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Permian tectonic framework and palaeogeography of SE Asia
Abstract
The principal continental lithospheric terranes, now comprising SE Asia and that existed in the Permian, are the South China/Indochina Super Terrane, and the Sibumasu, Simao, West Burma and SW Borneo/Semitau terranes. The Simao Terrane is here regarded a separate terrane, derived from South China by back-arc spreading in the Lower Carboniferous, rather than as an extension of Indochina. The main Palaeo-Tethys ocean in Thailand is identified as being represented by the Chiang Mai and Sra Kaeo sutures, and the eastern boundary of the Sibumasu Terrane is thus interpreted to lie farther west in Thailand than previously inferred. The Nan-Uttaradit Suture is interpreted as representing a marginal back-arc basin, and contiguous with the Ailaoshan and Jinshajiang sutures in SW China. The South China/Indochina Super Terrane, and the Simao Terrane were located within the Palaeo-Tethys in equatorial latitudes during the Permian, where they, together with North China, exhibit Cathaysian floras and faunas. The Sibumasu Terrane was located on the NW Australian margin of Gondwana until the Sakmarian. Major shifts in faunal affinities from Gondwana province faunas to an independent Sibumasu Province and then to assimilation into the Cathaysian Province, records the separation and rapid northward drift of Sibumasu after the Late Sakmarian. The principal Permian palaeogeographic models for the region are assessed for internal consistencies and conflicts.
... The second issue relates to the nature of the Ailaoshan Ocean. Based on fossil evidence and zircon ages of volcanic rocks within the ATZ, the Ailaoshan Ocean was suggested to open as a spreading back-arc Basin due to the eastward subduction of the Main Palaeo-Tethyan Ocean Metcalfe, 2002Metcalfe, , 2006Wang et al., 2000;Zi et al., 2010). In contrast, sedimentary and magmatic records supported the Ailaoshan Ocean as a mature Atlantic-type oceanic Basin Xia et al., 2016). ...
... Block to the same side of both the LSS and LTZ (Ding et al., 2013;Jin, 2002;Metcalfe, 2002). The subsequent subduction and closure of the ocean in this region were recorded by the Devonian-Triassic arcrelated magmatic rocks and the 243-217 Ma high-pressure metamorphic rocks in Qiangtang and post-collisional granitic rocks paralleling to those magmatic and metamorphic rocks from the LTZ (Figures 5, 7 and 8;Li et al., 2006;Li et al., 2009;Li et al., 2006;Pan et al., 2012;Peng et al., 2013;Peng et al., 2015;. ...
... The Ailaoshan Ocean was argued to open as a back-arc Basin accounting for the subduction of the Main Palaeo-Tethyan Ocean Metcalfe, 2002Metcalfe, , 2006Pan et al., 2012;Wang et al., 2000). However, the discovery of 383-334 Ma N-MORB type ophiolite in the ATZ indicated the opening of the Ailaoshan Ocean predating the initial subduction processes of the Main Palaeo-Tethyan Ocean at 289-237 Ma Jian et al., 2009aJian et al., , 2009bWang, Qian, et al., 2018). ...
Subduction and closure of the Palaeo‐Tethyan ocean in the south‐eastern (SE) Tibetan Plateau accounted for the amalgamation of the Indochina Block with the Sibumasu and Yangtze blocks during the Triassic, however, the spatial distribution of the Main Palaeo‐Tethyan ocean and the nature of the Ailaoshan ocean in this region remain controversial. This is partially due to the absence of related magmatic records in the middle‐north segment of the Lancangjiang tectonic belt (LTZ) and consequently, the lack of regional comparison with the Ailaoshan tectonic belt (ATZ). In this contribution, we reported for the first time the presence of subduction‐related Triassic dioritic‐granitic rocks from the Chongshan metamorphic belt (CMB) and the Diancangshan metamorphic belt (DMB) along both sides of the Simao terrane. Zircon U–Pb‐Hf isotopic and whole‐rock geochemical data for these dioritic‐granitic rocks and 135 previously published magmatic rocks in the LTZ, ATZ and the Longmu Co‐Shuanghu suture (LSS) are compared and place important constraints on (1) the spatial distribution of the Palaeo‐Tethyan ocean in this region and (2) the nature of the Ailaoshan Ocean. All these dioritic‐granitic samples from the CMB and DMB yielded Triassic crystallization ages from 225 to 251 Ma, representing late‐stage magmatic records for the Palaeo‐Tethyan evolution in the middle‐north segment of both the LTZ and ATZ in this region. These Triassic dioritic‐granitic rocks in the CMB and DMB share similar geochemical features. Dioritic samples display positive ε Hf ( t ) values and relatively high MgO, Cr, Ni contents, moderately differentiated rare earth element (REE) patterns and depletion in Nb‐Ta‐Ti, suggesting their generation from partial melts of metasomatized mantle wedge. Granitic rocks are mostly S‐type with low MgO contents but high K 2 O/Na 2 O and A/CNK ratios, mainly generated by regional clastic rocks dominant by juvenile contributions, except for granodiorite samples CS1601 and DC1734‐2, exhibiting identical geological features subduction‐derived hybridized magma from regional clastic sediments and basalts. Our discovery of the Triassic dioritic‐granitic rocks in the CMB stands as the first direct evidence for the Main Palaeo‐Tethyan evolution in the middle‐north segment of the LTZ. This discovery bridges 135 contemporaneous reported magmatic records and supports the spatial distribution of the Main Palaeo‐Tethyan ocean from the LTZ to the LSS. Our Triassic dioritic‐granitic rocks in the CMB and DMB recorded comparable late‐stage evolution involving slab break‐off of the Main Palaeo‐Tethyan ocean and the Ailaoshan Ocean, respectively. Together with previous studies, the Ailaoshan ocean should be a wide oceanic Basin that shares similar time span and evolution processes as the Main Palaeo‐Tethyan ocean.
... The eastern Paleo-Tethys is interpreted as an ancient Paleozoic ocean between Eurasian continental blocks (e.g. Indochina and South China) and Gondwanan Cimmerian continents (e.g. the Sibumasu Block) (Şengör, 1979;Şengör et al., 1984;Zhong, 1998;Metcalfe, 2002Metcalfe, , 2006Metcalfe, , 2011Metcalfe, , 2013Cawood et al., 2018). Understanding the opening and consumption of the Paleo-Tethys is important for reconstructing the tectonic evolution of Pangea in southeast Asia (Şengör, 1979;Şengör et al., 1984;Zhong, 1998;Metcalfe, 2002, 2006, 2011, 2013Cawood et al., 2018;Wang et al., 2018;Zhao et al., 2018). ...
... Indochina and South China) and Gondwanan Cimmerian continents (e.g. the Sibumasu Block) (Şengör, 1979;Şengör et al., 1984;Zhong, 1998;Metcalfe, 2002Metcalfe, , 2006Metcalfe, , 2011Metcalfe, , 2013Cawood et al., 2018). Understanding the opening and consumption of the Paleo-Tethys is important for reconstructing the tectonic evolution of Pangea in southeast Asia (Şengör, 1979;Şengör et al., 1984;Zhong, 1998;Metcalfe, 2002, 2006, 2011, 2013Cawood et al., 2018;Wang et al., 2018;Zhao et al., 2018). Remnants of the Paleo-Tethys in China are represented mainly by the Changning-Menglian-Longmu Co-Shuanghu orogenic belt (CMLS) (i.e. the central belt) between the Sibumasu and Indochina blocks and the Jinshajiang-Ailaoshan Suture Zone (i.e. the eastern belt) between the Lanping-Simao Block (the northwards extension of the Indochina Block) and the South China Block ( Fig. 1a; Metcalfe, 2002Metcalfe, , 2006Metcalfe, , 2011Metcalfe, , 2013Faure et al., 2014Faure et al., , 2016Wang et al., 2018). ...
... Understanding the opening and consumption of the Paleo-Tethys is important for reconstructing the tectonic evolution of Pangea in southeast Asia (Şengör, 1979;Şengör et al., 1984;Zhong, 1998;Metcalfe, 2002, 2006, 2011, 2013Cawood et al., 2018;Wang et al., 2018;Zhao et al., 2018). Remnants of the Paleo-Tethys in China are represented mainly by the Changning-Menglian-Longmu Co-Shuanghu orogenic belt (CMLS) (i.e. the central belt) between the Sibumasu and Indochina blocks and the Jinshajiang-Ailaoshan Suture Zone (i.e. the eastern belt) between the Lanping-Simao Block (the northwards extension of the Indochina Block) and the South China Block ( Fig. 1a; Metcalfe, 2002Metcalfe, , 2006Metcalfe, , 2011Metcalfe, , 2013Faure et al., 2014Faure et al., , 2016Wang et al., 2018). ...
The eastern Paleo-Tethyan Jinshajiang–Ailaoshan–Song Ma (JASM) orogenic belt in the Southeast Tibetan Plateau represents the tectonic boundary between the Indochina and South China blocks. Regional Cenozoic lithospheric strike-slip movements caused by the India–Asia collision have modified many of the pristine geological records associated with the Indosinian orogeny. The lack of reliable petrological evidences, particularly of high-pressure (HP) metamorphism, has hindered the tracing of the evolutionary history of the Paleo-Tethyan orogenic belt. We report the mineralogy, geochemistry, geochronology and thermodynamic modelling of eclogite lenses/blocks and their host garnet–phengite schists from the Song Ma Suture Zone (SMSZ) of Northwest Vietnam and reveal their protolith origins and metamorphic evolution. The eclogites are geochemically similar to mid-ocean ridge basalt, showing weak depletions in high field-strength elements, positive to slightly negative whole-rock ɛNd(t) ratios (–1.69 to +5.15) and slightly high 87Sr/86Sr(t) ratios (0.70466–0.70834). The igneous protolith of the eclogites formed in the late Silurian (425.4 ± 3.6 Ma; igneous zircon dating, 638–459 Ma TDM dating), which makes them the oldest known mid-ocean ridge mafic rocks in an ancient Paleo-Tethyan Ocean. Various eclogites preserve similar peak mineral assemblages (garnet + omphacite + phengite + rutile + quartz ± epidote/clinozoisite ± kyanite ± winchite) under indistinguishable peak conditions. Their prograde P–T trajectories show a uniform pattern of progressive heating and weak compression along a geothermal gradient of 8–10 °C/km, indicating a warm subduction setting at a low angle that contrasts with the cold oceanic subduction recorded in the adjacent Paleo-Tethyan suture zones. Combined with detrital U–Pb ages from previous studies, our geochronological data indicate that the host schists originated from continental crust within the South China Block and underwent a pervasive Triassic HP metamorphism related to the Indosinian orogeny. The eclogites and host schists yielded HP metamorphic ages of 239–234 Ma and retrogressive amphibolite-facies metamorphic ages of 231–229 Ma, suggesting rapid cooling (14.0–21.6 °C/Myr) and exhumation (6.4 km/Myr) from the mantle to the crust. The Song Ma eclogites and their host schists formed when the final ocean closure transitioned to the initial Indochina–South China collision. The Song Ma eclogites and their host schists provide essential information on the opening and closure of the eastern Paleo-Tethys and the subsequent amalgamation of southeast Asian continental fragments.
... The Sanjiang (Three River) orogen in southwestern China is regarded as the southeastern extension of the Tibetan-Himalayan orogen and formed by the amalgamation of Gondwana-derived continental blocks during the Paleozoic-Mesozoic (Sengör, 1984;Zhong, 1998;Sone and Metcalfe, 2008;Metcalfe, 2013;Deng et al., 2014aDeng et al., , 2017. The Changning-Menglian Suture Zone (CMSZ) represents the main Paleo-Tethys Ocean (Zhong, 1998;Feng, 2002;Metcalfe, 2002Metcalfe, , 2013Feng et al., 2005;Sone and Metcalfe, 2008;Hennig et al., 2009;Fan et al., 2015), and probably extends to the Longmuco-Shuanghu suture zone in the north and to the Chiang Mai-Inthanon suture zone in the south (Metcalfe, 2013;Deng et al., 2014b). Separating the Baoshan block to the west and the Simao block to the east, the CMSZ signifies the collision between these two blocks (Zhong, 1998;Feng, 2002;Metcalfe, 2002Metcalfe, , 2013Feng et al., 2005;Sone and Metcalfe, 2008;Deng et al., 2014c). ...
... The Changning-Menglian Suture Zone (CMSZ) represents the main Paleo-Tethys Ocean (Zhong, 1998;Feng, 2002;Metcalfe, 2002Metcalfe, , 2013Feng et al., 2005;Sone and Metcalfe, 2008;Hennig et al., 2009;Fan et al., 2015), and probably extends to the Longmuco-Shuanghu suture zone in the north and to the Chiang Mai-Inthanon suture zone in the south (Metcalfe, 2013;Deng et al., 2014b). Separating the Baoshan block to the west and the Simao block to the east, the CMSZ signifies the collision between these two blocks (Zhong, 1998;Feng, 2002;Metcalfe, 2002Metcalfe, , 2013Feng et al., 2005;Sone and Metcalfe, 2008;Deng et al., 2014c). The Simao block represents the northern segment of the Indochina block (Metcalfe, 1996(Metcalfe, , 2006(Metcalfe, , 2013Sone and Metcalfe, 2008), whereas the Baoshan block was suggested to be the northern segment of the Sibumasu block (Metcalfe, 1996(Metcalfe, , 2013Zhong, 1998;Feng, 2002;Sone and Metcalfe, 2008). ...
