LA-ICP-MS zircon U-Pb dating and geochemical characteristics of Tangang rhyodacite in Jiangxi Province

Abstract：LA-ICP-MS U-Pb zircon age of rhyodacite in Tangang area of Jiangxi Province is (136.2±1.5) Ma, belonging to the product of Early Cretaceous volcanic and magmatic activities. The main geochemical characteristics of the rhyodacite include SiO2=66.82%-68.04%, high alkali (K2O+Na2O=7.56%-7.73%), high Al2O3 (14.91%-15.17%), quasi-aluminous to weakly peraluminous nature (A/CNK=0.999-1.042), obvious enrichment of LLE and LREE, and relative loss of high field strength elements. The pattern of REE with enriched LREE is a right-oblique curve, with high ratio of LREE/HREE (10.04 in average) and intermediate negative Eu anomalies (the average of δEu is 0.48). The rhyodacite has comparable formation age and geochemical characteristics with Xiangshan rhyodacite porphyry, which suggests that they are comagmatic products. In addition, these rocks crystallized from the remelted sialic crust, which has been believed to be the first volcanic activity cycle of the Xiangshan rock body. A comparative study of the geological conditions shows that there exixts metallogenic potential in Tangang volcanic basin.