Ediacaran to Paleozoic magmatism in West Junggar Orogenic Belt, NW China, and implications for evolution of Central Asian Orogenic Belt

摘要

The formation of the Central Asian Orogenic Belt is thought to be related to the evolution of the Paleo-Asian Ocean surrounded by the Siberian, European, and Tarim-North China cratons. The West Junggar Orogenic Belt (WJOB) in the southern Central Asian Orogenic Belt is part of the Kazakhstan Junggar terrane between the Altay Orogenic Belt to the north and the Tianshan Orogenic Belt to the south. It is characterized by the development of the latest Ediacaran to Paleozoic intra-oceanic island arcs and accretionary complexes, including the latest Ediacaran to Ordovician Tangbale-Mayile arc-accretionary system in the south and Ordovician to Early Carboniferous Boshchekul-Chingiz arc and Zharma-Saur arc in the north, and a remnant ocean between them. Our work reveals that the Shinaizha, Kekesayi, and Barleik dioritic plutons within the Tangbale-Mayile arc are typical of arc-related magmatism and were formed between 572 and 505 Ma, which indicate the Ediacaran to Middle Cambrian subduction of the southern Paleo-Asian Ocean. However, these arc plutons were strongly deformed and surrounded by younger rocks, implying that the magmatic arc might be dismembered and involved into the Ordovician to Devonian accretionary complexes. The Boshchekul-Chingiz arc was recorded from Late Ordovician and its arc magmatism peaked in Late Silurian to Early Devonian. The arc moved northward due to the retreat of the south-facing Irtysh-Zaysan subduction zone, which resulted in the formation of contemporaneous A-type or peralkaline magmatic rocks or bimodal volcanics in response to the within-arc extension. The northward migration of the subduction zone led to the formation of the Devonian to Early Carboniferous Zharma-Saur arc. The earliest Late Carboniferous I-type granitoids occurred sporadically in WJOB, followed by pervasive occurrences of Late Carboniferous to Early Permian A- and I-type granitoids in WJOB and adjacent areas. The Late Carboniferous granitoids, combined with the Late Carboniferous stitching plutons within the Irtysh-Zaysan suture zone to the north and the North Tianshan suture zone to the south of WJOB, suggest the Kazakhstan-Junggar terrane collided with Altay and Tianshan orogenic belts in the latest Early Carboniferous (ca. 320 Ma). (C) 2019 Published by Elsevier B.V.