Porphyry copper deposits are commonly associated with porphyries generated in arc environments. Assessing the
contemporaneous arc volcanic rocks provides crucial insights into the potential for porphyry copper mineralization. The Triassic Yidun arc in the northern part of the Sanjiang orogen in southwest China, which formed in
association with the subduction of the Paleo-Tethys Oceanic slab, hosts several porphyry copper deposits.
However, the potential for porphyry copper mineralization in the Yunxian-Jinggu volcanic arc in the southern
part of the Sanjiang orogen, which was also linked to the subduction of the Paleo-Tethys Oceanic slab, remains
unclear. This study reports zircon U–Pb ages, trace element compositions and Hf isotopes, and whole-rock
element compositions and Sr–Nd–Pb isotopes of the basaltic-andesitic-dacitic rocks in the Yunxian-Jinggu volcanic arc. Zircon SHRIMP U–Pb dating of the Wenyu basalts and andesites yielded ages of 244.3 ± 1.9 Ma and
242.5 ± 2.5 Ma, respectively. The basalts have arc geochemical affinities with εHf (t) values of 2.3 to 9.3, εNd(t)
values of –0.6 to 0.2, and (
87Sr/86Sr)i values of 0.7065 to 0.7068. They have high Ba concentrations (~ 550
ppm), highly variable Ba/La ratios (0.01 to 0.10), and a narrow range of Th/Yb ratios (1.2 to 1.9). These
characteristics suggest that the basalts were derived from mantle metasomatized by fluids likely released from
the subducted Paleo-Tethys slab. The Wenyu andesites, with εHf (t) values range from 1.6 to 7.0, εNd (t) value of
–0.4, and (
87Sr/86Sr)i value of 0.7031, along with distinct Pb isotopes, were probably produced through basaltic
magmas undergoing crustal fractional crystallization. The Minle dacites, sharing similar εHf (t) value (–1.6 to
10.7) but lower εNd (t) values (–3.1 to –4.9) compared to Wenyu volcanics, are interpreted as derived from partial
melting of basaltic magmas with contamination from ancient crustal components. The zircon Eu/Eu* ratios
(mostly < 0.4), zircon ΔFMQ value (–0.6 ± 1.1), and bulk-rock Sr/Y ratios (< 10.3) for the Yunxian-Jinggu
volcanic rocks indicate that co-genetic intrusions, if present, would likely be less hydrous and less oxidized,
making them less favorable for porphyry copper mineralization.
... The Sn deposits in southwestern Yunnan are mainly distributed in the Tengchong Block, followed by the Baoshan Block and the CMSZ (Lu et al., 2009;Wang et al., 2014a;Deng et al., 2014Deng et al., , 2017 (Fig. 1). The CMSZ begins in Changning in the north and moves through Shuangjiang, Tongchangjie, and Laochang, which separates the Sibumasu Block in the west from the Indochina Block in the east (Fig. 1b, Fang et al., 1994;Metcalfe, 2002;Sone and Metcalfe, 2008;Wang et al., 2010;Sone et al., 2012;Fan et al., 2015;Deng et al., 2017;Wang et al., 2019aWang et al., , 2020Zhao et al., 2021a, b) (Fig. 1b). During the Late Paleozoic to the Mesozoic period, the CMSZ represented the central ocean basin of the Paleo-Tethys and was mainly influenced by the initial spreading and subduction to final closure of the Paleo-Tethys Ocean (Li et al., 2008;Zhai et al., 2011a, b;Metcalfe, 2013;Deng et al., 2014). ...
... There exists an affinity between the Baoshan-Tengchong Block and the Sibumasu Block. A cool-water fauna and glacial-marine diamictites suggest that the Baoshan-Tengchong Block is the remnant of a Gondwanan continent (Metcalfe, 2002;Fang et al., 1994;Zhong, 1998). A thick layer of Paleozoic and Mesozoic strata is unconformably surmounted by the Proterozoic amphibolite facies metamorphic basement (Yunnan, 1990). ...
... The outcrops and floated rocks of cumulus ultramafic rocks, such as dunite and peridotite, were also discovered along the Ma-Hin Creek and its distributary channels in the volcanic terrain [51]. These units have been interpreted as part of the Chiang Rai-Chiang Mai Volcanic Belt formed in back-arc and oceanic basin environments and potentially represented relics of the Palaeo-Tethys Ocean, which separated the Shan-Thai and Indochina cratons [52,53]. The emergence of ultramafic rocks in the study area is a result of a closure of the Palaeo-Tethys Ocean in the Late Triassic induced by an oceanic crust subduction and a subsequent collision of the cratons forming a suture zone. ...
Ultramafic rocks become promising candidates for carbon sequestration by enhanced carbon dioxide (CO2) mineralization strategies due to their highly CO2-reactive mineral composition and its abundant availability. This study reports a mineralogy and microtextures of a representative ultramafic rock from the Ma-Hin Creek in northern Thailand and observes evidence of CO2 mineralization occurring through the interaction between CO2 and the rock with the existence of water under ambient conditions. After sample collection, rock description was determined by optical petrographic analysis. The rock petrography reveals a cumulated wehrlite comprising over 50% olivine and minor amounts of clinopyroxene, plagioclase, and chromian spinel. Approximately 25% of the wehrlite has altered to serpentine and chlorite. A series of CO2 batch experiments were conducted on six different rock sizes at a temperature of 40°C and pressure of 1 atm over five consecutive days. The post-experimental products were dried, weighed, and geochemically analyzed to detect changes in mineral species. Experimental results showed that product weight and the presence of calcite increased with reducing grain size. Additionally, the modal mineralogy of the wehrlite theoretically suggests a potential CO2 uptake of up to 53%, which is higher than the average uptake values of mafic rocks. These findings support the suitable rock investigation approach and the preliminary assessment of carbon mineralization potential, contributing to enhanced rock weathering techniques for CO2 removal that could be adopted by mining and rock supplier industries.
... Southeast Asia is formed from an arrangement of small continental blocks, such as the Yangtze Block, Indochina Block, Simao terrane, Sibumasu terrane, and West Burma terrane, which are divided by suture zones or fault lines (Metcalfe, 2002). The Song Da district in northern Vietnam is limited by the Ailao Shan-Red River Fault to the northeast and the Song Ma suture to the southwest. ...
The Permian (~260 Ma) Song Da volcanic suite in Vietnam is one of very few known occurrences of Phanerozoic ultramafic volcanic rocks that are similar in composition to komatiites. Despite continuous efforts to determine the primary melt composition of Song Da ultramafic lavas, the concentrations of the volatile and fluid-mobile elements are still poorly constrained due to widespread alteration and low-grade metamorphism of bulk rocks. This study reports high-precision in-situ major- and trace element abundances in host olivine and inclusions of melt and Cr-spinel from the Song Da ultramafic lavas. Two different types were identified: low-Ti lavas, previously described as komatiites, and newly discovered Ti- and Na-rich picrites. The application of olivine-melt Sc/Y, olivine-spinel Al, and olivine-melt Fe/Mg geothermometers indicates crystallization temperatures of up to 1450 ◦C for the Song Da low-Ti suite, which are within the range of komatiite crystallization temperatures, and up to 1330 ◦C for the high-Ti picrites. These conditions correspond to mantle potential temperatures of 1590 ◦C and 1450 ◦C, respectively. The estimation of oxygen fugacity, based on V partitioning between olivine and melt and Fe2+/Fe3+ between spinel and melt, indicates that low-Ti melts crystallized in a closed system under reducing conditions starting from one to half an order of magnitude below the QFM buffer. The high-Ti melt crystallized at higher oxygen fugacity (ΔQFM +0.5) in a buffered open system. The primary melt of the Song Da komatiites contained 0.7 wt% H2O, which was likely entrained from the hydrated Mantle Transition Zone (MTZ) by a partially molten plume. Our results indicate that the Song Da low-Ti ultramafic volcanics were likely derived from an ultramafic komatiite- ike parental melt with an MgO content between 21 and 23 wt%. It was produced by a high degree (>26%) of partial melting of a depleted mantle source. The high-Ti picrite melt had 17–18 wt% MgO and was produced by a lower degree of partial melting (<9%) in a older part of the same plume.
... The outcrops and floated rocks of the ultramafic rocks, such as dunite and peridotite, were discovered along the Ma-Hin Creek and its distributary channels in volcanic terrain [51]. These units have been interpreted as part of the Chiang Rai-Chiang Mai Volcanic Belt formed in back-arc and oceanic basin environments and potentially represent relics of the Palaeo-Tethys Ocean, which separated the Shan-Thai and Indochina cratons [52,53]. The emergence of ultramafic rocks in the study area is a result of a closure of the Palaeo-Tethys Ocean in the Late Triassic induced by an oceanic crust subduction and a subsequent collision of the cratons forming a suture zone. ...
Ultramafic rocks are promising candidates for carbon sequestration by enhanced carbon dioxide (CO2) mineralization strategies due to their highly CO2-reactive mineral composition and their abundant availability. This study reports the mineralogy and microtextures of a representative ultramafic rock from the Ma-Hin Creek in northern Thailand and provides evidence of CO2 mineralization occurring through the interaction between CO2 and the rock in the presence of water under ambient conditions. After sample collection, rock description was determined by optical petrographic analysis. The rock petrography revealed a cumulated wehrlite comprising over 50% olivine and minor amounts of clinopyroxene, plagioclase, and chromian spinel. Approximately 25% of the wehrlite had altered to serpentine and chlorite. A series of CO2 batch experiments were conducted on six different rock sizes at a temperature of 40 °C and pressure of 1 atm over five consecutive days. The post-experimental products were dried, weighed, and geochemically analyzed to detect changes in mineral species. Experimental results showed that product weight and the presence of calcite increased with reducing grain size. Additionally, the modal mineralogy of the wehrlite theoretically suggests potential CO2 uptake of up to 53%, which is higher than the average uptake values of mafic rocks. These findings support the rock investigation approach used and the preliminary assessment of carbon mineralization potential, contributing to enhanced rock weathering techniques for CO2 removal that could be adopted by mining and rock supplier industries.
... The modern Southeast Asia consists of an assemblage of a series of continental blocks (e.g., Tarim, Qaidam, North Qiangtang, South Qiangtang, Lhasa, India, Sibumasu, Indochina, and South China). These microcontinents were successively rifted from northern Gondwana and then progressively accreted to the southern margin of Laurasia during the Late Paleozoic to Cenozoic, with the opening and closing of the Proto-, Paleo-, and Neo-Tethys oceans [e.g., Faure et al., 2014, Metcalfe, 2002, 2011, 2013, 2021, Metcalfe et al., 2017, Sone and Metcalfe, 2008. The tectonic event related to the Eastern Paleo-Tethys Ocean closure was called the "Indosinian movement" [Deprat, 1914, 1915, Fromaget, 1932, 1941. ...
... The north-south trending Loei fold belt (or Loei-Phetchabun Terrane) is considered as the western and southwestern part of the Indochina Terrane (Burrett et al., 2021). Tropical Permian limestones belonging to the histories of the terranes, platforms and the basin are still controversial (e.g., Helmcke, 1985;Chutakositkanon et al., 1999;Chonglakmani and Helmcke, 2001;Metcalfe, 2002Metcalfe, , 2011Ueno and Charoentitirat, 2011;Burrett et al., 2014). ...
... The South China Block was marked by significant tectonic events during the Triassic, specifically collision and amalgamation with the Indochina Block. This gave rise to a series of fault zones (including ductile shear zones) and magmatic rocks along the southern margin of the South China Block and northeastern Vietnam (Metcalfe, 1996(Metcalfe, , 2002Carter et al., 2001;Lepvrier et al., 2004;Cawood, Wang et al. (2007) 2005; Wang et al., 2007Wang et al., , 2013Wang et al., , 2021Lin et al., 2011;Chen et al., 2013Chen et al., , 2014. Wang et al. (2007) (Faure et al., , 2016Liu et al., 2015;. ...
The Triassic was a crucial period in the tectonic evolution of the South China Block. Research on tectonic deformation during this period provides information on intracontinental orogenic mechanisms in South China. In this study, alongside thermochronological analyses, we examine the macroscopic and microscopic structural features of the Rongxian ductile shear zone, located south of the Darongshan granite in the southeastern part of Guangxi Province, on the southern margin of South China. Sinistral shear is indicated by the characteristics of rotated σ‐type feldspar porphyroclasts, stretching lineations defined by elongated quartz grains and the orientations of quartz c ‐axes. LA‐ICP‐MS U‐Pb dating of zircons from two samples of granitic mylonite and one of granite yielded ages of ca. 256 Ma. Furthermore, two samples of granitic mylonite yield muscovite ⁴⁰ Ar/ ³⁹ Ar plateau ages of 249‐246 Ma. These results indicate that the Rongxian ductile shear zone resulted from Early Triassic deformation of the late Permian Darongshan granite. This deformation was likely related to the closure of the eastern Paleo‐Tethys Ocean and the subsequent collision of the South China and Indochina blocks, during the early stage of the Indosinian orogeny.
