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The Supercontinent Cycle: A Retrospective Essay
Abstract
The recognition that Earth history has been punctuated by supercontinents, the assembly and breakup of which have profoundly influenced the evolution of the geosphere, hydrosphere, atmosphere and biosphere, is arguably the most important development in Earth Science since the advent of plate tectonics. But whereas the widespread recognition of the importance of supercontinents is quite recent, the concept of a supercon-tinent cycle is not new and advocacy of episodicity in tectonic processes predates plate tectonics. In order to give current deliberations on the supercontinent cycle some historical perspective, we trace the development of ideas concerning long-term episodicity in tectonic processes from early views on episodic orogeny and continental crust formation, such as those embodied in the chelogenic cycle, through the first realization that such episodicity was the manifestation of the cyclic assembly and breakup of supercontinents, to the surge in interest in supercontinent reconstructions. We then chronicle some of the key contributions that led to the cycle's widespread recognition and the rapidly expanding developments of the past ten years.
... The breakup of the Rodinia supercontinent during the Neoproterozoic era and the subsequent assembly of the Gondwana supercontinent had a profound impact on Earth's lithospheric structure, leading to significant changes in geology, climate, and biological evolution (Hoffman, 1991;Murphy and Nance, 2003;Li et al., 2008;Nance et al., 2014;Cawood et al., 2016). Understanding the spatial arrangement of constituent fragments and the dynamic mechanisms of drifting is crucial for comprehending the evolutionary trajectory of supercontinent. ...
... Additionally, this uncertainty adds fuel to the ongoing debate surrounding the primary driving forces behind the breakup of Rodinia. Some researchers argue that it was primarily influenced by mantle plumes, while others contend that it resulted from a prolonged circum-Rodinia subduction system (Li et al., 2008;Nance et al., 2014;Ge et al., 2012Ge et al., , 2016Cawood et al., 2016). This ongoing discussion is central to our understanding of Earth's geological history. ...
In the Neoproterozoic era, the breakup of the Rodinia supercontinent had a profound impact on different aspects of Earth; yet, the precise driving mechanism behind this event has been a source of ongoing controversy. The Tarim block, as a crucial component, presents an opportunity to gain valuable insights into the breakup process through its tectonic-sedimentary evolution history and dynamic background. However, the comprehension of basin evolution is limited due to the presence of an ambiguous prototype basin during the late Neoproterozoic and its intricate interconnections with surrounding blocks. In this contribution, we integrate detailed field observations , U-Pb dating of detrital zircon and rutile, and trace element analysis of detrital rutile to elucidate the source-to-sink relationships and the tectonic setting of Ediacaran sedimentary strata in the Aksu area (northern Tarim block, China). Detrital zircon age spectra exhibit consistent distributions with ages between ~ 850 and ~ 600 Ma and between ~ 2100 and ~ 1800 Ma. Rutile age groups however exhibit an abrupt transition between the lower member of the Sugatbrak Formation and the succeeding upper member to the Qigebrak Formation in the basin, with ages between ~ 1800 and ~ 900 Ma and nearly identical to those between ~ 2100 and ~ 1800 Ma. Calculated Zr-in-rutile temperatures and Cr-Nb compositions imply that the majority of the detrital rutiles were sourced from amphibolite facies metapelites, with an abrupt transition from amphibolitic schist to amphibolite-granulite facies for the ~ 1800 Ma group grains. Provenance tracing shows that the detrital sediments of the lower Sugatbrak Formation are sourced from both the Central Tianshan and the Tarim blocks, and that the overlying strata have a single source in the Tarim block. A corresponding change from syn-rift detrital facies to a shallow-marine environment in on a passive continental margin is suggested in terms of depositional setting. In light of prior published evidence from petrology, geochronology and paleomagnetism, we propose that the Neoproterozoic northern Tarim margin was affected by a protracted subduction zone retreat. Associated back-arc spreading eventually was responsible for the opening of the southern Tianshan Ocean and rifting of the Central Tianshan block from the Tarim block in the late Ediacaran. This development ultimately prevented detrital material from the Central Tianshan block from reaching the northern Tarim depocenters as the latter evolved into a passive continental margin.
... We have identified non/polar/pan-glacial regimes controlled by the tropical appropriation of land and based on the observed paleogeography (Eyles, 2008;Bradley, 2011;Li et al., 2013;Nance et al., 2014), we offer the following interpretation of the glacio-epochs aided by the numbered stages shown in Fig. 4 (time moves to the left). Dashed lines are tropical-land thresholds that divide non/polar/pan-glacial regimes. ...
... Stage 4 represents the assembly of Pangea when Laurentia reattaches Gondwana to extend from pole-to-pole (Nance et al., 2014). Although there is more tropical land than Pannotia, the sizable polar land hence the associated warmth only allows polar-glaciation (Karoo) lasting about 100 million years (Eyles, 2008). ...
Precambrian tropical glaciations pose a significant challenge to our understanding of Earth’s climate. A popular explanation invokes runaway ice-albedo feedback leading to “iceball earth”, an extreme state conflicting however with the sedimentary evidence of an open ocean and active hydrological cycle. We point out flawed physics of the runaway scenario, which overlooks potency of the ocean heat transport in deterring the perennial sea ice. Nor is frozen ocean needed for tropical glaciation as the latter requires only that the tropical land be cooled to below the marking temperature of the glacial margin, which is necessarily above the freezing point to counter the yearly accumulation. Since tropical glaciations generally coincide with Precambrian supercontinents, we posit that it is their blockage of the brighter tropical sun that causes the required cooling. To test this hypothesis, we formulate a minimal two-box model, which is nonetheless thermodynamically closed and yields lowering tropical/polar temperatures with increasing tropical land, whose crossings of the glacial marking temperature would divide non/polar/pan-glacial regimes—the last being characterized by tropical glaciation abutting an open ocean. Given the observed chronology of paleogeography, our theory may provide a unified account of the faint-young-sun paradox, Precambrian tropical glaciations and glacio-epochs through Earth’s history.
... Deep plumes are most often looked upon as main causes of large continental masses breakup. Raise of heated plume matter causes extension, erosion, thinning, and rifting of the overlying continental lithosphere, and may have eventually resulted in its discontinuity (Nance et al., 2014;Koppers et al., 2021). The details of this process have been analyzed with numerical models (Burov et al., 2007;Lavecchia et al., 2017;Koptev et al., 2015Koptev et al., , 2021. ...
... The role of different mechanisms of supercontinent rifting at various stages of the Earth's tectonic evolution remains unanswered. As for the breakup of Pangea, the youngest supercontinent, both plume and subduction mechanisms are under discussion (Collins, 2003;Nance et al., 2014;Keppie, 2016;Lovecchio et al., 2020;Aldaajani et al., 2021). For older supercontinents, most researchers discuss the plume model, but only in such cases as Rodinia in the Neoproterozoic (Cawood et al., 2016;Wu et al., 2021), the role of subduction rupture has been substantiated. ...
Mafic intraplate magmatism is the main source of information about the geodynamics of processes that lead to the breakup of continental blocks. The article discusses geodynamics of the breakup of the Archean supercraton Superia in the Middle Paleoproterozoic. The discussion is based on data on 2.1 Ga mag- matism in the Karelian Craton, where mafic igneous rocks of this age are represented by tholeiites of two geo- chemical types: depleted and enriched. Geochemically close to N-MORB, depleted tholeiites were studied in the Northern Ladoga Region where they form dike swarms at ca. 2111 ± 6 Ma (U-Pb, SIMS, zircon) in the Hatunoiya locality, and pillow lavas and sills in the Lake Maloe Jänisjärvi locality. Enriched tholeiites were studied in the Lake Tulos locality where they form a large swarm of doleritic dikes of age 2118 ± 5 Ma (U-Pb, ID- TIMS, baddeleyite). The results of these studies provide deeper insight into 2.1 Ga mafic magmatism. Depleted tholeiites with N-MORB geochemistry have a wide spatial distribution in the Karelian Craton and could be formed via decompression melting of a depleted asthenospheric mantle, raising melts along the extension zones, and minimal contamination by the Archean crust. According to modelling results, enriched tholeiitic melts probably occurred due to differentiation and crustal contamination of rising depleted tholeiitic melts through more rigid Archean crustal blocks. Data on ca. 2.1 Ga mafic magmatism in the Kare- lian craton are difficult to explain within the mantle plume rise model, but are consistent with the model of lithosphere extension due to a retreat of a subduction zone in the northeastern margin of the craton, in the Lapland-Kola Ocean at 2.0–2.2 Ga. The intensive thinning and rupture of the Archean continental litho- sphere and opening of an oceanic basin at the western margin of the Karelian craton were probably controlled by the suture zone of the junction of Neoarchean and Paleoarchean crustal blocks, traced in the western part of the Karelian craton. An additional factor that led to the ca. 2.1 Ga lithospheric breakup could be a rise of a deep-seated mantle plume in the Hearne craton, neighboring to the Karelian craton in the Archean Superia supercraton.
... The crust's component continental blocks are in constant motion, driven across the planet's surface by plate tectonics. At times, these continental blocks are small and numerous, and scattered around the globe; at other times, they amalgamate into fewer, larger continental blocks, and at times into supercontinents (Nance et al., 2014). ...
A time discrepancy of at least 200-300 million years exists between the generally accepted onset of meta-zoan evolution as currently evidenced from fossils compared with that from studies at the molecular level. That temporal disparity coincides with the existence and subsequent breakup of the Rodinia Supercontinent when the earliest evolutionary crucibles were isolated intracratonic basins rather than the globally connected shallow seaways of subsequent eras. However, the discovery of fossil evidence to complement the extrapolations from molecular data has been, and continues to be, hampered, by both the geographical limitations of these isolated intracratonic basins and the fact that any such discovery would conflict with the global geological mindset that macrofossils of such age do not exist. Yet recently identified within the intracratonic Amadeus Basin of central Australia is a suite of macroscopic metazoan fossils that dates to ca 850-840 Ma, exemplifying an early attempt at animal evolution within the restrictions of the Rodinia Supercontinent. Such early metazoan evolution within such isolated crucibles, however, was extremely vulnerable to variations in climatic conditions, which threatened total extinction because the isolation of these basins limited metazoan distribution by denying them the possibility of migrating to safer havens. The Amadeus Basin evidence suggests that early metazoan evolution perhaps comprised cycles of about 10 million years when evolution flourished followed by climate change induced extinction and a subsequent evolutionary void of between 50 and 100 million years. Such cycles possibly characterised metazoan evolution until the Rodinia Supercontinent broke-up, after which connections between smaller oceans, shallow seas and narrow waterways provided metazoan life passageway to sanctuary during times of environmental stress. As the Amadeus Basin was just one of a number of isolated Rodinian-aged intracratonic basins, it is likely that similar fossils of the earliest metazoans are preserved elsewhere awaiting discovery. KEY POINTS 1. Metazoan evolution is widely believed to have followed the Gaskiers Glaciation at ca 580 Ma, yet studies at the molecular level suggest evolution began 200-300 million years earlier. 2. Fossils discovered in the Amadeus Basin of central Australia suggest that a diverse metazoan biota had evolved by 850 Ma. 3. Before the Rodinia Supercontinent fragmented during this temporal disparity, intracratonic basins acted as crucibles for early metazoan evolution. 4. Being isolated, intracratonic basins were vulnerable to periodic environmental change causing metazoans, with no means of escape, to periodically become extinct. 5. Amadeus Basin fossils suggest that pre-Ediacaran metazoan evolution possibly comprised cycles of ca 10 million years when evolution flourished before extinction and a following evolutionary void of between 50 and 100 million years.
