Whole rock geochemistry, zircon U-Pb dating and Sr-Nd and Hf isotopic studies of Cretaceous granitoids from Southern Pamir, Tajikistan: insights into Pamir Plateau formation

The Southern Pamir region, a critical part of the Alpine-Himalayan orogenic belt, exhibits a complex tectonomagmatic history that offers insights into the geodynamic evolution of the Pamir Plateau. This study presents comprehensive data on the Cretaceous granitoids from the Kyzylrabat area, including whole-rock geochemistry, zircon U-Pb geochronology and Sr-Nd-Hf isotopic analyses. The analysed granitoids are high-K calc-alkaline to shoshonitic, exhibiting A-type geochemical signatures. Zircon U-Pb ages range from 98.5 to 111.7 Ma, correlating well with contemporaneous volcanic activities. Isotopic data indicate a mixed magmatic origin involving a mantle-derived high-K magma and a crustal-derived felsic component. Petrogenetic analyses reveal co-magmatic trends and magma mixing processes, with geochemical evidence suggesting a mantle source metasomatized by subduction-related fluids. Geodynamic interpretations propose that the granitoids formed in an extensional back-arc setting during the northward subduction of the Shyok branch of the Neotethys Ocean. These findings provide critical constraints on the mid-Cretaceous tectonic and magmatic processes in the Southern Pamir, contributing to a deeper understanding of the orogenic plateau formation and evolution.

南帕米尔地区作为阿尔卑斯-喜马拉雅造山带的关键组成部分，拥有复杂的构造-岩浆演化历史，可为解析帕米尔高原的地球动力学演化提供重要依据。本研究公开了来自基兹拉巴特（Kyzylrabat）地区白垩纪花岗岩类的综合数据集，涵盖全岩地球化学、锆石U-Pb年代学以及Sr-Nd-Hf同位素分析数据。本次分析的花岗岩类属于高钾钙碱性至钾玄岩系列，具有A型花岗岩的地球化学特征。锆石U-Pb定年结果显示其形成年龄为98.5~111.7 Ma，与同期火山活动的时限高度吻合。同位素数据表明，该花岗岩类的岩浆起源具有混合特征，由幔源高钾岩浆与壳源长英质组分混合而成。岩石成因分析揭示了共岩浆演化趋势与岩浆混合作用，地球化学证据显示其幔源源区曾受到俯冲相关流体的交代改造。地球动力学研究表明，该花岗岩类形成于新特提斯洋什约克（Shyok）分支向北俯冲过程中的伸展弧后背景下。本研究结果为南帕米尔地区白垩纪中期的构造与岩浆作用过程提供了重要约束，有助于深入理解造山型高原的形成与演化机制。