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The ancient Tethys oceans of Asia: How many? How old? How deep? How wide? UNE Asia Centre UNEAC Paper

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I. Metcalfe at University of New England (Australia)
I. Metcalfe
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The Tethys in East Asia is represented by three successive ocean basins, the Palaeo-Tethys, Meso-Tethys and Ceno-Tethys. The Palaeo-Tethys ranges in age from late Early Devonian to Middle Triassic, Meso-Tethys from late Early Permian to Late Cretaceous, and Ceno-Tethys from Late Triassic (west)/Late Jurassic (east) to Cenozoic. These ocean basins had a range of water depths comparable to modern ocean basins and the concept of ‘Shallow Tethys’ should only be applied to the shallow regions of these oceans. All three Tethyan ocean basins, based on palaeogeographic reconstructions, had maximum widths between 2000 and 3000 km in their eastern parts at their maximum development.
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... Evolusi geologi Mersing boleh dibahagikan kepada beberapa fasa utama. Bukti lapangan berdasarkan singkapan batuan di sekitarnya menunjukkan evolusi bermula dengan fasa pemendapan sedimen di sekitaran laut dalam pada masa Karbon yang membentuk jujukan batuan Formasi Mersing (Cook & Suntharalingam, 1969;Foo, 1983;Hutchison, 1989;Suntharalingam, 1991;Bucher & Frey, 1994;Metcalfe, 1999;Metcalfe, 2000;Surjono & Leman, 2010). Pertembungan antara kepingan Malaya Timur dengan kepingan Sibumasu yang bermula semenjak akhir Karbon telah mengangkat dasar lautan menjadi daratan pertama pada masa Perm Awal. ...
... Proses tersebut telah mengangkat keseluruhan kawasan menjadi daratan, diikuti oleh proses luluhawa dan hakisan yang menghasilkan endapan daratan di dalam lembangan daratan yang terpencil dan terpisah-pisah membentuk jujukan batuan enapan daratan Formasi Tebak, Panti dan yang lain-lain berusia Jura hingga Kapur. Proses tersebut juga telah mengukir landskap daratan yang terlihat pada hari ini (Metcalfe, 1999;Metcalfe, 2000;Surjono et al., 2006;Metcalfe, 2017;JKSPMG, 2018;Komoo et al., 2019). Keseluruhan bukti-bukti lapangan yang menyokong evolusi geologi dalam jangka masa yang panjang tersebut adalah warisan geologi bernilai tinggi yang perlu dipelihara dengan baik untuk kita memahami sejarah tanah air yang menjadi kebanggaan semua komunitinya. ...
... Peristiwa canggaan (canggaan tektonik tempatan) dan metamorfisme rantau yang berlaku akibat penimbusan yang dalam (5 hingga 20 kilometer) dan rejarah granit yang membekalkan suhu yang tinggi (200 hingga 600 sentigred dengan tekanan 2 hingga 6 bar) ini ditafsirkan berlaku pada masa Paleozoik Atas telah menukar batuan tersebut menjadi filit, kuarzit dan meta-konglomerat hingga mencapai gred syis. Proses ini mengambil masa di antara 10 hingga 50 juta tahun (Bucher & Frey, 1994) dengan struktur canggaan yang sangat rencam dan telah mengangkat blok timur semenanjung terutama di bahagian Johor Timur yang ditafsirkan berlaku pada zaman Karbon Akhir disebabkan subdukan kepingan Paleo-Tethys dibawah Plat Indochina (Metcalfe, 1999;Metcalfe, 2000;Surjono & Leman, 2010). ...
Geological, Biological, Cultural And Local Wisdom Heritage A Key Element Of Mersing Geopark Development
Article
Full-text available
  • May 2021
The district of Mersing is bestowed with many national and international geological heritage sites dated since 350 million years ago. The high biodiversity and uniqueness of the local culture complements the geoheritage of the area. Thus, the National Geopark Committee has chosen Mersing as a territory to be developed as a geopark. Mersing Geopark development efforts were initiated in 2017 through the Mersing Geopark Scientific and Development Committee. The entire Mersing district of 6,371 square kilometers, including the marine areas right up to the Aur Archipelago is identified as the geopark area. The geoheritage here has been identified as 22 geosites, which cover land and island areas. Important flora and fauna have also been identified as being within the protected areas. The unique and preserved traditions of life, art and culture add to the value of this geopark. Several key elements were introduced to prepare Mersing Geopark before being evaluated as a national geopark candidate in December 2018, namely governance of the geopark - management based on ‘co-management’ mechanism, nature conservation – community, community economy through geotourism activities, and public education. Many programmes and activities have been carried out to face future plans for Mersing to become a UNESCO Global Geopark. Geopark enhances natural and cultural heritage resources through integrated development, geotourism development to increase income, preservation of heritage sites and empowerment of local communities to foster a strong sense of pride and belonging to a place.