... The assembly and break-up of the Paleoproterozoic-Mesoproterozoic supercontinent Nuna (also known as Columbia) is considered by some to represent Earth's first supercontinent cycle, profoundly influencing Earth's geosphere, biosphere, ocean circulation, and atmosphere (e.g., Rogers, 1996;Rogers and Santosh, 2009;Nance et al., 2014;Condie et al., 2015). Paleogeographic reconstructions of the Nuna interval have shown significant advances in the last two decades (e.g., Pesonen et al., 2003;Evans, 2013;Pisarevsky et al., 2014;Pehrsson et al., 2016;Elming et al., 2021), based on global paleomagnetic data and geological correlations. ...
... 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 direct corollary may be initiation and closure for many of the sedimentary basins with amalgamation and disintegration of Proterozoic supercontinents (cf. Cawood and Buchan 2007;Santosh 2010;Nance et al. 2014;Cawood et al. 2016). A revisit for most Indian Proterozoic basins thus warranted to ascertain their possible rift/foreland origin, going beyond the traditional claim for their intra/ epi-cratonic basin set-up. ...
Indian Proterozoic basins (traditionally referred to as the ‘Purana basins’) attracted attention of sedimentologists for decades and studies undertaken have benefited in our understanding near surface processes (including both continental and shallow marine realm), for the time period in the Earth history when continents were without land plants and subaquatic surfaces were proliferated by microbial mats in absence of grazers and burrowers. Additionally, these basin successions provided scope to decode several irreversible changes in the atmosphere, hydrosphere and biosphere that the time period had witnessed. The aim of present contribution is to assimilate data generated from the basin fills viz. Vindhyan, Mahakoshal, Bayana, Cuddapah, Kurnool, and Bhima in last four years (2020–2023) and to provide a roadmap for future work. Several worth-mentioning outcomes in recent past can be noted such as addition of new geochronological data (in Vindhyan, Mahakoshal, Kurnool basins), revision of stratigraphy (Gulcheru Formation, Cuddpah Basin), new taxonomical attribution of microfossils (Owk shale Formation, Kurnool Basin), new geochemical and paleohydrological data (Vindhyan, Bayana, Kurnool Basin successions), and depositional models for different Formations from the basin successions.
... However, the number of comparatively smaller additional fragments of this type is still unknown. In fact, identifying Archean crustal fragments is a difficult geological task, as they may have undergone regrouping and dispersion during the formation and destruction of continents and supercontinents (e.g., Nance et al. 2014;Pesonen et al. 2021). Paleomagnetic data have made a great contribution to tracking the trajectories of dispersed terranes over time (e.g., Evans and Pisarevsky 2008;Li et al. 2008). ...
Article Information Publication type: Research Papers Gamma-ray spectrometry, as well as magnetic and gravity data, are used to investigate the geophysical signatures of the Archean nuclei of the Borborema Province. Natural radioactivity, magnetic anomalies, and residual Bouguer gravity anomalies of the Archean nuclei exhibit distinct signatures in relation to adjacent Proterozoic domains. Gamma-ray spectrometry data reveal eTh enrichment in relation to K and eU contents in Archean units. Assuming that K and U were the dominant isotopes, this relative enrichment of eTh can be explained by the fact that Th radioisotopes have a longer half-life than the other two radionuclides and that 4.56 Ga has elapsed since Earth's formation. The intensity of the total magnetic gradient in Archean units is greater than in Proterozoic units in most nuclei. The Archean units underwent deformation and metamorphism in the Brasiliano/Pan-African Orogeny; therefore, the magnetic characteristics now observed in Archean mafic-ultramafic rocks, iron formations and gneiss-migmatite complexes are the joint result of their primary properties and the superposed effects of the orogeny. All Archean nuclei of the Borborema Province show positive residual Bouguer gravity anomalies. This could be due to the conservation of the main petrophysical properties of the Archean lithosphere, and their preservation during the intense granitization that occurred in the Brasiliano/Pan-African Orogeny. As magnetic and gravity methods provide information from depth, it is possible to infer the continuity of some Archean nuclei beyond the limits established by surface geological data. Based on these results, it will be possible to use geophysical signatures to investigate the possible existence of unknown Archean units in the province.
... 1.0 Ga where modern-style plate tectonics, referring to subduction of cold lithosphere and steep geotherms, existed (Palin & Santosh, 2021). During the late Paleoproterozoic to Mesoproterozoic, the supercontinent Columbia (also referred to as Nuna) was assembled through a complex network of accretionary orogenic belts and collisional orogens at 1.9 to 1.8 Ga (Zhao et al., 2004;2011;Johansson et al., 2022) and it is considered by some to be the first coherent supercontinent (Rogers & Santosh, 2002;Nance et al., 2014). This period represents an important period of continental crustal growth and preservation in Earth's history. ...
The Central Domain of the Ketilidian Orogen in South Greenland preserves two magmatic events that provide insight into crustal architecture and represent a major contribution to continental crustal growth in connection with the assembly of the late Paleoproterozoic-Mesoproterozoic supercontinent Columbia/Nuna. This study provides zircon U-Pb geochronology for the western parts of the Central Domain and, combined with previous published age data, documents crustal evolution in the orogeny. The geochronological data indicate an initial volumetrically-minor magmatic event at ca. 1850 Ma, referred to here as the Older Julianehåb Igneous Suite, followed by a pause in magmatic activity. This is followed by the Younger Julianehåb Igneous Suite, a major pulse of magmatism (comparable to magmatic flare-ups in Phanerozoic arcs) between ca. 1814 and 1795 Ma. The adjacent arcs in the Makkovik Province, Canada, and the Transscandinavian Igneous Belt, Scandinavia, preserve similarly-aged magmatic events and appear to young from west to east. Exposure levels in the Makkovik Province are shallower than in the Ketilidian Orogen, and shallower supracrustal deposits are significantly more abundant in the Makkovik Province, indicating significant differences in modern erosion levels.
... Deformed and metamorphosed lithospheric fragments preserving the complete history of rifting, spreading, and subsequent subduction and collision events are generally preserved in the axial zone of the orogenic belts [1][2][3]. These fragments can be derived from the thinned distal continental margins involved in the subduction immediately before the collisional event [4][5][6]. ...
The Lower Units of Alpine Corsica, France, are fragments of continental crust strongly deformed and metamorphosed under high-pressure metamorphic conditions. Three slices of Lower Units are well exposed in the area between the Asco and Tavignano valleys, Central Corsica. Despite their complex structural setting, they provide the opportunity for a reconstruction of the pristine stratigraphic setting of the Lower Units. In our reconstruction, these units consist of a Paleozoic basement topped by Triassic to Early Jurassic sedimentary rocks unconformably covered by Middle to Late Eocene foredeep deposits. However, the three units exposed in the study area display strong differences mainly in the thickness of the Mesozoic sequence. These differences are here interpreted as acquired during the first stage of the rifting process in a setting controlled by normal faults. During the collision-related tectonics and the accretion of the Lower Units to the Alpine orogenic wedge, these normal faults were probably reactivated with a reverse kinematics. The stratigraphic logs of the Lower Units strictly resemble those of the Pre-Piedmont Units from Western Alps. This similarity indicates a common origin of the Lower Units and the Pre-Piedmont Units from the same domain (i.e., the European distal continental margin).
... the supercontinent cycle (Nance et al., 2014). However, the nature of this boundary is variable and debated in the northern Appalachians. ...
Plain Language Summary
Approximately 250 million years ago, the supercontinent Pangea included most of the Earth's landmass. The northern Appalachians of Québec and Maine were in the center of Pangea and preserve a record of its assembly in the surface rocks and the deep structure of the lithosphere. Rock outcrops on the surface enable the crust to be subdivided into regions (terranes) that originated as parts of proto‐continents Laurentia and Gondwana. An ocean called Iapetus separated those continents and the trace of its eventual closure is recognized in the surface rocks of the region. We probe the structure beneath the trace of Iapetus Ocean closure using seismic waves from distant earthquakes that traverse the upper layers of the Earth and provide information on their properties. We identify a zone of well‐developed rock fabric that likely originated when blocks of Earth's crust moved relative to each other as Pangea was put together. This dipping boundary (called décollement) extends beneath the trace of the Iapetus Ocean closure without interruption, documenting a mismatch between the record of Pangea's assembly preserved on the surface and the deeper structure of the continent. Our findings are instructive for understanding how the supercontinent cycle, a process unique to Earth, operates.
... Correlation of macroevolutionary patterns and sedimentary rock volume in deep time is a well-documented phenomenon (Newell 1959;Raup 1972Raup , 1976Sepkoski et al. 1981;Foote 2001, 2002;Smith 2001Smith , 2007Smith et al. 2001;Peters 2005Peters , 2006Smith and McGowan 2007;McGowan and Smith 2008;Heim and Peters 2011;Peters et al. 2013;Rook et al. 2013;Dunhill et al. 2014;Benton 2015;Benson et al. 2021). Sloss sequences linked to expansion and contraction of marine shelf area have also long been recognized in Phanerozoic strata as a second-order (∼10 7 yr) control on the continental distribution of sedimentary rocks (e.g., Sloss 1963;Mackenzie and Pigott 1981;Haq et al. 1987;Miller et al. 2005;Haq and Schutter 2008;Meyers and Peters 2011;Peters and Heim 2011b;Nance et al., 2014;Husson and Peters 2018). A matter of continuing debate is whether or not the correlation between rock and fossil records in deep time is indicative of preservation bias distorting patterns observed in the fossil record, or whether it is instead a signal of geologic process that acted as a "common cause" mechanism, driving both patterns of biological diversity and preserved rock quantity (Crampton et al. 2003;Peters 2008;Peters and Heim 2011a;Peters et al. 2013Peters et al. , 2022Holland 2017;Husson and Peters 2018;Nawrot et al. 2018). ...
Strata of the Ediacaran Period (635–538.8 Ma) yield the oldest known fossils of complex, macroscopic organisms in the geologic record. These “Ediacaran-type” macrofossils (known as the Ediacaran biota) first appear in mid-Ediacaran strata, experience an apparent decline through the terminal Ediacaran, and directly precede the Cambrian (538.8–485.4 Ma) radiation of animals. Existing hypotheses for the origin and demise of the Ediacaran biota include: changing oceanic redox states, biotic replacement by succeeding Cambrian-type fauna, and mass extinction driven by environmental change. Few studies frame trends in Ediacaran and Cambrian macroevolution from the perspective of the sedimentary rock record, despite well-documented Phanerozoic covariation of macroevolutionary patterns and sedimentary rock quantity. Here we present a quantitative analysis of North American Ediacaran–Cambrian rock and fossil records from Macrostrat and the Paleobiology Database. Marine sedimentary rock quantity increases nearly monotonically and by more than a factor of five from the latest Ediacaran to the late Cambrian. Ediacaran–Cambrian fossil quantities exhibit a comparable trajectory and have strong ( r s > 0.8) positive correlations with marine sedimentary area and volume flux at multiple temporal resolutions. Even so, Ediacaran fossil quantities are dramatically reduced in comparison to the Cambrian when normalized by the quantity of preserved marine rock. Although aspects of these results are consistent with the expectations of a simple fossil preservation–induced sampling bias, together they suggest that transgression–regression and a large expansion of marine shelf environments coincided with the diversification of animals during a dramatic transition that is starkly evident in both the sedimentary rock and fossil records.
