Early Paleozoic to Devonian multiple-accretionary model for the Qilian Shan, NW China

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• 作者：Wenjiao Xiao ; Brian F. Windley ; Yong Yong ; Zhen Yan ; Chao Yuan ; Chuanzhou Liu ; Jiliang Li
• 关键词：Qilian ; Subduction– ; accretion ; Tectonic architecture ; Northern Tibetan Plateau
• 刊名：Journal of Asian Earth Sciences
• 出版年：2009
• 出版时间：1 July 2009
• 年：2009
• 卷：35
• 期：3-4
• 页码：323-333
• 全文大小：1823 K

文摘

The Qilian Shan, located in the northern Tibetan Plateau of NW China, has an excellent record of early to middle Paleozoic subduction–accretion that resulted from convergence between the Alax and Qaidam blocks, but there is no consensus about its detailed tectonic history. This paper summarizes its tectonic divisions and discusses its tectonic evolution from the Cambrian to Devonian. The belt has the following tectonic divisions: In the far north the southern passive margin of the Alax block is juxtaposed against an early Cambrian to Ordovician, Marianan-type intra-oceanic arc (North Qilian). The North Qilian arc is separated from a Japanese-type arc (Central Qilian) to the south by a high-pressure metamorphic belt composed mostly of ophiolitic slices and oceanic crusts. The Central Qilian is bounded to the south by a wide mélange zone (South Qilian), consisting of ophiolitic slices and continental margin sequences. Farther to the south lies the Oulongbuluk microcontinent that is separated from the Qaidam block and farther south by an ultrahigh-pressure metamorphic belt. Tectonostratigraphic analysis, together with geochemical, geochronological, and geophysical data, indicates a complex evolution by subduction–accretion processes from the Cambrian to the Devonian before final amalgamation and docking to the northern Alax block. This model solves the long-lasting discussion on the polarity of subduction in Paleozoic time; this multiple subduction–accretion history sheds light on the continuity of Paleozoic sutures along the Qilian Shan and the nature of the Altyn Tagh fault, and thus contributes to an improved understanding of the tectonic architecture of Central Asia.