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... Eclogites with well-preserved high-pressure (HP)-ultrahigh-pressure (UHP) assemblages record unique information on the physical-chemical conditions and tectono-metamorphic evolution of palaeosubduction zones (Ota & Kaneko, 2010;Chen et al., 2013;Erdman & Lee, 2014). The Palaeo-Tethys existed during a particularly important period in the geological evolution of SE Asia, from the Palaeozoic to the early Mesozoic (S¸engö r, 1979;Şengö r et al., 1984;Metcalfe, 1996Metcalfe, , 1999Metcalfe, , 2002Metcalfe, , 2006Metcalfe, , 2013. The opening and closure of the Palaeo-Tethyan Ocean were associated with the successive northwards drift of the South China, Indochina and North Qiangtang continental fragments from Gondwana, and the final assemblage of the Gondwana-derived Cimmerian Continent (made up, for example, of the Baoshan-Tengchong, Sibumasu and South Qiangtang blocks) to form SE Asia (Fig. 1a;S¸engö r et al., 1984;Metcalfe, 1996Metcalfe, , 2002Metcalfe, , 2006Metcalfe, , 2013Zhong, 1998). ...
... The opening and closure of the Palaeo-Tethyan Ocean were associated with the successive northwards drift of the South China, Indochina and North Qiangtang continental fragments from Gondwana, and the final assemblage of the Gondwana-derived Cimmerian Continent (made up, for example, of the Baoshan-Tengchong, Sibumasu and South Qiangtang blocks) to form SE Asia (Fig. 1a;S¸engö r et al., 1984;Metcalfe, 1996Metcalfe, , 2002Metcalfe, , 2006Metcalfe, , 2013Zhong, 1998). The Changning-Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau is a typical Palaeo-Tethyan subduction-accretionary belt with a lithological assemblage of ophiolite suites, oceanic seamount sequences, arc and back-arc volcanic rocks and high-pressure/low-temperature (HP/LT) rocks (YBGMR, 1990;Metcalfe, 1992Metcalfe, , 1996Metcalfe, , 1999Metcalfe, , 2002Zhang et al., 1993;Fang et al., 1994;Wu et al., 1995;Zhong, 1998;Feng, 2002;Jian et al., 2009aJian et al., , 2009bFan et al., 2015;Wang et al., 2019aWang et al., , 2019b. The CMOB extends northwestward to the Longmu Co-Shuanghu suture (LCSS) in the northern Tibetan Plateau, and southeastwards to the Chiang Mai-Inthanon suture zone in northern Thailand and the Bentong-Raub suture zone in Peninsular Malaysia, and it marks the main branch of the Palaeo-Tethyan Ocean in SE Asia (Fig. 1a;Fang et al., 1994;Metcalfe, 1996Metcalfe, , 1999Metcalfe, , 2002Metcalfe, , 2013Zhong, 1998;Sone & Metcalfe, 2008;Wang et al., 2018b). ...
... The Changning-Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau is a typical Palaeo-Tethyan subduction-accretionary belt with a lithological assemblage of ophiolite suites, oceanic seamount sequences, arc and back-arc volcanic rocks and high-pressure/low-temperature (HP/LT) rocks (YBGMR, 1990;Metcalfe, 1992Metcalfe, , 1996Metcalfe, , 1999Metcalfe, , 2002Zhang et al., 1993;Fang et al., 1994;Wu et al., 1995;Zhong, 1998;Feng, 2002;Jian et al., 2009aJian et al., , 2009bFan et al., 2015;Wang et al., 2019aWang et al., , 2019b. The CMOB extends northwestward to the Longmu Co-Shuanghu suture (LCSS) in the northern Tibetan Plateau, and southeastwards to the Chiang Mai-Inthanon suture zone in northern Thailand and the Bentong-Raub suture zone in Peninsular Malaysia, and it marks the main branch of the Palaeo-Tethyan Ocean in SE Asia (Fig. 1a;Fang et al., 1994;Metcalfe, 1996Metcalfe, , 1999Metcalfe, , 2002Metcalfe, , 2013Zhong, 1998;Sone & Metcalfe, 2008;Wang et al., 2018b). Eclogites and blueschists have been studied extensively in the LCSS ( Fig. 1a; e.g. ...
A New HP-UHP Eclogite Belt Identified in the Southeastern Tibetan Plateau: Tracing the Extension of the Main Palaeo-Tethys Suture Zone
Article
Full-text available
  • Oct 2020
The Changning-Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau is an important link between the Longmu Co-Shuanghu suture (LCSS) in the northern Tibetan Plateau and the Chiang Mai-Inthanon and Bentong-Raub sutures in Thailand and Peninsular Malaysia. These belts and sutures are generally regarded as containing the remnants of the oceanic crust of the Palaeo-Tethys that formed by seafloor spreading as a result of the separation of Gondwana-and Eurasia-derived blocks during the Middle Cambrian. In this paper we report the first discovery of abundant unaltered and retrograde eclogites that occur as irregular lenses and blocks in metasedimentary rocks of the CMOB, and these eclogites form an elongate and almost north-south-trending high-pressure (HP)-ultrahigh-pressure (UHP) metamorphic belt that is $200 km long and $50 km wide. The newly discovered phengite/talc/epidote-glaucophane eclogites, lawsonite-talc-phengite eclo-gites, dolomite/magnesite-kyanite eclogites and phengite-kyanite-bearing retrograde eclogites have enriched (E-) and normal mid-ocean ridge basalt (N-MORB)-like affinities and mainly positive as well as some negative whole-rock e Nd values (-4Á34 to þ7Á89), which suggest an enriched and depleted oceanic lithosphere source for their protoliths. Magmatic zircons separated from the epi-dote-glaucophane, magnesite-kyanite and (phengite-kyanite-bearing) retrograde eclogites gave protolith ages of 317-250 Ma, which fit well within the time frame of the opening of the Palaeo-Tethys during the Middle Cambrian and its