... Granitoids in continental arcs may characterize the subduction process of oceanic lithosphere beneath continental plate (Qi et al. 2014(Qi et al. , 2016Moghadam et al. 2015;Pereira et al. 2015;Faisal et al. 2016;Li et al. 2018;Sajid et al. 2018), which provide important constraints on the subduction history and the amalgamation of continents and supercontinents (Ashwal et al. 2002(Ashwal et al. , 2013Pham et al. 2012;Qi et al. 2014Qi et al. , 2016Li et al. 2018;Mastoi et al. 2020;Baig et al. 2021;Rehman et al. 2021). The South China and Indochina blocks are important integral components in the palaeogeographic reconstruction of the Rodinia supercontinent (Metcalfe 2002(Metcalfe , 2006Lepvrier et al. 2004;Boger 2011;Johnson et al. 2011). Previous studies have reported widely distributed Neoproterozoic granitoids in the Panxi-Hannan Belt and Jiangnan Orogen of the South China Block, as well as Phan Si Phan Zone in NW Vietnam ( Figure 1a) (Pham et al. 2009;Qi et al. 2014Qi et al. , 2016Yang et al. 2016;Cawood et al. 2018), and various tectonic models have been proposed to interpret the tectonic settings of these granitoids, such as rift setting (Zheng et al. 2008), subduction setting (Zhao and Zhou 2007;Pham et al. 2009;Huang et al. 2009;Zhao et al. 2011;Qi et al. 2014Qi et al. , 2016, and intracontinental orogeny (Shu et al. 2011). ...
... Granitoids in continental arcs may characterize the subduction process of oceanic lithosphere beneath continental plate (Qi et al. 2014(Qi et al. , 2016Moghadam et al. 2015;Pereira et al. 2015;Faisal et al. 2016;Li et al. 2018;Sajid et al. 2018), which provide important constraints on the subduction history and the amalgamation of continents and supercontinents (Ashwal et al. 2002(Ashwal et al. , 2013Pham et al. 2012;Qi et al. 2014Qi et al. , 2016Li et al. 2018;Mastoi et al. 2020;Baig et al. 2021;Rehman et al. 2021). The South China and Indochina blocks are important integral components in the palaeogeographic reconstruction of the Rodinia supercontinent (Metcalfe 2002(Metcalfe , 2006Lepvrier et al. 2004;Boger 2011;Johnson et al. 2011). Previous studies have reported widely distributed Neoproterozoic granitoids in the Panxi-Hannan Belt and Jiangnan Orogen of the South China Block, as well as Phan Si Phan Zone in NW Vietnam ( Figure 1a) (Pham et al. 2009;Qi et al. 2014Qi et al. , 2016Yang et al. 2016;Cawood et al. 2018), and various tectonic models have been proposed to interpret the tectonic settings of these granitoids, such as rift setting (Zheng et al. 2008), subduction setting (Zhao and Zhou 2007;Pham et al. 2009;Huang et al. 2009;Zhao et al. 2011;Qi et al. 2014Qi et al. , 2016, and intracontinental orogeny (Shu et al. 2011). ...
A combined study of whole-rock geochemical and Sr-Nd isotopic data, and zircon U-Pb geochronological and Hf isotopes has been carried out for several Neoproterozoic intrusions, including the Lung Thang, Posen and Sin Quyen in the Phan Si Pan Zone, northwest Vietnam to constrain their age, petrogenesis and tectonic implications. The Lung Thang and Posen intrusions, mainly composed of granodiorite, were formed at 803–777 Ma and are characterized by moderate SiO2 (64.43–66.65 wt.%), and K2O (4.05–4.89 wt.%), with A/CNK and A/NK values of (0.94–1.03) and (1.72–2.11), respectively. They have negative whole-rock εNd(t) (−6.16 to −3.73) and zircon εHf(t) values (−7.9 to −4.1), which suggest that the Lung Thang and Posen intrusions were generated by partial melting of ancient, K-rich crustal rocks. The Sin Quyen intrusion, occurring as dykes, is composed of monzodiorite and was emplaced at 742 ± 3 Ma. The Sin Quyen intrusion has high alkalies (K2O+Na2O = 7.42–7.47 wt.%), and low MgO (<1.31 wt.%) and Ni (6.55–6.93 ppm), with A/CNK and A/NK values of (0.67–0.68) and (1.64–1.68), respectively. Their whole-rock εNd(t) and zircon εHf(t) values are −6.15 to −5.92 and −5.8 to + 8, respectively. These geochemical characteristics suggest that the Sin Quyen intrusion was produced by the partial melting of ancient crustal sources mingled with mantle-derived components. Geochemically, the Lung Thang, Posen and Sin Quyen intrusions are medium- to high-K, calc-alkaline in nature and show enrichment in LILE (Th, U, K, Rb) and LREE, and strong negative anomalies of Nb, Ta, and Ti. Such geochemical characteristics suggest that they formed in a subduction-related tectonic environment. The geochronological and geochemical correlation of these intrusions with those along the southwestern margin of the Yangtze Block in South China suggests that the Phan Si Pan zone in northwestern Vietnam is a constituent of the SW Yangtze Block. Additionally, these intrusions show a significant correlation with other contemporaneous magmatic rocks in the northeast Indochina Block, Lhasa Block, the northwestern margin of Greater India as well as those in Seychelles and northern Madagascar. This correlation suggests a similar history and synchronous episode of crustal growth/recycling in an Andean-type arc system along the western and northern margin of the Rodinia supercontinent during the Neoproterozoic.
... From west to east, the CMOB is dominantly composed of ophiolitic mélange, oceanic seamount volcano-sedimentary suites, LT/HP metamorphic complexes, Lincang granite batholiths, and Yunxian-Jinggu arc volcanic rocks (Fang et al., 1994;Mo et al., 1998;Peng et al., 2008;Jian et al., 2009a;Jian et al., 2009b;Fan et al., 2015;Wang et al., 2019Wang et al., , 2020. The spatial distribution patterns of distinct tectonic zones in the belt suggest that the Paleo-Tethyan plate subducted beneath the Lanping-Simao Block (Metcalfe, 2002(Metcalfe, , 2013Jian et al., 2009a;Jian et al., 2009b). The Lincang batholith is composed of monzogranite, syenogranite, and alkalifeldspar granite which formed mainly during Triassic and to a lesser extent during Permian (Peng et al., 2013;Dong et al., 2013a;Wang et al., 2015;Catlos et al., 2017;Deng et al., 2018). ...
... ASRRB was part of the Indochina Block owing to it exhibiting a similar metamorphic grade and paleobiota to Gondwana (Metcalfe, 2002;Nakano et al., 2008) and the ASRRB finally separated from Gondwana continent (Leloup et al., 1995(Leloup et al., , 2001. ...
The study of K-enriched intrusive rocks is essential for deciphering mantle metasomatism beneath active con-tinental arcs. In this contribution, high-precision zircon U–Pb–Hf isotope, whole-rock geochemistry, Sr–Ndisotope, and mineral chemistry analyses were performed to evaluate the petrogenesis and geodynamic system ofthe Yunnongfeng intrusion on the southwestern margin of the Yangtze Block. The Yunnongfeng intrusion consistsof a high-K to shoshonitic rock assemblage with variable lithology from gabbro-diorite to granite. Zircon U–Pbdating gives concordant crystallization ages of ca. 782.5 ± 3.8 Ma for gabbro-diorite, ca. 774 ± 4.1 and 776 ±4.1 Ma for diorite, ca. 770 ± 4.7 Ma for quartz monzonite, ca. 763 ± 3.4 Ma for quartz syenite, and ca. 764 ± 16Ma for granite. These samples also show similar Sr–Nd, and Lu–Hf isotopic compositions, implying a commonmagma source. The similar crystallization age and regular variation of major and trace element contents suggestthat these rocks were formed through fractional crystallization of cogenetic primitive mantle magmas. Theenriched εNd(t) ( 5.7 to 5.1) and εHf(t) ( 6.7 to 1.2) values, high Rb/Y and Th/La ratios, slight Nd–Hfdecoupling, and high-K and Th contents demonstrate that their lithospheric mantle source was enriched by slab-related fluid and sediment-related melt. The samples also exhibit remarkable enrichment in large-ion lithophileelements and depletion in high-field-strength elements, indicative of subduction-related arc magmatism. Takinginto account previous studies, we suggest that the western margin of the Yangtze Block experienced a long-termsubduction process during the Neoproterozoic, and the Yunnongfeng intrusion formed in an extensional back-arcbasin. Based on the K-enriched mafic–intermediate rocks from the western margin of the Yangtze Blockcommonly show high K2O/Na2O, Rb/Sr, low Ba/Rb ratios, and enriched εNd(t) values, our study, coupled withnumerous previous reports, proposes that the K-enrichment resulted from the breakdown of phlogopite, owing tosubduction-related sediment melt reacting with peridotite in the mantle source area
... South China consists of the Yangtze Block to the west and the Cathaysia Block to the east which were welted together during the Neoproterozoic (Zhao et al., 2011). The Jinshajiang-Ailaoshan suture zone represents the remnant of a major eastern branch of the Paleo-Tethys in China (Wang et al., 2000), its closure marks breakup of the Gondwana and formation of the eastern Asian Bock (Li et al., 2004;Metcalfe, 2002). ...
... The Lower Yangtze region was situated within the Yangtze platform, along the northeastern margin of the Yangtze block in South China (Figure 1a). During the Permian-Triassic Boundary (PTB), the region exhibited a NE-SW structural pattern and was connected to the Qinling paleoocean in the northwest and the Cathaysian Block in the southeast [27,28]. The Yangtze platform underwent a transformation from a continental marginal basin to a rift basin in the Late Permian. ...
The rare earth elements (REEs) provide significant geological information and serve as a reliable indicator for predicting the paleoclimate, paleoenvironment, and paleotectonic evolution of sedimentary rocks. The REEs, major elements, and trace elements of 75 marine shale samples collected from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region were analyzed. The results revealed that the major elements Al2O3, K2O, and TiO2 were primarily influenced by clay minerals associated with terrigenous detrital, whereas SiO2 and Na2O were not affected by clay minerals. The ΣREE values obtained from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region were found to be lower than those of the Post-Archean Average Shale (PAAS) (184.8 μg/g). The study of REE indicators related to the source, redox conditions, and tectonic settings led to the following conclusions: (a) ΣREE showed strong positive correlations with TiO2, Al2O3, K2O, and Na2O, but exhibited relatively weak correlations with Fe2O3 and P2O5, suggesting that REEs were mainly associated with clay minerals, but were also influenced by pyrite, phosphates, and other minerals; (b) The high values of Ce/Ce*, MoEF, UEF, and Corg/P were mainly concentrated in Stages I, II, III and V of the Dalong Formation at the FTS and PTL sections, and the corresponding strong anoxic environment was more conducive to the preservation of organic matter; (c) The diagram between La/Yb and ΣREE, Al2O3-TiO2, TiO2-Zr, and La/Th-Hf bivariate diagrams indicated that the provenance of the rocks from the Dalong formations was primarily felsic igneous rocks; (d) Discriminant-function diagrams and La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 triangular diagrams show that the clastic sediments of the Dalong formations were derived most likely from continental island arcs. This study corresponds to the background of the transition from continental margin to continental collision structure in South China during the Late Permian.
... The Central Belt, located east of the Bentong-Raub Suture Zone, is composed of metasediment and sequences of deep to shallow marine clastic sediments [29,53], carbonates with abundant intermediate to felsic volcanic rocks, and volcaniclastic turbidites that accumulated in deep basins during the Permian-Triassic period [54][55][56][57][58]. ...
