标题：Zircon U-Pb geochronology and geochemistry of the post-collisional volcanic rocks in eastern Xinjiang Province, NW China: implications for the tectonic evolution of the Junggar terrane
作者：Du, Qingxiang; Han, Zuozhen; Shen, Xiaoli; Han, Chao; Han, Mei; Song, Zhigang; Gao, Lihua; Liu, Hui; Zhong, Wenjian; Yan, Junlei
作者机构：[Du, Qingxiang; Han, Zuozhen; Shen, Xiaoli; Han, Chao; Han, Mei; Song, Zhigang; Gao, Lihua; Liu, Hui; Zhong, Wenjian; Yan, Junlei] Shandong Univ Sci & 更多
通讯作者地址：[Han, ZZ]Shandong Univ Sci & Technol, Coll Earth Sci & Engn, Shandong Prov Key Lab Deposit Mineralizat & Sedim, Qingdao 266590, Peoples R China.
来源：INTERNATIONAL GEOLOGY REVIEW
关键词：Post-collisional volcanic rocks; late Carboniferous; Junggar terrane;; basement; slap breakoff
摘要：We report zircon U-Pb geochronologic and geochemical data for the post-collisional volcanic rocks from the Batamayineishan (BS) Formation in the Shuangjingzi area, northwestern China. The zircon U-Pb ages of seven volcanic samples from the BS Formation show that the magmatic activity in the study area occurred during 342-304Ma in the Carboniferous. The ages also indicate that the Palaeo-Karamaili Ocean had already closed by 342Ma. Moreover, the volcanic rocks also contained 10 inherited zircons with ages ranging from 565 to 2626Ma, indicating that Precambrian continental crust or microcontinents with accretionary arcs are two possible interpretations for the basement underlying the East Junggar terrane. The sampled mafic-intermediate rocks belong to the medium-K to high-K calc-alkaline and shoshonitic series, and the formation of these rocks involved fractional crystallization with little crustal contamination. These Carboniferous mafic-intermediate rocks show depletions in Nb and Ta and enrichments in large ion lithophile elements (e.g. Rb, Ba, U, and Th) and light rare earth elements. The low initial Sr-87/Sr-86 values (0.7034-0.7042) and positive epsilon(Nd)(t) values (+2.63 to +6.46) of these rocks suggest that they formed from depleted mantle material. The mafic-intermediate rocks were most likely generated by 5-10% partial melting of a mantle source composed primarily of spinel lherzolite with minor garnet lherzolite that had been metasomatized by slab-derived fluids and minor slab melts. In contrast, the felsic rocks in the BS Formation are A-type rhyolites with positive epsilon(Nd)(t) values and young model ages. These rocks are interpreted to be derived from the partial melting of juvenile basaltic lower crustal material. Taken together, the mafic-intermediate rocks formed in a post-collisional extensional setting generated by slap breakoff in the early Carboniferous (342-330Ma) and the A-type rhyolites formed in a post-collisional extensional setting triggered by the upwelling asthenosphere in the late Carboniferous (330-304Ma).