Paleotethyan subduction process revealed from Triassic blueschists in the Lancang tectonic belt of Southwest China

Wu, Fan; Wang, Yuejung; Zhang, Yanhua; Zhang, Yuzhi; Jourdan, Fred; Zi, Jian–Wei; Liu, Huichuan

doi:10.1016/j.tecto.2014.12.021

Cited by 94 publications

(75 citation statements)

References 74 publications

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“…In addition, the retrograded eclogites fall in the field of the seamount in the (La/Sm) N versus Th/Yb diagram (Figure f; John, Schenk, Haase, Scherer, & Tembo, ). Thus, we infer that the igneous precursors of retrograded eclogites were generated from a basaltic seamount in an intra‐oceanic setting, similar to the case of Suyi blueschists in the CMOB (Fan et al., ). Taking into account the protolith age of 451 ± 3 Ma for the retrograded eclogite (Figure b), we infer that the igneous precursor for the retrograded eclogites in the CMOB corresponds to Ordovician oceanic crust.…”

Section: Discussionmentioning

confidence: 53%

“…Evidence for the closure of an ancient seafloor in this region includes the latest arc volcanics at 248.5 ± 6.3 Ma (Peng et al., ), discontinuous lithostratigraphic sequences in the Triassic (e.g., Feng, ; Wu et al., ) and the metamorphic age of LT/HP rocks generated in the subduction zone (Ernst & Liou, ; Maruyama, Liou, & Terabayashi, ). A phengite 39 Ar/ 40 Ar age of 242 ± 5 Ma corresponding to the time of the continental collision event was identified from the Suyi blueschists in the CMOB (Fan et al., ). Retrograded eclogite samples 16BD01‐2 and 16BD11‐2 from the CMOB contain no magmatic zircon or inherited zircon cores (Figure c,d).…”

Section: Discussionmentioning

confidence: 99%

“…These rocks were interpreted as the products of Proto‐Tethyan subduction (Figure a; Nie, Feng, Qian, & Wang, ; Xia et al., ). Blueschists in the study area commonly occur within micaschists (Lancang Group) as interlayered or lenticular bodies, and (from west to east) are mainly exposed in the Damangguangfang, Suyi and Nanlang areas (Fan et al., ; Wang et al., ; Zhang, Li, Lü, Yu, & Wang, ). Rare retrograded eclogites exposed as N–S trending blocks within micaschists in the CMOB show intense retrogression, but the peak metamorphic mineral assemblages are partly preserved (Li et al., ).…”

Section: Geological Backgroundmentioning

confidence: 99%

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Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Wang

Liu

Li³

et al. 2018

Journal Metamorphic Geology

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The Changning–Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau, is considered as the main suture zone marking the closure of the Palaeo‐Tethys Ocean between the Indochina and Sibumasu blocks. Here, we investigate the recently discovered retrograded eclogites from this suture zone in terms of their petrological, geochemical and geochronological features, with the aim of constraining the metamorphic evolution and protolith signature. Two types of metabasites are identified: retrograded eclogites and mafic schists. The igneous precursors of the retrograded eclogites exhibit rare earth element distribution patterns and trace element abundance similar to those of ocean island basalts, and are inferred to have been derived from a basaltic seamount in an intra‐oceanic tectonic setting. In contrast, the mafic schists show geochemical affinity to arc‐related volcanics with the enrichment of Rb, Th and U, and depletion of Nb, Ta, Zr, Hf and Ti, and their protoliths possibly formed at an active continental margin tectonic setting. Retrograded eclogites are characterized by peak metamorphic mineral assemblages of garnet, omphacite, white mica, lawsonite and rutile, and underwent five‐stage metamorphic evolution, including pre‐peak prograde stage (M1) at 18–19 kbar and 400–420°C, peak lawsonite‐eclogite facies (M2) at 24–26 kbar and 520–530°C, post‐peak epidote–eclogite facies decompression stage (M3) at 13–18 kbar and 530–560°C, subsequent amphibolite facies retrogressive stage (M4) at 8–10 kbar and 530–600°C, and late greenschist facies cooling stage (M5) at 5–8 kbar and 480–490°C. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) U–Pb spot analyses of zircon show two distinct age groups. The magmatic zircon from both the retrograded eclogite and mafic schist yielded protolith ages of 451 ± 3 Ma, which is consistent with the ages of Early Palaeozoic ophiolitic complexes and ocean island sequences in the CMOB reported in previous studies. In contrast, metamorphic zircon from the retrograded eclogite samples yielded consistent Triassic metamorphic ages of 246 ± 2 and 245 ± 2 Ma, which can be interpreted as the timing of closure of the Palaeo‐Tethys Ocean. The compatible peak metamorphic mineral assemblages, P–T–t paths and metamorphic ages, as well as the similar protolith signatures for the eclogites in the CMOB and Longmu Co–Shuanghu suture (LCSS) suggest that the two belts formed part of a cold oceanic subduction system in the Triassic. The main suture zone of the Palaeo‐Tethyan domain extends at least 1,500 km in length from the CMOB to the LCSS in the Tibetan Plateau. The identification of lawsonite‐bearing retrograded eclogites in the CMOB provides important insights into the tectonic framework and complex geological evolution of the Palaeo‐Tethys.