The Pulai gold deposit is one of the most promising gold prospects in the Central Belt of Peninsular Malaysia. It is found within the Permian-Triassic Gua Musang sequence of metasediments and metavolcanics and in a structurally controlled NE-SW major fault. Various ore minerals, including pyrite, arsenopyrite, chalcopyrite, sphalerite, pyrrhotite, and galena are typically associated with this deposit. Four types of pyrite (Pyrite 1, Pyrite 2, Pyrite 3, and Pyrite 4) and two types of arsenopyrite (Arsenopyrite 1 and Arsenopyrite 2) were characterised based on their morphological and textural differences. In this region, gold occurs as refractory gold in the nanoparticle form and in the state of Au+ within the structure of sulphides of variable concentrations. Through the detailed laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) trace element mapping analysis of pyrite and arsenopyrite, the main Au-bearing sulphides were found within vein-hosted Pyrite 4 and Arsenopyrite 2 during late phase mineralisation, while Pyrite 3 had the lowest Au concentration. Two phases of Au enrichment were recorded in Pyrite 4, mainly in the core (2 to 11.7 ppm; average 1.4 ppm) and margin of the grain (0.3 to 8.8 ppm; average 1.2 ppm), whereas the highest Au content was detected in the core of Arsenopyrite 2 (0.3 to 137.1 ppm; mean 31.9 ppm). The enrichment of Au is associated with As, forming a zoning elemental pattern distribution. Other trace elements, including Co, Ni, Sb, Pb, Bi, Cu, and Zn, show systematic variation in their composition between the various types of pyrite and arsenopyrite. For early-phase sulphides, the Au enrichment localised at the margin of Pyrite 2 and Arsenopyrite 1, together with Co–Ni, Pb–Bi–Sb, and Ag in the same oriented pattern, suggesting the remobilisation and redistribution of Au in sulfides. Meanwhile, the late crystallisation phase of vein-hosted sulphides formed a rich Au–As ore zoning pattern in the core of Arsenopyrite 2 and Pyrite 4. The second phase of Au enrichment continued at the margin of Pyrite 4 through the remobilisation and precipitation of Au together with Ni, Co, Sb, Pb, Bi, Ag, and Cu. Subsequent deformation then reactivated the late fluid system with the enrichment of Sr, Ba, Rb, Ag, and Zn along the fractures and outermost rim of Pyrite 4 and Rb–Sr–Ba–Pb–Bi along the rim of Arsenopyrite 2. The Pulai gold prospect is interpreted as an orogenic-style gold mineralisation where arsenic can be used as an indicator for proximity to ore mineralisation in exploration.
... Limestone was also deposited with intermediate to felsic volcanic and volcaniclastic rocks [5,[28][29][30]. The plutonic rocks in the Central Belt are very similar to those in the Eastern Belt [31]. ...
Selected Malaysian black shale sequences of the Permo-Triassic and Devonian ages that crop out in the Central Belt were investigated to discuss their chemical composition, provenance, tectonic setting, and weathering history. X-ray fluorescence (XRF) analysis shows that the BRSZ Unit 1 black shale has elevated SiO2, TiO2, and K2O contents compared to the Semantan and Gua Musang black shale. In terms of trace elements, the BRSZ Unit 1 black shale has elevated trace element contents compared to the Semantan and Gua Musang black shales. The BRSZ Unit 1 has the highest V, U, Pb, and Mo contents relative to the other two formations. The Mo content is significant in the BRSZ Unit 1 and is thought to be associated with the elevated total organic carbon (TOC) in the BRSZ Unit 1 black shale. Compared to Post-Archean Australian Shale (PAAS), the BRSZ Unit 1 and Gua Musang black shales are low in Fe2O3, MnO, CaO, Na2O, and P2O5. The Semantan black shales are deficient in CaO, K2O, and P2O5 and enriched in MnO. The black shales of BRSZ Unit 1 are enriched in V, Cu, Ga, Rb, Mo, Sn, Pb, and U. Except for Pb (mean: 32.3 ppm), the Gua Musang black shales are largely depleted in trace elements. Similar to the Semantan black shales, all trace element concentrations are largely depleted with the exception of Sc (mean: 22.3 ppm), which is slightly higher. Provenance analysis shows that the BRSZ Unit 1, Semantan, and Gua Musang black shales derived from felsic and intermediate parental source rocks. The BRSZ Unit 1 and Gua Musang black shales indicate a collision setting, whereas the Semantan black shales show affinity to a continental arc setting. The CIA values for all the samples analyzed in this study range between 79.4 and 95.8, indicating an intense chemical weathering in warm and wet paleoclimatic conditions. The average CIW values of samples from the BRSZ Unit 1, Semantan, and Gua Musang are 99.4, 94.5, and 98.6, respectively, implying an intense degree of weathering of the source rocks.
... ； 在泰国的难河-程逸构造带较早发现了蛇 绿岩 [6] ， 因此该构造带很长一段时间被认为是古特 提斯洋的主缝合线 [7][8] ， 但随着清迈地区远洋沉积序 列的不断完善， 有的学者认为昌宁-孟连带南延与 清迈缝合带相连 [4,[9][10][11][12] ， 难河-程逸构造带则被当做 古特提斯多岛洋的分支或弧后盆地的缝合线 [13][14][15] [19][20] Table 2 The data of trace elements of clastic rocks in 192±88 698±62 352±127 429±91 400±79 410±76 405±88 333±84 1103±47 837±86 493±52 332±74 481±77 256±82 323±72 584±116 357±58 588±99 363±123 260±70 473±83 437±104 890±121 627±221 163±69 128±110 226±105 232±109 637±116 304±105 322±69 596±34 209±48 1517±22 389±79 2015±37 478±67 3269±29 183±64 456±74 267±99 325±95 148±96 354±97 143±79 1221±53 207 Pb/ 235 U 1378±22 2018±16 2626±22 1148±26 1274±32 421±15 981±15 505±18 1603±23 1015±17 481±9 848±13 398±14 400±10 260±9 454±16 257±11 274±6 269±12 430±11 437±12 249±9 605±14 366±18 381±13 267±9 276±9 260±9 272±9 1066±16 856±30 467±9 269±8 287±9 257±8 282±8 286±17 261±9 281±14 261±16 281±10 280±12 373±18 891±33 307±25 260±9 250±14 252±12 257±13 306±18 247±10 254±7 577±8 255±5 1523±11 272±9 2012±16 274±8 3279±20 241±6 381±11 242±9 249±9 253±10 266±10 233±7 1198±20 206 Pbq/ 238 U 1352±17 2045±19 2648±26 1104±16 1181±17 425±6 978±10 493±8 1650±17 1080±15 507±5 912±9 390±5 397±5 264±3 440±7 264±3 254±2 264±3 440±6 450±9 253±3 581±6 373±7 374±5 251±3 261±4 246±3 264±3 1037±9 831±26 460±4 260±3 263±3 257±3 278±4 259±5 248±3 250±4 254±4 282±3 262±4 362±5 891±10 267±6 270±3 262±4 258±3 258±3 269±5 244±3 246±2 569±5 259±2 1521±10 258±3 2010±15 251±3 3275±27 245±2 366±4 240±2 241±3 262±4 258±3 240±3 1179±12 表 4 清莱地区碎屑岩 LA-ICP-MS 锆石 U-Th-Pb 同位素年龄部分测试数据 Table 4 Part of LA-ICP-MS U-Th-Pb analyzed data of zircons from clastic in ChiangRai area [36] ， 在扬子地区不发育 [37] (图 10)。据 Kent 等 [38] 统计， 1100Ma 的年龄峰值出 现在西澳大利亚克拉通地区， 代表着罗迪尼亚大陆 (Rodinia) 形成过程中的碰撞事件。指示南邦地体 在中元古代与西澳大利亚存在比较亲密的关系。 500~440Ma： 研究区存在 500~440Ma 的年龄峰 值， 略晚于西澳大利亚 [36] 、 喜马拉雅 [39][40][41][42] 、 拉萨 [43][44] 、 羌塘 [43,[45][46][47] 等地区存在被认为受到泛非运动影响的 600~500Ma 的年龄峰值， 比较接近扬子板块 (年龄峰 值 为 470~430Ma) [48] ， 以 及 越 南 中 部 ( 年 龄 峰 值 为 460~400Ma) [ ...
... This belt also hosts limestones with intermediate-to-felsic volcanic and volcaniclastic rocks, which were deposited in a fore-arc portion of the palaeo-arc basin [1,[31][32][33][34][35]. The basement of the Central Belt consists of a Carboniferous-Permian sequence composed of felsic-to-intermediate volcanic rocks, limestone, shale and subordinate sandstone, siltstone, and conglomerate [36]. ...
Several orogenic/sediment-hosted gold deposits are widely distributed in the Central Belt of Peninsular Malaysia. This study combines U-Pb dating with the isotope composition of lead as well as gold content in ore and magmatic rock-hosted pyrite. It aims to investigate the age of gold mineralization and possibly establish a link between gold mineralization and magmatic intrusion in the district. The results show that the S-type magmatic rocks yield crystallisation ages ranging from 204.1 ± 4.7 Ma to 223 ± 3.2 Ma with low magnetic susceptibility measurements below 3 × 10−3 SI unit. These ages fit within the 200–250 Ma Pb-Pb model age of the Pb isotopic composition of K-feldspars. Pyrite trace element mapping has shown that gold and lead show zoning patterns occurring at the same time in pyrite. The Pb isotope composition of the cores of pyrite grains indicate that the approximate model age of gold mineralization is 200 Ma. This age is close to 197–199 Ma (Early Jurassic), previously determined by K-Ar dating of sericite which was interpreted to be the age of gold mineralization. In this study, gold content varies up to 793 ppb in the analysed magmatic rock-hosted pyrites, indicative of a likely magmatic contribution to gold mineralization.
... In general, Central Belt is deposited in a forearc portion of the palaeo-arc basin (Gobbett & Hutchison 1973;Leman 1994;Makoundi et al. 2014;Metcalfe 2002;Richardson 1939;Tan 1984). This belt consists of deep to shallow marine clastic sediments and limestone with predominantly abundance of intermediate to felsic volcanic and volcaniclastic rocks. ...
The Ulu Sokor gold deposit is classified as orogenic type deposit with evidence from previous studies on the structural, mineralogical, alteration, fluid inclusion, and stable isotope data. This study focuses on the mineralogy and geochemical analysis of representative ore rock samples from southern part of Ulu Sokor gold deposits. The project area is situated at the North of Kelantan state which lies on the Central Belt of Peninsular Malaysia. The main objective of this research is to determine the gold mineralization enrichment pattern relative to other trace elements based on the new data of mineralogy and geochemical analysis. Gold mineralization is primarily hosted in structurally controlled quartz vein which occurs in various degrees of ductile-brittle environment. Based on the field relationships, ore microscopy and geochemical data analysis, there are two main gold mineralization type in the southern part of Ulu Sokor gold deposit, namely (1) Gold associated and as inclusions in bismuthinite based on the mineralogy study, and (2) Refractory gold occurs as lattice bound in pyrite based on the Au/As molar ratio. In terms of mineral exploration and gold prospecting, the significant enrichment in this study area is Bi. However, some other metals can also be considered as a significant value in this area such as Pb, As, Cu and Zn. From the bulk ore chemistry, the geometric mean values of Au and Bi are 1.9 ppm Au (n=23) and 96 ppm Bi (n=22), respectively. The knowledge base for bismuth minerals in Malaysia would provide a significant targeting clue for the gold mineralization.
... Sumatra Island, located in the western Sunda Arc in southern Sundaland, is the product of accretion of three terranes: the East Sumatra Block, West Sumatra Block and Woyla Nappe (Hutchison 1994;Metcalfe 1996). The East Sumatra Block is a part of the Sibumasu (Shan-Thai, Bunopas 1982) Block that collided with Indochina during the Middle Triassic period (Hutchison 1994;Metcalfe 2002). The West Sumatra Block arrived on the southern side of Sibumasu after the Mid-Triassic (Barber and Crow 2003;Barber et al. 2005) and was separated from West Burma by the opening of the Andaman Sea at around 15 to 13 Ma (Curray 2005). ...
Sumatra is located at the western end of the Sunda Arc, which resulted from the subduction of the Indo-Australian Plate beneath the Eurasian Plate. In this study, we report detailed zircon U-Pb and Hf isotope data for Cenozoic igneous rocks from the entire island of Sumatra to better constrain the temporal and spatial distribution of arc magmatism. The new dataset, combined with literature information, identifies the following two magmatic stages: (1) Palaeocene to Early Eocene (66-48 Ma) and (2) Early Miocene to Recent (23-0 Ma), with a 25-my-long period of magmatic quiescence in between. The magmatic zircons show predominantly positive and high ε Hf ( t ) values, ranging from +19.4 to +7.1 in western Sumatra, +17.1 to +1.6 in central Sumatra and +18.0 to +7.0 in eastern Sumatra, indicating an isotopically juvenile magma source in the mantle wedge along the western Sunda Arc. We explain the negative and low ε Hf ( t ) values (+0.5 to −13.1) of young samples around the supervolcano Toba as evidence for the subduction of sediment. We argue for a change in the subduction processes, where the first magmatic stage ceased owing to the termination of the Neo-Tethyan subduction and the following stage corresponded to the modern Sunda subduction.
Supplementary material at https://doi.org/10.6084/m9.figshare.c.6366009
... This evidence suggests that the Paleo-Tethys Ocean opened in the Middle Devonian and closed in the Late Permian to Early Triassic. This hypothesis is consistent with the paleogeographic reconstructions based on multidisciplinary data (Zhong, 1998;Metcalfe, 1996Metcalfe, , 2002Metcalfe, , 2011Metcalfe, , 2013Metcalfe, , 2021Sone and Metcalfe, 2008). ...
