The Central Tianshan Block is one of numerous microcontinental blocks within the Central Asian Orogenic Belt (CAOB) that overlies Precambrian basement rocks. Constraining the evolution of these ancient basement rocks is central to understanding the accretionary and collisional tectonics of the CAOB, and their place within the Rodinia supercontinent. However, to date, the timing and tectonic settings in which the basement rocks in the Central Tianshan Block formed are poorly constrained, with only sparse geochemical and geochronological data from granitic rocks within the northern segment of the block. Here, we present a systematic study combining U–Pb geochronology, whole-rock geochemistry, and the Sr–Nd isotopic compositions of newly-identified granitic gneisses from the Bingdaban area of Central Tianshan Block. The analyzed samples yield a weighted mean Neoproterozoic 206Pb/238U ages of 975–911 Ma. These weakly-peraluminous granitic rocks show a common geochemical I-type granite affinity. The granitic gneisses are calc-alkaline and enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), but they are depleted in high field strength elements (HFSEs); these characteristics are similar to those of typical subduction-related magmatism. All samples show initial (87Sr/86Sr)(t) ratios between 0.705136 and 0.706745. Values for ?Nd(t) in the granitic gneisses are in the range from –5.7 to –1.2, which correspond to Nd model ages of 2.0–1.7 Ga, indicating a role for Mesoproterozoic to Paleoproterozoic rocks in the generation of the granitic protoliths. The documented geochemical features indicate that the protoliths for the gneisses have a similar petrogenesis and magmatic source, which may reflect partial melting of thickened crust with the addition of small amounts of mantle-derived material. The Central Tianshan Block probably constitute part of an exterior orogen that developed along the margin of the Rodinian supercontinent during the Early Neoproterozoic and underwent a transition from subduction to syn-collision compression at 975–911 Ma.

SONG Yujia;LIU Xijun;XIAO Wenjiao;ZHANG Zhiguo;LIU Pengde;XIAO Yao;LI Rui;WANG Baohua;LIU Lei;HU Rongguo

Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,College of Earth Sciences,Guilin University of Technology,Guilin 541004,China;Xinjiang Research Center for Mineral Resources,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,China;Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resource,Guilin University of Technology,Guilin 541004,China

干旱区科学

[1]SONG Yujia;LIU Xijun;XIAO Wenjiao;ZHANG Zhiguo;LIU Pengde;XIAO Yao;LI Rui;WANG Baohua;LIU Lei;HU Rongguo-.Neoproterozoic I-type granites in the Central Tianshan Block (NW China): geochronology, geochemistry, and tectonic implications)[J].干旱区科学,2022(01):82-101

microcontinental,overlies,Bingdaban,Rodinian

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