... 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. While, the singular melt extraction age of 145 Ma for the NHO mantle peridotites is coherent with emergence of Neo-Tethyan embryonic ocean in response to disintegration of Gondwana Supercontinent resulting into peeling off and detachment of older SCLM fragments ( Fig. 9b) (Nance et al., 2014;Santosh, 2003, Chatterjee et al., 2013). The mantle section of the Neo-Tethyan ophiolitic peridotites of this study accounts for intriguing histories of elemental depletion, enrichment and recycling developed in a wide spectrum of tectono-magmatic domains attributed to relative plate motion of bounding continental blocks (Fig. 9c). ...
... The East Antarctica Ice Sheet (EAIS) covers a continent that remains poorly understood in terms of its topography and geology [1,2]. A complex tectonic evolution history was formed by the supercontinent process, including the composite shield dominated by Columbia and Rodinia in the Precambrian era [3][4][5][6][7][8][9], as well as the convergence and fragmentation of Gondwana [10][11][12]. Research data deficiencies and the complexity of the causal mechanisms have hindered the knowledge of the basement characteristics and splicing position of the suture belt in this region, making it a research focus under the EAIS. ...
The Princess Elizabeth Land landscape in East Antarctica was shaped by a complex process, involving the supercontinent’s breakup and convergence cycle. However, the lack of geological knowledge about the subglacial bedrock has made it challenging to understand this process. Our study aimed to investigate the structural characteristics of the subglacial bedrock in the Mount Brown region, utilizing airborne geophysical data collected from the China Antarctic Scientific Expedition in 2015–2017. We reconstructed bedrock density contrast and magnetic susceptibility models by leveraging Tikhonov regularized gravity and magnetic inversions. The deep bedrock in the inland direction exhibited different physical properties, indicating the presence of distinct basement sources. The east–west discontinuity of bedrock changed in the inland areas, suggesting the possibility of large fault structures or amalgamation belts. We also identified several normal faults in the western sedimentary basin, intersected by the southwest section of these survey lines. Furthermore, lithologic separators and sinistral strike-slip faults may exist in the northeast section, demarcating the boundary between Princess Elizabeth Land and Knox Valley. Our study provides new insights into the subglacial geological structure in this region, highlighting the violent impact of the I-A-A-S (Indo-Australo-Antarctic Suture) on the subglacial basement composition. Additionally, by identifying and describing different bedrock types, our study redefines the potential contribution of this region to the paleocontinent splicing process and East Antarctic basement remodeling.
... There is a complex sequence of events involved in the formation of a supercontinent, beginning with the rifting of an old supercontinent, forming a new oceanic crust, then starting subduction and forming volcanic arcs, subsequently colliding among these arcs, and finally experiencing continental-continental collisions (Nance et al., 2014;Wilson et al., 2019;Hassan et al., 2020). As a result of all these processes, different basin types are formed in different tectonic settings (Bentor, 1985;Middleton, 1989;Stoeser and Camp, 1985;Brooijmans et al., 2003;Moghazi, 2003;Jarrar et al., 2003;Eliwa et al., 2008;Be'eri-Shlevin et al., 2011;Johnson et al., 2011;Allen et al., 2015;Daly et al., 2018). ...
Rodinia to Gondwana evolution record, South Sinai, Egypt: Geological and geochronological constraints
... The Columbia supercontinent is considered the Earth's oldest coherent and closely packed assembly of continental fragments into a united landmass (Rogers and Santosh, 2002;Nance et al., 2014;Meert and Santosh, 2017). The rifting and disintegration of Columbia during the late Paleoproterozoic led to diverse magmatism processes, and sizeable intracratonic rift basins in the constituent continents witnessed prolonged sedimentation (Rogers and Santosh, 2004). ...
The disintegration of the Columbia supercontinent during the late Paleoproterozoic generated major rift basins in the constituent continental fragments. The Kaladgi basin, located between the southern part of the Deccan volcanic province (DVP) and the northern part of the Dharwar craton, is a Columbia rift-related basin in southwestern India that preserves a complex history from initial fault-controlled mechanical subsidence during rifting, thermal subsidence along a collision zone, crustal thinning due to stretching and erosion associated with doming. The Paleoproterozoic basins worldwide show higher uranium concentration and many deposits are also established in the Purana basins of India. In the present study, the lithotectonic architecture of this basin using broadband magnetotelluric (∼320 Hz–3000 s) soundings in the western segment of the Kaladgi rift basin along two profiles. Two-dimensional (2-D) inversion of data using a 2-D nonlinear conjugate gradient algorithm along both profiles provides insights into the deeper structure of the basin. Our results reveal a thin sheet of Deccan volcanic, sedimentary successions belonging to the Badami and Bagalkot groups, and Proterozoic sediments from top to bottom beneath this basin. The crustal structure is highly heterogeneous and associated with deep-seated faults, and its thickness increases from the eastern Dharwar craton (∼30 km) to the western Dharwar craton (∼45 km). The crustal conductors are interpreted as mafic intrusions derived from the underplated basalts. The moderate conductive features may correspond to carbonate fluids trapped within the faults/fractures zone during basin initiation. The conductive features in the lower crust and the Moho are interpreted as fluids derived from underplated intrusions through plume impact. The NNW trending Chitradurga Suture Zone (CSZ) signature and the Bababudan-Nallur Shear (BNS) in the crust and upper mantle depth are imaged along both MT profiles. This study provides insights into the lithology and tectonic architecture of a long-lived rift basin involved in multiple tectonic events from the late Paleoproterozoic to the late Cretaceous.
... The assembly and breakup of supercontinents have controlled the evolution of our planet since at least the Paleoproterozoic (Nance et al. 2014). Efforts to describe the kinematic mechanisms of supercontinent amalgamation have resulted in the establishment of two end-member conditions for their formationintroversion and extroversion (Nance et al. 1988;Hartnady 1991;Hoffman 1991). ...
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.
... Although the exact initiation time of plate tectonics is debated, most scholars believe that plate tectonics appeared in the Archean-Proterozoic, making the large-scale horizontal movement of continents possible (Dhuime et al., 2012(Dhuime et al., , 2015van Hunen and Moyen, 2012;Griffin et al., 2014;Cawood et al., 2018b. Periodically, during the second half of Earth's history, continental fragments assembled into supercontinents (Nance et al., 2014;Zhao G C et al., 2018). The earliest recognizable supercontinent formed in the late Archean (the Kenor supercraton, ca. ...
The composition and geological evolution of pre-Cryogenian material in the Tibetan Plateau and its surrounding areas have played an important role in studying the formation and evolution of early supercontinents on Earth. This paper systematically summarizes the characteristics of pre-Cryogenian sedimentation, paleontology, magmatism, and metamorphism in the Tibetan Plateau and its surrounding areas. Based on existing data, the records of pre-Cryogenian sedimentation and paleontology are mainly concentrated in the Meso–Neoproterozoic, with relatively few records from the Paleoproterozoic or earlier. The oldest geological record is the Hadean detrital zircons in the metamorphosed sedimentary rocks of the Himalaya and Qamdo areas (ca. 4.0 Ga). The Tibetan Plateau and surrounding areas preserve records related to the formation and evolution of the Kenor supercraton, and the Columbia, Rodinia, and Gondwana supercontinents. Pre-Cryogenian basements can be divided into three types: Tarim-, Yangtze-, and Lhasa-type. The Tarim-type basement has a paleogeographic affinity with the northern margins of the Australian and Indian continents and lacks detrital zircon age peaks and magmatic-metamorphic records related to the Rodinia assembly (ca. 1.3–0.9 Ga). The Yangtze-type basement records volcanic activity related to global cooling in the latest pre-Cryogenian period and contains Meso–Neoproterozoic stromatolite and micropaleoflora fossils, as well as magmatic-metamorphic records related to Rodinia assembly (ca. 1.1–1.0 Ga). The Lhasa-type basement is characterized by Neoproterozoic rift-related sediment records (ca. 900 Ma) and high-pressure metamorphic events (ca. 650 Ma), with a prominent peak of detrital zircon ages of ca. 1.2–1.1 Ga. It is likely to have a paleogeographic affinity with the African continent.
... No known examples are older than 3 billion years (London 2008), which suggests that more than a billion years of element selection and concentration in the crust and upper mantle were required to produce minerals enriched in these elements. The concentration of incompatible elements was most likely enhanced by subduction-related processes (Bradley 2011;Tkachev 2011;Grew and Hazen 2014;Hazen et al. 2014;Nance et al. 2014). ...
Part VII of the evolutionary system of mineralogy catalogs, analyzes, and visualizes relationships among 919 natural kinds of primary igneous minerals, corresponding to 1665 mineral species approved by the International Mineralogical Association—minerals that are associated with the wide range of igneous rock types through 4.566 billion years of Earth history. A systematic survey of the mineral modes of 1850 varied igneous rocks from around the world reveals that 115 of these mineral kinds are frequent major and/or accessory phases. Of these most common primary igneous minerals, 69 are silicates, 19 are oxides, 13 are carbonates, and 6 are sulfides. Collectively, these 115 minerals incorporate at least 33 different essential chemical elements.
Patterns of coexistence among these minerals, revealed by network, Louvain community detection, and agglomerative hierarchical clustering analyses, point to four major communities of igneous primary phases, corresponding in large part to different compositional regimes: (1) silica-saturated, quartz- and/or alkali feldspar-dominant rocks, including rare-element granite pegmatites; (2) mafic/ultramafic rock series with major calcic plagioclase and/or mafic minerals; (3) silica-undersaturated rocks with major feldspathoids and/or analcime, including agpaitic rocks and their distinctive rare-element pegmatites; and (4) carbonatites and related carbonate-bearing rocks.
Igneous rocks display characteristics of an evolving chemical system, with significant increases in their minerals’ diversity and chemical complexity over the first two billion years of Earth history. Earth’s earliest igneous rocks (>4.56 Ga) were ultramafic in composition with 122 different minerals, followed closely by mafic rocks that were generated in large measure by decompression melting of those ultramafic lithologies (4.56 Ga). Quartz-normative granitic rocks and their extrusive equivalents (>4.4 Ga), formed primarily by partial melting of wet basalt, were added to the mineral inventory, which reached 246 different mineral kinds. Subsequently, four groups of igneous rocks with diagnostic concentrations of rare element minerals—layered igneous intrusions, complex granite pegmatites, alkaline igneous complexes, and carbonatites—all first appeared ~3 billion years ago. These more recent varied kinds of igneous rocks hold more than 700 different minerals, 500 of which are unique to these lithologies.
Network representations and heatmaps of primary igneous minerals illustrate Bowen’s reaction series of igneous mineral evolution, as well as his concepts of mineral associations and antipathies. Furthermore, phase relationships and reaction series associated with the minerals of a dozen major elements (H, Na, K, Mg, Ca, Fe, Al, Si, Ti, C, O, and S), as well as minor elements (notably Li, Be, Sr, Ba, Mn, B, Cr, Y, REE, Ti, Zr, Nb, Ta, P, and F), are embedded in these multi-dimensional visualizations.
... Numerous studies have documented dramatic changes for minerals of varied chemical elements, for example, U [4], Hg [5], C [6], Be [7], Li [8], and P [9], as well as clay minerals [10] and igneous minerals [11]. These studies reveal both episodic mineralization associated with periods of supercontinent assembly (e.g., [12][13][14][15]) and systematic changes in oxidation states associated with Earth's evolving near-surface redox environment [16,17]. ...
A survey of the average Mohs hardness of minerals throughout Earth's history reveals a significant and systematic decrease from >6 in presolar grains to~5 for Archean lithologies to <4 for Phanerozoic minerals. Two primary factors contribute to this temporal decrease in the average Mohs hardness. First, selective losses of softer minerals throughout billions of years of near-surface processing lead to preservational biases in the mineral record. Second, changes in the processes of mineral formation play a significant role because more ancient refractory stellar phases and primary igneous minerals of the Hadean/Archean Eon are intrinsically harder than more recently weathered products, especially following the Paleoproterozoic Great Oxidation Event and the production of Phanerozoic biominerals. Additionally, anthropogenic sampling biases resulting from the selective exploration and curation of the mineralogical record may be superimposed on these two factors.