The timing and mechanism of the combination between the South China Block (SCB) and the Indochina Block (IB) are controversial. Three ophiolitic mélange zones (Ailaoshan, Song Ma, and Song Chay) have been proposed as suture zones within this collisional orogen. However, the relationships among the three corresponding tectonic belts are unclear. In this study, we present detailed structural data for the three tectonic belts. The bulk architectures of the Ailaoshan, Song Ma, and Song Chay belts correlate well with one another. This similarity is also revealed by our new zircon UPb geochronological results from the Song Ma and Song Chay ophiolites. The regional deformation age is constrained to between 250 and 240 Ma by our new muscovite ⁴⁰Ar/³⁹Ar ages, and the medium-low temperature conditions are revealed by the quartz c-axis fabric. Considering the transformation effect of the Cenozoic large-scale sinistral strike-slip of the RRF and DBF, the Early Mesozoic Ailaoshan, Song Ma, and Song Chay suture zones should represent different segments of the same belt. Based on this hypothesis, we compiled the ages of the magmatism in this region, which allows us to propose an evolutional model as follows: i) ~380–310 Ma continental rifting and subsequent Ailaoshan–Song Ma–Song Chay ocean spreading as a branch of the Paleo-Tethys, ii) ~310–250 Ma oceanic subduction coeval with continental-arc magmatism, iii) ~250–240 Ma continental collision, iv) ~240–220 Ma post-collisional extension.
... The Sanjiang region constitutes the southeastern part of the Tibetan Plateau and western Yunnan Province (Deng et al. 2014a(Deng et al. , 2014b, with a collage of Paleozoic arc terranes and Gondwana-derived microcontinental blocks ( Fig. 1; Mo et al. 1994;Metcalfe 2002Metcalfe , 2013Deng et al. 2014a;Wang et al. 2018b;Zhao et al. 2018a). These blocks were amalgamated to form part of the Eurasian continent during multiple Tethyan suture events (i.e., Paleo-, Meso-, and Neo-Tethys; Fig. 1A) prior to the Early Cenozoic Deng et al. 2014a). ...
Magmatic sources of porphyry deposits in postcollisional settings remain controversial. We have used new and published petrological and geochemical data for the Eocene–Oligocene porphyry Cu ± Mo ± Au deposits in the Sanjiang region, SW China, to address this outstanding issue. New data for three deposits (Machangqing, Tongchang, and Beiya) in the Ailaoshan–Red River porphyry Au-Cu-Mo belt (southern part of the Sanjiang region) suggest that ore-forming porphyries were emplaced at ~ 35 Ma, have high (⁸⁷Sr/⁸⁶Sr)i (0.7068–0.7071) and negative εNd(t) (− 6.9 to − 5.0), low zircon εHf(t) (− 5.3 to 4.5), and relatively high δ¹⁸O (5.9–9.0‰). Magmatic amphibole phenocryst compositions indicate that the parental magmas are all relatively oxidized (ΔFMQ = 1.7 ± 0.6), and H2O-rich (3.8 ± 0.3 wt% H2O). These results are consistent with those estimated from zircon compositions (ΔFMQ = 1.8 ± 0.8) and high whole-rock Sr/Y ratios (75 ± 31), respectively. Based on the new and published data, we suggest that the parental magmas for the Ailaoshan–Red River porphyry Au-Cu-Mo belt were derived from a preserved juvenile arc lower-crust and the underlying metasomatized subcontinental lithospheric mantle (SCLM) attributed to a Neoproterozoic subduction event, whereas the parental magmas for the Yulong porphyry Cu-Mo belt (northern part of the Sanjiang region) originated from the Permian–Triassic juvenile arc lower-crust and metasomatized SCLM. Additionally, parental magmas for these porphyry deposits are all oxidized and H2O-rich, and we attribute such characteristics to inheritance from mixed mantle-crust sources that were modified by previous oceanic slab subduction.
... Khu vực Đông Nam châu Á được hình thành từ các khối vi lục địa có nguồn gốc từ khối Gondwana, tức là các khối như Sibumasu, Indochina, nam Trung Hoa (Hình 1a). Các khối này được hợp nhất lại với nhau sau khi đại dương Tethyan diễn ra quá trình khép kín trong giai đoạn từ Paleozoi sớm và Mesozoi (Metcalfe, 2002;2013). Lãnh thổ Việt Nam theo quan điểm của các nhà địa chất thuộc về 3 cấu trúc lớn, phía bắc là đai tạo núi Trường Sơn, khu vực cao nguyên trung bộ là địa khối Kon Tum (khối nhô Kon Tum) và đới _____________________ * Tác giả liên hệ E -mail: nguyenhuutrong@humg.edu.vn ...
The Chu Lai granitogneiss is widespread throught the Northern Kontum massif. The Chu Lai body is located in the W-SW of the Nui Thanh Townlet (Nui Thanh Dists., Quang Nam Prov.). On an areas of ~ 300 km2. The Chu Lai intrusion mainly consists two mica gneiss, it is light grey and have porphyritic textures. Its major minerals include plagioclase (25÷40%), K-feldpar (20÷40%), quartz (25÷35%), biotite (5÷13%) and mustcovite (0÷6%). Accessory minerals are apatite, zircon, orthit. Garnet and tourmaline are occiasionally found. Zircons separated from a granitogneiss sample colleted in Chu Lai body are generally euhedral to subhedral, dark gray and prissmatic in shape with 100÷300 µm, with length/witdth ratios from 1:1÷1:3. There are many Neoproterozoic - Cambrian ages among the zircon cores in the Chu Lai samples, and these are regarded as inherited zircons. The LA-ICP-MS zircon age is 431 Ma, corresponding to the Silurian. The Chu Lai granitogneiss strongly negative zircon εHf (-4.2÷-11.4) and complex inherited zircon components, characteristics of typical S-type granite. Hf model ages TDM2 1.5÷1.9 Ga, suggests that the Chu Lai granitogneiss was derived from partial melting of old crustal basement rocks, probaly Paleoproterozoic in age.
Porphyry deposits in magmatic arcs form coincident with changes to steady-state oceanic subduction conditions, such as changes in plate convergence rate and vector or angle of subduction. However, it remains unclear whether such processes also operated during formation of postsubduction porphyry deposits. The Yulong magmatic belt in the eastern Tibetan Plateau consists of middle to late Eocene igneous rocks (~51–35 Ma) that formed during the India-Asia collision, whereas all known porphyry deposits are associated with late Eocene rocks (43–35 Ma). A synthesis of new and published geochemical data shows marked variations from the middle to late Eocene, including increasing whole-rock La/Yb, Sr/Y, and EuN/EuN* values, as well as zircon EuN/EuN* values. These geochemical variations, together with petrographic observations, indicate a transition from plagioclase-dominated to amphibole-dominated fractionation from the middle to late Eocene.
Coupled changes of magma compositions and porphyry Cu metallogeny from the middle to late Eocene coincided with, or were slightly preceded by, the onset of regional uplift and crustal thickening, triggered by the India-Asia hard collision and rapid deceleration of the India-Asia convergence rate at ca. 50 to 44 Ma. Crustal thickening may have caused prolonged magma differentiation at greater depths and accumulation of dissolved H2O, both of which contributed to amphibole-dominated fractionation and generation of hydrous melt that are prospective for porphyry Cu mineralization. Our study highlights the importance of tectonic changes in the formation of the Yulong and other postsubduction porphyry Cu belts—a scenario similar to that operated in subduction-related settings such as the Andes.
The Sanjiang Tethyan Orogen plays a pivotal role in elucidating the geodynamic processes related to the evolution of the Paleo-Tethys Ocean. Research on the Gicha Complex within this orogen is imperative for comprehending the intricate evolution of the region. This study presents new findings from zircon U‒Pb dating, Hf isotope analysis, and whole-rock elemental analyses of gabbro, olivine gabbro, and the recently discovered mylonitic rhyolite and diabase in the Gicha Complex. The zircon U‒Pb dating yields ages of 703 ± 3 Ma for the diabase, 296 ± 2 Ma for the gabbro, and 231 ± 1 and 228 ± 2 Ma for the mylonitic rhyolite, demonstrating that these rocks record the extended evolution from the breakup of Rodinia to the closure of the Paleo-Tethys Ocean. The Neoproterozoic diabase samples exhibit shoshonitic and arc-like geochemical properties, with positive zircon εHf(t) values ranging from 1.1 to 3.7 and high Th/Yb values ranging from 1.34 to 3.07, suggesting that they were generated by partial melting of enriched subduction-modified lithospheric mantle in an active continental margin. The early Permian gabbro samples are part of the tholeiitic series and exhibit low SiO2 and K2O contents; depletions in Nb, Ta and Ti; and enrichment in Pb, indicating derivation from a combination of depleted mantle peridotite and subduction-related components. The whole-rock geochemical features suggest that these rocks formed in a back-arc setting featuring a small, mature ocean basin. The mylonitic rhyolite samples exhibit weakly peraluminous characteristics (A/CNK = 0.98–1.12) with high-K calc-alkaline geochemical features. The samples are depleted in Ba, Nb, Ta, and Ti and enriched in Th, U, Pb, and LREEs and exhibit negative to positive zircon εHf(t) values ranging from − 0.5 to + 5.9, indicating that they originated from partial melting of Meso-Neoproterozoic juvenile lower crust. Geochronological, petrological, and geochemical analyses indicate that the subduction of oceanic crust occurred along the western margin of the Yangtze Block until the late Neoproterozoic (~ 703 Ma).
Neoproterozoic mafic magmatism generated by partial melting of an enriched subduction-modified lithospheric mantle in active continental margins
The Jinding deposit is well-known to contain high concentrations of metals Zn, Pb, Cd, Tl, Ag, etc. in the world. The associated critical metals and their substitution mechanisms were wildly concerned. This study investigated and compared sphalerites using a combination of textural, trace element, and sulfur isotopic analyses to give insights into element substitution mechanisms and possible sources of ore-forming fluids and to constrain processes involved in ore genesis of the world-class Jinding sediment-hosted Zn-Pb deposit. LA-ICP-MS analyses reveal chemical zoning in the sphalerites together with the coupling of two main groups of trace elements substitution mechanisms: one is Fe+Ge+Mn+Pb+As+Tl and vacancies to substitute Zn, and the other is Cd+Cu+Ag+Sb to substitute Zn. The incorporation of trace elements is facilitated by the replacement of Zn by Cd and Fe. These two group elements have distinct color oscillatory zonation and are intertwined in the trace element LA-ICP-MS element maps. The sulfur isotopic values show high isotope fractionation in the sphalerite from -28.4 to -0.5‰, suggesting a bacteriogenic sulfur origin at Jinding. Sphalerite sample has observed that sulfur isotope is correlated with Fe concentration and anti-correlated with Cd concentration. These variations in isotope fractionation and trace element disequilibrium partitioning were interpreted as the effects of temperature and pH with less influence from sulfur activity. These variability zones of sphalerite alternately enriched in Cd- and Fe-related elements suggested that ore fluids may flow from metal-fertile sedimentary/basement sequences during their ascent, and colloform sphalerite was likely formed by a high degree of supercooling, over-saturation, and rapid mixing between bacteriogenic sulfur and metal-rich in spaces of collapse dome. Based on our observations, we suggested that these variability zones of layered sphalerite alternately enriched in Cd and Fe would likely provide useful insight for a potential economic Zn-Pb and associated critical metals mineral exploration deposit.
Understanding the tectonic evolution of the Proto-Tethys Ocean is important for exploring the initial assembly of the Gondwana supercontinent. The closure of the Proto-Tethys Ocean represents the end of convergence along the northern edge of Eastern Gondwana. However, the timing and processes of the closing of the ocean have different interpretations. This work focuses on the early Paleozoic granitic rocks in the Baoshan Block (BSB), SW China, to constrain the tectonic evolution of the Proto-Tethys Ocean. Zircons from the Pinghe and Zhen'an granitic plutons yield concordant U–Pb ages from 489.8 Ma to 467.7 Ma. The bulk-rock geochemical features suggest that these samples are high-K, calc-alkaline, S-type granites enriched in LREEs and depleted in HREEs. With obvious negative Eu-anomalies and high K 2 O/Na 2 O ratios (1.01–2.57), they are enriched in LILEs and depleted in HFSEs. Thus, these rocks were derived from partial crustal melting associated with subduction of the converging plate. Previous studies on the Changning–Menglian suture zone suggested that the Early Paleozoic magmatic activity in the BSB was related to the westward subduction of the Proto-Tethys Ocean, combining the Early Paleozoic subduction-related magmatic activity to the east, it is suggested that the Changning–Menglian Ocean experienced bidirectional subduction.
Tungsten and Sn deposits in China are widely distributed in the South China block (i.e., Yangtze craton-Cathaysian block), Himalaya, Tibetan, Sanjiang, Kunlun, Qilian, Qinling, Dabie, and Sulu orogens, and Central Asian orogenic belt. Among these, the South China block hosts the majority of the mineralization with about 73% (9.943 million tonnes WO3) and 85% (6.561 million tonnes Sn) of the country’s total W and Sn resources, respectively. The W resource mainly occurs as skarn (63%), quartz-vein (17%), porphyry (17%), and greisen (3%) Sulu deposits, whereas Sn is present in skarn (81%), quartz veins that are typically tourmaline-bearing (6%), sulfide-rich veins or mantos (5%), greisen (5%), and porphyry (3%) Sulu deposits.
