Neoproterozoic back-arc and arc-type magmatisms in the Rutong and Shiquanhe region, west of Tibet: Tectonic implications for the early-stage evolution of the Bangong-Nujiang suture zone and North Lhasa terrane

作者：Xu Zhang, Dizhu Cai, Harald Furnes, Weiliang Liu, Rui Wang, Wei Li, Liao Xing, Chi Yan, Ruxin Ding, Yun Zhong · 发表于：Precambrian Research · 年份：2024 · DOI：10.1016/j.precamres.2024.107374 · 被引用次数：8 · 研究领域：Geological and Geochemical Analysis、Geochemistry and Geologic Mapping、Geochemistry and Geochronology of Asian Mineral Deposits

Due to limited exposure of the Precambrian rocks in the Tibetan Plateau, their affinities and evolutions are inadequately studied. Here we report the newly identified Neoproterozoic metabasites (including metagabbros and metadolerites) at the western end of the Bangong-Nujiang suture zone (BNSZ) and the west part of the North Lhasa terrane. The Rutong Dong (RTD) metagabbros and Shiquanhe Nan (SQN) metadolerites yield zircon U-Pb ages of 838 Ma and 748 Ma, respectively. The RTD metagabbros are tholeiitic and exhibit both MORB- and arc-like geochemical characteristics, and we consider these to have formed in a back-arc basin setting. Combined with positive zircon ε Hf (t) (+6.3 to +13.8) and whole-rock ε Nd (t) (+4.4 to +5.3) values, the geochemical features of the RTD metagabbros indicate that they originated from a depleted mantle source enriched by subduction-related components (e.g., Th and U). The SQN metadolerites are mainly of transitional character (between tholeiitic and calc-alkaline), as well as representing typical calc-alkaline basalts. Their arc-like geochemical characteristics, as well as low positive whole-rock ε Nd (t) (+1.7 to +3.4), and positive zircon ε Hf (t) (+4.3 to +5.9) values, indicate generation by partial melting of an enriched subduction components modified mantle in an arc-type setting. Based on previous research, we propose that the North Lhasa terrane likely separated from India at ca. 925–860 Ma by the opening of the Mozambique Ocean. As the sub...