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203. Multi-system geochronological and isotopic constraints on age and evolution of the Gaoligongshan metamorphic belt and shear zone system in western Yunnan, China

Author

Eroglu, S., Siebel, Wolfgang, Danisik, Martin, Pfänder, Jörg A., Chen, Fukun, Eroglu, S., Siebel, Wolfgang, Danisik, Martin, Pfänder, Jörg A., and Chen, Fukun

Abstract

The Gaoligongshan metamorphic belt, located east of the Eastern Himalayan Syntaxis (EHS) in the Yunnan province, southwestern China, is a compelling region in which to determine temporal constrains on crustal dynamic processes related to the Himalayan orogeny. We applied multi-system geo- and thermochronology (900 °C to <50 °C) to orthogneiss and mylonites from a major shear zone in the southern Gaoligongshan in order to elucidate the magmatic, cooling and exhumation history of this belt. Zircon U/Pb data reveal three magmatic events at ∼486 Ma, ∼136 Ma and ∼76 Ma. Similar ages are found in orthoderivative rocks of the neighboring Tengchong and Baoshan blocks, and the Gangdese batholith, suggesting that the southern Gaoligongshan is composed of an assemblage of Lhasa and Qiangtang terrane derived rocks. Muscovite Rb/Sr ages of 35–21 Ma are coeval with the onset of lateral crustal displacement along major shear zones in Eastern Tibet and Indochina, and with the post-collision volcanic activity in western Yunnan. Biotite Rb/Sr and mica 40Ar/39Ar ages provide evidence that mylonitization along the Gaoligongshan shear zone and crustal rotation of the Tengchong and Baoshan blocks proceeded during the Miocene, between 19 and 12 Ma, when the rocks rapidly cooled through the 350–280 °C temperature range. Almost identical 40Ar/39Ar ages reported for the Karakorum–Jiali–Parlung Fault system in Western Tibet suggest that the Gaoligongshan shear zone is the southeastern continuation of this fault, recording the eastward extrusion of Tibet and crustal movement around the EHS. The final stage of exhumation of the Gaoligongshan occurred between 8 and 5 Ma at an average exhumation rate of ∼3 km/Ma as documented by apatite fission-track and apatite (U–Th–Sm)/He data. This rapid exhumation was triggered by crustal root delamination and opening of the Andaman sea. Our results clearly show that the complex tectonothermal evolution of the Gaoligongshan was influenced by Tibetan extrusio

Published
2013
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233. Age Constraints on Late Mesozoic Lithospheric Extension and Origin of Felsic Volcanism in the Songliao Basin, NE China.

Author

Li, Shuang-Qing, Yang, Yi-Zeng, Xie, Qing-Lu, Wang, Yan, and Chen, Fukun

Subjects
VOLCANISM, FELSIC rocks, LITHOSPHERE, MESOZOIC Era, ZIRCON, ANORTHITE, INDUCTIVELY coupled plasma mass spectrometry
Abstract

Late Mesozoic lithospheric extension in NE Asia resulted in the development of a large extensional province and widespread formation of volcanosedimentary basins. Songliao basin is the biggest in that region, situated between the Siberian and Sino-Korean (North China) cratons. The Songliao basin contains voluminous volcanic rocks as a major part of the basin fill. Volcanic successions form a significant but unexposed part of the late Mesozoic magmatic province in NE China. Here we report zircon U-Pb ages and geochemical data for felsic volcanic rocks from the Songliao basin. Zircon populations of two types of rhyolites with distinct I- and A-type affinities, analyzed by laser ablation inductively coupled plasma mass spectrometry, yielded similar U-Pb ages of 114 ± 2 and 113 ± 2 Ma, respectively. Whole-rock Nd and zircon Hf isotope data of the felsic rocks indicate an origin from newly formed crustal protoliths. The I-type dacites and rhyolites show geochemical signatures with subduction-related affinity, indicating generation by partial melting of juvenile crust that originated from melting of subduction-modified mantle sources, whereas the A-type rhyolites have higher heavy rare earth element and high field strength element concentrations and lower Ba/Nd ratios that are interpreted as evidence for melting of I-type felsic lower crustal sources in an intraplate tectonic environment. Typical geochemical compositions of A-type rhyolites indicate anorthite-rich plagioclase as a residual magmatic phase and imply melting at shallow crustal levels. The A-type felsic rocks were generated during a period of maximum lithospheric extension below eastern China around 110 Ma, and this thinning process was probably related to the retreat of the Paleo-Pacific trench. [ABSTRACT FROM AUTHOR]

