Zircon U-Pb dating and whole-rock elemental geochemistry of the Shazi anatase deposit in Qinglong, Western Guizhou, SW China

摘要

The Shazi deposit is a large-scale anatase deposit in Qinglong,Guizhou Province.Zircon grains from this deposit yielded a zircon U-Pb age of ～ 259 Ma,representing the formation age of the deposit's parent rocks.This age is identical to the eruption age of the Emeishan large igneous province,indicating a synchronous magmatic event.The rare-earth-element patterns of laterite samples were similar to those of the weathered basalt sample,and sub-parallel to those of the Emeishan high-Ti basalts,implying a genetic relationship between the laterite and the basalt.The Chemical Index of Alteration values of laterite ranged from 96 to 98,suggesting a high degree of weathering.SiO2,MgO,and alkaline metal elements decreased with increasing degree of weathering,while Al2O3,Fe2O3,and TiO2 increased.We found the highest TiO2 in laterite and the lowest in pillow basalts,indicating that Ti migrated from basalt to laterite.Our U-Pb dating and whole-rock elemental geochemistry analyses suggest that the Emeishan basalt is the parent rock of the Shazi anatase ore deposit.Based on our analysis,we propose a metallogenic model to explain the ore-forming process,in which the karst terrain formed by the Emeishan mantle plume and the subsequent basaltic magma eruption were the key factors in the formation the Shazi anatase ore deposit.