closure during the Triassic. Abundant metamorphic zircons in the eclogites indicate a Triassic metamorphic event related to the subduction of the Palaeo-Tethys oceanic crust from 235 to 227 Ma. Taking into account previous isotopic age data, we now establish the periods of Early-Middle Triassic (246-227 Ma) and Late Triassic (222-209 Ma) as the ages of subduction and exhumation of the Palaeo-Tethyan oceanic crust, respectively. Thermodynamic modelling revealed that the eclogites record distinct HP-UHP peak metamorphic conditions of 23Á0-25Á5 kbar and 582-610 C for the phengite-glaucophane eclogites, 24Á0-25Á5 kbar and 570-586 C for the talc-glaucophane eclogites, 29Á0-31Á0 kbar and 675-712 C for the dolomite-kyanite eclogites, and 30Á0-32Á0 kbar and 717-754 C for the magnesite-kyanite eclogites. These P-T estimates and geochronological data indicate that the Palaeo-Tethys oceanic slab was sub-ducted to different mantle depths from 75 km down to 95 km, forming distinct types of eclogite with a variety of peak eclogite-facies mineral assemblages. The eclogites consistently record clockwise metamorphic P-T-t paths characterized by a heating-compression prograde loop under a low geo-thermal gradient of 5-10 C km-1 , indicating the rapid subduction of cold oceanic crust at a rate of 4Á5-6Á0 km Ma-1 , followed by isothermal or cooling-decompressive retrogression and exhumation at an average rate of 3Á2-4Á2 km Ma-1. The newly discovered eclogites of the CMOB with their signatures of ocean-crust subduction are petrologically, geochemically and geochronologically V C The Author(s) comparable with those of the LCSS, providing powerful support for the idea that a nearly 2000 km long HP-UHP eclogite belt extends from the northern Tibetan Plateau to the southeastern Tibetan Plateau, and that it represents the main boundary suture of the Palaeo-Tethyan domain. These results have far-reaching implications for the tectonic framework and complex metamorphic evolution of the Palaeo-Tethyan domain.
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... The metamorphic pressure-temperature-time (P-T-t) trajectories recorded by these HP rocks provide robust insights into the burialexhumation process at convergent plate boundaries (Hacker et al., 2003;Ernst and Liou, 2008;Ota and Kaneko, 2010). Understanding the evolutionary history of Eastern Paleo-Tethys is critical for the reconstruction of the tectonic and geodynamic evolution of southeastern Asia (Sengör, 1979;Sengör et al., 1984;Metcalfe, 1992Metcalfe, , 1996Metcalfe, , 1999Metcalfe, , 2002Metcalfe, , 2006Metcalfe, , 2011Metcalfe, , 2013. The evolution of the Paleo-Tethys witnessed separation of a series of continental fragments, such as the Yangtze and Indochina blocks, from the northern margin of the Gondwana supercontinent and their subsequent incorporation into the Gondwana-derived Cimmerian continent (e.g., the Sibumasu Block and Baoshan-Tengchong Block) shaping the tectonic framework of southeastern Asia during the Paleozoic to Early Mesozoic (Sengör et al., 1984;Metcalfe, 1996Metcalfe, , 2002Metcalfe, , 2006Metcalfe, , 2011Metcalfe, , 2013Zhong, 1998). ...
... The evolution of the Paleo-Tethys witnessed separation of a series of continental fragments, such as the Yangtze and Indochina blocks, from the northern margin of the Gondwana supercontinent and their subsequent incorporation into the Gondwana-derived Cimmerian continent (e.g., the Sibumasu Block and Baoshan-Tengchong Block) shaping the tectonic framework of southeastern Asia during the Paleozoic to Early Mesozoic (Sengör et al., 1984;Metcalfe, 1996Metcalfe, , 2002Metcalfe, , 2006Metcalfe, , 2011Metcalfe, , 2013Zhong, 1998). The Changning-Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau has been interpreted as the main suture of the Paleo-Tethys (Fang et al., 1994;Metcalfe, 1996Metcalfe, , 1999Metcalfe, , 2002Metcalfe, , 2013Zhong, 1998;Sone and Metcalfe, 2008;Wang et al., 2018). Blueschist facies rocks are widely distributed in the CMOB, defining an elongated N-Sextending HP metamorphic belt that is~300 km in length and 10-12 km in width ( Fig. 1A; Zhang et al., 1993). ...
... The Changning-Menglian orogenic belt is located within the southeastern Tibetan Plateau and extends approximately 300 km from north to south (Fig. 1A). The orogenic belt records the final closure of the main Paleo-Tethyan Ocean and is correlated northwestward with the Longmu Co-Shuanghu suture (LCSS) in the northern Tibetan Plateau and southeastwards with the Chiang Mai-Inthanon suture zone in northern Thailand and the Bentong-Raub suture zone in Peninsular Malaysia ( Fig. 1A; Liu et al., 1991;Fang et al., 1994;Metcalfe, 1996Metcalfe, , 1999Metcalfe, , 2002Metcalfe, , 2013Zhong, 1998;Li et al., 2006;Sone and Metcalfe, 2008;Wang et al., 2018). The CMOB is bounded by the Baoshan-Tengchong Block to the west and the Lanping-Simao Block to the east and is dominantly composed of ophiolitic mélanges, oceanic seamount volcano-sedimentary suites, HP metamorphic complexes and subduction-related arc volcanic rocks ( Fig. 1A; YBGMR, 1990;Liu et al., 1991;Fang et al., 1994;Wu et al., 1995;Metcalfe, 1996Metcalfe, , 1999Metcalfe, , 2013Zhong, 1998;Feng, 2002;Peng et al., 2008Peng et al., , 2013Jian et al., 2009aJian et al., , 2009bFan et al., 2015;Wang et al., 2018;H. ...
