for their tectonic evolution. This work identified a three-stage tectonic evolution along the Eastern Cathaysia Block and northern boundary of ICB: First stage- Neoarchean oceanic subduction and arc magmatism beneath the Eastern Cathaysia Block; Second stage: c. 1950 Ma divergent double subduction, corresponding to slab-rollback/break off of the oceanic crust and asthenospheric upwelling beneath the Eastern Cathaysia Block, with synchronous subduction of the oceanic plate and formation of the LHCS magmatic belt along the ICB; Third stage: c. 1900 ̶ 1800 Ma soft collision between both domains, forming syn-collisional granites, which is synchronous with back-arc rifting and formation of anorogenic granites in both domains.
The North American continent has a rich record of the tectonic environments and processes that occur throughout much of Earth history. This Memoir focuses on seven “turning points” that had specific and lasting impacts on the evolution of Laurentia: (1) The Neoarchean, characterized by cratonization; (2) the Paleoproterozoic and the initial assembly of Laurentia; (3) the Mesoproterozoic southern margin of Laurentia; (4) the Midcontinent rift and the Grenville orogeny; (5) the Neoproterozoic breakup of Rodinia; (6) the mid-Paleozoic phases of the Appalachian-Caledonian orogen; and (7) the Jurassic–Paleogene assembly of the North American Cordillera. The chapters in this Memoir provide syntheses of current understanding of the geologic evolution of Laurentia and North America, as well as new hypotheses for testing.
Detrital zircon age patterns are reported from quartz sandstones and metaquartzites in the Russet and Wangapeka formations (Western Province, Takaka Terrane) in Fiordland and northwest Nelson, and the Pegasus Group on Stewart Island. The latter indicate a possible maximum early Carboniferous depositional age with a significant Lower Devonian zircon component that suggests a source on the Campbell Plateau or Marie Byrd Land, West Antarctica. In contrast, Russet Formation ages indicate a correlation with Upper Ordovician, Wangapeka Formation quartz sandstones in northwest Nelson. These zircon age patterns have two major groups: late Mesoproterozoic (1200–1000 Ma) of Rodinia origin and Cambrian–late Neoproterozoic (700–500 Ma) of early Gondwana derivation. Both groups have local Zealandia provenances. In addition, there are unusually high proportions (to 20%) of early Paleoproterozoic and Archean zircons, 3500–2000 Ma, with significant age components, 2550–2450 Ma and ca 2800 and 2650 Ma, which are characteristic of an Expanded-Ur continent. Their high proportions of euhedral grains indicate a local source within a postulated Archean basement block at or near the eastern margin of the Takaka Terrane. A proposed Rodinia supercontinent reconstruction locates this Precambrian basement as a Zealandia component placed between Gawler and North Australia cratons of Australia and Yangtze Block of the South China Craton.
• KEY POINTS
• Pegasus Group, metaquartzites, Stewart Island are not correlated with the Russet Formation, Fiordland but are an Upper Devonian or lower Carboniferous sedimentary unit.
• Russet Formation high-grade metasandstones in Fiordland are correlated with the lower-grade and fossiliferous Upper Ordovician Wangapeka Formation in Nelson.
• Upper Ordovician sandstones in Western Province, New Zealand contain unusually high proportions of Neoarchean euhedral detrital zircons that suggest a local Zealandia source.
• An Archean block is proposed within the Rodinia supercontinent, between the Gawler and North Australia cratons of Australia and Yangtze Block of the South China Craton.
Incorporates the majority of the papers presented at a symposium on the Middle Proterozoic evolution of the North American and Baltic Shields, held in St. Johns, Newfoundland, May 1988. Following an introductory chapter the 31 papers are divided into eight sections: isotopes and crustal evolution; geochronology; regional case histories; structural studies; anorthositic magmatism; anorogenic felsic magmatism; mafic magmatism; and sedimentary depocentres. A subject index concludes the volume. -S.J.Stone
Prior to the Grenvillian continentcontinent collision at about 1.0 Ga, the southern margin of Laurentia was a long-lived convergent margin that extended from Greenland to southern California. The truncation of these 1.8-1.0 Ga orogenic belts in southwestern and northeastern Laurentia suggests that they once extended farther. We propose that Australia contains the continuation of these belts to the southwest and that Baltica was the continuation to the northeast. The combined orogenic system was comparable in length to the modern American Cordilleran or Alpine-Himalayan systems. This plate reconstruction of the Proterozoic supercontinent Rodinia called AUSWUS (Australia-Southwest U.S.) differs from the well-known SWEAT (Southwest U.S.-East Antarctic) reconstruction in that Australia, rather than northern Canada, is adjacent to the southwestern United States. The AUSWUS reconstruction is supported by a distinctive "fingerprint" of geologic similarities and tectonic histories between Australia and the southwestern United States from 1.8 to 0.8 Ga, and by a better agreement between 1.45 and 1.0 Ga paleomagnetic poles for Australia and Laurentia.
The early geological development of the Pilbara and Kaapvaal cratons has many features in common. Attempts have been made to correlate geologically similar features of the two cratons, and it has been postulated that they originated as contiguous components of a single continent, ‘Vaalbara’, during this time. The early geological histories of the Pilbara and Kaapvaal cratons are here compared in detail and the evidence that they were initially contiguous is assessed. These comparisons indicate significant differences in the chronologies of magmatic events within the granite–greenstone crusts of the Pilbara and Kaapvaal cratons. In addition, igneous correlatives emplaced during ca 2985 and 2782 Ma magmatic events on the Kaapvaal Craton have not been identified on the Pilbara Craton, and a well-defined 2760 Ma magmatic event, manifest as widespread emplacement of granitic rocks into the Pilbara granite–greenstone basement and eruption of flood basalts of the lower part of the Fortescue Group, is absent from the Kaapvaal Craton. Furthermore, similarities in first- and second-order transgression–regression cycles within the sedimentary supracrustal sequences may be attributable to global sea-level fluctuations, and thus may be irrevelant to the question of former contiguity. However, similarities in some aspects of the geological development of the Pilbara and Kaapvaal cratons imply that there were periods, extending for between 60 and 200 Ma, of the Archaean era during which the style of crust formation, intensity of volcanism and subaerial erosion, and magnitude of sea-level fluctuations may have varied on a global scale. Such similarities include the overall duration of formation of the granite–greenstone crusts from ca 3650 to 3100 Ma, the onset of craton-wide erosion in the interval ca 3125 to 3000 Ma, the major episodes of flood basaltic volcanism between 2760 and 2680 Ma, the predominance of chemical (carbonate and banded iron-formation) sedimentation between ca 2630 and 2440 Ma and the transition to widespread clastic sedimentation within the interval 2440 to 2200 Ma.
Mantle Plumes and Their Record in Earth History provides a timely and comprehensive review of the origin and history of mantle plumes throughout geologic time. The book describes the new and exciting results of the last few years, and integrates an immense amount of material from the fields of geology, geophysics, and geochemistry that bear on mantle plumes. Included are chapters on hotspots and mantle upwelling, large igneous provinces (including examples from Mars and Venus), mantle plume generation and melting in plumes, plumes as tracers of mantle processes, plumes and continental growth, Archean mantle plumes, superplumes, mantle plume events in Earth history, and their effect on the atmosphere, oceans, and life.
