喜马拉雅琼嘉岗锂矿肉切村群钙质糜棱岩的流变学约束OA

In recent years,a series of spodumene pegmatites have been discovered along South Tibetan detachment system(STDS),with the Qiongjiagang lithium orefield constituting the first giant lithium orefield recognized in the Himalayan region.Its formation is controlled by the couple tectonic-magmatic-mineralization evolution,providing an ideal case for studying rare-metal metallogenesis in continental collision settings.However,the dynamics of lithium-bearing melt migration and emplacement,and the extent to which these processes are governed by regional rheological conditions,remain poorly constrained quantitatively.This study investigates the calcareous mylonite of the Rouqiecun Group,the host rock of the Qiongjiagang main ore body,through macro-and microstructures,and mineral assemblage studies,enabling a detailed tectonic-rheological interpretation.The results indicate that the spodumene pegmatite forms thick,plate-like or vein-like bodies,intruding in alignment with the foliated structure of the surrounding rock,exhibiting typical syn-tectonic emplacement characteristics.Microscopic analyses show that dynamically recrystallized calcite in the calcareous phyllite and marble has mean grain sizes of 118±61.3 μm and 78.9±52.6 μm,respectively.Both lithologies are characterized by the widespread development of geometric type Ⅱ twins with widths exceeding 1 μm,indicating plastic deformation dominated by diffusion creep under mid-to low-temperature conditions.Paleostress estimates based on these microstructures indicate differential stresses of 95.9 MPa and 64.1 MPa for the calcareous phyllite and marble,respectively,At an assumed temperature of 300℃,these correspond to strain rates on the order of 10-13s-1,suggesting that pegmatite emplacement occurred within the mid-to low-temperature brittle-ductile transition zone.This study quantitatively defines the differential stress and strain rate conditions during the formation of the main Qiongjiagang ore body.It provides crucial rheological constraints for constructing a model of tectonic-magmatic-mineralization coupling in the High Himalayan region and offers important predictive indicators for future exploration of concealed or deep-seated spodumene pegmatites within the STDS.