Rapid cold slab subduction of the Paleo-Tethys: Insights from lawsonite-bearing blueschist in the Changning–Menglian orogenic belt, southeastern Tibetan Plateau
Article
  • Jun 2020
  • GONDWANA RES
The Changning–Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau is considered as the main suture of the Paleozoic Paleo-Tethys that separates Gondwana-derived continental fragments from Eurasia-derived ones. Understanding the evolutionary history of this orogenic belt is of critical importance in the reconstruction of the tectonic history of Paleo-Tethys. The CMOB preserves well-exposed blueschist facies rocks, albeit their tectonometamorphic history and protolith signatures remain poorly constrained. Here we present, for the first time, results from a detailed investigation of lawsonite-bearing blueschist rocks, including epidote-magnesioriebeckite schist and garnet-ferroglaucophane schist from the CMOB and involving petrological, mineralogical, thermodynamic modeling, whole-rock geochemical, and geochronological studies. The epidote-magnesioriebeckite schist samples and garnet-ferroglaucophane schist samples display OIB- and E-MORB-like geochemical affinities, respectively, and have whole-rock εNd (t) values in the range of −5.4–+4.4, suggesting that their protoliths were mainly oceanic crust with limited degree of crustal assimilation. Magmatic zircon grains from the garnet-ferroglaucophane schist samples yield protolith ages of 253–250 Ma. Combined with previous data, our data represent the youngest ages of rock formation in the Paleo-Tethyan Ocean reported to date. The epidote-magnesioriebeckite schist samples show a peak assemblage of magnesioriebeckite + lawsonite + augite-aegirine + phengite + titanite + allanite, with peak P–T conditions of 12.4–16.8 kbar and 350–406 °C. In contrast, the garnet-ferroglaucophane schist samples preserve a peak assemblage of garnet + ferroglaucophane + omphacite + lawsonite + phengite + titanite/ilmenite/rutile ± allanite and yield peak P–T conditions of 19.5–22.6 kbar and 490–510 °C. The epidote-magnesioriebeckite schists and garnet-ferroglaucophane schists record a nearly complete clockwise P–T loop characterized by a steep prograde P–T path with a low thermal gradient of ~5–8 °C/km followed by cooling or overprinting by isothermal decompression. Reconstruction of the metamorphic P–T evolution, together an evaluation of previous age data, allows us to propose rapid subduction of cold oceanic lithosphere to depths of 50–75 km at a rate of ~6.3–9.3 km/Myr during Early-Middle Triassic (248–240 Ma), followed by exhumation in the Late Triassic (231–214 Ma). The short time lag (<10 Ma) between the protolith generation and the high-pressure metamorphic peak further supports a rapid subduction process. Our results suggest that the young oceanic slab was dragged down by the thicker, long-lived, and cold downgoing Paleo-Tethyan Ocean plate, where it experienced blueschist-facies metamorphism. The co-occurrence of lawsonite-bearing epidote-magnesioriebeckite schists and garnet-ferroglaucophane schists and eclogites further points to a cold thermal structure at the convergent plate interface, leading to the interpretation that the CMOB represents a typical oceanic subduction-accretion belt. The results presented in this study provide important insights into the geodynamic evolution of the Paleo-Tethys.
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... In the present work, the chert samples were collected in Alluvial Kızılırmak Delta Basin, Bafra District, Northern Anatolia (Fig. 1). During formation of silicious sediment layer in Archean period, primitive organisms and microorganisms like cyanobacteria and amoeba lived in warm and shallow parts of Tethys oceans between Eurasia and Africa main lands until the end of Proterozoic Period, (until 541 Ma) [10][11][12]20]. Silicious sediments mixed with fossils of microorganisms lying in deeper layers of ground raised upward in the following Paleozoic and Mesozoic eras and Anatolian land, and hence Pontic Mountains along North Anatolia emerged over sea. ...
... Silicious sediments mixed with fossils of microorganisms lying in deeper layers of ground raised upward in the following Paleozoic and Mesozoic eras and Anatolian land, and hence Pontic Mountains along North Anatolia emerged over sea. Silicious sediment containing fossils of microorganisms suffered from extraordinary heat and pressure by tectonic movements of the North Anatolian Fault, (NAF,(11)(12)(13)(14)(15), under the stress of main lands and hot magmatic material [10,[20][21][22][23]. After experiencing metamorphosis for enough time span and slow cooling, cryptocrystalline or microcrystalline chert pieces including organic impurities were formed. ...
EPR Investigation of Organic Radicals in Chert Found in Alluvial Soil of Kızılırmak Delta Basin
Article
Full-text available
  • Aug 2022
  • APPL MAGN RESON
Chert samples found in alluvial soil of Kızılırmak Delta basin, Bafra District on the shore of Black Sea, were investigated with Electron Paramagnetic Resonance (EPR) spectroscopy which is one of the basic spectroscopic methods used to obtain information about free radicals trapped in various environments and the structure of paramagnetic centers. Organic impurities in chert samples are sensitive to high-energy radiation and are stable under normal environmental conditions. Microcrystalline chert samples include various organic radicals which are preserved in leakproof cages in SiO2 lattices. The origin of organic impurities from primitive microorganisms in Archean silicified sediments of Tethys oceans, crystallization of chert from sediments in North Anatolian Fault and formation of organic radicals were discussed. EPR investigations of radicals were carried out on non-irradiated and irradiated chert samples to see the radiation response, under variable microwave power and temperature conditions to determine the dynamics and stabilities of radicals in chert samples.