The Proterozoic connection between northeastern Siberia and western
Laurentia that we proposed in 1978 is strongly supported by several new
lines of evidence. New age data and refined structural trends in
predrift basement rocks improve the resolution of the fit between the
cratons. The mouth of the large river that is inferred to have provided
the point source for the lower part of the Mesoproterozoic Belt-Purcell
Supergroup in western Laurentia aligns with the Mesoproterozoic Udzha
trough of Siberia. The elbow bend in the Udzha trough bypasses the
Archean Wyoming Province to link the Belt-Purcell basin with
Paleoproterozoic regions in southwest Laurentia having appropriate Nd
crustal-residence ages and zircon crystallization ages to have provided
sources for much of the sediment. The Grenville and Granite-Rhyolite
provinces of southwest Laurentia provide sources for detrital zircons
and felsic volcanic fragments in the east-derived Mesoproterozoic
Mayamkan Formation of Siberia. The ages of mafic sills in the
Sette-Daban region of Siberia overlap those in southwest Laurentia.
Ediacara occur in off-shelf environments on both margins. The two
margins have very similar latest Neoproterozoic earliest Cambrian
rift-drift signatures, including a breakup unconformity and Tommotian
shelf assemblages that record the onset of thermally driven subsidence.
Two possible submarine volcanoes with archeocyathan caps may confirm the
establishment of Early Cambrian seafloor spreading. The Siberian west
Laurentian connection provides better correlations among prerift
terranes than does the southwest United States East Antarctic connection
(SWEAT), and is more compatible with the overall geologic history of
Laurentia and Gondwana.
A hypothesis for a late Precambrian fit of western North America with the Australia-Antarctic shield region permits the extension of many features through Antarctica and into other parts of Gondwana. Specifically, the Grenville orogen may extend around the coast of East Antarctica into India and Australia. The Wopmay orogen of northwest Canada may extend through eastern Australia into Antarctica and thence beneath the ice to connect with the Yavapai-Mazatzal orogens of the southwestern US. The ophiolitic belt of the latter may extend into East Antarctica. Counterparts of the Precambrian-Paleozoic sedimentary rocks along the US Cordilleran miogeocline may be present in the Transantarctic Mountains. Orogenic belt boundaries provide useful piercing points for Precambrian continental reconstructions. The model implies that Gondwana and Laurentia rifted away from each other on one margin and collided some 300 m.y. later on their opposite margins to from the Appalachians.
The about 500 km long coastal stretch of central Dronning Maud Land (DML), East Antarctica, is critical for understanding both Gondwana and Rodinia assembly. In common Gondwana reconstructions central DML lies at the potential southern extension of the Mozambique Belt. We report the first extensive geochronological study of magmatic and metamorphic rocks from the area. These new U-Pb SHRIMP zircon and Sm-Nd-data of rocks sampled during the German international GeoMaud 1995/96 expedition indicate that the oldest rocks in central DML are Mesoproterozoic in age. The crystallization ages of metavolcanic rocks were determined at c.1130 Ma. Syn-tectonic granite sheets and plutons give ages of c.1080 Ma, contemporaneous with metamorphic zircon growth at granulite facies conditions. An anorthosite intrusion and a charnockite are dated at c.600 Ma. Subsequent metamorphism is recorded for at least two different episodes at c.570-550 Ma and between 530 to 515 Ma. The latter metamorphic event reached granulite facies and is associated with the syn-tectonic intrusion of a granodiorite body at Conradgebirge. Initial εNd,t-values of the U-Pb dated rocks with crystallization ages around 1.1 Ga range from c. +7 to -4. These values suggest that their magmatic precursors represent variable mixtures of a primitive mantle-derived and continental crust component generated within a mature island arc. Initial Nd isotope data of Cambrian meta-igneous rocks are indistinguishable from the Grenville-age rocks, probably representing partial melts of the Grenville-age basement. The occurrence of Pan-African syn-tectonic granitoids is unique in DML. The structure and shape of this body indicates that the main structural ENE-WSW trend of the region is Pan-African in age and not older, as previously assumed. Some major late ductile sinistral shear zones occurring in the study area fit well in the overall sinistral transpressional setting of the Mozambique Belt. Thus, central DML very probably represents the southern continuation of the Mozambique Belt into East Antarctica.
The composition, chronology, and structural relations of the Saskatchewan Craton and enveloping mylonitic rocks exposed in basement windows of the Glennie Domain, Trans-Hudson Orogen, have been determined by geochemical, geochronologic, and structural studies accompanying detailed field mapping. Basement windows lie along the hinge zone of a regional crustal culmination and consist mostly of 2.4-2.5 Ga felsic plutonic rocks enveloped by the Nistowiak Thrust. The Nistowiak Thrust is a folded, 1-2 km thick, upper amphibolite faciès mylonite zone formed during emplacement of the Flin Flon-Glennie Complex across the Saskatchewan Craton. It is likely correlative to the Pelican Thrust, which envelops basement windows in the Hanson Lake Block -100 km to the east. An internal high strain zone within the overlying nappe pile, the Guncoat Thrust, is composed primarily of mylonitized porphyroclastic pelitic and psammitic migmatites. U-Pb geochronological results suggest calc-alkaline plutonism from 1889-1837 Ma, thrust stacking, peak metamorphism and associated anatexis between 1837 and 1809 Ma, isotopic closure of titanite at 1790-1772 Ma, and intrusion of late granitic rocks at 1770-1762 Ma. This is in agreement with ages from the Hanson Lake Block, and La Ronge, Kisseynew, and Flin-Flon domains in Saskatchewan and Manitoba, and from the Ungava-Baffin portion of Trans-Hudson Orogen, suggesting broadly synchronous thermotectonic processes along a strike length of 2000 km. We speculate that the Saskatchewan Craton, rather than representing an exotic continental fragment, rifted from the Superior and/or Hearne Provinces at ca. 2.1 Ga and that the Trans-Hudson Orogen is an internal orogen. In this scenario the Maniwekan Ocean, developed between the Rae-Hearne and Superior cratons, opened and closed about similar pole(s) of plate motion.
Metamorphic and protolith ages of five rock types (mafic granulite, orthopyroxene granulite, leptynite, sillimanite granite, and metapelite) from Rayagada, in the north-central part of the Eastern Ghats Granulite Belt (EGGB), India, were determined from Rb-Sr and Sm-Nd whole rock and mineral isochrons in combination with SHRIMP U-Pb zircon data. Most of the whole rock isochron ages in both Sm-Nd and Rb-Sr systems point to either ∼ 1450 or ∼ 1000, Ma, and the mineral isochron ages are ∼ 1000, ∼ 800, and ∼ 550 Ma. SHRIMP U-Pb zircon ages of ∼ 940 Ma were obtained from metapelite, which are in close agreement with the Sm-Nd and Rb-Sr isochron ages. From all these data, four age clusters (∼1450, ∼1000, ∼800, and ∼550 Ma) have been noted. The 1450 Ma ages are interpreted to represent igneous protolith formation of mafic granulite and leptynite. The 1000 Ma age cluster is regarded as the intrusion ages of sillimanite granite, and charnockite, and associated granulite facies metamorphism. Two other age clusters (800 and 550 Ma) are regarded as metamorphic heating events. Earlier reports from the EGGB show two major agegroupings, one around 1450 Ma, characterized by alkaline magmatism and anorthositic intrusions, and the other at 1000 Ma, considered to be the major metamorphic and tectonothermal event. The present data are broadly similar with those reported from parts of East Antarctica with respect to the 1000 Ma and 550 Ma events and reconfirm that EGGB has been an integral part of eastern Gondwana.
