Re-Os isotopic data for molybdenum from Hejiangkou tungsten and tin polymetallic deposit in Chenzhou and its geological significance

摘要

Hejiangkou W-Sn-polymetallic deposit is a newly found deposit in Xitian ore field,one of the important and large scale W-Sn-polymetallic ore fields in the middle segment of Nanling metallogenic zone.Re-Os isotope dating was used on three molybdenite samples from Hejiangkou deposit to determine the ore forming period.The result is（224.9±2.6）Ma-（225±3.1）Ma and isochron age is（225.5±3.6）Ma.The field geological observations,geochronological data and optical petrography indicated that Hejiangkou deposit underwent multi-period of superimposed mineralization.It can be differentiated into three periods composed of six mineralization stages.The first period is the initial period for hydrothermal metasomatism and metal element enrichment during Indosinian Epoch.Further enrichment,strong brittle fracturing and hydrothermal metasomatism,remobilization and superimposition happened in the second period,during early Yanshanian.It is the major mineralization period of Hejiangkou deposit and can be subdivided into four mineralization stages,namely the skarn stage,oxide stage,high-temperature sulfide stage and low-temperature sulfide stage.And the third period is the mineralization period of a porphyry-skarn system related to the emplacement of the granite porphyry dyke.As minerogenic epoch of Hejiangkou deposit is similar with Hehuaping deposit,they show the possibility of Indosinian mineralization event in Nanling metallogenic zone.It can be an important perspective in any future mineral exploration in the same metallogenic zone.