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... The Changning-Menglian orogenic belt in the south-eastern Tibetan Plateau is an important oceanic subduction-accretion belt, and has been considered as the main suture of the Paleo-Tethys bound by the Gondwana-derived Baoshan-Tengchong Block and Eurasia-derived Lanping-Simao Block ( Fig. 1; Fang et al., 1994;Metcalfe, 1996Metcalfe, , 1999Metcalfe, , 2002Metcalfe, , 2011Metcalfe, , 2013Mo et al., 1998;Sone and Metcalfe, 2008;Wang et al., 2018;YBGMR, 1990;Zhang et al., 1993;Zhong, 1998). This belt consists mainly of ophiolitic suites, oceanic seamount series, arc volcanic rocks, granites, eclogites, blueschists, and voluminous metasedimentary rocks ( Fig. 1; Fan et al., 2015;Fang et al., 1994;Feng, 2002;Jian et al., 2009aJian et al., , 2009bWang et al., 2019aWang et al., , 2019bWu et al., 1995;YBGMR, 1990;Zhang et al., 1993;Zhong, 1998). ...
... The Changning-Menglian orogenic belt is located in southeastern Tibetan Plateau, and extends NNW-SSE for 300 km, separating the Baoshan-Tengchong Block to the west from Lanping-Simao Block to the east (Metcalfe, 1996(Metcalfe, , 1999(Metcalfe, , 2013Wang et al., 2018;YBGMR, 1990;Zhong, 1998). This belt consists mainly of the Paleo-Tethyan Oceanderived ophiolitic mélanges and oceanic island volcano-sedimentary sequences, island-arc volcanic rocks, Lincang granites, and metamorphic complex rocks (Fan et al., 2015;Fang et al., 1994;Feng, 2002;Jian et al., 2009aJian et al., , 2009bLiu et al., 1991;Peng et al., 2008Peng et al., , 2013Wang et al., 2019aWang et al., , 2019bWu et al., 1995;YBGMR, 1990;Zhong, 1998). ...
Subduction erosion associated with Paleo-Tethys closure: Deep subduction of sediments and high pressure metamorphism in the SE Tibetan Plateau
Article
Full-text available
  • Feb 2020
  • GONDWANA RES
Subduction erosion along active convergent plate margins involves arc subduction, tectonic erosion and sediment subduction. Here we investigate the metasedimentary rocks enclosing blueschists and eclogites in the Changning–Menglian orogenic belt (CMOB) of the southeastern Tibetan Plateau which marks the main suture associated with the closure of the Paleo-Tethyan Ocean between the Baoshan–Tengchong and Lanping–Simao blocks. We present an integrated study of petrology, mineral chemistry, whole-rock geochemistry, zircon U–Pb geochronology, and phengite ⁴⁰Ar/³⁹Ar isotopes. These rocks consist mainly of Ph-Qz schist, Ab-Qz-Ph schist, Grt-Ph schist, St-Ky-bearing Grt-Ms schist, and Cld-Pg-Ph schist. They display compositions similar to arkose and subarkose with trace element patterns overlapping those of the upper continental crust, and suggest immature and weak to moderate chemical weathering. The detrital zircon age spectra are dominated by two major age groups of 600–450 Ma with a peak at 550 Ma, and 1150–850 Ma with a peak at 950 Ma, suggesting that the metasedimentary rocks were sourced from a mixture of Precambrian sediments in the Lanping–Simao Block and Pan-African Orogeny-related magmatic rocks with minor Early Paleozoic Proto-Tethyan subduction- and volcanic rocks related to the onset of oceanic spreading of Paleo-Tethys. Combined with the maximum depositional age of ~428 Ma based on the youngest detrital age peaks, we infer that the Lancang Group could be the Early Paleozoic sedimentary sequence of the Lanping–Simao Block and was deposited in a foreland setting. The metasedimentary rocks display high-pressure (HP) mineral assemblages involving Ph + Ab + Qz, Grt + Ph + Qz, Grt + Ky + Ph, and Cld + Pg + Ph, and record blueschist facies to eclogite facies peak P–T conditions of 18.8–21.6 kbar at 392–553 °C (Grt-Ph schists) and 20–24.2 kbar at 592–654 °C (St-Ky-bearing Grt-Ms schists). Metamorphic zircon U–Pb and phengite ⁴⁰Ar/³⁹Ar isotopic analyses from these rocks yield consistent peak HP ages of 238–235 and 237–231 Ma, respectively, whereas ⁴⁰Ar/³⁹Ar dating for the Grt-Ph schist with low Si contents in phengite yields the post-peak age at 226.2 ± 1.3 Ma. We propose that a significant volume of sediments in Lancang Group at the western margin of the Lanping–Simao Block were off scraped by the downgoing oceanic lithosphere associated with the Paleo Tethyan ocean closure, and subducted to depths of ~60–80 km during Middle Triassic. These were subsequently rapidly exhumated at a rate of ~5.7–6.5 km/myr in the Late Triassic. The subduction erosion model proposed in our study has important implications for reconstructing the evolutionary history of the Paleo-Tethys as well as the architecture variation of the paleosubduction zone.