A new fit for Siberia and Laurentia in the Late Proterozoic places Siberia north of the Franklin orogenic front in the Canadian Arctic such that the Akitkan fold belt in Siberia aligns with the Thelon magmatic zone in Canada. Zircon ages from both belts range from 2.0 to 1.9 Ga and appear to record additions of juvenile crust. The match between the Archean Slave province in Canada and the Aldan province in Siberia also supports this fit. Common plutonic zircon ages in both provinces are >3.5 to 3.2 Ga, 3.1-2.9 Ga, and 2.8-2.6 Ga. The ˜1 Ga Grenville orogen may have extended northward between southern Greenland and Scandinavia, passing through east-central Greenland and adjacent Barentsia, and possibly into the Angara fold belt in Siberia. It is possible that three Early Proterozoic fold belts associated with the Aldan province are extensions of the Coronation Supergroup, an Early Proterozoic rift- to passive-margin succession deposited on the western margin of the Slave province.
The supracrustal rocks of the Older Metamorphic Group (OMG), consisting of metasediments and ortho-amphibolite, constitute the oldest unit in the Archaean nucleus of Singhbhum. However, there are indications that still older (3.4–3.8 Ga) crust of both sialic and mafic composition existed in this region. The OMG ortho-amphibolites were formed by partial melting of mantle with near chondritic composition ca. 3.3 Ga ago, probably as a result of plume activity. Shortly afterwards, partial melting of the underplated mafic material produced a tonalitic melt (Older Metamorphic Tonalitic Gneiss — OMTG), which intruded the OMG supracrustals and the entire suite was deformed and metamorphosed to upper amphibolite facies. Subsequent to this, melting of the OMG ortho-amphibolites and the lower crustal material of probable andesitic composition produced melts varying in composition from tonalite to granite and these intruded in different phases to produce plutons of Singhbhum Granite, Bonai Granite and Kaptipada Granite, which together form volumetrically the major part of the Archaean nucleus. The older OMG and OMTG occur as enclaves within these younger granitoids. The time difference between the emplacements of the OMTG and the early phases of younger granitic intrusion was of the order of 100–200 Ma. Thus, serial additions of juvenile material led to the formation of a stable microcontinent by 3.2 Ga. Thermally triggered stretching in this microcontinent produced basins peripheral to the present day Singhbhum Granite pluton, and in these basins the younger supracrustal rocks of the Iron Ore Group (IOG), consisting of BIF, associated argillaceous and subordinate arenaceous rocks, and mafic lavas were laid down. There is inadequate field or geochronological evidence to resolve the issue of whether the different iron ore basins were coeval or not. Meagre geochronological data suggest that some of the BIFs are older than ca. 3.1 Ga. Post-IOG activity is confined to the intrusion of mafic dyke swarms and formation of intracratonic basins, the ages of both being uncertain.
The Neoproterozoic Adamastor-Brazilide Ocean was generated during the breakup of the Rodinia supercontinent, and remnants of its oceanic lithosphere have been found in the Brasiliano-Pan African orogenic system that includes the Araçuaı́, West-Congo, Brası́lia, Ribeira, Kaoko, Dom Feliciano, Damara and Gariep belts. The Araçuaı́ and the West-Congo belts are counterparts of the same Neoproterozoic orogen. The first belt comprises two thirds of the Araçuaı́-West-Congo Orogen. This orogen is rather unique owing to its confined nature within the embayment outlined by the São Francisco and Congo cratons. In spite of this, the presence of ophiolitic remnants, and a calc-alkaline magmatic arc, indicate that the basin/orogen evolution comprise both oceanic spreading and consumption. It is assumed that coeval Paramirim and Sangha aulacogens played a key role by making room for the Araçuaı́-West-Congo Basin. Sedimentary successions record all major stages of a basin that evolved from continental rift, when glaciation-related sedimentation was very significant, to passive margin. Rifting started around 1.0–0.9 Ga. The oceanic stage is constrained by an ophiolitic remnant dated at 0.8 Ga. If the cratonic bridge that once linked the São Francisco and Congo palaeocontinental regions did not hinder the opening of an ocean basin, it certainly limited its width. As a consequence, only a narrow oceanic lithosphere was generated, and it was subducted afterwards. This is also suggested by orogenic calc-alkaline granitoids occuping a small area of the orogen. Geochronological data for pre-, syn- and late-collisional granitoids indicate that the orogenic stage lasted from 625 Ma to 570 Ma. A period of magmatic quiescence was followed by intrusion of postcollisional plutons at 535–500 Ma. The features of the Araçuaı́-West-Congo Orogen suggest the development of a complete Wilson Cycle in a branch of the Adamastor Ocean, which can be interpreted as a gulf with limited generation of oceanic lithosphere.
The results of field, geochronologic, geochemical and isotopic studies are presented for the granitoids that occur east of the Closepet batholith up to the Kolar schist belt (KSB). Field data, such as common foliation, strong shear deformation occasionally leading to mylonitization, together with petrographic data, including reduction in grain size with corroded borders, show characteristics of the syn-kinematic emplacement of the granitoids. Single zircon evaporation ages define a minimum age of 3127 Ma for the tonalitic–trondhjemitic–granodioritic (TTG) basement and 2552–2534 Ma plateau ages for the emplacement of the granitoids, which slightly predate (20–30 Ma) the emplacement of the 2518 Ma Closepet batholith.Major and trace element data, together with isotopic data, suggest at least four magmatic suites from Closepet batholith to the east, which have independent magmatic evolution histories. The observed data are compatible with magma mixing for the Closepet batholith, melting of TTG and assimilation–fractional crystallization processes for Bangalore granites, either melting of heterogeneous source or different degree of melting of the same source for the granitoids of Hoskote–Kolar and fractional crystallization for the western margin of the KSB. Isotopic (Nd–Sr) and geochemical data (LREE and LIL elements) suggest highly enriched mantle and ancient TTG crust for the Closepet batholith, enriched mantle and TTG crust for the Bangalore granites, c.a. chondritic mantle source for the granitoids of Hoskote–Kolar and the quartz monzonites of the western margin of the KSB and slightly depleted mantle for granodiorites of the eastern margin of the KSB.We interpret all these geochronologic, geochemical and isotopic characteristics of granitoids from the Closepet batholith to the east up to the KSB in terms of a plume model. The centre of the plume would be an enriched ‘hot spot’ in the mantle that lies below the present exposure level of the Closepet batholith. Melting of such an enriched mantle hot spot produces high temperature magmas (Closepet) that penetrate overlying ancient crust, where they strongly interact and induce partial melting of the surrounding crust. These magmas cool very slowly, as the hot spot maintains high temperatures for a long time; thus they appear younger (2518 Ma). On the contrary, to the east the plume induces melting of c.a. chondritic or slightly depleted mantle that produces relatively colder and less enriched magmas, which show less or no interactions with the surrounding crust and cool rapidly and appear slightly older (2552–2534 Ma). This plume model can also account for late Archaean geodynamic evolution, including juvenile magmatism, heat source for reworking, inverse diapirism and granulite metamorphism in the Dharwar craton.
