关键词: 东昆仑, 花岗闪长岩脉, 早泥盆世, 原特提斯洋, 地球化学, U-Pb年代学, 岩石成因, 构造背景

Abstract:  The northward subduction of the Proto-Tethys Ocean, the subsequent ocean closure, and the continent-continent collision represent major tectonic events in the Paleozoic evolution of the East Kunlun region. To investigate the petrogenesis and tectonic setting of granitic rocks in the Gouli area, and to constrain the Late Paleozoic geological evolution of the eastern segment of the South East Kunlun orogenic belt, we conducted detailed petrographic, whole-rock geochemical, zircon U-Pb geochronological, and isotopic geochemical analyses on granodiorite dikes from the Walega South ore district. The results indicate that the granodiorites are characterized by high contents of SiO2 (74.90%-79.07%), Al2O3 (13.66%-16.21%), and total alkalis (K2O+Na2O=5.83%-7.08%). They exhibit relatively low total rare earth element (REE) concentrations (ΣREE = 32.05×10-6-54.18×10-6), with an average (La/Yb)N ratio of 15.99, indicating moderate fractionation between light and heavy REEs. Both Eu and Ce display weakly positive to weakly negative anomalies. The samples are enriched in large-ion lithophile elements (LILEs; e.g., Rb, Ba, Pb) and depleted in high-field-strength elements (HFSEs; e.g., Nb, Ce), consistent with the geochemical affinities of medium-K calc-alkaline, weakly peraluminous I-type granites. LA-ICP-MS zircon U-Pb dating yields a crystallization age of (403±6) Ma, corresponding to the Early Devonian. The granodiorites are crust-derived granites that formed predominantly by partial melting of juvenile basaltic lower crust, with input from ancient felsic crustal materials. Trace element characteristics suggest that the granodiorite pluton was emplaced in an intraplate tectonic setting.

Key words: East Kunlun, granitic diorite, Early Devonian, Proto-Tethys Ocean, geochemistry, U-Pb geochronology, petrogenesis, tectonics setting