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Section: Discussionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

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Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Wang

Liu

Li³

et al. 2018

Journal Metamorphic Geology

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“…In contrast, the Lancang giant igneous rocks easterly adjacent to the Wuliangshan area mainly formed at ~230 Ma with seldom data yielding zircon U-Pb age of older than 245 Ma (Peng et al, 2013;Wang et al, 2010). Available data show that the Suyi blueschists, which originated from a seamount, give a zircon U-Pb age of 260±4 Ma and glaucophane minerals formed during prograde metamorphism yield a 40 Ar/ 39 Ar plateau age of 242±5 Ma (Fan et al, 2015). The associated ophiolite and volcanic rocks along the Changning-Menglian suture and Lancangjiang tectonic zone suggest a switch from the eastward subduction of the Paleotethyan main ocean to the collision of the Baoshan with Simao-Indochina blocks most likely occurring at ~240 Ma (Fan et al, 2015).…”

Section: Provenance and Tectonic Implicationsmentioning

confidence: 99%

“…Available data show that the Suyi blueschists, which originated from a seamount, give a zircon U-Pb age of 260±4 Ma and glaucophane minerals formed during prograde metamorphism yield a 40 Ar/ 39 Ar plateau age of 242±5 Ma (Fan et al, 2015). The associated ophiolite and volcanic rocks along the Changning-Menglian suture and Lancangjiang tectonic zone suggest a switch from the eastward subduction of the Paleotethyan main ocean to the collision of the Baoshan with Simao-Indochina blocks most likely occurring at ~240 Ma (Fan et al, 2015). The Lincang granitic batholith and related igneous rocks represent the derivation of the mantle wedge in a post-collisional setting at 210-232 Ma .…”

Section: Provenance and Tectonic Implicationsmentioning

confidence: 99%

Detrital zircon U-Pb geochronology and Lu-Hf isotopic compositions of the Wuliangshan metasediment rocks in SW Yunnan (China) and its provenance implications

Xing

Wang

Zhang³

2016

J. Earth Sci.

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The Wuliangshan Group occurs to the east of the Lancang giant igneous zone in SW Yunnan, and is mainly composed of low-grade metamorphosed sedimentary rocks. The group has been considered as the syn-orogenic product of the Baoshan with Simao-Indochina blocks. However, its depositional time and provenance remain to be poorly constrained. This paper presents zircon U-Pb dating and Lu-Hf-isotopic data for five representative sandstone samples from the Wuliangshan Group. The detrital grains yield a major age-peak at ~259 Ma, and four subordinary age-peaks at ~1 859, ~941, ~788, and ~447 Ma, respectively. Our results suggest that the Wuliangshan metasedimentary sequence was deposited after Middle Triassic rather than previously-thought Cambrian. The detrital zircon age spectrum, along with in-situ Lu-Hf isotopic data suggest that the Wuliangshan Group might be a syncollisional sedimentary product related to the collision of Baoshan with Simao-Indochina blocks. It is inferred that the provenance of the Wuliangshan Group is mainly from the Simao/Yangtze blocks to the east rather than the Baoshan Block or Lancang igneous zone to the west. KEY WORDS: detrital zircon U-Pb dating, Lu-Hf isotopic composition, Wuliangshan sandstone sequence, Middle Triassic, Simao-Indochina. INTRODUCTIONThe SE Asia has been assembled by a series of collision and accretion processes involving numerous continental blocks or fragments separated from the East Gondwana since the Paleozoic (Faure et al., 2014;Metcalfe, 2006). The catchment areas of the Lancang, Jinsha and Nujiang rivers (also named Sanjiang in Chinese literature) in SW Yunnan (SW China) have preserved abundant paleotethyan heritages (e.g., the Lincang giant igneous zone) at which kilometer-thick Triassic volcanic rocks and Upper Triassic/Lower Jurassic molasse sediments are considered to have resulted from closure of the Paleotethys main ocean and subsequent continental collision (Peng et al., 2008(Peng et al., , 2006 Jian et al., 2003a, b;Mo et al., 1998;Zhong, 1998; Cong et al., 1993;Mahawat et al., 1990;Liu et al., 1989;Zhang et al., 1985).It has been commonly accepted that the Paleotethys main ocean was closed by an eastward subduction beneath the Indochina-Simao Block in the Permian-Triassic (Zaw et al., 2014;Wang et al., 2010). However, the precise timing of the initial collision of the Baoshan and Simao-Indochina blocks remains to be disputed. Previous studies focused on the origin of the Triassic igneous rocks along the Lancangjiang tectonic zone. Little attention has been paid to the coeval sedimentary rocks which preserved abundant geological records on the Paleotethyan tectonic evolution. The sedimentary rocks can provide key information to the time of closure of the Paleotethyan Ocean and subsequent collision of the Baoshan and Simao-Indochina blocks. The Wuliangshan Group occurs to the east of the Lancang giant igneous zone. It is mainly composed of low-grade metamorphosed sedimentary rocks. This group is likely syn-orogenic product of the Paleotethyan orog...