The Rodinia hypothesis for the Neoproterozoic Supercontinent reconstruction is associated with five major problems: (i) The palaeomagnetic test requires continental break-up hundreds of millions of years before the geological evidence for this event is recognised near the dawn of the Cambrian. (ii) The reconstruction separates cratons with strong Late Archaean–Early Proterozoic affinities by large distances and then recombines them into Gondwana by early Phanerozoic times. (iii) The stratigraphic correlation, upon which it was originally based, incorporates successions dated ∼ 850–550 Ma during which interval palaeomagnetic data fail to predict continuity between Western North America, Australia and South China. (iv) The protracted history of break-up from 800–550 Ma is in conflict with the global subsidence record of passive margins defining initial continental break-up at ∼ 600 Ma and diverse isotopic/environmental signatures concentrated between 600–500 Ma. (v) It predicts no intrinsic link (such as a peripheral subduction zone) to large-scale mantle constraining forces.
In this classic series-generating paleontology/geology book published by Columbia University Press, Mark and Dianna McMenamin explore the evolutionary and paleoecological questions associated with the Cambrian Explosion. This book both names and maps the initial paleogeographic reconstruction of the billion year old supercontinent Rodinia. The observations and interpretations in this book, particularly as regards the timing of the Cambrian Explosion, have stood the test of time. The issues identified herein as most important for understanding the Proterozoic-Cambrian transition, remain so today.
A new statistical method is proposed to compare crustal terranes and to cluster terranes into crustal provlnces, regions and realms. Geochronological data on mafic igneous rocks, felsic igneous rocks, deformation history and Nd model age were collected from the recent literature for over 100 terranes. The 54 selected Laurentian terranes cluster into 9 provinces including a previously well recognized very distinctive SW USA province, region and realm. The 38 selected Australian terranes cluster into six provinces including a distinctive Gawler Province. A combined dendrogram of the 100 terranes from Laurentia, Australia and Antarctica results in 8 superprovinces and 11 provinces. Five of the superprovinces contain both Laurentian and Australian terranes. The inclusion of the Nevada-Califomian Mojave and the San Gabriel terranes in an otherwise Australian superprovince that includes Broken Hill and Mt Isa terranes, strongly supports the AUSWUS Laurentia-Australia reconstruction rather than the SWEAT reconstruction. Low statistical similarities between western Laurentia and eastern Antarctica fail to support the SWEAT hypothesis whilst high similarities between Canadian and north Australian terranes provides weak support for AUSWUS.
Recent geological information allows us to constrain a re-assembly of Mesoproterozoic East Gondwanaland. Juxtapositions of South Africa-Antarctica, India-Sri Lanka-Antarctica, and Australia-Antarctica do not conflict each other, supporting the reliability of the proposed re-assembly. A Mesoproterozoic Circum-East Antarctic Mobile Belt (CEAMB) is identified in the re-assembled East Gondwana. Lithologic characteristics indicating continental margin and shallow marine sedimentary conditions, and the association of extensive acid to intermediate magmatic rocks are common to many areas of CEAMB. Possible dismembered ophiolitic rocks are also known sporadically. These structural and lithologic characteristics point to a convergent tectonic setting. The Pan-African tectonothermal events are principally intracratonic, developed in most areas of the CEAMB and its surroundings, and are less intense eastwards. -from Author
Estimates of stabilization ages of the world's Precambrian cratons reveal a pattern in which all blocks stabilized at ages ≥3.0 Ga occur in one area of the end-Paleozoic supercontinent Pangea. These blocks center around India, where at least two cratons (Western Dharwar and Singhbhum) show evidence of crustal growth terminating at or before ~3.0 Ga. This concentration of ≥3.0-Ga blocks is regarded as an Archean supercontinent referred to as "Ur'. -Author
Evidence supports the hypothesis that the Laurentian and East Antarctic-Australian cratons were continuous in the late Precambrian and that their Pacific margins formed as a conjugate rift pair. A geometrically acceptable computer-generated reconstruction for the latest Precambrian juxtaposes and aligns the Grenville front that is truncated at the Pacific margin of Laurentia and a closely comparable tectonic boundary in East Antarctica that is truncated along the Weddell Sea margin. Geologic and paleomagnetic evidence also suggests that the Atlantic margin of Laurentia rifted from the proto-Andean margin of South America in earliest Cambrian time. -from Author
Central Indian Tectonic Zone (CITZ), which divides the Indian subcontinent into Bundelkhand Block in the north and the Deccan Block in the south, is represented by a collage of different lithotectonic terranes ranging in age from Archaean to Recent. It comprises two parallel structural domains, namely the Son-Narmada (SONA) subzone in the north and the Sausar mobile belt (SMB) in the south. The ancestry of the SONA subzone is indicated by the Neoarchaean - Palaeoproterozoic ages yielded by the rocks of Mahakoshal fold belt; the Sausar belt, on the other hand, has yielded Meso- to Neoproterozoic ages. The present response of CITZ to accumulation of stress and attendant seismicity is governed by the structures generated due to early tectonic history of rocks within it, particularly the development of number of E-W to ENE-WSW striking, brittle and ductile shear zones. While the Sausar belt has remained more or less stable since the late Precambrian, the SONA and Tapti lineament zones have been reactivated several times. Two prominent ENE-WSW trending deep faults, termed the Son-Narmada North Fault (SNNF) and Son-Narmada South Fault (SNSF) have been episodically active from Neoarchaean onwards. The SNSF in particular has witnessed protracted reactivation well into the Phanerozoic. Intraplate seismicity in continents is commonly concentrated along ancient fault zones. Reactivation of faults or shear zones is favoured over new fault generation, since the SNSF is in a high shear stress orientation. Although the Sausar mobile belt is marked by a number of E-W trending parallel ductile shears, mass transfer processes such as silicification, recrystallization and grain growth during Precambrian appear to have healed them.
Peninsular India can be separated into 5 discrete crustal areas: the Bhandara, Singhbhum, and Aravalli (Bundelkhand) cratons; the Eastern Ghats; and a block in S India containing the Dharwar craton and adjoining Granulite terrain. These areas are separated by 4 major joins: Eastern Ghats front, Godavari rift, Mahanadi rift/Sukinda thrust, and Narmada-Son lineament and associated thrusts. All joins except the Godavari rift are former orogenic belts, where thrusts juxtapose rocks of different metamorphic grade. These thrusts, and the absence of clear correlation of suites among different cratons, suggest that the Indian shield formed by accretion of separate continental fragments. Epicontinental Late Archean/Early Proterozoic sediments throughout India, however, may indicate that the joins are intracontinental, formed within a coherent block. -from Author
The Rodinia reconstruction of the Neoproterozoic Supercontinent has dominated discussion of the late Precambrian Earth for the past decade and originated from correlation of sedimentary successions between western North America and eastern Australia. Subsequent developments have sited other blocks according to a distribution of ~1100 Ma orogenic belts with break-up involving a putative breakout of Laurentia and rapid reassembly of continent crust to produce Gondwana by early Phanerozoic times. The Rodinia reconstruction poses several serious difficulties, including: (a) absence of palaeomagnetic correlation after ~730 Ma which requires early fragmentation of continental crust although geological evidence for this event is concentrated more than 150 Ma later near the Cambrian boundary, and (b) the familiar reconstruction of Gondwana is only achieved by exceptional continental motions largely unsupported by evidence for ocean consumption. Since the geological evidence used to derive Rodinia is non-unique, palaeomagnetic data must be used to evaluate its geometrical predictions. Data for the interval ~1150-500 Ma are used here to test the Rodinia model and compare it with an alternative model yielding a symmetrical crescent-shaped analogue of Pangaea (Palaeopangaea). Rodinia critically fails the test by requiring Antarctica to occupy the location of a quasi-integral Africa, whilst Australia and South America were much closer to their Gondwana configurations around Africa than implied by Rodinia. Palaeopangaea appears to satisfy palaeomagnetic constraints whilst surmounting geological difficulties posed by Rodinia. The relative motions needed to produce Gondwana are then relatively small, achieved largely by sinistral transpression, and consistent with features of Pan-African orogenesis; continental dispersal did not occur until the Neoproterozoic-Cambrian boundary. Analogies between Palaeopangaea and (Neo)pangaea imply that supercontinents are not chaotic agglomerations of continental crust but form by episodic coupling of upper and lower mantle convection leading to conformity with the geoid.