The W and Sn mineralization formed during numerous events from Neoproterozoic to Paleocene with a peak in the period from the Middle Jurassic to Early Cretaceous, and with an uneven spatial and temporal distribution pattern. The Neoproterozoic Sn (W) deposits (850–790 Ma) occur on the southern and western margins of the Yangtze craton, the early Paleozoic W(Sn) deposits (450–410 Ma) are mainly distributed in the northern Qilian and the westernmost part of the eastern Kunlun orogens, the late Paleozoic Sn and W deposits (310–280 Ma) are mainly developed in the western part of the Central Asian orogenic belt, the Triassic W and Sn deposits (250–210 Ma) are widely scattered over the whole country, the Early Jurassic to Cretaceous W and Sn deposits (198–80 Ma) mainly occur in eastern China, and the late Early Cretaceous to Cenozoic Sn and W deposits (121–56 Ma) are exposed in the Himalaya-Tibetan-Sanjiang orogen.
The petrologic characteristics of W- and Sn-related granitoids in China vary with the associated ore elements and can be divided into the Sn-dominant, W-dominant, W-Cu, and Mo-W (or W-Mo) groups. The granitoids associated with the Sn- and W-dominant magmatic-hydrothermal systems are highly fractionated S- and I-type, high-K calc-alkaline and (or) shoshonitic intrusions that show a metaluminous to peraluminous nature. They exhibit enrichments in F, B, Be, Rb, Nb, and Ta, depletions in Ti, Ca, Sr, Eu, Ba, and Zr, and strongly negative Eu anomalies. The granitoids associated with W-Cu and W-Mo deposits are of a high-K calc-alkaline to shoshonitic nature, metaluminous, depleted in Nb and Ta, and display weakly negative Eu anomalies. Granitoids associated with Sn- and W-dominant deposits are reduced, whereas those linked to W-Cu and Mo-W deposits are relatively more oxidized. The magma sources of W-dominant granitoids are ancient crust, whereas those connected with Sn, Mo-W, and W-Cu deposits are from variable mixing of ancient and juvenile crustal components.
The spatial and temporal distribution pattern of W and Sn deposits in China is intimately related to the regional geodynamic evolution. The Neoproterozoic Sn deposits are associated with peraluminous, highly fractionated, and volatile-enriched (boron and fluorine) S-type granites sourced from the melting of an ancient crust in a postcollisional setting related to the assembly of the Rodinia supercontinent. The early Paleozoic W deposits are genetically associated with highly fractionated S-type granites formed during postcollisional events and were derived from the partial melting of a thickened continental crust in the context of Proto-Tethyan assembly. Granitoids associated with late Paleozoic Sn and W deposits were derived from the melting of an ancient and juvenile crust with I-type affinity associated with the closure of the Paleo-Asian Ocean. Although the Triassic W and Sn deposits are related to the assembly of Asian blocks within the Pangea supercontinent, their geologic settings are variable. Those in the South China block and the Himalaya-Tibetan-Sanjiang belt are associated with collision and magma derivation through the partial melting of a thickened continental crust, whereas in the Kunlun-Qilian-Qinling-Dabie-Sulu orogen and the Central Asian orogenic belt, a postcollisional extensional setting dominates. The Early Jurassic (198–176 Ma) W deposits, located in the northern part of northeast China, are associated with highly fractionated I-type granites derived from melting of juvenile crust and emplaced during the subduction of the Mongol-Okhotsk oceanic plate. The extensive group of Middle Jurassic to Cretaceous W and Sn deposits formed at two stages at 170 to 135 and 135 to 80 Ma. The former stage is associated with highly fractionated S- and I-type granites that are the products of partial melting of thickened crust with heat input possibly derived from a slab window associated with the Paleo-Pacific oceanic plate subduction beneath the Eurasian continent. The later stage is closely associated with NNE-trending strike-slip faults along the Eurasian continental margin and is coeval with the formation of rift basins, metamorphic core complexes, and porphyry-epithermal Cu-Au-Ag deposits. These processes, which were instrumental for the formation of a wide range of mineral deposits, can be ascribed to the regional lithospheric thinning and delamination of a thickened lithosphere and thermal erosion in a postsubduction extensional setting. The 121 to 56 Ma Sn deposits in the Himalaya-Tibetan-Sanjiang orogen are associated with S-type granite or I-type granodiorite emplacement in a back-arc extensional setting during Neo-Tethys plate subduction.
The Late Permian was marked by a series of important geological events and widespread organic‐rich black shale deposition, acting as important unconventional hydrocarbon source rocks. However, the mechanism of its organic matter (OM) enrichment is still controversial. Based on geochemical data, we studied the marine redox conditions, paleogeographic and hydrographic environment, primary productivity, volcanism, terrigenous input during the Late Permian in the Lower Yangtze region, and provided new insights into the OM accumulation. Five Phases were distinguished based on the TOC and environmental variations. In Phase I, anoxic conditions driven by water restriction enhanced the OM preservation. In Phase II, euxinic and hydrological cycling environments were the two most substantial controlling factors for the massive OM deposition. During Phase III, intensified terrestrial input potentially diluted the OM in sediment and presence of oxygen in bottom water weakened the preservation condition. The Phase IV was characterized by relatively higher abundance of mercury (Hg) and TOC (peak at 16.98 wt%), indicating that enhanced volcanism potentially stimulated higher productivity and euxinic environment. In Phase V, extremely lean OM was preserved as a result of terrestrial dilutions and the decreasing primary productivity. Eventually, Phase I, Phase II and Phase IV were characterized as the most prominent OM‐rich zones due to the effective interactions of the controlling factors, namely paleogeographic, hydrographic environment, volcanism, and redox conditions.
Significant progress in the classification, definition, and understanding of the main Au deposit types could significantly aid improvements in Au exploration. Because of the wide occurrence of Au in the central part of the Tethyan Eurasian Metallogenic Belt, Iranian structures composed of more than seventeen zones (arcs and blocks) are considered as having one of the largest Au reserves in the Middle East. Without attempts at understanding the tectono-magmatic evolution of Iran and the geodynamic settings of Au deposition, the establishment of a reliable predictive exploration model for Au-type deposits in Iran and other parts of the world will be unsuccessful. By considering, a total number of 33 Au deposits and prospects in Iran, a mineralization sequence is revealed from VMS, orogenic, Carlin-type, epithermal/ porphyry Cu-Au/ skarn, epithermal/ and IOCG, respectively. The trend of deposition gradually changes in the SW-NE axis to intrusion-related, epithermal, and porphyry Cu-Au deposits at UDMA and post-arc magmatism. Orogenic and volcanogenic massive sulfide (VMS) deposits occur adjacent to the northeast Zagros Fold and Thrust Belt, at the SSZ. The Zagros Orogeny and associated post-collisional magmatism at Urumieh-Dokhtar Magmatic Arc (UDMA) host many porphyry, epithermal, and intrusion-related Au deposits, with a major magmatism peak in the Miocene. The finding of the manuscript reveals that orogenic and Carlin-type Au mineralization are linked genetically. After each associated subduction for paleo-tethys (286-215 Ma) and Neo-tethys (210-68 Ma) in Iran, VMS and orogenic Au-deposits are formed in the border of the subduction (±obduction) zone. The porphyry, intrusion-related, epithermal, and IOCG mineralization are emplaced in appropriate formations and structures during collision and post-collision processes.
Characteristic granites of the East Tethyan Tectonic Domain (ETTD) are primarily exposed along the Himalayan orogenic belt and Gangdese batholith in the north, extend from western Yunnan in the centre, and through the Burma batholith to Peninsular Malaysia in the south. Western Yunnan is an important part of the ETTD magmatic arc, featuring characteristic granites that mainly developed between the Jurassic and Paleogene. Nonetheless, compared to other regions of the ETTD, Miocene magmatism has been poorly documented in western Yunnan. The Xiaomasa granite occurs in the Ximeng area of western Yunnan. In this study, we present U–Pb ages, and Hf–O isotope data for zircon crystals from the Xiaomasa granite pluton. Laser Ablation–Multicollector–Inductively Coupled Plasma–Mass Spectrometry (LA–MC–ICP–MS) zircon U–Pb dating yields precise emplacement ages of 15.8–16.1 Ma for the Xiaomasa granite, indicating that Miocene granitic magmatism occurred in western Yunnan. Zircons from the Xiaomasa granite have negative ε Hf (t) values ranging from −6.6 to −11.6, relatively high δ ¹⁸ O values (6.8%–10.2‰), and two‐stage Hf isotopic model ages (1.51–1.83 Ga). Zircon Hf–O isotopic characteristics indicate that the Xiaomasa granite was mainly derived from partial melting of ancient continental crust. The Ximeng Precambrian metamorphic basement is a probable material source for the granite. The Xiaomasa granite was probably produced by partial melting of the thickened Ximeng ancient metamorphic basement under a reduced pressure environment, reflecting a cumulative effect of the escape of Sundaland caused by the dynamics of the continuous India–Asia collision.
Skarn ores have recently been identified beneath the historically mined placer Sn deposit at Kanbauk of the Dawei region, southern Myanmar. A large-tonnage skarn ore reserve at Kanbauk is estimated to be over 100 million tonnes, with reported ore grades of 0.17% WO3, 0.26% Sn, and 15.4% CaF2, potentially making it one of the largest W-Sn skarn deposits in the Southeast Asian tin belt. The mineralized skarns lie between marbles to the east and metasediments of the Mergui Group to the west. The timing of the mineralization is unclear, and thus the genetic relationship with regional magmatic events is not known. We report laser ablation-inductively coupled plasma-mass spectrometry U-Pb ages of garnet and cassiterite from the mineralized skarns. Garnet grains from the massive prograde skarns are typically subhedral to euhedral and show both sector and oscillatory zoning. They have 15 to 23% andradite (Ad), 55 to 67% grossularite (Gr), and 16 to 30% pyralspite (Py) (Ad15-23Gr55-67Py16-30) and contain 0.08 to 306 ppm U with a lower intercept 206Pb/238U age of 56.0 ± 1.5 Ma. Cassiterite grains from retrograde veinlets are subhedral to anhedral and have U contents from 110 to 12,000 ppm with a lower intercept 206Pb/238U age of 54.2 ± 1.7 Ma. Garnet and cassiterite have ages consistent within error and can be taken to indicate the formation of the Kanbauk W-Sn(-F) skarn deposit at around 55 Ma. Together with published ages of primary Sn-W deposits in the Dawei region, our study confirms a westwardly younging trend of mineralization toward the coast and provides support for rollback of the Neo-Tethyan subducting slab since the Late Cretaceous, which is considered as the main mechanism for the regional, extensive Sn-W mineralization.
The giant Yulong porphyry Cu (‐Mo‐Au) deposit was formed in a post‐collisional setting in eastern Tibet, which is associated with Eocene potassic to ultrapotassic felsic intrusive rocks. The origin of the Yulong potassic intrusion remains highly disputed. Hence, we present new zircon U–Pb ages, whole‐rock geochemistry and zircon Lu‐Hf isotopes for the Yulong intrusion. Zircon U–Pb dating from the porphyritic monzogranite and porphyritic quartz monzonite yield ages of 41.1 ± 0.2, 40.8 ± 0.1 and 40.5 ± 0.2 Ma, respectively. Samples from the Yulong intrusion exhibit high K2O (4.13–4.85%), and high K2O/Na2O (1.00–1.25), [La/Yb]n (30.37–40.37) and Sr/Y (57.86–87.68) ratios, low Mg#, MgO, Ni, and Cr contents, enrichment in light rare earth elements (LREEs) and depletion of high‐field‐strength elements (HFSEs, e.g., Nb, Ta, and Ti). Zircon grains from this study have mostly positive εHf(t) values (+1.6 to +2.9), and crustal model ages (TDMC) of 0.90–1.19 Ga. These features suggest that the Yulong intrusion is derived from a thickened juvenile lower crust. During the Permian to late Triassic, Jinshajiang‐Ailaoshan Palaeo‐Tethyan oceanic subduction from the eastern margin of the North Qiangtang produced metasomatic domains within the continental lithospheric mantle and lower crust. During the late Eocene, the continuing India‐Asia continental collision may have preferentially overthickened the crust. Convective removals in the lower part of the thickened lithosphere resulted in the hot asthenosphere upwelling along the Jinshajiang‐Ailaoshan Suture, which induced the partial melting of the residual metasomatized lithospheric mantle, as well as the thickened lower crust in the Eocene, which formed the Yulong intrusion. Yulong potassic intrusion magmatism model has been established. During the Permian to late Triassic, Jinshajiang‐Ailaoshan Palaeo‐Tethyan oceanic subduction from the eastern margin of the North Qiangtang produced metasomatic domains within continental lithospheric mantle and lower crust; During the Palaeocene‐Eocene, Neo‐Tethyan oceanic slab broke off from the India continental lithosphere, triggered hot upwelling asthenosphere and formed the Yulong shoshonitic magmas.
