EARLY STAGE OF THE CENTRAL ASIAN OROGENIC BELT BUILDING: EVIDENCES FROM THE SOUTHERN SIBERIAN CRATON

Abstract Gennaeocrinus tariatensis new species is an Emsian (Devonian) monobathrid crinoid described from the Tarvagatay Terrane of Mongolia and part of the Central Asian Orogenic Belt. The Tarvagatay Terrane is an arc terrane that accreted to the southern margin of the Siberian Craton. Gennaeocrinus tariatensis was collected from the Emsian Tariat Formation, a terrigenous sequence of conglomerates, sandstones, and siltstones. Associated faunas include brachiopods, molluscs, and rare tabulate corals. Although Gennaeocrinus is well known from the Emsian–Givetian of North America, this is the first occurrence of the genus outside Laurussia. Mongolia is a large country with many terranes having varied paleogeographic, sedimentological, and tectonic histories; but reports of Paleozoic echinoderms are rare. The crinoid occurrence from the Tariat Formation is from the same age as previously described Emsian crinoids from the Chuluum Formation but differs significantly in sedimentology, paleogeography, and paleolatitude. UUID: http://zoobank.org/d87cb083-4360-41e5-ac90-1b8ef625a31d

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Arc-arc collision in the Central Asian Orogenic Belt: insight from the eastern segment of the Irtysh Shear Zone, NW China.

10.5194/egusphere-egu21-1653 ◽

2021 ◽

Author(s):

Wanwan Hu ◽

Pengfei Li

Keyword(s):

Shear Zone ◽

Early Stage ◽

Development Program ◽

Orogenic Belt ◽

Central Asian Orogenic Belt ◽

Southern Chinese ◽

Central Asian ◽

Tectonic Reconstruction ◽

Eastern Segment ◽

Parallel Extension

As the largest accretionary orogen, the Central Asian Orogenic Belt (CAOB) involved episodic accretion/collision of arc terranes or microcontinental blocks from Neoproterozoic to late Paleozoic. Understanding the time and processes of such collisional events is crucial for the tectonic reconstruction of the CAOB. Here we focus on the Irtysh Shear Zone that represents the suture of the Peri-Siberian orogenic system (Chinese Altai Orogen) with the Kazakhstan orogenic system/East Junggar Terrane. On a basis of a combined structural and chronological study along the eastern segment of the Irtysh Shear Zone (Qinghe area), we reconstructed the collisional processes of the Chinese Altai Orogen with an intra-oceanic island arc of the East Junggar Terrane. Our results show that the oceanic basin between the Chinese Altai Orogen and the East Junggar Terrane was completely consumed in the late Carboniferous. The following arc-arc collision was characterized by early stage of orogen-perpendicular contraction, followed by orogen-parallel extension and transpressional deformation. The orogen-parallel extension, which is demonstrated by originally sub-horizontal foliation and associated orogen-parallel stretching lineation, may have be responsible for Permian high-temperature metamorphism and extensive magmatism in the southern Chinese Altai. On a scale of the western CAOB, the sinistral kinematics of the Irtysh Shear Zone, together with dextral shearing farther south in the Tianshan, suggests eastward tectonic wedging in the Permian, possibly in response to the coeval convergence of the Siberian, Baltic, and Tarim cratons.E-mail addresses: [email protected], [email protected] (P. Li).Acknowledgements: this study was financially supported by the National Natural Science Foundation of China (41872222), the National Key Research and Development Program of China (2017YFC0601205), Hong Kong Research Grant Council (HKU17302317) and a project from Guangdong Province (2019QN01H101).

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