... In general, mafic magmatism is commonly observed in both orogenic and anorogenic settings. Both volcanic and plutonic mafic magmatic rocks, developed in different tectonic settings, are linked to the Wilson cycle, and hence to the supercontinent cycle (Chen & Zhao, 2017;Frost et al., 2016;Nance et al., 2014;and references therein). In orogenic setting, evolution of mafic magmatic rocks takes place in subduction zone-in the arc and back-arc settings and characterized by calc-alkaline and boninitic affinities and have geochemical characters like negative Nb-Ta anomaly, Ni depletion, LILE enrichment, HFSE and Pb depletion, fractionated REE pattern (Pearce, 1982;Pearce et al., 2005;Pearce & Parkinson, 1993;Pearce & Stern, 2006;Quanshu & Xuefa, 2014). ...
An east–west‐trending medium‐grained mafic sill containing co‐genetic Fe–Ti oxide ore lenses is found disposed within granite gneisses around Saltora‐Mejia area in the eastern part of the Chotanagpur Granite Gneissic Complex (CGGC) of eastern India. CGGC is considered as a Proterozoic mobile belt as it witnessed multiple phases of deformation and high‐ grade metamorphism during 1.8–0.8 Ga. Occurrence of such Fe–Ti oxide ore‐bearing mafic sill is unique in the entire CGGC which is a vast Proterozoic orogenic belt and has witnessed many phases of voluminous mafic and felsic magmatisms. The mafic rock is of gabbronorite composition which contains plagioclase, clinopyroxene, orthopyroxene as major constituent primary minerals and amphibole as late magmatic mineral. The rock shows sub‐ophitic, intergranular, mosaic and poikilitic texture (defined by larger pargasitic grain). The gabbronorite shows iron enriched tholeiitic character, low Mg#, low abundances of Ni and Cr, slight enrichment in LILE, LREE and slight depletion in HFSE like Nb and Ti. The computed melt in equilibrium with the studied gabbronorite shows transitional orogenic to anorogenic, within‐plate and E‐MORB‐like geochemical character. In this study, the U–Pb zircon crystallization age (~960 Ma) of the Saltora‐Mejia gabbronorite is reported for the first time which coincides with the late tectonic stage of the most pervasive orogenic activity in the CGGC around 1.2–0.9 Ga. Transitional orogenic to anorogenic geochemical character, late tectonic evolution and other field and laboratory evidences together suggest evolution of the Saltora‐Mejia gabbronorite sill in a late tectonic extensional environment which might have been facilitated by delamination of a subducted plate and upwelling of asthenospheric mantle during the waning stage of a major orogeny in the CGGC.
... 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]. ...
This paper investigates the origin of ultra-deep dolostone and the factors influencing large-scale dolostone reservoirs, focusing on the Sinian Dengying Formation and the Cambrian Longwangmiao Formation in the Sichuan Basin. The study involves petrology, microscale X-ray diffraction, trace element analysis, and C-O-Sr-Mg isotope experiments to provide a detailed analysis. The research findings indicate that the Dengying and Longwangmiao formations comprise six types of matrix dolostone and four types of cement. The Dengying Formation, which developed under a sedimentary background of a restricted platform, contains special microbial and microcrystalline dolostones. The dolomite grains are small (<30 µm) and have a low order degree (Min=0.55), with large unit cell parameters and an extremely high Na content (Max=788 ppm). The 87Sr/86Sr value of the dolostone is consistent with contemporaneous seawater, while the δ13C and δ18O values are lower than those of the contemporaneous seawater. The δ26Mg value is small (Min=−2.31‰). Powder crystal, fine-crystalline, and calcite dolostones with coarser and more ordered crystals exhibit similar δ13C and 87Sr/86Sr values to microbial and microcrystalline dolostone. During the sedimentary period of the Dengying Formation, ancient marine conditions were favorable for microbial survival. Microorganisms induced the direct precipitation of primary dolomite in seawater, forming microbial and microcrystalline dolostones during the seawater diagenesis period. During the subsequent diagenesis period, dolostones underwent the effects of dissolution-recrystallization, structures, and hydrothermal fluids. This resulted in the formation of dolostone with coarser crystals, a higher degree of order, and various types of cement. The Longwangmiao Formation was developed in an inter-platform beach characterized by special particle dolostone. The particle dolostone has a large grain size (>30 µm), high order degree (Min=0.7), small unit cell parameters, high Na content (Max=432 ppm), and low Fe and Mn content. The δ26Mg and δ13C values are consistent with the contemporaneous seawater, while the δ18O and 87Sr/86Sr values are higher than those of the contemporaneous seawater. There is mutual coupling between multiple-period varying δ26Mg values and sedimentary cycles. The dolostone in the Longwangmiao Formation resulted from the metasomatism of limestone by evaporated seawater. The thickness and scale of the dolostone in the Longwangmiao Formation are controlled by the periodic changes in sea level. The period of dolostone development from the Sinian to the Cambrian coincides with the transition from Rodinia’s breakup to Gondwana’s convergence. These events have resulted in vastly different marine properties, microbial activities, and sedimentary climate backgrounds between the Sinian and the Cambrian. These differences may be the fundamental factors leading to the distinct origins of dolostone formed in the two periods. The distribution of sedimentary facies and deep tectonic activities in the Sichuan Basin from the Sinian to the Cambrian is influenced by the breakup and convergence of the supercontinent. This process plays a key role in determining the distribution, pore formation, preservation, and adjustment mechanisms of ultra-deep dolostone reservoirs. To effectively analyze the genesis and reservoir mechanisms of ultra-deep dolostone in other regions or layers, especially during the specific period of supercontinent breakup and convergence, it is crucial to consider the comprehensive characteristics of seawater properties, microbial activities, sedimentary environment, and fault systems driven by tectonic activities. This can help predict the distribution of high-quality and large-scale ultra-deep dolostone reservoirs.
In Northeast Africa, a greenschist to lower amphibolite facies dominated collisional Pan-African belt extends along the Western flank of the Red Sea. The belt is known as the Egyptian Nubian Shield (ENS) in Egypt. The ENS represents the northern tip of the Arabian-Nubian Shield (ANS) and exhibits most of the essential lithological/structural features of the Midyan terrane exposed in western Saudi Arabia. The low-grade ANS was regarded as the upper crustal equivalent of the high granulite facies-dominated Mozambique Belt (MB), with both forming the N–S oriented East African Orogen (EAO), which formed during a ~200 Ma prolonged stage of closure of the Pacific-sized Mozambique Ocean, and convergence of East and West Gondwana that culminated in arc suturing and terrane accretion. The main objective of the present chapter is to introduce the ENS belt exposed in Northeast Africa. The Neoproterozoic ENS litho-units are typically juvenile and experienced a polyphase deformation history. Following this introduction, the setting of the ANS in Northeast Africa, the broad relations of the ANS with the EAO, and the tectonic components of the ANS will be addressed with reference to their lithotectonic associations, geochemistry and geochronology, and structural and tectonic framework. The chapter provides an opportunity to review the magmatic-metamorphic-tectonic history of the Pan-African belt in Northeast Africa.
The Inland Pacific Northwest documents geologic processes from Proterozoic time to the Present. This volume presents field trips from the 2024 GSA Cordilleran and Rocky Mountain Joint Sections Meeting, exploring the genesis of bedrock in Idaho, Neoproterozoic development of supercontinents in Washington, Cambrian tectonic and biostratigraphic history of Washington, and paleoecology of Miocene woodlands in Idaho. An overview of Pleistocene megaflood effects is shown through outcrops and drone images. Advances in understanding of the Columbia River Basalt Group are presented with a strong emphasis on volcanology and flood basalt evolution. The story of the Sevier orogeny accretionary margin is examined, as are the landmark studies of the Mesoproterozoic Belt Basin through a Missoula to Spokane transect.
As a tectonic window into the Lesser Himachal Himalaya, India, a group of metasediments and gneissic rocks, known as the Jutogh Group and Wangtu Gneissic Complex (WGC), occurs near the Jhakri thrust to the west and Wangtu to the east. In the Jutogh Group, chlorite-mica schist, garnet-staurolite schist and sillimanite-schist develop successively. The formation of chemically zoned garnet, which destabilized low-temperature assemblages, is predicted to be at 550–650 °C and 0.8–0.9 GPa by phase equilibria modelling. The retrograde segment consists of exhumation and cooling, yielding a tight clockwise P–T path. Moreover, textural observations and in-situ U-Th-Pb chemical dating indicate that metasedimentary rocks contain Cambrian monazites. These monazites have ages that cluster around 500 Ma. The ƐNd[1.8Ga] of Jutogh rocks ranges from − 1.0 to -8.1, with depleted mantle-model ages between 3.07 and 2.25 Ga. The garnet core and its leachates yield an Sm-Nd isochron age of 472 Ma. Another Sm-Nd isochron age of 454 Ma is obtained from biotite, garnet rim, and garnet rim leachate. According to phase equilibrium modelling, Sm-Nd dating, and monazite geochronology, the Jutogh Group experienced metamorphism along the northeast margin of Gondwana during the Cambro-Ordovician accretion.
Surface geologic features form a detailed record of Venus’ evolution. Venus displays a profusion of volcanic and tectonics features, including both familiar and exotic forms. One challenge to assessing the role of these features in Venus’ evolution is that there are too few impact craters to permit age dates for specific features or regions. Similarly, without surface water, erosion is limited and cannot be used to evaluate age. These same observations indicate Venus has, on average, a very young surface (150–1000 Ma), with the most recent surface deformation and volcanism largely preserved on the surface except where covered by limited impact ejecta. In contrast, most geologic activity on Mars, the Moon, and Mercury occurred in the 1st billion years. Earth’s geologic processes are almost all a result of plate tectonics. Venus’ lacks such a network of connected, large scale plates, leaving the nature of Venus’ dominant geodynamic process up for debate. In this review article, we describe Venus’ key volcanic and tectonic features, models for their origin, and possible links to evolution. We also present current knowledge of the composition and thickness of the crust, lithospheric thickness, and heat flow given their critical role in shaping surface geology and interior evolution. Given Venus’ hot lithosphere, abundant activity and potential analogues of continents, roll-back subduction, and microplates, it may provide insights into early Earth, prior to the onset of true plate tectonics. We explore similarities and differences between Venus and the Proterozoic or Archean Earth. Finally, we describe the future measurements needed to advance our understanding of volcanism, tectonism, and the evolution of Venus.
The Precambrian terranes of the Eastern Indian Shield (EIS) comprise the Bundelkhand, Singhbhum, and Bastar cratons with intervening Proterozoic mobile belts such as Central Indian Tectonic Zone, Eastern Ghats Mobile Belt, Singhbhum Mobile Belt and Chotanagpur Granite Gneissic Complex; and the Proterozoic Mahanadi Rift, Chhattisgarh and Vindhyan Basins, with significant coverage of Indo-Gangetic Plain sediments in the northern part. This study presents the results of a seismically well-constrained 2-D multi-scale potential field modelling to delineate the lithosphere structure across different Precambrian terranes of the EIS. The joint interpretation of the potential field data reveals that (i) the mobile belts are bounded by the deep crustal faults with denser crust, (ii) presence of thick underplated crust below Singhbhum Craton, Singhbhum Mobile Belt, Chotanagpur Granite Gneissic Complex and the surrounding rift basin, (iii) localised Moho upwarp at a depth of ~ 36–37 km below the Proterozoic basins, and (iv) the Lithosphere-Asthenosphere Boundary (LAB) varying between 90 and 200 km below the EIS region. The distinct crustal structure and deeper LAB (130–200 km) below the mobile belts suggest the Proterozoic amalgamation and lithosphere reworking. Below the Singhbhum Craton, the LAB is observed at a depth of ~ 145–155 km, which is comparatively thinner than other cratonic areas elsewhere. The observed crustal underplating and the thinner LAB below the Singhbhum Craton indicate that the lithospheric erosion and magmatic upwelling was caused by the major Paleo-Mesoproterozoic and Early-Cretaceous large igneous province events.