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... Considering the estimated divergence time of members of the genus shown in the molecular clock trees, the ancestors are likely to have originated in the Panthalassic Ocean (ancestral Pacific) sometime during the Late Jurassic to Early Cretaceous period, spread westward to the Tethys Sea during the Cretaceous just before India rifted from the Antarctic plate (Dietz and Holden 1970) and later settled in the present-day Indian Ocean and the Mediterranean Sea in the Late Cretaceous. After the closure of Meso-Tethys and complete opening of Ceno-Tethys in the Late Cretaceous (Metcalfe 1999), the allopatric speciation events leading to the extant species are supposed to have occurred in the Mediterranean Sea in the early Paleogene (ca. 55 Ma) onwards. ...
Global Diversity and Geographic Distributions of Padina Species (Dictyotales, Phaeophyceae): New Insights Based on Molecular and Morphological Analyses
Article
  • Sep 2020
  • J PHYCOL
The taxonomic status and species diversity of the brown algal genus Padina (Dictyotales, Phaeophyceae) was assessed based on DNA sequences and the morpho-anatomy of specimens collected worldwide, especially from tropical and subtropical western Pacific regions. Phylogenetic analyses using chloroplast rbcL and mitochondrial cox3 gene sequences demonstrated four distinct clades for newly collected samples with high bootstrap support. Each species clade possesses a suite of morphological features that are not shared by any known species of Padina. These are P. imbricata sp. nov., Padina lutea sp. nov., P. moffittianoides sp. nov. and P. nitida sp. nov. The occurrence of these and other species of Padina clearly points to an elevated diversity of the genus in tropical/subtropical waters of the western Pacific. Phylogenetic analyses provided new insights into biogeographical characteristics of the genus, with many species in the Pacific Ocean showing shared/overlapping distributions, whereas species from the Mediterranean/Atlantic and/or the Indian Ocean tend to be confined to particular regions. Consideration has also been given to the evolutionary time frame of the genus Padina based on molecular time trees: a time tree of the concatenated data set (rbcL+cox3) revealed the estimated divergence time in the mid-Cretaceous, whereas those of cox3 and rbcL showed older estimates pointing to the periods of mid-Jurassic and Early Cretaceous, respectively.
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... In south-east Asia, three successive ancient ocean basins -i.e., the Palaeo-Tethys, Meso-Tethys, and Neo-Tethys, represent the Tethys Ocean whose origin is linked with the rifting of continental slivers from the northern margin of the Gondwanaland since the Palaeozoic (Metcalfe 1996). Rifting of continental slivers (i.e., Lhasa, West Myanmar, and other small continental fragments now located in SW Sumatra, Borneo and Sulawesi) from the Gondwanaland during Late Jurassic/Late Triassic to Cenozoic triggered the formation of the Neo-Tethys (Gaetani and Garzanti 1991;Metcalfe 1999). Relics of this oceanic lithosphere are now dispersed along the Indo-Myanmar Ranges (IMR) and the Yarlung Zangpo Suture Zone (YZSZ) in southern Tibet (Mitchell 1993;Gopel et al. 1984) Figure 1. ...
Petrogenesis of neo-Tethyan ophiolites from the Indo-Myanmar ranges: a review
Article
Full-text available
  • Jun 2020
A comprehensive whole-rock geochemical study of peridotites and volcanic rocks from the Indo-Myanmar Ranges (IMR) ophiolites deduces the source and extent of mantle melting and role of subduction components in modifying its melt composition. Melt modelling yields partial melting in the range of ~5–25% (with a maximum up to 20%) from a depleted MORB mantle (DMM) source. Two types of subduction component seem to have modified the IMR volcanics. The addition of hydrous fluids from a subducting slab has enriched few IMR volcanics in large-ion lithophile elements (LILEs) while those enriched in LREEs were affected by melts derived from subducting sediments. The MORB-Arc basalt geochemical signatures of the IMR volcanics are attributed to the evolving magma as the extent of mantle melting increases under the influence of fluids/melts from the dehydrating slab/sediments in the later stages of subduction initiation (SI).
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Mesozoic transformation of Western Australia: rifting and breakup of Gondwana
Book
Full-text available
  • Feb 2023
Mesozoic transformation of Western Australia spans 252 to 66 Ma, an era represented by sedimentary deposits that cover about 23% of the onshore part of the State and virtually all offshore basins, with Upper Jurassic – Cretaceous deposits extending beyond the continent onto oceanic crust. These sedimentary successions are up to 15 km thick in offshore depocentres and the Perth Basin, and contain only minor igneous rocks apart from areas near the continent–ocean boundary where intrusions are abundant. Because of subdued tectonic events, the major resources within the Mesozoic are hydrocarbons in the offshore basins whereas, onshore, the most significant resources in, or uses of, Mesozoic strata are heavy mineral sand deposits on the Dampier Peninsula, water resources and gas storage. The Mesozoic depositional and structural history of the State and its surrounding waters is illustrated with a series of state-wide paleogeographic reconstructions paired with isopach mages — which represent ‘time slices’ derived from regional correlations largely based on biostratigraphic studies. The four main phases of basin evolution are: Triassic intracratonic rifting, Early–Middle Jurassic rifting, Late Jurassic – Early Cretaceous breakup and separation, and lastly trailing-edge rifting and marginal sag. However, these phases are not synchronous, as there are differences between some areas in their timing, especially with the progressive breaking away of continental fragments from north to south.