Stratigraphic correlations and tectonic analysis suggest that the Yangtze block of South China could have been a continental fragment caught between the Australian craton and Laurentia during the late mesoproterozoic assembly of the supercontinent Rodinia. The Cathaysia block of southeast China may have been part of a 1.9 1.4 Ga continental strip adjoining western Laurentia before it became attached to the Yangtze block around 1 Ga. This configuration provides a western source region for the clastic wedges in the Belt Supergroup of western North America which contain detrital grains of 1.8 1.6 Ga and 1.22 1.07 Ga. The breakup of Rodinia around 0.7 Ga separated South China (Yangtze plus Cathaysia blocks) from the other continents.
The recognition of Precambrian ophiolite suites and their dismembered remnants in association with intraoceanic island-arc volcanic and plutonic terrains across much of the Arabian-Nubian Shield of E Egypt, Sudan, Ethiopia, Yemen, W Saudi Arabia, and Sinai has been used by many authors to support the hypothesis of crustal accretion during late Proterozoic time (approx 950-550 Ma). Reassembly of the various fragments provides a mosaic of Proterozoic microplates in a regular pattern in which at least 5 oceanic terrains, bounded by the remains of ophiolite belts, lie between remobilized continental plates to E and W.-Author
The production of juvenile continental crust in the South American Platform (SAP) and other continents was larger in the Proterozoic than in the Archean. In the SAP the juvenile crust production was about 65% during the Proterozoic, while during the Archean it was around 34% of the total volume. Similar proportions are found in the Australian continent. The largest accretion from mantle to crust happened between 2.2 to 1.8 Ga and corresponded to 35% of the total volume of the present SAP continental crust. During the Archean an intense recycling between mantle and continental crust took place, while in the Paleoproterozoic the rate of mantle accretion to continental crust was larger than the assimilation. For the other continents (Europe and North America) the Paleoproterozoic was also the main accretion event. In the SW USA, rapid continental growth (about 45% of actual volume) occurred in a short time interval between 1.9-1.7 Ga. During Meso and Neoproterozoic little accretion of juvenile material occurred in the SAP, where crustal reworking predominated, but in Eurasia much juvenile continental crust was generated during the Phanerozoic in Central Asia.
We report age data on zircon, monazite, uraninite and huttonite from a suite of 29 samples covering four major granulite blocks in southern India using an electron microprobe technique. The rocks analysed in this study cover all of the major lithounits in these terrains and include garnet-bearing and garnet-free charnockites, garnet-biotite gneisses, khondalites, calc-silicate rocks, and a suite of orthogneisses (biotite gneiss, biotite-hornblende gneiss). Two pink metagranites representing the magmatic phase were also analysed. Zircons from the Madras Block yield well-defined isochrons at 2.5-2.6 Ga. Core to rim analyses of single zircon grains show age zoning with 2.6-2.9 Ga igneous cores mantled by 2.4-2.5 Ga rims. Detrital zircons show age up to ca. 3.2 Ga. Monazites in this block have cores and rims with 2.5-2.3 Ga. A suite of 19 samples from the Madurai Block brings out the multiple tectonothermal events in this terrain. Zircons from an orthogneiss yield well-defined isochrons at 1.7±0.1 Ga, 0.82±0.05 Ga and 0.58±0.04 Ga from core, inner rim and rim portions, respectively. Zircon grains in other rocks preserve either core or secondary growth ages at 0.8-1.0 Ga. Zircons in a pink metagranite from this block show sharply defined isochrons of 0.68±0.03 Ga for the core and 0.57±0.01 Ga for the secondary portion. A late Pan-African overprint is observed throughout this block with zircon rims, monazite, uraninite and huttonite yielding age values in the range of 0.45-0.60 Ga. Zircons from both the Trivandrum and Nagercoil blocks show a major tectonothermal event at 0.55 Ga with faint indications of previous tectonothermal events during 0.8-1.0 and 1.7-2.0 Ga. Monazite data from both the Trivandrum and Nagercoil blocks are essentially similar to those from the Madurai Block except for presence of relic monazite in the former.
The evolution of the Indian Shield has been envisaged from the analysis of available tectono-lithostratigraphic, geochronological, geochemical and geophysical data. It appears that the Dharwar schist belts and their equivalents, except the Kolar schist belt, are not typical greenstone belts, but are representative of a transitional era of rapid transformation from simatic to sialic crust. In the Archaean—Proterozoic tract of India, relics of rocks older than 3.0 b.y. are identified in five widely separated regions of distinct tectono-litho-stratigraphic assemblages which probably represent the primordial continental nucleii. It is suggested that the growth of the Indian Shield has taken place through nucleation, accretion and merger into three protocontinents named Dharwar, Aravalli and Singhbhum. The cratonisation of the Indian unit seems to have been rapid and almost completed by the middle Proterozoic, as there is no significant variation in the composition of the clastic sediments and basalts from middle Proterozoic onwards. The continental nucleii appear to merge along the deep-seated lineaments, which are reflected on the tectonic map of India. Further, the Dharwar, Aravalli and Singhbhum protocontinents also seem to merge along a Y=shaped Narmada—Son—Godavari lineament which along with the Mahanadi lineament, between the two continental nucleii of the Singhbhum protocontinent have later developed into rift valleys.
The end-Paleozoic Pangea appears to have contained three continents that had grown in the Precambrian and remained intact until Mesozoic rifting: Ur, formed at ∼3 Ga and accreted to most of East Antarctica in the middle Proterozoic to form East Gondwana; Arctica, an approximately 2.5-2 Ga continent that contained Archean terranes of the Canadian and Siberian shields and Greenland; and Atlantica, formed at ∼2 Ga of cratons of ∼2 Ga age that now occur in West Africa and eastern South America. Arctica grew at ∼1.5 Ga by accretion of most of East Antarctica plus Baltica to form the continent of Nena. Collision of Nena, Ur, and Atlantica, plus minor plates, formed the supercontinent of Rodina at ∼1 Ga. Rifting of Rodinia between 1 and 0.5 Ga formed three continents: East Gondwana; Atlantica (which became the nucleus for West Gondwana); and Laurasia (which contained North America, Greenland, Baltica, and Siberia). Gondwana formed at ∼0.5 Ga by amalgamation of its eastern and western parts. Various plates accreted to Laurasia during the Paleozoic, and collision of Gondwana with Laurasia created Pangea at ∼0.3 Ga.