The Tirodi Gneissic Complex (TGC) represents the basement sequence of the Central Indian Tectonic Zone (CITZ), underlying the Proterozoic supracrustal sequences of the Sausar and Betul Groups of rocks. Lithologically, the TGC constitutes a combination of pink and grey granitic gneiss assemblages, characterised by biotite-rich, hornblende-biotite-rich, and muscovite-biotite-rich granite gneiss. Compositionally, the TGC granitoids represent tonalite-trondhjemite-granodiorite to granite, and have calc-alkaline lineage with metaluminous to peraluminous characteristics. Geochemically, they dominantly belong to A2-type granitoids. Chondrite normalised REE ratios of La/Sm, La/Yb, La/Gd, and Gd/Yb indicate diverse LREE/HREE enrichment. Multi-element patterns for the TGC granitoids are characterised by light rare earth elements (LREE) and large ion lithophile elements (LILE) enrichment and depletion of high field strength elements (HFSE: Nb, P, and Ti) and strong positive Pb and Th anomalies. The observed negative anomalies for HFSE are attributed to diverse crustal/lithospheric sources, with some influence from K-feldspar, plagioclase and Ti-oxide fractionation. Sm–Nd data presents initial ¹⁴³Nd/¹⁴⁴Nd (t = 1.7 Ga) ratios (0.509898 to 0.510508), and εNd (t = 1.7 Ga) is (+ 0.58 to -10.59), with TDM model ages ranging from 2.11 to 2.95 Ga. Such a wide range of εNd (t = 1.7 Ga), indicates heterogeneous crustal/lithosphere sources, which have probably experienced longer crustal residence times. Zircon U–Pb ages for individual TGC samples are 1506 ± 11 Ma (TG-01), 1534 ± 26 Ma (MU-5), 1675 ± 9 Ma (BT-4), 1724 ± 11 Ma (BT-3), 1730 ± 13 Ma (BT-4), and 1960 ± 2 Ga (Ms-2), respectively. These ages have probably recorded the key periods of the Columbia supercontinent's assembly, growth, and breakup. Geochemical and geochronological results suggest that the TGC granitoids have a crustal/lithospheric origin and are formed by partial melting of felsic sources in dominantly VAG (volcanic arc granite) and, to some extents, WPG (within-plate granite) settings.
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.
Tectonic evolution from the breakup of the Rodinia supercontinent to the assembly of the Gondwana megacontinent has been well investigated on major continents/cratons. However, the role of microcontinents during the evolution from Rodinia to Gondwana has been poorly discussed. The Jiamusi Block, an important Precambrian microcontinent in the easternmost Central Asian Orogenic Belt (CAOB), is characterized by Pan-African metamorphic records and can be a suitable research objective for reconstructing Gondwana. Here we present a field-based zircon geochronological and Hf isotopic study for the paragneiss of the Mashan Complex in the Jiamusi Block. Four paragneiss samples yielded detrital zircon ages ranging from 2712 to 714 Ma, with the youngest age group of 787, 852, 812, and 915 Ma, respectively. Considering the Neoproterozoic orthogneisses (757, 725, and 898 Ma) intruding the studied paragneisses, we propose that the Mashan Complex contains two sets of supracrustal rocks, with their protoliths deposited at 915–898 Ma and 812–725 Ma, respectively. The metamorphic zircons from the paragneisses yield concordant ages of 566–484 Ma. Considering zircon morphology, internal structures, U-Pb ages, trace elements, and Hf isotopes, we figure out that the metamorphic zircons with ages of 566–560 Ma record granulite-facies metamorphism, which are characterized by high initial Hf isotopic ratios (0.282212–0.282359) and steep chondrite-normalized REE patterns. The 546–484 Ma metamorphic zircons record retrograde metamorphism and exhibit lower initial Hf isotopic ratios (0.281999–0.282204) and relatively flat chondrite-normalized heavy REE patterns.
Based on new data and geological comparison, a unified Bureya-Jiamusi-Khanka Block in the Neoproterozoic is proposed, which was initially originated as part of Northeast India. It was collided with Australia-East Antarctica resulting in the Kuunga-Pinjarra Orogen in the late Pan-African (570–550 Ma). Subsequently, at sometime after 470 Ma, the Jiamusi Block was detached from the Kuunga-Pinjarra Orogen and drifted northward to collide with the Songnen Block of the CAOB in the Middle Jurassic.
Reliable reconstruction of global paleogeography through deep geologic time provides a key surface boundary condition for investigating many first-order Earth system and geodynamic processes such as climate change, geomagnetic field stability, regional geological and tectonic history, and biological evolution. Over the past decade, the development of the GPlates software led to a resurgence of community efforts in creating state-of-the-art plate tectonic models that integrate paleomagnetic, geological, and paleontological datasets, resulting in a plethora of reconstruction models. In this paper, we briefly review the strengths and weaknesses of existing global models, which depict alternative and sometimes contradictory tectonic scenarios. We then provide an overview of the general procedure in our construction of a revised Phanerozoic global paleogeographic model, including (1) evaluation of the paleomagnetic data that quantitatively dictate continental paleolatitudes and orientations, (2) selection of reference frames in which continents were positioned, and (3) calibration of continental longitudes in deep time. We update the apparent polar wander paths (APWPs) of the major continents using a recently developed weighted running mean approach, which rectifies two major issues with the conventional running mean approach regarding missing paleopoles in age windows and the enforced assumption of the Fisherian distribution. We re-evaluate the Phanerozoic continental reconstructions in a paleomagnetic framework using the updated APWPs, and calibrate continental paleolongitudes following the extended orthoversion hypothesis by placing the centroids of supercontinents Rodinia and Pangea 90◦ _apart, with that of Rodinia at ~90◦E. We emphasize that the resulting global model is not intended to provide solutions to all global tectonic issues throughout the entire Phanerozoic Eon. Rather, we present our results as one viable model of Phanerozoic tectonic history which, like many existing interpretations, is built upon our understanding of the paleomagnetic, geological, and paleontological observations. Our goals are for this study to highlight the fundamental differences between reconstruction models and to serve as a starting point for future studies to fill key data gaps and test alternative hypotheses and tectonic scenarios.
Strata of the Ediacaran Period (635–538.8 Ma) yield the oldest known fossils of complex, macroscopic organisms in the geologic record. These “Ediacaran-type” macrofossils (known as the Ediacaran biota) first appear in mid-Ediacaran strata, experience an apparent decline through the terminal Ediacaran, and directly precede the Cambrian (538.8–485.4 Ma) radiation of animals. Existing hypotheses for the origin and demise of the Ediacaran biota include: changing oceanic redox states, biotic replacement by succeeding Cambrian-type fauna, and mass extinction driven by environmental change. Few studies frame trends in Ediacaran and Cambrian macroevolution from the perspective of the sedimentary rock record, despite well-documented Phanerozoic covariation of macroevolutionary patterns and sedimentary rock quantity. Here we present a quantitative analysis of North American Ediacaran–Cambrian rock and fossil records from Macrostrat and the Paleobiology Database. Marine sedimentary rock quantity increases nearly monotonically and by more than a factor of five from the latest Ediacaran to the late Cambrian. Ediacaran–Cambrian fossil quantities exhibit a comparable trajectory and have strong (rs > 0.8) positive correlations with marine sedimentary area and volume flux at multiple temporal resolutions. Even so, Ediacaran fossil quantities are dramatically reduced in comparison to the Cambrian when normalized by the quantity of preserved marine rock. Although aspects of these results are consistent with the expectations of a simple fossil preservation–induced sampling bias, together they suggest that transgression–regression and a large expansion of marine shelf environments coincided with the diversification of animals during a dramatic transition that is starkly evident in both the sedimentary rock and fossil records.
Ancient orogens within the supercontinent like Columbia can remain stable evolution as long as the cratons. What kind of lithospheric mantle was beneath those orogens and how it evolved into a stable state are still enigmatic. The Trans‐North China orogen (TNCO) is one of the typical collisional orogens within the Columbia supercontinent and was formed at ca. 1.85 Ga. Our work reveals that a cluster of kimberlites intruded the orogenic belt at ca. 1.54 Ga. These rocks were originally generated under a thick lithosphere (>200 km). Their entrained olivine cores show a composition of overlapping olivines from refractory mantle peridotites. The results suggest a thick and refractory lithospheric mantle beneath the TNCO at ca. 1.54 Ga. Such craton‐like property may result from large volume melt extraction from the lithospheric mantle, possibly caused by the ca. 1.78 Ga large igneous event, which eventually induces the long‐term stability of the TNCO during the subsequent supercontinent cycle.
The concept of cyclic closure and opening of oceans along the same crustal scar was introduced by J.T. Wilson (1966) based on the example of the Atlantic Ocean and its continental borders. At that time, the only Variscan orogen cited south of Europe along the Atlantic coast of Africa was the Mauritanides of Mauritania. Here we report on the recent achievements in the Mauritanides from Mauritania to Morocco, and on the Moroccan Meseta orogen, which also records the Variscan orogeny. The Southern and Central Mauritanides are a poly-orogenic, Pan-African and Variscan orogen characterized by a thin-skinned tectonic style that mirrors the structure of the southern Appalachians, but with a different tectonic history. The Northern Mauritanides crops out in the Moroccan Oulad Dlim massif, northwest of the Reguibat Rise. This part of the belt compares with the southern part, but additionally exhibits in the west a Silurian-Devonian sector that shows possible affinities with Gondwana-derived Appalachian terranes. The Western Meseta is only affected by Variscan events, which were mild in the westernmost Meseta Coastal Block, while the Eastern Meseta was also affected by Eo-Variscan events. The along-strike change from the Mauritanides to the Meseta orogen is interpreted as a transition from a head-on collision south of the South Meseta transform fault (SMF, precursor of the South Atlas Fault, SAF) to a dextral, transpressional collision north of the SMF. South of the SAF, the Anti-Atlas and the Dhlou-Zemmour expose the foreland foldbelts of the Meseta and northernmost Mauritanides. The Coastal Block was likely displaced from the south-westernmost Anti-Atlas during the Early Carboniferous.
The Wilson Cycle concept mostly applied in that the Atlantic Ocean opened where the prior Rheic Ocean had closed. Possible exceptions are the Sehoul Block north of Western Meseta and the Silurian-Devonian Sector of the Oulad Dlim massif, which may have separated from NW-Africa and re-amalgamated to it during the Variscan orogeny. Likewise, a NW-African fragment from the Anti-Atlas may have stranded in offshore Massachusetts in eastern North America. An early Ediacaran-Cambrian Wilson cycle nested in the classic cycle introduced by Wilson (1966) occurred along the margin of NW-Africa, where Cadomian terranes rifted off Africa, and some were transferred to Europe and some accreted back to NW-Africa. This early cycle likely controlled the localization of the subsequent Rheic rift, and that of the Atlantic rift along the Mauritanides after the Variscan collision.
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.