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Cross Orogenic Belts in Central China: Implications for the tectonic and paleogeographic evolution of the East Asian continental collage
Article
  • May 2022
  • GONDWANA RES
The East Asian continent records a complex geologic and tectonic history that involved the amalgamation of several small- to medium-sized blocks from Laurasia or Gondwana. The China continent is located at the core of East Asia, and is the key to understanding the formation and evolution of the East Asian Continent. The most important tectonic framework controlling the formation and evolution of the main China continent is the EW-trending Central China Orogenic Belt and the NS-trending Helan-Chuandian Orogenic Belt, defined as the ‘Cross Orogenic Belts’. The former includes, from east to west, the Qinling, Qilian and Kunlun Orogens, which were formed by the subduction-collision between the southern and northern continental blocks during the Early Paleozoic–Triassic and constitute the mainland of China Continent. Following this, the Central China Orogenic Belt was overprinted by the Mesozoic to Cenozoic intracontinental orogenic events, resulting in a prominent north and south division of geology, geography, ecology, environment, economy and culture. The latter inherited the Paleoproterozoic and the Neoproterozoic plate tectonic frameworks in its north and south, respectively, and was gradually transformed into the continental margin of the Paleo-Asian Ocean or Paleo-Tethys tectonic domain. Associated with the Neo-Tethys tectonic evolution, it evolved into the eastern boundary of the uplift and expansion of the Tibetan Plateau, controlling the Late Mesozoic–Cenozoic reverse evolution of the western and eastern China Continent. The Cross Orogenic Belts experienced multiple phases of uplift, which were dominated by deep geological process together with surface geomorphologic influence. The uplift of the Cross Orogenic Belts resulted in differential evolution of the climate, environment, as well as economy and culture in four quadrants of the China Continent.
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Dynamics of closure of the Proto-Tethys Ocean: A perspective from the Southeast Asian Tethys realm
Article
  • Oct 2021
  • EARTH-SCI REV
The force that drives continental drift has been one of the most challenging subjects of extensive discussions in the last decades. The Proto-Tethys evolution exemplifies a scenario of drifting of continental plates during closure of the Proto-Tethys Ocean. The Pan-Cathaysian blocks in the Southeast Asian tectonic realm (SATR) derived from break-up of the Rodinia supercontinent witnessed the entire process of the Proto-Tethys evolution. The blocks and suture zones between them offer information on the dynamics of continental drifting linked to shallow mantle convection and deep mantle flow. Early Proto-Tethys break-up tectonics is evidenced by volcano-sedimentary records and their source affinities in the SATR. Gondwana-centered convergence of the blocks initiated when the Rodina supercontinent broke-up in the Neoproterozoic. The Proto-Tethys convergent tectonics in the SATR was formed from the subduction of the Proto-Tethys Changning-Menglian (CM) Ocean beneath the northern margin of the Gondwana and of a subsidiary basin, i.e., the Tam Ky-Phuoc Son-Po Ko (TPP) Ocean. Occurrence of tectonic mélanges (e.g., the Lancang mélange) and extensive arc (continental or intra-oceanic) magmatic rocks attests the switch from passive to active plate margins, forming advancing subduction zones (Andean-type) along both distal and proximal margins of the CM Ocean, and within and along the proximal margin of the TPP Ocean. Rifting (Jinshajiang-Ailao Shan-Song Ma, or JAS) and back-arc rifting (Dapingzhang) occurred during or subsequent to the transition from advancing subduction to retreating subduction along the southern margin of the Indochina block. Suturing and collision of the blocks in the SATR occurred in the late early Paleozoic, which is evidenced by, e.g., existence of high-pressure rocks along the CM suture and post-collisional magmatic rocks along the Tam Ky-Phuoc Son suture. The Proto-Tethys evolution narrates a scenario of supercontinent break-up and assembly. Progressive Gondwana-centered convergent drifting of the Pan-Cathysian blocks induced progressive closure of the Proto-Tethys main and subsidiary oceans, and rifting and closing of the rift basin or back-arc basin. Advancing subduction-ridge spreading-retreating subduction systems (ARRs) or subduction-spreading-subduction systems (SSSs) were formed and transported toward the Gondwana during the convergent drifting of the continental blocks. It is suggested that coupled shallow- and deep mantle flow (i.e., stratified mantle convection) is the major driving mechanism of the Gondwana-centered convergence of the Pan-Cathaysian blocks. In the model, the shallow-mantle convections directly affected the subduction geometries and plate kinematics, while the deep-mantle convection is responsible for the drifting of the continental blocks, formation of ARRs and migration of the SSSs.
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The Fit of the Continents around the Atlantic
Article
Full-text available
  • Oct 1965
The geometrical fit of the continents now separated by oceans has long been discussed in relation to continental drift. This paper describes fits made by numerical methods, with a `least squares' criterion of fit, for the continents around the Atlantic ocean. The best fit is found to be at the 500 fm. contour which lies on the steep part of the continental edge. The root-mean-square errors for fitting Africa to South America, Greenland to Europe and North America to Greenland and Europe are 30 to 90 km. These fits are thought not to be due to chance, though no reliable statistical criteria are available. The fit of the block assembled from South America and Africa to that formed from Europe, North America and Greenland is much poorer. The root-mean-square misfit is about 130 km. These geometrical fits are regarded as a preliminary to a comparison of the stratigraphy, structures, ages and palaeomagnetic results across the joins.
