Geochronology and geological significance of newly discovered granitoid dikes in Chigou Cu-Mo deposit,Shaanxi Province
Chigou is one of the few medium-sized porphyry-skarn copper deposits recently discovered in the East Qin-ling metallogenic belt.Previous studies suggested that the shallow copper orebodies are genetically related to the Late Mesozoic dioritic magma,and it is unclear whether there are multiple stages of magmatism and mineraliza-tion.Recently,a deep drill hole ZK701(1615 m)discovers numerous Cu orebodies and granitoid dikes around el-evations of 573 m and-558 m in the northern part of the mining area.The orebodies are mainly hosted in the skarn contact zone around the fine-grained granite dikes.This paper chooses the fine-grained granite and skarn minerals for EMPA,zircon U-Pb dating and trace element analysis.The results indicate that the prograde skarns consist of andradite(And86-94Gro0-8)+diopside(Di60-72Hd26-38),suggesting an oxidizing formation state.The zircon U-Pb age of fine-grained granite is(146.3±5.7)Ma,which is close to the age of quartz diorite porphyry,and the Early Paleozoic and Neoproterozoic inherited zircons are developed.The calculation of zircon trace elements shows that △FMQ=0.8～1.0 and EuN/EuN*＞0.4,suggesting the high oxygen fugacity and water content of fine-grained granite.Through comprehensive research,this paper proposes that fine-grained granite has the potential for copper,and forms multi-stage diagenesis and mineralization with quartz diorite porphyry,so the Chigou has the possibility of discovering larger-scale copper deposit.
万方数据
维普