Opinion is still divided whether Precambrian crustal evolution followed uniformitarian principles and is thus compatible with contemporary plate tectonics, or whether global tectonic mechanisms have changed progressively since the Archaean. Major uncertainties are the earth 's thermal history, growth of continental crust and the generation of igneous rocks of calc-alkaline affinity. lf Archaean heat flow was 2.5-3 times its present value all lithosphere was buoyant and there could have been no gravitational instability and subduction. This implies the early development of a globe-encircling scum crust through recycling and vertical accretion, an evolution which is in conflict with isotope data. An alternative appears to be a hotspot
model with the formation of closely spaced (100-500 km) thermal plume systems and vigorous mantle convection where viscous drag pulls juvenile lithosphere partly back into the mantle. Partial melting and differentiation yields tonalite, the oldest surviving continental crustal rock yet known. The Archaean oceanic crust consisted of piles of komatiitic to tholeiitic lavas and ultramafic intrusives produced over the plumes and was not layered in the same manner as today. Aggregation of sialic proto-continental material (tonalite with remnants of mafic rocks) yielded buoyant semi-rigid and migrating miniplates which grew through under·
plating and subsequent attenuation. The following granite/greenstone phase was characterized by still vigorous sublithospheric convection which induced varying degrees of crustal stretching, rifting and limited
ocean opening. Under favourable conditions sag-subduction, partial melting and crust-mantle mixing processes added new crust to the early nuclei and culminated in a series of "continental accretion-differentiation events" (Moorbath, 1977) which established continents or even supercontinents by the end of the Archaean some 2500 Ma ago, resembling their modern counterparts in size and elevation. With further cooling and thickening of lithosphere in the Proterozoic the average density increased and limited buoyancy-powered subduction began. Relative motion between rigid oceanic plates caused the intervening weaker continental blocks to take up most of the necessary deformation through internal distortion and generated fundamental fractures and shear zones. Differential stresses between light continental crust and underlying negatively buoyant mantle lithosphere favoured their decoupling and may have led to intracontinental orogeny involving underthrusting or subduction of substantial segments of sialic crust (see Molnar and Gray, 1979).
Towards the end of the Precambrian the continuous decline of heat flow resulted in present-day lithospheric thicknesses and the establishment of plate-generation mechanisms which produced layered oceanic crust. With progressive thickening of continental lithosphere through cooling and basalt depletion (Jordan, 1979) the likelihood of crust-mantle decoupling became much lower and, consequently, ensialic orogeny and intracontinental subduction were less frequent.
Finally, further cooling enhanced the negative buoyancy of oceanic lithosphere and established the Phanerozoic Wilson-cycle regime. The worldwide late Precambrian to early Palaeozoic events reflect a transition from predominantly intracontinental to predominantly modern-type plate-margin orogeny. It is suggested that plate tectonics is non-uniformitarian if the entire history of the Earth is considered and began in the Archaean with the generation of small semi-rigid plates. The style and mechanism of plate tectonics changed progressively with the gradual decline in heat flow and increased lithospheric rigidity, and it is therefore not necessary to invoke alternative models in order to explain Precambrian crustal evolution.
The geological evolution of Australia is closely linked to supercontinent cycles that have characterised the tectonic evolution of Earth, with most geological and metallogenic events relating to supercontinent/ supercraton assembly and breakup. Australia mainly grew from W-E, with two major Archean cratons, the Yilgarn and Pilbara cratons, forming the oldest part of the continent in the West Australian Element. The centre of the continent consists of the mainly Paleoproterozoic- Mesoproterozoic North and South Australian elements, whereas the E is dominated by the Neoproterozoic- Mesozoic Tasman Element. The West, North and South Australian elements initially assembled during the Paleoproterozoic amalgamation of Nuna, and the Tasman Element formed mostly as a Paleozoic accretionary margin during the assembly of Gondwana-Pangea. Australia's present position as a relatively stable continent resulted from the breakup of Gondwana. Australia is currently moving northward toward SE Asia, probably reflecting the earliest stages of the assembly of the next supercontinent, Amasia. Australia's resources, both mineral and energy, are linked to its tectonic evolution and the supercontinent cycle. Australia's most important Au province is the product of the assembly of Kenorland, whereas its major Zn-Pb-Ag deposits and iron oxide-Cu-Au deposits formed as Nuna broke up. The diverse metallogeny of the Tasman Element is a product of Pangea-Gondwana assembly and most of Australia's hydrocarbon resources are a consequence of the breakup of this supercontinent.
Various geological and geophysical evidence show that at least two supercontinents, Nuna and Rodinia existed during the Paleoproterozoic and Mesoproterozoic eras. In this paper we have used updated paleomagnetic and isotope age data during 2.45–1.04 Ga to define the amalgamation and breakup times of these supercontinents. The Nuna and Rodinia supercontinents were predominantly at moderate to low paleolatitudes except during the earliest Paleoproterozoic when some of the continents, notably India (Dharwar craton) and Australia (Yilgarn craton), occupied polar latitudes. Sedimentological indicators of paleoclimate are generally consistent with the paleomagnetic latitudes, with the exception of the Early Proterozoic, when low latitude glaciations took place on several continents. The new data suggest that the Nuna supercontinent started to form at about 1.8 Ga, but the final amalgamation took place as late as ca. 1.53 Ga. The orogenic belts formed within Nuna resulted from a complex set of collisions, rotations and strike slip faultings of the docking cratons. Notably, continuation of 1.8–1.5 Ga accretional belts from Laurentia to Baltica is supported by paleomagnetic data. However, the position of Amazonia in the Laurentia-Baltica unity is still controversal. The occurrence of coeval accretional belts in Amazonia and Baltica and the occurrence of ca. 1.53 Ga rapakivi intrusions in a belt from Baltica to Amazonia support their unity, but the strict paleomagnetic data keeps them separated at 1.53 Ga. Nuna began to break up after 1.2 Ga during several rifting episodes, followed by a short period of independent drift of most of the continents. The amalgamation of Rodinia took place during the period of 1.10–1.04 Ga when most of the Earth’s continents were fused together.
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.
Earth as an Evolving Planetary System explores key topics and questions relating to the evolution of the Earth's crust and mantle over the last four billion years. This Second Edition features exciting new information on Earth and planetary evolution and examines how all subsystems in our planet-crust, mantle, core, atmosphere, oceans and life-have worked together and changed over time. Kent Condie synthesizes data from the fields of oceanography, geophysics, planetology, and geochemistry to address Earth's evolution. Two new chapters on the Supercontinent Cycle and on Great Events in Earth history New and updated sections on Earth's thermal history, planetary volcanism, planetary crusts, the onset of plate tectonics, changing composition of the oceans and atmosphere, and paleoclimatic regimes Also new in this Second Edition: the lower mantle and the role of the post-perovskite transition, the role of water in the mantle, new tomographic data tracking plume tails into the deep mantle, Euxinia in Proterozoic oceans, The Hadean, A crustal age gap at 2.4-2.2 Ga, and continental growth.
Earth as an Evolving Planetary System presents the key topics and questions relating to the evolution of the Earth's crust and mantle over the last four billion years. It examines the role of plate tectonics in the geological past via geological evidence and proposed plate reconstruction. Kent Condie synthesizes data from the fields of oceanography, geophysics, planetology, and geochemistry to examine the key topics and questions relating to the evolution of the Earth's crust and mantle. This volume provides a substantial update to Condie's established text, Plate Tectonics and Crustal Evolution, 4E. It emphasizes the interactive nature of various components of the Earth system on time scales of tens to hundreds of millions of years, and how these interactions have affected the history of the atmosphere, oceans, and biosphere. * New insight on interaction and evolution of Earth system * Examines the role of castrophic events in Earth's history * New section on the evolution of the mantle.
The beginnings of biospheric evolution had far-reaching biogeochemical consequences for the related evolutions of atmosphere, hydrosphere, and lithosphere. Feedback to the sedimentary record from these several simultaneously interacting aspects of crustal evolution provides the evidence from which historical biogeology is reconstructed. The interpretation of that evidence, however, is beset with pitfalls. Both biogenicity and a primary origin need to be demonstrated, or confidence limits established for each supposed morphological and biochemical fossil. Relevance to biospheric or related evolutions must be critically evaluated for every geochemical and sedimentological anomaly.
Indirect evidence suggests primitive, oxygen-generating autotrophy by ∼ 3.8 × 10 ⁹ years ago (3.8 Gyr or gigayears), while free O 2 first began to accumulate only ∼ 2 Gyr ago. Various reduced substances in the atmosphere and in solution functioned as oxygen sinks, keeping photolytic and biogenic O 2 at levels tolerable by primitive anaerobic and microaerophilic procaryotes.
The oldest demonstrably biogenic and certainly primary microstructures are procaryotes from ∼ or > 2 Gyr old strata around Lake Superior. Improved biologic O 2 mediation, continued carbon segregation, and filling of O 2 sinks initiated atmospheric O 2 buildup, leading to an ozone screen ∼ or < 2 Gyr ago. Consequences were essential termination of banded iron formation, onset of red beds, and O 2 shielding of anaerobic intracellular processes, heralding the eucaryotic cell.
Probable eucaryotes appear in ∼ 1.3 Gyr old rocks in California as large unicells and large-diameter, branched, septate filaments. Likely consequences of eucaryotic evolution were increased atmospheric O 2 , increased carbonate and sulfate ion, and the rise of sexuality. Meiosis had definitely evolved > 0.7 Gyr ago and probably > 1.3 Gyr ago, perhaps simultaneously with the mitosing cell. Whatever the timing, it completed the evolution of the eucaryotic heredity mechanism and foreshadowed (given sufficient free O 2 ) the differentiation of tissues, organs, and advanced forms of life—with all their potential for biogeochemical feedback to sedimentary, diagenetic, and metallogenic processes. The first Metazoa appeared ∼ 0.7 Gyr ago. Being dependent on simple diffusion for O 2 , they lacked exoskeletons. The latter appeared, perhaps 0.6 Gyr ago, when increasing O 2 levels favored the emergence of more advanced respiratory systems.
The only remaining areas of pristine 3.6-2.7 Ga crust on Earth are parts of the Kaapvaal and Pillbara cratons. General similarities of their rock records, especially of the overlying late Archean sequences, suggest that they were once part of a larger Vaalbara supercontinent. Here we show that the present geochronological, structural and palaeomagnetic data support such a Vaalbara model at least as far back as 3.1 Ga, and possibly further back to 3.6 Ga, Vaalbara fragmented prior to 2.1 Ga, and possibly as early as 2.7 Ga, suggesting supercontinent stability of at least 400 Myr, consistent with Neoproterozoic and Phanerozoic analogues.
