Evolution of calc-alkaline to alkaline magmatism through Carboniferous convergence to Permian transcurrent tectonics, western Chinese Tianshan

Abstract

Continuous magmatic activity occurred in the western Chinese Tianshan, Central Asia, from the Carboniferous to the Permian, i.e. before and after the Late Carboniferous amalgamation of Junggar and the Yili Blocks. Zircon U-Pb LA-ICPMS and Ar-Ar data reveal a coincidence in time between regional wrench faulting and granitoid emplacement. Permian post-collisional granitoids crop out within or at the margins of large-scale dextral strike-slip shear zones, some of them show synkinematic fabrics. The whole rock geochemical features of the Early-Middle Permian granitoids indicate an evolution from high-K calc-alkaline towards alkaline series. In other places of the North Tianshan, alkaline magmatism occurred together with deep marine sedimentation within elongated troughs controlled by wrench faults. Therefore, in contrast with previous interpretations that forwarded continental rift or mantle plume hypotheses, the coexistence of diverse magmatic sources during the same tectonic episode suggests that post-collisional lithosphere-scale transcurrent shearing tightly controlled the magmatic activity during the transition from convergent margin to intraplate anorogenic processes.

Reconstructing the Late Palaeozoic – Mesozoic topographic evolution of the Chinese Tian Shan: available data and remaining uncertainties

“…1 and 3a) (e.g. Han et al, 2009;Wang et al, 2009;Charvet et al, 2011;Xia et al, 2012). However, the modalities of that last accretion event are still discussed.…”

“…Hence, alternative models proposed that the Carboniferous magmas would have been generated during southward subduction of the North Tian Shan Ocean (in these models a branch of the wide Paleo-Asian Ocean) underneath the Yili block (e.g. Wang et al, 2006Wang et al, , 2009Han et al, 2009;Charvet et al, 2011). The North Tian Shan ophiolite sequence would correspond to an accretionary wedge developed in front of a Carboniferous forearc.…”

Sr, Nd and O isotopic characters of quartz syenite in the Weiya magmatic complex from eastern Tianshan in NW China: Melting of the thickened juvenile lower crust

“…Then, tectonic regime of eastern Tianshan change from compression to extension, resulting in emplacement of numerous postcollisional granitoids and mafic-and ultra-mafic rocks with ages ranging from around 300 Ma to 260 Ma in Central Tianshan , and in the Ooltag (Mao et al, 2002;Qin et al, 2002;Xu et al, 2003;Han et al, 2004;Zhou et al, 2004), Bogda (Gu et al, 2001b;Xia et al, 2007;Wang et al, 2009) and Kelameili-Harlik orogenic belts (Gu et al, 1999;Sun et al, 2007;Xiao et al, 2008). In accompany with these events, the Aqikkudug-Shaquanzi (ASF, Fig.…”

New structural data on Late Paleozoic tectonics in the Kyrgyz Tien Shan (Central Asian Orogenic Belt)

“…In China, observations on this margin two magmatic events are observed and correspond to the closure of two different oceanic domains: (i) the northward subduction of an oceanic domain located between the Tarim craton and the Yili-NTS block during the Ordovician (Allen et al, 1993;Chen et al, 1999;Gao et al, 2009Gao et al, , 1998Qian et al, 2009;Windley et al, 1990;Xiao et al, 2014Xiao et al, , 2004 ; (ii) the southward subduction of an oceanic domain located between the NTS and the Junggar block during the Carboniferous (Allen et al, 1993;Charvet et al, 2011;Wang et al, 2009Wang et al, , 2008Windley et al, 1990).…”