Three Grenville-age provinces can be distinguished in East Antarctica with U-Pb zircon data. The Maud, Rayner, and Wilkes provinces each have a distinctive age signature for late Mesoproterozoic early Neoproterozoic magmatism and high-grade metamorphism and are correlated with similar rocks in the Namaqua-Natal (Africa), Eastern Ghats (India), and Albany-Fraser (Australia) provinces, respectively. These crustal segments represent three separate collisional orogens. They are separated by regions of intense late Neoproterozoic Early Cambrian tectonism, consistent with their juxtaposition during the final assembly of Gondwana and indicating that previous models for a single, continuous, Grenville-age mobile belt around the East Antarctic coastline should be discarded.
The early Proterozoic Taltson Magmatic Zone (TMZ) comprises the southern part of the Taltson-Thelon orogenic belt of northwestern Canada. The TMZ is dominated by 1.96–1.99-Ga I-type and 1.93–1.95-Ga S-type suites of granitoids. Previous workers attributed the formation of the I-type granitoids to subduction of oceanic crust beneath the Churchill craton in an Andean-type setting, and generation of the S-type granitoids to subsequent collision between the Churchill craton and the Buffalo Head Terrane. To test this hypothesis, we carried out a geochemical and isotopic (Nd, Pb and O) study of granitoids and associated metasedimentary rocks and basement gneisses from the southern part of the TMZ. Both I- and S-type suites of granitoids are characterized by relatively high SiO2 content, with the great majority of samples containing more than 64 wt.% SiO2. The two suites also have strongly crustal εNd(T) values of −3.8 to −9.8 and an average TDM of 2.8 Ga. The initial Pb isotope composition of the granitoids as determined from leached feldspar mineral separates forms a linear array that is bracketed by the isotopic compositions of basement orthogneisses and metasediments. Similarly, δ18O values of the granitoids overlap those of the orthogneisses and metasediments. These isotopic data are consistent with derivation of the granitoids from a mixture of metaigneous and metasedimentary source rocks similar to those presently exposed in the TMZ. Importantly, the data suggest that both I- and S-type granitoids of the southern TMZ had an exclusively intra-crustal origin unlike Phanerozoic examples of subduction-related magmatism where a significant mantle contribution is easily recognized. Therefore, we argue that the existing Andean-type model for early TMZ magmatism is not viable. The TMZ granitoids show geochemical and isotopic similarities to the Cordilleran interior granitoids of western North America, which formed in response to crustal thickening in the distant hinterland of a convergent plate margin. We propose that these hinterland granitoids are a more appropriate analogue for TMZ magmatism than are the granitoids of plate margins. The tectonic implication of this proposal is that the Taltson-Thelon orogenic belt does not mark the location of the plate boundary in western Laurentia at 1.9–2.0 Ga. Rather, the tectonic setting of the TMZ at that time may have been more akin to the present-day intra-continental mountain belts of central Asia (e.g. Tian Shan Mountains) where compressional tectonism and crustal thickening are occurring well inboard from a convergent plate margin.
The reconstruction of a Palaeoproterozoic continental block requires correlation between the major structural and lithological features of the main continental provinces. The African and American circum-South Atlantic continents, for example, can be brought together in a pre-ocean-opening fit and have therefore been the subject of many attempts at such correlation.The tectonic evolution of the Palaeoproterozoic fluvio-deltaic deposits in the West African, Guiana, Congo and São Francisco provinces is related to the 2-Ga collision orogeny. These formations either rest directly upon Archaean blocks, as is the case for the Francevillian in Gabon and the Jacobina Unit in Brazil, or they rest on the upper part of the Palaeoproterozoic, as with the Tarkwaian in Ghana and in French Guiana.They were deposited, in Guiana and Gabon, in tectonic settings of extension, in foreland and pull-apart basins. They are composed mainly of conglomerate and sandstone, and range from fluviatile, locally with debris flows, to deltaic. These sedimentary rocks were deposited after the initial stages of a collision orogeny dated at more than 2.1 Ga. This event was recorded, in Guiana and West Africa, by the inheritance of detrital zircons and pebbles of foliated metamorphic rocks in the basal conglomerates. In Gabon and Brazil, these detrital formations were deposited on Archaean continental margins that became involved in the orogeny only at a late stage. They are all interpreted as products of the collapse and breakup of the early orogenic mountain belt formed during the Palaeoproterozoic collision.The structural and metamorphic evolution of these deposits show many similarities throughout the provinces. The margins of the basins are overthrust by older Palaeoproterozoic or by Archaean rocks. Structural geometry and kinematics of deformation in shear zones and recumbent folds are consistent with the overall tectonic evolution of the Palaeoproterozoic provinces during the latest stages of the collision orogeny. Metamorphism was generally in the greenschist facies, but muscovite-andalusite parageneses are common and may be replaced by kyanite-chloritoid assemblages in relation with the thickening and burial during overthrusting of the older rocks. The P-T conditions (450°C and 3.5 kbar to 600°C and 5 kbar) indicate that some of the fluvio-deltaic rocks were buried to depths of more than 10 km. This implies significant underthrusting and the formation of mountain belts.Comparison of the tectonic evolution on either side of the South Atlantic shows that major convergence of the Archaean and Palaeoproterozoic terranes took place at ∼ 2 Ga, contributing to the establishment of new continental blocks. The tectonic style of the fluvio-deltaic formations indicates a frontal collision between the Congo and São Francisco provinces, whereas the collision between West Africa and Guiana was oblique, at least during the latest stages of the orogeny.
The Paleoproterozoic Taltson magmatic zone is one of the key tectonic features of western Laurentia. The existing tectonic model for the belt envisions its formation by subduction of oceanic crust beneath a continental margin, followed by direct collision between formerly separate crustal blocks. We tested this model by comparing the large geochemical and isotopic database available for Taltson magmatic zone granitoids with similar databases for Phanerozoic granitoid suites from different tectonic environments. The comparison reveals that the early granitoid suite of the Taltson magmatic zone, which had been ascribed to the subduction phase of orogenesis, lacks the mantle signature apparent in granitoids of Phanerozoic continental-margin arc settings. Instead, both early and late suites appear to have an intracrustal origin, similar to Mesozoic and Cenozoic granitoids of the Cordilleran interior of western North America, which formed in the distant hinterland of a convergent plate margin. In light of these findings, we propose an alternative tectonic model, which envisions formation of the Taltson magmatic zone in a plate-interior rather than a plate-margin setting. Modern-day examples of this setting are found in the mountain belts of central Asia, such as the Tian Shan, which are located many hundreds of kilometres away from the plate margin. The critical feature of these belts that make them an appealing analogue for the Taltson magmatic zone is that there is no subduction zone closely associated with their formation. Rather, magmatism occurs in response to thickening of crust in the continental interior.