The recent hypothesis that the margins of the western United States and Antarctica were conjugate prior to the breakout of Laurentia from Gondwana is consistent with the record of events in the Late Proterozoic-early Palaeozoic Ross Oregon of the Transantarctic Mountains. Isotopic data indicate that basement to the Ross orogen is 2.0-1.7 Ga continental crust, temporarily matching basement in the southwestern United States. The onset of activity in the Ross Orogen was Late Proterozoic basin development with widespread deposition of turbidites. Rifting within this basin is indicated by bimodal volcanism dated at ~750 Ma, coincident with volcanism in the basal Windermere Supergroup in North America. Actual separation is presumed to have occurred shortly before accumulation of Early Cambrian platform carbonates on the margins of both continents. Subsequent to this, the histories of the two margins evolved independently. Limited data indicate that plutonism had begun in the Ross orogen by ~550 Ma. By the Middle Cambrian an association of carbonates and bimodal volcanics was accumulating outboard of the Early Cambrian carbonate platform. Deformation, metamorphism, and voluminous plutonism culminated during the Late Cambrian with cooling ages ~500 Ma. This activity, recorded throughout widespread parts of Gondwana, occurred while the western margin of Laurentia remained passive. -Author
The book is a concise, integrated history of the climatic conditions of the Earth throughout all geolic time. Basin his interpretations on global reconstructions from rock magnetism and sea-floor spreading data, and using sedimentological, biological and chemical indicators of climate, the author documents and discusses the evolution of the Earth's climates on the world scale. New information on oceanic climates from DSDP is used in detailed reconstruction of the climatic changes of the Mesozoic and Cenozoic eras. An analysis of the thermal history of the Earth reveals a number of anomalies, the two most outstanding being the late Precambrian, with its widespread low-latitude glaciation, and the Mesozoic, when the ocean-atmosphere system retained an extraordinary amount of solar energy. -D.G.Tout
Although biomarker, trace element, and isotopic evidence have been used to claim that oxygenic photosynthesis evolved by 2.8 giga-annum before present (Ga) and perhaps as early as 3.7 Ga, a skeptical examination raises considerable doubt about the presence of oxygen producers at these times. Geological features suggestive of oxygen, such as red beds, lateritic paleosols, and the return of sedimentary sulfate deposits after a approximate to 900-million year hiatus, occur shortly before the approximate to 2.3-2.2 Ga Makganyene "snowball Earth" (global glaciation). The massive deposition of Mn, which has a high redox potential, practically requires the presence of environmental oxygen after the snowball. New age constraints from the Transvaal Supergroup of South Africa suggest that all three glaciations in the Huronian Supergroup of Canada predate the Snowball event. A simple cyanobacterial growth model incorporating the range of C, Fe, and P fluxes expected during a partial glaciation in an anoxic world with high-Fe oceans indicates that oxygenic photosynthesis could have destroyed a methane greenhouse and triggered a snowball event on timescales as short as 1 million years. As the geological evidence requiring oxygen does not appear during the Pongola glaciation at 2.9 Ga or during the Huronian glaciations, we argue that oxygenic cyanobacteria evolved and radiated shortly before the Makganyene snowball.
The distinctively large, subcircular, older Precambrian-rich Canadian, West African, and Central African shields, each with circumjacent mainly younger Precambrian-Phanerozoic rocks and broad central infilled basin, are here called ring-shields to express the resulting annular Precambrian pattern. Stage-by-stage shield development is attributed to first-order thermotectonic events affecting a cooling, lithosphere-thickening, uniform volume Earth. The three ring-shields are not only presently aligned on a great circle that crosses the Atlantic Ocean but have maintained this alignment during the past 600 Ma (Phanerozoic) and possibly 1200 Ma at least. A plausible explanation for sustained shield alignment during inter-shield oscillation emphasizes the role of deep, episodically-generated, sub-shield tectospheric roots to depths of 400 to 700 km or greater. A plausible mantle-crust instability mechanism related to episodic supercontinental break-up, in turn, focuses on thermal imbalances developed in thickening crust leading to crustal reversal. Non-random cyclic plate motion, a function of terrestrial heat flow, takes the form of repeated supercontinent assembly that, however, never completely disperses, due in part to tectospheric drag caused by the deeply rooted sheilds. A 400 to 500 Ma-long tectonic oscillation results. -from Author
The Archean mantle was probably warmer than the modern one. Continental plates underlain by such a warmer mantle would have experienced less subsidence than modern ones following extension because extension would have led to widespread melting of the underlying mantle and the generation of large volumes of mafic rock. A 200 °C increase in mantle temperature leads to the production of nearly 12 km of melt beneath a continental plate extended by a factor of 2, and the resulting thinned plate rides with its upper surface little below sea level. The thick, submarine, mafic-to-ultramafic volcanic successions on continental crust that characterize many Archean regions could therefore have resulted from extension of continental plates above warm mantle. Long-term subsidence of passive margins is driven by thermal relaxation of the stretched continental plate (cf. McKenzie). With a warmer mantle, the relaxation is smaller. For a continental plate stretched by a factor of 2, underlain by a 200 °C warmer mantle than at present, the cooling-driven subsidence drops from 2.3 km to 1.1 km. The combined initial and thermal subsidence declines by more than 40%, and by even more than this if initial continental crustal thicknesses were lower. The greatly reduced subsidence results in a concomitant decline in accommodation space for passive-margin sediments and may explain the scarcity of passive-margin sequences in the Archean record. The formation of diamonds in the Archean requires geotherms similar to modern ones, which in turn probably reflect the presence of cool mantle roots beneath the continents. Stretching of continents underlain by cool mantle roots would yield passive margins similar to modern ones. Thus, development of significant passive margins may have occurred only through rifting of continents underlain by cool mantle roots. Furthermore, the widespread subcontinental melting associated with rifting of continents devoid of roots may have been a significant contributor to development of the roots themselves.
Large continents that include most or all of the existing continents are referred to as Supercontinents. Matching of continental borders, stratigraphic sections, and fossil assemblages are some of the earliest methods used to reconstruct supercontinents. Apparent polar wander paths, seafloor spreading directions, hotspot tracks, and correlation of crustal provinces using piercing points are the new methods of reconstruction. Pangea, the youngest supercontinent, formed between 450 and 320 Ma and includes most of the existing continents. Gondwana, a Southern Hemisphere supercontinent comprised of South America, Africa, Arabia, Madagascar, India, Antarctica, and Australia. Later it became incorporated in Pangea as the largest piece. Laurentia, also a part of Pangea, includes most of North America, Scotland and Ireland north of the Caledonian suture, Greenland, Spitzbergen, and the Chukotsk Peninsula of eastern Siberia. The oldest supercontinent for which at least a partial configuration is known is Rodinia. It formed between about 1200 and 900 Ma, fragmented at 750–600 Ma. The configuration of older supercontinents is not well known. Geologic data suggest the existence of supercontinents in the Paleoproterozoic and in the late Archean. A supercontinent cycle consists of rifting and breakup of one supercontinent, followed by a stage of reassembly in which dispersed cratons collide to form a new supercontinent, with most or all fragments in different configurations from the older supercontinent. Supercontinents have aggregated and dispersed several times during Earth History. Geologic record of supercontinent cycles is only well documented for the last two cycles: Gondwana-Pangea and Rodinia. Supercontinent cycle is closely tied to mantle processes, including convection, superplumes, and mantle plumes.
The only long-term record of climatic change is the geologic record, which suggests that the surface of the planet has had a remarkably stable thermal history. This stability is remarkable because of an inferred 30% increase in solar lumninosity since Early Archean time. The glacial record provides some of the best evidence of thermal perturbation. The major cause of glaciation may be the periodic reduction of atmospheric CO 2, which is linked, via plate tectonics, to the weathering cycle. Different glacial epochs may, however, have had different controls. What of the future? In the short term, the "Little Ice Age' climatic cycle suggests warming for about the next 1000 years. Global cooling should follow as the Earth descends into the next severe glaciation predicted by Milankovitch theory. Anthropogenic contribution to the greenhouse effect should enhance the short-term warming trend. -from Author
Precambrian palaeomagnetic data from Gondwana are reviewed with the goal of assessing the duration and magnitude of major intercratonic movements which may have occurred within the supercontinent during its evolution. The data suggest that Gondwana existed only from latest Precambrian or early Palaeozoic times up until its breakup in the Mesozoic. Prior to latest Precambrian times at least two major fragments are identifiable, East Gondwana (Australia, India, Antarctica) and West Gondwana (Africa, South America); these probably collided along the Pan-African Mozambique belt.
Earth as an Evolving Planetary System explores key topics and questions relating to the evolution of the Earth's crust and mantle over the last four billion years. This Second Edition features exciting new information on Earth and planetary evolution and examines how all subsystems in our planet-crust, mantle, core, atmosphere, oceans and life-have worked together and changed over time. Kent Condie synthesizes data from the fields of oceanography, geophysics, planetology, and geochemistry to address Earth's evolution. Two new chapters on the Supercontinent Cycle and on Great Events in Earth history New and updated sections on Earth's thermal history, planetary volcanism, planetary crusts, the onset of plate tectonics, changing composition of the oceans and atmosphere, and paleoclimatic regimes Also new in this Second Edition: the lower mantle and the role of the post-perovskite transition, the role of water in the mantle, new tomographic data tracking plume tails into the deep mantle, Euxinia in Proterozoic oceans, The Hadean, A crustal age gap at 2.4-2.2 Ga, and continental growth.
The temporal pattern of ore deposits on a constantly evolving Earth reflects the complex interplay between the evolving global tectonic regime, episodic mantle plume events, overall changes in global heat flow, atmospheric and oceanic redox states, and even singular impact and glaciation events. Within this framework, a particular ore deposit type will tend to have a time-bound nature. In other words, there are times in Earth history when particular deposit types are absent, times when these deposits are present but scarce, times when they are abundant, and still other times for which we lack sufficient data. Understanding of such secular variation provides a critical first-order tool for exploration targeting, because rocks that have formed or were deformed during a certain time slice may be very permissive for a given deposit type, whereas identification of rocks of less favorable ages would help eliminate large areas during exploration programs. Secular analysis, therefore, is potentially a powerful tool for mineral resource assessment in poorly known terranes, providing a quick filter for favorability of a given deposit type using age of host rocks.
Factors bearing on the known age distribution of a particular type of deposit include the following: (1) uneven preservation, (2) data gaps, (3) contingencies of plate motions, and (4) long-term secular changes in the Earth System. The present special issue of Economic Geology is focused on the latter factor, although all of these are interrelated. The selective preservation of certain mineral deposit types and the greater susceptibility for shallowly formed ores in tectonically active environments to be lost to erosion define a pattern that is superimposed on the secular formational trends (e.g., Groves et al., 2005a, b; Kerrich et al., 2005). With improved geochronological methods and the availability of information on important mineral deposits from most parts of the …
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
I present a general model for true polar wander (TPW), in the context of supercontinents and simple modes of mantle convection. Old, mantle-stationary supercontinents shield their underlying mesosphere from the cooling effects of subduction, and an axis of mantle upwelling is established that is complementary to the downwelling girdle of subduction zones encircling the old supercontinent. The upwelling axis is driven to the equator by TPW, and the old supercontinent fragments at the equator. The prolate axis of upwelling persists as the continental fragments disperse; it is rotationally unstable and can lead to TPW of a different flavor, involving extremely rapid (≤m/year) rotations or changes in paleolatitude for the continental fragments as they reassemble into a new supercontinent. Only after several hundred million years, when the new supercontinent has aged sufficiently, will the downwelling zone over which it amalgamated be transformed into a new upwelling zone, through the mesospheric shielding process described above. The cycle is then repeated.