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Allochthonous Terrane Processes in Southeast Asia [and Discussion]
Article
Full-text available
  • Jun 1990
Southeast Asia comprises a complex agglomeration of allochthonous terranes located at the zone of convergence between the Eurasian, Indo-Australian and Philippine Sea plates. The older continental `core' comprises four principal terranes, South China, Indochina, Sibumasu and East Malaya, derived from Gondwana-Land and assembled between the Carboniferous and the late Triassic. Other terranes (Mount Victoria Land, Sikuleh, Natal, Semitau and S. W. Borneo) were added to this `core' during the Jurassic and Cretaceous to form `Sundaland'. Eastern Southeast Asia (N. and E. Borneo, the Philippines and eastern Indonesia) comprises fragments rifted from the Australian and South China margins during the late Mesozoic and Cenozoic which, together with subduction complexes, island arcs and marginal seas, form a complex heterogeneous basement now largely covered by Cenozoic sediments. Strike-slip motions and complex rotations, due to subduction and rifting processes and the collisions of India with Eurasia and Australia with Southeast Asia, have further complicated the spatial distribution of these Southeast Asian terranes. A series of palinspastic maps showing the interpreted rift-drift-amalgamation-accretion history of Southeast Asia are presented.
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The Ocean Basins and Margins. Vol 4A: The Eastern Mediterranean
Article
  • Jan 1977
The boundary between the Eurasian and the African plates, formerly the suture between Eurasia and Gondwana, has been the locus of violent tectonic diastrophism and rapidly changing geography since the Triassic. The Mesozoic seas, and sometimes the Paleozoic seas, of this zone and its extension into the Himalayan region are known as the Tethys (Neumayr, 1883; Bittner, 1896; Suess, 1893, 1901; cf. e.g., Kamen-Kaye, 1972), while Tertiary seas are usually called the Mediterranean. From the viewpoint of plate tectonics, it would appear appropriate to talk in general of the African—Eurasian boundary seas. We can try to trace the history of the Tethyan or Mediterranean seas from the breakup of Pangea at the end of the Triassic through the Mesozoic and Cenozoic. The most ambitious attempt to do this has been by Dewey et al. (1973) as a sequel to a model for the opening of the Atlantic Ocean proposed by Pitman and Talwani (1972). However, although the general postulates are valid and, within the framework of plate tectonics, even obvious, the actual implementation of this kinematic jigsaw puzzle is very difficult. It is also ambiguous because of large gaps in information and in the differences in language and interpretation by the various investigators. Indeed, at present, there is no model that would not be seriously questioned by one part or another of the earth science community.
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Provenance and Depositional Setting of Paleozoic Chert and Argillite, Sierra Nevada, California
Article
  • Jan 1996
The Shoo Fly Complex, the remnants of an early to middle Paleozoic subduction system, contains the Culbertson Lake allochthon. Included in the Culbertson Lake allochthon are the post-Cambrian and pre-Upper Devonian Quartz Hill, Toms Creek, and McMurray Lake cherts. Geochemical data derived from these three units plot on the Fe 2O 3/TiO 2 versus Al 2O 3/(Al 2O 3 + Fe 2O 3) and La n/Ce n versus Al 2O 3/ (Al 2O 3 + Fe 2O 3) discrimination diagrams within either the continental margin-island arc field, or that part of the pelagic field overlapping the continental margin-island arc field. These relationships are consistent with the presence of argillaceous turbidites interstratified with radiolarite, and suggest a relatively distal continental-island arc setting where muddy turbidity currents episodically interrupted pelagic deposition. Specimens from the Quartz Hill and Toms Creek cherts with Al 2O 3/ TiO 2 values > 20 make up Group I samples, whereas specimens with Al 2O 3/TiO 2 values < 10 are classified as Group II samples. The Al 2O 3/ TiO 2 ratios of Group II specimens suggest derivation from mafic rock. Mean Th/Sc and Th/U values, as well as LREE-enriched patterns, are consistent with this interpretation, and indicate a source area dominated by alkalic seamount or ocean island material. The Al 2O 3/TiO 2 ratios of Group I samples indicate a source area with an average andesitic to rhyodacitic composition. Chondrite-normalized REE distribution patterns, as well as mean Th/Sc and Th/U values, support such an interpretation. Samples from the McMurray Lake chert have Al 2O 3/TiO 2 values ranging between ∼ 19 and ∼ 28, and REE patterns characterized by LREE enrichment, negative Eu anomalies, and slightly fractionated HREE patterns. These features, along with mean Th/Sc and Th/U values, indicate a source area dominated by old upper continental crust. The location of the source area(s) supplying material to cherts and argillites of the Culbertson Lake allochthon is unknown. However, existing tectonic models commonly portray the source of old upper continental crustal material in the Shoo Fly Complex as being located somewhere along the western North American continental margin, whereas the source of island-arc debris is portrayed as being located in a fringing arc system. Our data suggest that a relatively high-standing seamount or ocean island probably resided on the subducting oceanic plate. Thus, our work supports the idea that Al, Fe, Ti, Th, Sc, and the REEs in chert and argillite deposited in proximal continental-island arc settings can be used to assess the characteristics of sources supplying particulate matter to ancient trench systems.
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