Hydrogeochemical processes and water–rock interactions of a geothermal system are important for understanding of the hydrochemical evolutionary process and genetic mechanisms of the geothermal system. The hydrochemistry, hydrogen and oxygen isotopes, and rare-earth elements (REEs) are discussed to reveal the hydrochemical characteristics and processes of these geothermal systems in Kahui and Gezha geothermal waters in the Ganzi–Litang fault in western Sichuan, China. The results show that the geothermal waters are Na-HCO3 type and influenced by combination of evaporite dissolution and silicate weathering. The isotopic compositions of δ²H and δ¹⁸O indicate that the geothermal water is recharged by atmospheric precipitation, and the oxygen isotope drifts in the Gezha geothermal water may be caused by water–rock interactions. The total REE content of the geothermal water is 0.059‒0.547 ug/L, and the REE contents are significantly influenced by pH and HCO3⁻, Na⁺, and Mn minerals. The chondrite-normalized REE pattern show geothermal water, cold springs, and surrounding rocks are rightward. The fractionation of rare-earth elements is affected by HCO3⁻ complexation reactions, the dissolution of Mn minerals, and alternating cation adsorption. Moreover, the geothermal water exhibited positive Eu anomalies, which may be caused by the dissolution of feldspar minerals in surrounding rocks. In addition, the complexation patterns of REEs in geothermal water and cold springs in the Ganzi–Litang fault mainly include Ln(CO3)2⁻ and LnCO3⁺, and the changes in the complexation patterns are influenced by the stability constants of complexation reactions and pH.
The lithology and genesis of a dark grey clastic interlayer first encountered within the deepest potassium-rich salt body in the Simao Basin, southwestern China, were analysed. Analyses of the petrography, mineralogy, and element geochemistry of the layer revealed that (1) the layer contains quartz crystals with gulf corrosion edges and explosion cracks and angular volcanic ash-sized glasses; (2) the main mineral components of the crystal fragments are chlorite, illite, biotite, quartz, anhydrite, gypsum, magnesite, pyrite, molybdenite, clinopyroxene, and zircon; (3) the rare earth element patterns, Zr/TiO2 and Nb/Y diagrams as well as boron content all indicate a volcanic origin for the layer. Based on these observations, the layer is suggested to be an altered tuff associated with various volcanic fragments dominated by chlorite and formed after alteration of a parent tuff in an alkaline, salty, and low-temperature water body. Discovery of the layer indicates that the potash-bearing salt rocks could have taken in volcanic materials during these volcanic activities and provides the possibility of reliable zircon U‒Pb dating to determine the absolute age of the host rock, which is fundamental in studying the genetic mechanism of this deeply buried salt body.
Well-preserved Late Paleozoic–Early Mesozoic igneous rocks in Peninsular Malaysia are important for investigating the Paleotethyan tectonic evolution. This study presents new zircon U-Pb dating, whole-rock geochemical, and Sr-Nd-Pb-Hf isotopic data for granitoids identified from the East Malaya. By utilizing all available data, the Permian–Middle Triassic granitoids in Eastern Peninsular Malaysia can be divided into three groups. Group A (289–270 Ma) I-type granites have higher εNd (t) values of −6.6 to −2.6 and zircon εHf (t) values of −7.1 to +4.9 than Group B S-type granites (285–272 Ma) with εNd (t) = −10.1 and zircon εHf (t) = −23.1 to +1.5. Group C (254–244 Ma) with A-type characteristics, has εNd (t) and zircon εHf (t) values ranging from −7.3 to −3.8 and −8.9 to +2.2, respectively. The Pb isotopic values for three groups are similar with (²⁰⁶Pb/²⁰⁴Pb)i = 18.71–19.43, (²⁰⁷Pb/²⁰⁴Pb)i = 15.66–15.71 and (²⁰⁸Pb/²⁰⁴Pb)i = 38.27–39.43. Group A was derived from metaigneous rocks with a juvenile mafic component, while Group B was from metasedimentary rocks. Group C had a mixed source of “ancient” meta-mafic rocks with a juvenile mafic component. This study proposes that the Late Paleozoic–Early Mesozoic granitoids were formed in response to the subduction of the Paleotethyan Ocean, and that a tectonic transition from subduction to slab roll-back might occur at ∼270 Ma. Subduction-related granitoids in East Malaya can northernly extend to the Tachileik Batholith in eastern Myanmar and Jinghong in SW China, and southernly link with W Borneo.
Palaeomagnetic data for relevant continents and terranes have been extracted from the Global Palaeomagnetic Database (GPMDB Version 3.1: Lock and McElhinny,1991; McElhinny and Lock, 1993,1994,1996) through careful scrutiny of individual results. The ACCESS version of the database covers palaeomagnetic data published in established international joumals up to the end of 1994. Further results of 1995 and 1996 vintage have been extracted directly from relevant publications as available. Datasets for Australia and India have been complemented with relevant data published in the grey
literature and with unpublished data obtained from studies on the Indian Gondwana succession, carried out at the Research School of Earth Sciences (Agarwal,1980; Klootwijk and Agarwal, unpublished), and from studies on Australian cratonic basins, the Tasman Orogenic System and the Tamworth Belt of the New England Fold Belt, carried out at AGSO (e.g. Klootwijk and Giddings,1993; Klootwijk et al.,1993; Klootwijk,1995,1996).
The palaeomagnetic data have been checked for errors, represented as south pole positions, complemented with local palaeolatitude detail, supplied with comments as required, and catalogued in younging order. Results from fold belts peripheral to the Indian Shield (Himalayas, Salt Range, Baluchistan) have been corrected for local or regional rotations wherever established, with corrected results added to the datasets for India, Nepal and Pakistan. Mean results have been collated for the major continental blocks, either from published sources (Siberia [Khramov and Rodionov,1980; Khramov
et al.,1981; Zonenshain et al.,1990], North China, South China [Enkin et al.,1992; Zhao et al.,1996], Tarim, Alashan - Hexi corridor [Zhao et al.,1996]), or have been determined for Australia and India from the tabled data (Tables 1-6) for time-intervals according to the AGSO Phanerozoic Timescale (Young and Laurie,1996) as specified in Table 7.
For construction of palaeolatitude plots, individual palaeomagnetic results have been converted to palaeolatitudes at an easily identifiable common site for each continental block or terrane as listed in Table 8, and stratigraphic ages have been converted to absolute ages following the AGSO Phanerozoic Timescale. The GMAP for Windows program (Torsvik and Smethurst, 1995) has been used for relocation of several of the Cathaysian continents In pre-break reconstructions within eastern Gondwana, and the
ATLAS program (Cambridge Paleomap Services,1992) has been used for geographical overviews.
In the Manang area (north Annapurna Range; Nepal Himalaya), the Permo-Carboniferous succession is 1000 to 1500 m thick. Crinoidal biocalcarenites (Tilicho Lake Fm.) pass upward to alternating black shales and sharp-based white quartzose sandstones (Thini Chu Group). Detailed stratigraphic analysis of this unit allowed 5 new formations and 8 new members to be recognised. The stratigraphy and tectonic evolution of the area is outlined. -from Authors
The stratigraphical data collected during four geological expeditions to the Northern Karakorum are discussed. The sedimentary succession has been classified by 9 formations, here formalised, and subdivided into members and lithozones. The biochronology has been established on fusulinids, brachiopods, and conodonts. Several plates illustrate the most significant fossil species as well as the litho- and microfacies. The Permian of the Karakorum is the sedimentary evidence of the passive margin of a lithospheric block, detached from the Gondwana continent during the Permian, that will later migrate towards the centre of the Paleo-Tethys, along with other lithospheric blocks of the Mega Lhasa plate. -Authors
The geological and tectonic evolution of East and Southeast Asia is essentially one of dispersion of continental terranes from the margin of Gondwana, their northwards drift and subsequent amalgamation and accretion to form present-day Asia. Dispersion of terranes, as three elongate continental slivers, from the Margin of Gondwana took place in three episodes in the Devonian, Early-Middle Permian, and Late Triassic-Late Jurassic. The separation of the three continental slivers was accompanied by the opening of three successive Tethyan ocean basins, the Palaeo-Tethys, Meso-Tethys and Ceno-Tethys. These ocean basins were subsequently destroyed by subduction as the continental slivers drifted northwards and remnants of them are now found in the various suture zones of Asia. Amalgamation and accretion of the Gondwana-derived terranes took place progressively between the Carboniferous and the Cenozoic and palaeogeographic reconstructions are presented which illustrate the spatial evolution of the various East and Southeast Asian continental terranes during the Phanerozoic.
Eastern Southeast Asia is composed of continental fragments, rifted from the Australian and South China margins during the Late Mesozoic and Cenozoic, together with subduction complexes, island arcs and marginal seas. The spatial distribution of the small continental fragments in eastern Southeast Asia is a result of the interaction between the Eurasian, Indo-Australian and Philippine Sea plates during the Cenozoic. A series of palaeogeographic maps are presented showing interpreted palaeopositions of the various Southeast Asian terranes in the Palaeozoic, Mesozoic, and Cenozoic, in relation to Gondwanaland and Tethys, consistent with the current geological and geophysical constraints. -from Author
The older continental part of Southeast Asia is a composite of four tectonic blocks (Sibumasu, Manabor, Indochina and South China Blocks) which have had independent pre-Triassic histories. Carboniferous sediments on these blocks are predominantly shallow marine with subordinate epicontinental and continental deposits. The Carboniferous of the Sibumasu Block consists of continental margin deposits including extensive glacial-marine diamictites. Shallow marine clastics (with reefal limestones) and abundant volcanics are the main Carboniferous deposits on the Manabor Block which is interpreted as a possible Island Arc during the Carboniferous. The central part of the Indochina Block was emergent throughout the Carboniferous and was bordered by epicontinental and shallow marine deposits. Carboniferous faunas of Southeast Asia are predominantly of Eurasian aspect but genera typical of Australian and North American provinces also occur indicating connections between these and Southeast Asia at cerlain times. Stratigraphical and palaeomagnetic evidence suggests that the Sibumasu Block was adjacent to Gondwana throughout the Carboniferous. The relative positions of the Manabor and Indochina Blocks are however uncertain.
Most east and southeast Asian continental blocks, comprising North and South China, Indochina (including the
Qamdo-Simao Block), Tarim (including the Kunlun and Ala Shan Terranes), Qaidam, Sibumasu, Qiangtang,
Lhasa, Kurosegawa, Northwest and Southeast Hainan, West Burma and Woyla Terranes, had their origins on the northern margin of Gondwanaland. Phanerozoic evolution of eastern Gondwanaland and Tethys involved the successive rifting and separation of three continental slivers (now recognised as collages of terranes) from northern Gondwanaland, their northwards drift, and amalgamation/accretion to form east and southeast Asia. These continental slivers separated from the margin of Gondwanaland in the Late Devonian (North China, South China, Indochina, Qaidam, Tarim and Hainan Island Terranes), Early-mid-Permian (the Cimmerian continent including the Sibumasu and Qiangtang Terranes), and Late Triassic-Late Jurassic (Lhasa, West Burma and Woyla Terranes). The northwards drift of these terranes was accompanied by the opening and closing of three successive oceans, the Palaeo-Tethys, Meso-Tethys and Ceno-Tethys. Assembly of Gondwanaland-derived Asian terrenes began with the amalgamation of South China and Indochina during the Early Carboniferous along the Song Ma Suture to form 'Cathaysialand'. Cathaysialand and North China formed large continental regions at low northern/equatorial latitudes within the Palaeo-Tethys during the Late Carboniferous and Permian. The Tarim, Kunlun, Qaidam and Ala Shan Terranes accreted to Kazakstan/Siberia in the Permian. Separation and northward drifting of the Cimmerian continent from northeast Gondwanaland in the late Early Permian was accompanied by the opening of the Meso-Tethys. This was followed by the suturing of Sibumasu and Qiangtang to Cathaysialand in the Late Permian-Early Triassic, largely closing the Palaeo-Tethys. North and South China amalgamated in the Permian-Triassic and accreted to Laurasia in the Late Triassic-Early Jurassic. The Lhasa, West Burma and Woyla Terranes separated from northwest Australian Gondwanaland during the Late Triassic to Early Cretaceous as the Ceno-Tethys opened and the Meso-Tethys was destroyed by subduction beneath Eurasia. These terranes accreted to proto-southeast Asia in the Early to Late Cretaceous.
East and Southeast Asia comprises a giant 'jigsaw puzzle' of continental fragments (terranes) which had their origins on the margin of the ancient supercontinent Gondwana in the southern hemisphere. During the last 400 off Gondwana, drifted northwards and re-assembled. The separation of Asian terranes from Gondwana occurred in three episodes which were accompanied by the opening, and subsequent closure of three ocean basins, the Palaeo-Tethys, Meso-Tethys and Ceno-Tethys. The remnants of these now destroyed ancient ocean basins are preserved in narrow suture zones between the Asian continental terranes. The eighteen contributions in this book by internationally renowned geoscientists, are the culmination of the six-year long International Geological Correlation Programme Project 321, 'Gondwana dispersion and Asian accretion'. The contributions reflect the multidisciplinary and international collaborative nature of the project and provide important new data, and interpretations and syntheses of the region. The papers cover both continental terranes and suture zones and collectively provide exciting new insights, especially on the timings of events, relating to the Gondwana dispersion and Asian accretion processes that led to the assembly of modern-day Asia.