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Three types of Triassic granitoids in Changning‐Menglian suture zone: Petrological, geochemical, and geochronological constraints for source characteristics and petrogenesis

Zhao

Xue

et al. 2022

Geological Journal

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The Triassic granitoids are widely exposed along the Changning‐Menglian suture zone (CMSZ) in SW China, which are the products of Palaeo‐Tethyan closure and are characterized by highly variable geochemical compositions. However, details of the implied source heterogeneity and magma genesis have not been well constrained. In this study, we present zircon U–Pb isotopes and trace elements, whole‐rock major and trace element compositions and Sr–Nd isotopes of Triassic granitoids from the giant Yunling and Lincang plutons developed in the CMSZ. Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating indicates that they were emplaced at ca. 227–216 Ma. Geochemically, these Triassic granitoids can be classified into three types. The Yunling low‐silica granodiorites (Type 1) are characterized by the presence of amphibole‐bearing mineral assemblages, high TiO2 and FeOT + MgO, belonging to I‐type granite and calc‐alkaline series. The Lincang low‐silica granodiorites (Type 2) are metaluminous to peraluminous with the occurrence of amphibole, consistent with transitional I‐S‐type granites. Compared to Type 1 and 2, the Lincang high‐silica (SiO2 > 70%) alkali feldspar granites and syenogranites (Type 3) display lower CaO, TiO2, P2O5, MgO + FeOT, Eu, Sr, and Zr contents, belonging to fractionated‐type granites. Three types of granitoids collectively show enriched Rb, Th, K, and Pb, depleted Ba, Sr, Ti, and Eu, negative whole‐rock εNd(t) (−11.0 to −10.7) and old TDM2 ages of 1,886–1,855 Ma, indicating the affinity of middle‐upper crustal derivation. New zircon U–Pb dating yields an age range of 2,391–322 Ma for inherited zircons with two clusters at ca. 460 and 956 Ma, suggesting that their crustal source might be the basement of the Simao Block rather than the basement of the Proterozoic Lancang Group. Diverse geochemical compositions indicate that the parental magma of the Triassic granitoids in the CMSZ originated from the partial melting of a heterogeneous source, and experienced magma mixing, assimilation with Lancang Group meta‐sandstone and fractional crystallization. Considering the exhumation of the high‐pressure metamorphic rocks in the CMSZ at Triassic, the upwelling of the asthenosphere after the Palaeo‐Tethyan closure increased the geothermal gradient of the lithosphere and triggered extensive crust melting in a post‐collisional setting.

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Paleotethyan subduction process revealed from Triassic blueschists in the Lancang tectonic belt of Southwest China

Cited by 94 publications

References 74 publications

Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Petrology, geochemistry and P–T–t path of lawsonite‐bearing retrograded eclogites in the Changning–Menglian orogenic belt, southeast Tibetan Plateau

Detrital zircon U-Pb geochronology and Lu-Hf isotopic compositions of the Wuliangshan metasediment rocks in SW Yunnan (China) and its provenance implications

Three types of Triassic granitoids in Changning‐Menglian suture zone: Petrological, geochemical, and geochronological constraints for source characteristics and petrogenesis

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