The basement in the Pointe Geologie Archipelago, around the French Dumont d'Urville station in Terre Adelie, comprises a metapelitic migmatitic complex with a 1.7 Ga metamorphic evolution differing from that generally found in other areas of the East Antarctic Shield. In Terre Adelie, although the oldest crustal precursors (Nd T (sub DM) model ages) are ca. 2.2-2.4 Ga old, inherited zircon SHRIMP ages are ca. 1.73-1.76, 2.6 and 2.8 Ga. The migmatitic evolution is restricted to a single event which is dated at 1.69 Ga by newly formed zircons (SHRIMP) and by U-Pb and (super 207) Pb/ (super 206) Pb evaporation TIMS ages of monazite. When interpreted as cooling ages, Sm-Nd garnet (1.60 Ga) and Rb-Sr micas (1.50 Ga) ages would be indicative of a slow cooling rate, suggestive of a long-lived major thermal anomaly. Geological processes such as sediment deposition, HT-LP metamorphism and anatexis and coeval intrusion of mafic magmas occurred during a very short time. This suggests that the migmatite complex is related to a major lithospheric thinning associated with a thermal anomaly coeval with syn-metamorphic mafic magmatism. Such thinning may have developed in a 2.8/2.4 Ga old basement, comparable with the Port Martin formations located 50 km further east. In the Gawler Craton (South Australia) similar units are found which could have formed, together with the Terre Adelie basement, as a single shield by a collage of various terrains that existed prior to ca. 1.5 to 1.6 Ga ago, comprising the tt" Mawson Continenttt" .
The present data argue that the protolith of much of the West African continent was created around 2.1 Ga in an environment remote from Archean crust. Intrusion of calc-alkaline magmas into the tholeiitic units suggests that island arcs formed on top of the assumed oceanic plateaus which then collided with the Man Archean craton. Taking the Birimian formations from the Guyana shield into account, the minimum crustal growth rate at 2.1 Ga is about 1.6 km3/a, some ~60% higher than the present growth rate. A comparison of the Birimian crustal growth rate with the average crustal growth rate over the Earth history implies that a large part of the Birimian crust has been recycled into the mantle or incorporated into younger orogenic segments. This apparent deficit in the crustal budget is even more dramatic for the Archean crust. -from Authors
Lead and Sr isotopic compositions of whole rocks and feldspar separates from several fielddefined suites of rocks from the Western Dharwar craton of southern India elucidate a complex history of the area. The evolution of the craton earlier than ≈3.0 Ga is difficult to determine because of thermal and metasomatic overprinting at ≈3.0 Ga. Many whole rocks were completely reset then, but feldspar separates preserve some of the earlier history.Apparently, a series of terranes evolved from the mantle over the period > 3.4 to ≈3.0 Ga to form the Western Dharwar craton. In each case, metamorphism and anatexis of older terranes accompanied extraction of juvenile material from the mantle. The oldest gneisses (≈3.4 Ga) had radiogenic Pb and Sr isotopic compositions when they formed and were derived from older crustal protoliths that were plausibly accreted to the crust at, or even before, 3.8 Ga. The old gneisses were greatly depleted in Rb, probably at ≈3.4 Ga when the protoliths of younger magmatic rocks may have separated from the mantle. Younger gneisses apparently formed from these mafic-intermediate protoliths in the age range of ≈3.2 to ≈3.0Ga.The ≈3.0 Ga event in the central part of the craton was accompanied by intrusion of small diapiric trondhjemites, formed by melting of older crust, and penecontemporaneous metasomatism of country rocks by hydrous fluids carrying U and other lithophilic elements. The resultant deep crust was greatly depleted in heat-producing elements, and the craton has been inactive since ≈3.0 Ga except for production of minor granites from depleted source regions at 2.5–2.6 Ga. The lack of activity at ≈2.5 Ga contrasts strongly with extensive magmatism and metamorphism in surrounding areas that had not undergone depletion at ≈3.0 Ga. Lower-crustal depletion also has caused present-day reduced heat flow to be very low.
Available lithostratigraphic, tectonothermal, geochronological and paleomagnetic data from 2.1–1.8 Ga collisional orogens and related cratonic blocks around the world have established connections between South America and West Africa; Western Australia and South Africa; Laurentia and Baltica; Siberia and Laurentia; Laurentia and Central Australia; East Antarctica and Laurentia, and North China and India. These links are interpreted to indicate the presence of a supercontinent existing before Rodinia, referred to herein as Columbia, a name recently proposed by Rogers and Santosh [Gondwana Res. 5 (2002) 5] for a Paleo-Mesoproterozoic supercontinent. In this supercontinent, the Archean to Paleoproterozoic cratonic blocks were welded by the global 2.1–1.8 Ga collisional belts. The cratonic blocks in South America and West Africa were welded by the 2.1–2.0 Ga Transamazonian and Eburnean Orogens; the Kaapvaal and Zimbabwe Cratons in southern Africa were collided along the ∼2.0 Ga Limpopo Belt; the cratonic blocks of Laurentia were sutured along the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava, Torngat and Nagssugtoqidian Orogens; the Kola, Karelia, Volgo–Uralia and Sarmatia (Ukrainian) Cratons in Baltica (Eastern Europe) were joined by the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn–Central Russian and Pachelma Orogens; the Anabar and Aldan Cratons in Siberia were connected by the 1.9–1.8 Ga Akitkan and Central Aldan Orogens; the East Antarctica and an unknown continental block were joined by the Transantarctic Mountains Orogen; the South and North Indian Blocks were amalgamated along the Central Indian Tectonic Zone; and the Eastern and Western Blocks of the North China Craton were welded together by the ∼1.85 Ga Trans-North China Orogen.
Supercontinent Atlantica was formed in South America by the orogenies of the Trans-Amazonian Cycle, namely the accretionary Encantadas Orogeny (2250-2100 Ma) and the collisional Camboriú Orogeny (2100-2000 Ma). Large belts 500 to more than1000 km long formed during the Trans-Amazonian Cycle in the three major cratons of South America, in the northern part of the Amazon Craton, in the São Francisco Craton and in the Rio de la Plata Craton. However, other large (1000 km) segments of Archean crust remained little deformed in the cratonic interior of Supercontinent Atlantica, such as a major portion of the Tocantins Province in central Brazil. In addition, smaller fragments, up to 100 km, of Trans-Amazonian Cycle continental crust are present inside the Neoproterozoic Brasiliano Cycle orogenic belts in the eastern half of extra-Andean South America. In contrast, the dominant volume, about 90%, of Neoproterozoic belts was formed by reworking of Archean and Paleoproterozoic crust. Zircon U-Pb geochronology, associated with Nd isotopes, indicates the widespread presence of Supercontinent Atlantica crust in South America and sensitive high-mass resolution ion microprobe investigation of zircons indicates that crust in southern Brazil was formed mostly in the Trans-Amazonian Cycle. Zircon geochronology also reveals that Supercontinent Atlantica was preceded by an intra-cratonic period lasting about 300 my and was succeeded by an intra-cratonic period of about 1000 to 1300 my.Many of the Trans-Amazonian Cycle belts and crustal fragments may have been accreted to South America during the Neoproterozoic. The demonstration that they all were once part of Supercontinent Atlantica must await further multi-technique investigations.