Correlations of Paleozoic paleogeography and tectonics in Northern Vietnam and Southeast China were used to estimate the debated amount of Cenozoic offsets affecting the Indochina Peninsula along the Red River Fault Zone. The NW trending Caledonian orogenic belts in Vietnam, can be traced in Southern China with a NE trend. The virgation of the belt was observed in the Da Nang area in central Vietnam. Coeval ophiolitic sutures, islands arc terrains and back arc basin sedimentary sequences can be correlated between China and Vietnam. Taking into account the original curvature of the early Paleozoic orogenic belt, and minimising the effects of the late Triassic Indosinian orogeny, the observed offsets between the two branches of the belt are assumed to be Cenozoic in age. We claim for a left lateral displacement of less than 300 km along the Red River fault zone. Subsidiary parallel faults affecting the Annamitic belt in northern Vietnam and Southern China did not significantly displace the segments of this early Paleozoic orogen.
The Carboniferous flora of eastern Peninsular Malaysia and the first significant Carboniferous flora recently discovered in NE Thailand exhibit a typical Euramerian aspect. Besides their interest from a systematical and biostratigraphical point of view, these Carboniferous fossil-plant remains play a key role in the palaeogeographical debate concerning East and SE Asia. It is now ascertained that the Indo-China block, to which NE Thailand belonged, was in terrestrial connection with a north palaeotethyan land mass, most probably the South China block, at least since Early Carboniferous times. The East Malaya block, to which eastern Peninsular Malaysia belonged, was also undoubtedly related to the north palaeotethyan domain. However, additional data are needed to settle more precisely exact palaeogeographical locations and relationships during Carboniferous times.
Precambrian granulite facies rocks occur over an area of 100 km in the eastern part of Kontum Massif of Vietnam. This unusual occurrence of Precambrian high grade metamorphic rocks is separated from the closest similar rocks to the west in the Indian Eastern Ghats by over 2000 km. The intervening area is occupied by the Mesozoic-Cenozoic Burma-Malay orogen. In the reconstruction of Precambrian Gondwanaland a granulite facies mobile belt can be traced from Sri Lanka, India, Antarctica through to Australia. The tectonic history of the Indochina Block in the Precambrian is debatable, however, some latest Precambrian paleotectonic interpretations join this block and the Tibetan, Chinese and Iranian Blocks with Precambrian Gondwanaland. If the Kannack Complex is proved to be Archaean/Proterozoic, preliminary and incomplete information suggest that it could have been placed adjacent to the Eastern Ghats of India in the earliest Precmbrian. -from Author
Remnants of a Late Carboniferous volcanic arc extend through central northern Thailand. The assemblage consists of predominantly basaltic aquagene tuffs, agglomerates, and flows with diabasic and pyroxene-olivine porphyry intrusions and pyroxene and olivine cumulates. Having been subjected to deformation and low-grade regional metamorphism, the rocks are locally foliated and commonly contain chlorite, amphibole, calcite, and sericite. Chemical analyses and plots of relatively immobile elements show that the rocks are essentially tholeiitic basalts, possible generated in an island-arc environment. As the arc lies west of younger andesitic arcs and an ultramafic belt, it is interpreted to have been a precursor to convergence and eventual collision in the Trissic-Jurassic between the Thai-Burma-Malay and Indochina continental blocks. The distribution of volcanic and granitic rocks in northern Thailand implies convergence along a westward-dipping subduction zone.-Authors
Chert and associated fine-grained clastic rocks of Thailand and Peninsular Malaysia contain rich radiolarian faunas of Upper Devonian to Middle Triassic ages. Our serial study has clarified details of the geologic ages of these radiolarian-bearing rocks. We summarize the stratigraphic occurrences of the Radiolaria and discuss their paleobiogeographic and tectonic significance. The following 13 radiolarian assemblages are discriminated in these rocks; Helenifore laticlavium, Entactinia variospina, Pseudoalbaillela bulbosa, Pseudoalbaillella elegans, Pseudoalbaillella lomentaria, Pseudoalbaillella scalpra-ta, Follicucullus monacanthus, Follicucullus scholasticus, Neoalbaillella optima, Neoalbaillella ornithoformis, Entactinia nikorni, Parentactinia nakatsugawaensis, and Eptingium manfredi assemblages in stratigraphic order. Based on our radiolarian studies and accumulated paleobiogeographical data, the timing of collision of Shan-Thai with East Malaya, and of Shan-Thai with Indochina, are respectively assigned to the Early Triassic and Late Triassic or more recent.
Four suture zones are probably present in Burma. Regional evidence indicates that the eastern Burma-Chiang Rai-medial Malaya suture resulted from closure of an oceanic basin, ocean I, in the early Triassic Projection from Tibet suggests that ocean II, north of the Lhasa block, closed in the end-Jurassic, but together with the Lhasa block itself, the suture is largely or entirely buried in Burma. The Mount Victoria Land block rifted from Gondwanaland in the Jurassic and collided with Burma, following northeastward subduction of ocean III, in the early Cretaceous. Triassic flysch and ophiolite overlying this block in western Burma correlate with the Triassic flysch and overlying Zangbo ophiolite in Tibet, suggesting that the Triassic flysch of Tibet was never adjacent to India. In the Eocene, before dextral displacement on the Sagaing Fault, India collided with northern Burma following subduction of ocean IV. This resulted in elevation of the Mogok Belt and Shan Plateau above a southeastward continuation of the Himalayan Main Central Thrust.
Late Paleozoic diversified foraminiferal faunas indicating a middle or early late Viséan, early Serpukhovian, Moscovian, late Yakhtashian, late Bolorian or early Kubergandian, probably late Kubergandian, late Murgabian, and Murgabian or Midian age are disclosed from widespread carbonate rocks distributed in the Chiang Dao area, Northern Thailand. The area has been explained as a part of the Sibumasu (or Shan-Thai) Block of Gondwana origin. In this paper, we describe the detailed composition and characteristics of each foraminiferal fauna with illustrations of most diagnostic forms. Furthermore, we discuss the geologic age and affinity of the fauna, which give some critical constraints for the consideration of the geotectonic and paleobiogeographic evolution of Southeast Asia. All the Late Paleozoic foraminiferal faunas discovered in the Chiang Dao area show a close Tethyan affinity although the Early Carboniferous ones should be defined as cosmopolitan. Characteristics and succesion of the Late Paleozoic foraminiferal faunas observed in Northern Thailand are quite similar to those observed in the Indochina Block rather than the Sibumasu Block, and strongly suggest that carbonate rocks in Northern Thailand were deposited in a tropical condition. This means that the Northern Thailand area should be excluded from the currently defined Sibumasu domain. In the mainland of Thailand, the Nan-Uttaradit-Sa Kaeo Suture has long been regarded as a tectonic suture bounded the eastern limit of the Sibumasu domain, which was formed by the closure of the Palaeotethys having oceanic crust in Triassic time. However, it is highly probable that, at least in the northern part of Thailand, the eastern limit of the Sibumasu domain corresponds to the Mae Yuam (or Mae Sariang by some workers) Fault Zone running with the north-south direction near the border between Thailand and Burma, although its southern extension in Western and Central Thailand is further debatable.
The notion that the whole of South China was a post-Caledonian platform is clearly proven wrong by the evidence of Mesozoic deformation and igneous activity. Reinterpretation of map patterns suggests the presence of a Mesozoic orogenic belt comparable to Southern Appalachians in dimensions and in style of deformation. Field work in 1985 led to the discovery of possible flysch and rigid basement nappes, which have been thrust onto a carbonate platform. A suture zone has been identified. The Huanan Alps owed their origin to the early Mesozoic Indosinian Orogeny, which eliminated a Paleo-Tethyan Seaway, the Xiangganjhe Ocean between the Yangtze and Huanan Terranes.
Palaeomagnetic results from Malaya show that the Malay Peninsula lay at 15° N during the late Palaeozoic, a result incompatible with the hypothesis that it once formed a part of Gondwanaland adjacent to India or Australia. Cretaceous results suggest the Peninsula was not at that time finally welded to the Asian mainland.
The classical Paleozoic stratigraphic column in NW Thailand was described as a single Ordovician to Permian marine succession (including undated radiolarites), considered to be tectonized in Triassic time. Ages obtained from radiolarite dating (Carboniferous to Triassic) demonstrate the existence of a separated sedimentary basin far from detritic sources and far from the deposition area of the Carboniferous to Triassic limestones. The present structural imbrication of radiolarites with limestones and detritic series is interpreted in terms of tectonic nappes with considerable shortening, and olistostrome deposits. There is an abridged English version. -English summary
The rocks of the Sa Kaeo - Chanthaburi segment of the Nan-Chanthaburi suture zone between the Shan-Thai and Indochina/East Malaya continental blocks in Thailand comprise two parallel belts; a western belt of chert- clastic sequence, and an eastern belt of serpentinite melange. In order to understand the nature of the suture zone and to build up its tectonic sequence, we have investigated the lithology, age, stratigraphy, structure and relationships of their components. The core of all the questions is the radiolarian biostratigraphy and fusulinacean faunas in the suture zone and the continental blocks. Indochina/East Malaya had rifted away from northeastern margin of Gondwanaland by the Late Devonian. It is characterized by the mid-Permian fusulinids of the Lepidolina territory. In contrast, the Shan-Thai continental block had rifted from Gondwanaland by latest Permian time and its fusulinacean faunas are characterized by species of the Misellina - Maclaya - Neoschwagerina lineage of the Yabeina territory in the mid-Permian. However, it belongs to another lineage of Colania - Lepidolina evolutionary lineage in the late mid-Permian. The change of biofacies of the Shan-Thai block indicates the northward drift of the block crossing the equator. Middle Triassic Radiolaria have been obtained from red chert clasts of the red bed which unconformably overlies the serpentinite melange of the suture zone. Accordingly, the Shan-Thai block moved further towards the Indochina/East Malaya block and eventually collided with its southern margin in the Late Triassic.
All along the Tethys Himalaya, sandstones and conglomerates interbedded with transgressive arenites rich in bryozoans and brachiopods were deposited in estuarine to shallow-marine environments since the Late Sakmarian, at the end of the Gondwana glaciation. These elastics, representing the base of the Kuling Group in Spiti, disconformably overlie arenaceous to carbonate sedimentary units of various age, from Silurian and Devonian in the Parahio Valley to Lower Carboniferous in the Pin Valley, whereas they paraconformably follow lowermost Permian diamictites in the Spiti Valley. This major unconformity, which can be traced to the adjacent Zanskar and Lahaul regions where the Paleozoic succession is eroded more and more towards the west (western Zanskar) and south (Tandi Syncline), marks the end of rifting, followed by initial opening of Neo-Tethys and thermal subsidence of the newly-formed Indian passive margin. The Killing Group in Spiti consists of glaucony-rich pebbly arenites yielding brachiopods of Late Sakmarian age at the base and Midian/Early Djulfian age at the top (Gechang Formation), overlain by black phosphatic shales rich in brachiopods of Djulfian age (Gungri Formation). The much thicker Zanskar succession consists of glaucony-rich arenites containing brachiopods of Late Sakmarian age, mudrocks and microconglomerates (Chumik Formation), overlain by the Panjal Trap basaltic lavas and in turn by glaucony-rich arenites yielding brachiopods of Midian/Early Djulfian age, equivalent to the top of the Gechang Formation in Spiti. The overlying black shales of the Gungri Formation, deposited on an open shelf in warm climates, seal the Paleozoic succession in all studied areas, and thus document the final submergence of rift shoulders following the opening of Neo-Tethys.
In today's oceans, surface water masses exert a controlling effect on biogeographic provinces, climate-sensitive sediments and organic productivity, so it is important to understand the factors that generate and differentiate these water masses. A generalised temperature and salinity map of the Recent, with related effects like upwelling, sea ice, and surface runoff, has been compiled in a new attempt to define marine climates. Present-day climate-sensitive sediments are included to test their reliability as water mass indicators in the geological past. Then, reversing the approach, water mass maps for the nine Permian stages have been reconstructed from the sediment types as well as from biogeographic considerations. It is clear from the Present-day water mass map that geographically or bathymetrically restricted seaways are more likely to reflect local climate and be distinct from open ocean water masses in salinity or temperature. Our Permian maps have been prepared with this duality in mind: epeiric seaways are portrayed with the most differentiated water masses, while narrow continental shelves are generally similar to adjacent oceanic areas.
The Tethysides are the orogenic belts that grew out of the mostly collisional obliteration of the Tethyan domain. The Tethyan domain includes both the Palaeo-Tethys (the original triangular gap in Pangaea), and the Neo-Tethys (Tethys opened behind the Cimmerian Continent as it rifted away from northern Gondwana-Land and rotated to close Palaeo-Tethys) plus their continental margins of diverse types. The term Tethys was defined as a tectonic equivalent of the Centrall Mediterranean of Neumayr and should not be used as a palaeogeographic entity only. The evolution of the Tethysides discloses large amounts of orogen parallel (or subparallel) strike-slip faulting that significantly disrupted the Tethyan orogenic collage. The concept of “allochthonous terranes” is viewed to be little more than the concept of nappes (since the latter also included strike-slip generated slivers) and found a retrogressive step, if used in place of genetic concepts that have long superceded nappe descriptions in the Alpine System at least.