Where plates converge, one-sided subduction generates two contrasting thermal environments in the subduction zone (low dT/dP) and in the arc and subduction zone backarc or orogenic hinterland (high dT/dP). This duality of thermal regimes is the hallmark of modern plate tectonics, which is imprinted in the ancient rock record as penecontemporaneous metamorphic belts of two contrasting types, one characterized by higher-pressure-lower-temperature metamorphism and the other characterized by higher-temperature-lower-pressure metamorphism. Granulite facies ultrahigh-temperature metamorphism (G-UHTM) is documented in the rock record predominantly from the Neoarchean to the Cambrian, although it may be inferred at depth in some younger Phanerozoic orogenic systems. Medium-temperature eclogite-high-pressure granulite metamorphism (E-HPGM) also is first recognized in the Neoarchean, although well-characterized examples are rare in the Neoarchean-to-Paleo-proterozoic transition, and occurs at intervals throughout the Proterozoic and Paleozoic rock record. The first appearance of E-HPGM belts in the rock record registers a change in geodynamics that generated sites of lower heat flow than previously seen, inferred to be associated with subduction-to-collision orogenesis. The appearance of coeval G-UHTM belts in the rock record registers contemporary sites of high heat flow, inferred to be similar to modern arcs, abd backarcs, or orogenic hinterlands, where more extreme temperatures were imposed on crustal rocks than previously recorded. Blueschists first became evident in the Neoproterozoic rock record, and lawsonite blueschists, low-temperature eclogites (high-pressure metamorphism, HPM), and ultrahigh-pressure metamorphism (UHPM) characterized by coesite or diamond are predominantly Phanerozoic phenomena. HPM-UHPM registers low to intermediate apparent thermal gradients typically associated with modern subduction zones and the eduction of deeply subducted lithosphere, including the eduction of continental crust subducted during the early stage of the collision process in subduction-to-collision orogenesis. During the Phanerozoic, most UHPM belts have developed by closure of relatively short-lived ocean basins that opened due to rearrangement of the continental lithosphere within a continent-dominated hemisphere as Eurasia was formed from Rodinian orphans and joined with Gondwana in Pangea, and then due to successive closure of the Paleo-Tethys and Neo-Tethys Oceans as the East Gondwanan sector of Pangea began to fragment and disperse. The occurrence of both G-UHTM and E-HPGM belts since the Neoarchean manifests the onset of a "Proterozoic plate tectonics regime," which evolved during a Neoproterozoic transition to the "modern plate tectonics regime" characterized by HPM-UHPM. The "Proterozoic plate tectonics regime" may have begun locally during the Mesoarchean to Neoarchean and may only have become global during the Neoarchean-to-Paleoproterozoic transition. The age distribution of metamorphic belts that record extreme conditions of metamorphism is not uniform. Extreme meta-morphism occurs at times of amalgamation of continental lithosphere into supercra-tons (Mesoarchean to Neoarchean) and supercontinents (Paleoproterozoic to Phaner-ozoic), and along sutures due to the internal rearrangement of continental lithosphere within a continent-dominated hemisphere during the life of a supercontinent.
Laurentia, the Precambrian core of the North American Continent, is surrounded by late Precambrian rift systems. Within the supercontinent of Pangea, North America therefore constitutes a "suspect terrane' because its origin as a discrete continent and geographic location prior to the late Paleozoic are uncertain. A geometric and geologic fit can be achieved between the Atlantic margin of Laurentia and the Pacific margin of the Gondwana craton. In the reconstruction, the ca. 1.0 Ga Grenville belt continues beneath the ensialic Andes of the present day to join up with the 1.3-1.0 Ga San Ignacio and Sonsas-Aguapei orogens of the Transamazonian craton. The fit supports and refines suggestions that Laurentia broke out from between East Antarctica-Australia and embryonic South America during the Neoproterozoic, prior to the opening of the Pacific Ocean basin and amalgamation of the Gondwana supercontinent. This implies that there may have been two supercontinents during the Neoproterozoic, before and after opening of the Pacific Ocean. -from Author
The transfer of heat to the Earth's surface shapes crustal evolution. Reactions between the lithosphere, atmosphere, hydrosphere, and biosphere produce the extreme geochemical anomalies typical of ore deposits. Transitions to ore-types characteristic of the Archaeozoic, Proterozoic and Palaeozoic represent important stages in the evolution of the Earth. The mid-Proterozoic transition is mainly related to chemical changes at the surface of the Earth. -K.A.R.
Systematic temporal variations in the distribution of several important groups of metal deposits reflect the cyclic aggregation and breakup of large continents. In particular, metal deposits that form in continental basins or are associated with anorogenic magmatism were extraordinarily abundant in the Middle Proterozoic (2.0 to 1.4 Ga), corresponding to the assembly of the first large continents. It is important to note that peaks in the abundance of continental metal deposits also coincide with the postulated Late Proterozoic supercontinent (1.0 to 0.8 Ga) and the near maximum extent of Pangea. In contrast, metal deposits that form, or are preserved, in convergent-margin orogens were most abundant in the late Archean (2.9 to 2.6 Ga), corresponding to a period of high global heat flow and rapid stabilization of continental crust, and the past 200 my, which corresponds to the present tectonic cycle. Similar mineralization was also present, albeit less abundant, in Early Proterozoic orogens, as well as in Late Proterozoic and Phanerozoic orogens. -from Authors
Middle-to-Late Proterozoic stratigraphy and metallogeny in the eastern part of the Canadian Cordillera and in South Australia are strikingly similar. In both areas, thick, predominantly shallow-water strata and their contained mineral deposits can be divided into three sequences (A, B, C) that record eposodic and prolonged continental rifting. It is proposed that Adelaidean strata of Australia were deposited adjacent to Belt-Purcell, Mackenzie Mountains and Windermere strata of the Canadian Cordillera within an epicontinental trough of a "Hudsonia' megacontinent. With the final rifting of this trough, the paleo-Pacific ocean was born. By Early Cambrian time, Australia-Antarctica was on the trailing "east' side of the nascent megacontinent, Gondwana, and was being modified on the "west' by accretion in the Pan-African event. North America, more or less surrounded by trailing edges at this time, was analogous to the Cenozoic African plate. This hypothesis accommodates the available paleomagnetic and radiometric data. It has implications for pre-Pangean plate tectonics, paleogeography, and the predictive metallogeny of both areas. -Authors
During the Proterozoic, two types of orogenesis were in operation. One involved the collision of two or more continental blocks and gave rise, where collision was orthogonal, to orogens with thickened and commonly uplifted and eroded crust and to much reworking (by thrusting and partial melting) of older continental crust. These collisional orogens were associated with little or no crustal growth. The second type of orogenesis involved the growth and amalgamation of many juvenile island arcs and the slices of oceanic crust or oceanic plateaus, which were in places mutually sealed by intervening accretionary wedges, and this process typically gave rise to orogens that contained little or no older crustal material. These accretionary orogens are characterised by considerable crustal growth; their crustal thickening, uplift, and erosion were variable. This subdivision of Proterozoic orogens into two different types is important for the understanding of crustal evolution. This chapter describes key examples for evaluating the principal features of Proterozoic orogens in the light of current ideas of late Phanerozoic tectonics.
In this review we summarize the major lithological and geochemical characteristics of the Mesoarchean (ca. 3075 Ma) Ivisaartoq greenstone belt, Nuuk region, southern West Greenland. In addition, the geological characteristics of the Ivisaartoq greenstone belt are compared with those of other Archean greenstone belts in the area. The Ivisaartoq greenstone belt is the largest Mesoarchean supracrustal lithotectonic assemblage in the Nuuk region. The belt contains well-preserved primary magmatic structures including pillow lavas, volcanic breccias, and cumulate (picrite) layers. It also includes variably deformed gabbroic to dioritic dikes, actinolite schists, serpen-tinites, siliciclastic sediments, and minor cherts. The Ivisaartoq rocks underwent at least two stages of postmagmatic metamorphic alteration, including seafloor hydro-thermal alteration and syn- to post-tectonic calc-silicate metasomatism, between 3075 and 2961 Ma. The trace element systematics of the least altered rocks are consistent with a subduction zone geodynamic setting. On the basis of lithological similarities between the Ivisaartoq greenstone belt and Phanerozoic forearc/backarc ophiolites, and intra-oceanic island arcs, we suggest that the Ivisaartoq greenstone belt represents a relic of dismembered Mesoarchean suprasubduction zone oceanic crust. The Sm-Nd isotope system appears to have remained relatively undisturbed in picrites, tholeiitic pillow lavas, gabbros, and diorites. As a group, picrites have more depleted initial Nd isotopic signatures (eNd = +4.2 to +5.0) than gabbros, diorites, and tholeiitic basalts (eNd = +0.3 to +3.1), consistent with a strongly depleted mantle source. In some areas gabbros include up to 15 cm long white inclusions (xenoliths). These inclusions are composed primarily (>90%) of Ca-plagioclase and are interpreted as anorthositic cumulates of the lower oceanic crust brought to the surface by upwelling gabbroic magmas. Alternatively, the inclusions may represent the xenoliths from older (>3075 Ma) anorthositic crust onto which the Ivisaartoq magmas were emplaced as an autochthonous sequence. However, no geological evidence has been found for such older anorthositic crust in the region. The anorthositic cumulates have significantly higher initial eNd values (+4.8 to +6.0) than the surrounding gabbroic matrix (+2.3 to +2.8), suggesting two different mantle sources for these rocks.
Many, if not all, of the long-term fluctuations in geological processes operating on Earth’s surface are tectonically driven and related to the interplay of plate tectonics and deep mantle dynamics resulting in supercontinental cycles and (super)plume events (Condie et al. 2001; Condie 2004). These processes include the amalgamation, dispersal, collision and geographic position of major land-masses which dictate volcanic and hydrothermal activities, changes in sea level and the global patterns of ocean circulation, thermal isolation of continents, climate change, rate of continental weathering and its influence on seawater composition, and atmospheric oxygen budget via control of burial and recycling of carbon and sulphur. Further, all of these are reflected in biological processes. However, well-documented and well-constrained examples of this conceptual model have been developed and tested largely on Phanerozoic rocks (Valentine and Moores 1970; Fischer 1984; Marshall et al. 1988; Hardebeck and Anderson 1996; Berner 2006; Rampino 2010). Although there have been a number of attempts to apply such concepts to “Deep Time”, in particular, the Palaeoproterozoic (Nance et al. 1986; Windley 1993; Lindsay and Brasier 2002; Condie et al. 2009), testing and verification of the models is challenging. The existence of continental masses, their palaeogeography and sizes in the late Archaean-early Palaeoproterozoic remain hypothetical and robust plate reconstructions are hampered by the small number of reliable palaeomagnetic data (Evans and Pisarevsky 2008).
The main conclusion of this paper is that some form of plate tectonics started at ca. 3.0 Ga or possibly as early as 3.1 Ga., and that, since then, plate tectonics has steadily become dominant over plumes as a mechanism of heat loss. Modern plate tectonics started at ca. 0.6 Ga. The volume history of the continental crust is one of fast Early Archean growth to generate a, probably, globally continuous crust, then a growth, probably exceeded or balanced, long-term, by crustal return to the mantle reservoir.
Geophysical and geological observations document that beneath the submerged forearc, processes of sediment subduction and subduction erosion move large volumes of material toward the mantle. The conveying system is the subduction channel separating the upper plate from the underthrusting ocean plate. Globally, the zero-porosity or solid-volume rate at which continental debris is shuttled toward the mantle is estimated to be similar to 2.5 km(3)/yr. To deliver this volume, the average thickness of the subduction channel is similar to 1.0 km. Some deeply subducted material is returned to the surface of Earth as a component of arc magma or as tracks of high-P/T crustal underplates. But over long periods of time (>50 m.y.), most of the removed material is evidently recycled to the mantle. Applying Cenozoic recycling rates to the past astonishingly implies that since 2.5 Ga a volume of continental crust equal to the standing inventory of similar to 6 x 10(9) km(3) has been removed from the surface of Earth. This minimum estimate does not include crustal material recycled at continental collision zones nor reliable estimates of recycling where large accretionary bodies form. The volume of demolished crust is so large that recycling must have been a major factor determining the areal pattern and age distribution of continental crust. The small areal exposure of Archean rock is thus probably more a consequence of long-term crustal survival than the volume originally produced. Reconstruction of older supercontinents is made difficult if not unachievable by the progressive truncation of continental edges effected by subduction zone recycling, in particular by subduction erosion.