The Warrawoona Megasequence comprises a ∼3.46 Ga assemblage of tholeiitic and calc-alkaline volcanic rocks interlayered with cherty sedimentary rocks. Deposition occurred in a range of shallow- to deeper-water environments ranging from the shoreline to distal deposits in sediment starved basins. Volcanism provided the dominant, or only, source of clastic sediment. Sedimentary rocks also contain evaporites, probable stromatolites, other evidence for the existence of microbial life and possible evidence of meteorite impact. The tectonostratigraphic assemblage and its contained facies associations are most similar to those developed in younger volcanic-arc, or near-arc settings. The compositions of volcanic rocks are also comparable with those of younger tholeiitic and calc-alkaline suites developed above subduction zones. The calc-alkaline suite has a complex petrogenesis which probably involves mantle-derived basaltic melts, intermediate to silicic melts derived from subducted mafic crust, magma mixing and fractional crystallization. Intense hydrothermal alteration and a distinctive association of metal deposits are also compatible with the interpretation that the Warrawoona Megasequence contains examples of early Archaean volcanic-arc and near-arc assemblages.
Twelve main stages of sedimentary basins of the South American Platform have been identified as follows: one Neoarchean, seven Proterozoic and four Phanerozoic. Basin-forming tectonics are related to the accretion/fusion and fission of the major continental landmasses of the Earth's history, such as Atlantica, Nena, Rodinia, Gondwana/Pannotia and Pangea. The first proposed stage of basin development precedes the formation of these major landmasses and was developed on Mesoarchean microcontinents. The last stage succeeds the fission of Pangea and is still in progress.
The Siberian-West Laurentian connection is a postulated reconstruction of a Proterozoic craton that formed between 1800 Ma and 1500 Ma. Correlation of geological trends and of rift facies between the Siberian platform and western Laurentia indicates that, although the two cratons underwent significant intracontinental rifting in Mesoproterozoic and Neoproterozoic times, they did not undergo complete separation until early Cambrian, ca. 530 Ma. Although this interpretation does not support the hypothetical Columbia supercontinent model of Rogers (2000) and Rogers and Santosh (2002), some elements of it are compatible with that model.
An unresolved question in Precambrian geology is the relationship between Archean crustal fragments that are now separated by younger orogens: were they once contiguous? Williams et al. (1991)proposed the name `Kenorland' for a speculative Neoarchean supercontinent comprising the Archean provinces in North America. Recently, a large number of ca. 2.5–2.0 Ga magmatic, metamorphic, detrital and xenocrystic ages have been reported from North America. We interpret that the wide geographic distribution and temporal spread of these ages may signify long-lived, regional-scale mantle upwelling, and anorogenic magmatic and metamorphic processes related to the protracted breakup of Kenorland. Breakup may have extended from ca. 2.5 to 2.1 Ga, culminating with dispersion of continental fragments at ca. 2.1–2.0 Ga. In North America, ca. 2.5–2.1 Ga intracratonic basin successions (e.g. Hurwitz Group) formed in the interior of Kenorland before dispersion, and passive margin sequences flanking the Superior Province (e.g. Huronian Supergroup) and the Wyoming Province (e.g. Snowy Pass Supergroup) defined the edges of Kenorland. Earliest Paleoproterozoic magmatic and sedimentary rocks, which include voluminous quartz arenites and glacigenic deposits, are consistent with a high-standing supercontinent and a mantle superplume. The Paleoproterozoic record from the Baltic and Siberian shields is similar to that of North America, suggesting inclusion in Kenorland. A slightly different record from the southern continents suggests a second, coexisting supercontinent that included the Zimbabwe, Kaapvaal, and Pilbara cratons, (`Zimvaalbara' of I.G. Stanistreet), the São Francisco Craton, and possibly, cratonic blocks in India. Attenuation of this second supercontinent started earlier than in Kenorland (ca. 2.65 Ga) and was accompanied by high sea level and deposition of vast Lake Superior-type iron formations. Immediately thereafter, both supercontinents became emergent and were subject to global cooling and glaciation.
The Neoproterozoic Gondwana supercontinent cycle includes the break-up of a Mesoproterozoic supercontinent here termed Pangea Y, followed by the fusion of several cratons and the large East Gondwana continent to form Gondwanaland. The accretion can be analysed in terms of plate tectonics. Rifting of Pangea Y was active in the 1100-650 Ma interval. Collision and deformation events occurred in the 820-540 Ma interval. The earliest collision event at 820 Ma between the Sao Francisco-Congo craton and East gondwana formed the Zambezi belt. Major shear zones in transpressional mobile belts developed from 820 to 550 Ma. Post orogenic magmatism and extension events affected the Gondwana supercontinent in the 660-500 Ma interval.
A supercontinent, here named Columbia, may have contained nearly all of the earth's continental blocks at some time between 1.9 Ga and 1.5 Ga. At that time, eastern India, Australia, and attached parts of Antarctica were apparently sutured to western North America, and the eastern margin of North America, southern margin of Baltica/North China, and western margin of the Amazon shield formed a continuous zone of continental outbuilding. Fragmentation began at ∼1.6 Ga, when rifting occurred in North China. Rifting continued until about 1.4 Ga in most of Columbia, and a similar age of rifting north of the Zimbabwe craton of southern Africa suggests that an entire continental block stretching from Australia to South Africa separated from Columbia at this time. Further separation of North America from South America/Africa and rotation of the different blocks ultimately resulted in their reattachment during the Grenville orogeny to form the supercontinent Rodinia.
Six thematic tectonic maps are used to analyse the makeup of the North American continent. Themes are: 1.(1) major tectonic elements of the continent2.(2) time of last major deformation3.(3) time of first major deformation4.(4) miogeoclines and terranes by kindred5.(5) suture zones and terrane boundaries by age, and6.(6) time of accretion.Features illustrated include distribution of orogenic belts and their extensions beneath cover sequences to the continental edge, contrast between juvenile and reworked crust in orogenic belts, geometry of ancient continental margins, distribution and classification of accreted terranes, geometry of suture zones and courses of ancient oceans, and how the continent evolved from an assemblage of Archean minicontinents to its present configuration. It is suggested that essentially similar plate tectonic processes controlled continental breakup and assembly from the Archean onwards, albeit with gradual increase in size of continental lithospheric plates and quantitative change in other parameters such as heatflow and character of the mantle.
An integrated chronicle of major events leading to the growth of the pre-2.0 Ga Indian Craton, which is the aim of this paper, is an essential requirement to constrain the possibility of Neoarchaean unification between Africa and India. The primordial sialic crust that eventually developed into the early Indian Craton segregated from the mantle before 3.8 Ga. Intially there were two seperate Indian blocks, the northern (NIB) and the southern (SIB), and they possibly amalgamated before 2.5 Ga. Rapid and extensive crustal growth at ca 3.1, 2.5 and 2.0 Ga, in conjunction with a related rise in relative sea level due to ocean basin volume reduction, kept the continental freeboard at a moderate level. The 2.5 Ga event was the greatest in magnitude and is likely to have led to the formation of an Indian supercontinent. Four sedimentary basins, one in the NIB and three in the SIE, developed on the typical Archaean tonalite-trondhjemite-granodiorite basement, through rifting induced by mantle upwelling. Continental freeboard was lowered as a consequence and transgressions generally followed. Rifting persisted in all the pre-2.0 Ga basins, except one (Bastar) in the SIE, which only underwent a Wilson cycle as the two blocks collided. All the SIE basins were closed by 2.0 Ga, while the basin in the NIB, which only developed at ca 2.5 Ga, still persisted. Neoarchaean continuity between the Central Indian Tectonic Zone and the Limpopo Belt appears likely from all major aspects, but for the deformation history, which still remains elusive.