Published
2015
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234. Geochemistry and zircon ages of mafic dikes in the South Qinling, central China: evidence for late Neoproterozoic continental rifting in the northern Yangtze block.

Author

Zhu, Xiyan, Chen, Fukun, Liu, Bingxiang, Zhang, He, and Zhai, Mingguo

Subjects
*GEOCHEMISTRY, *ZIRCON, *MAFIC rocks, *NESOSILICATES, *MASS spectrometry
Abstract

Neoproterozoic volcanic-sedimentary sequences of the southern Qinling belt, central China, were intruded by voluminous mafic dikes. secondary ion mass spectrometry zircon U-Pb dating indicates that these dikes were emplaced at 650.8 ± 5.2 Ma, coeval with mafic rocks occurring at the northern margin of the Yangtze block. The dikes are characterized by enrichment of large ion lithophile elements, high Ti contents (up to 3.73 wt%) and Nb/Ta ratios between 14.5 and 19.6, suggesting a mantle source of oceanic island basalt affinity. Initial Sr/Sr ratios show positive correlation with SiO contents and negative correlation with Zr/Nb ratios, implying that these rocks were affected by crustal contamination during the magma ascend and emplacement process. The dikes have initial ε values of +0.2 to +3.3, low Pb/Pb ratios of 16.96-17.45, and moderate Sr/Sr ratios of 0.7043-0.7076, likely pointing to the involvement of an enriched mantle source. The mafic dikes and coeval mafic volcanic equivalents in the South Qinling and the northern Yangtze are hypothesized to be related with the prolonged breakup of the supercontinent Rodinia, suggesting that continental rifting lasted until ca. 650 Ma. [ABSTRACT FROM AUTHOR]

Published
2015
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249. Sequencing of 19,219 exomes identifies a low-frequency variant in FKBP5promoter predisposing to high myopia in a Han Chinese population

Author

Su, Jianzhong, Yuan, Jian, Xu, Liangde, Xing, Shilai, Sun, Mengru, Yao, Yinghao, Ma, Yunlong, Chen, Fukun, Jiang, Longda, Li, Kai, Yu, Xiangyi, Xue, Zhengbo, Zhang, Yaru, Fan, Dandan, Zhang, Ji, Liu, Hui, Liu, Xinting, Zhang, Guosi, Wang, Hong, Zhou, Meng, Lyu, Fan, An, Gang, Yu, Xiaoguang, Xue, Yuanchao, Yang, Jian, and Qu, Jia

Abstract

High myopia (HM) is one of the leading causes of visual impairment and blindness worldwide. Here, we report a whole-exome sequencing (WES) study in 9,613 HM cases and 9,606 controls of Han Chinese ancestry to pinpoint HM-associated risk variants. Single-variant association analysis identified three newly identified -genetic loci associated with HM, including an East Asian ancestry-specific low-frequency variant (rs533280354) in FKBP5. Multi-ancestry meta-analysis with WES data of 2,696 HM cases and 7,186 controls of European ancestry from the UK Biobank discerned a newly identified European ancestry-specific rare variant in FOLH1. Functional experiments revealed a mechanism whereby a single G-to-A transition at rs533280354 disrupted the binding of transcription activator KLF15 to the promoter of FKBP5, resulting in decreased transcription of FKBP5. Furthermore, burden tests showed a significant excess of rare protein-truncating variants among HM cases involved in retinal blood vessel morphogenesis and neurotransmitter transport.

Published
2023
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