Study On The Chemical Compositions Of Epidote In The Duobaoshan Porphyry Copper-Molybdenum Deposit,Heilongjiang

The Duobaoshan porphyry copper deposit in Heilongjiang Province is a large-scale Early Paleozoic deposit in the eastern part of the Central Asian orogenic belt.The geotectonic location is located in the northeast of the Xing'an block in the western Hegengshan-Heihe fault zone,which is an important part of the Central Asian porphyry copper deposit belt,and also is a typical representative of porphyry deposit research.As the new direction of research in porphyry deposits in recent years,epidote is of great significance to the mineralization indication.Therefore,this thesis studies the composition of epidote in the Duobaoshan and Tongshan porphyry copper?molybdenum?deposits,and discusses the significance of epidote in the porphyry copper deposit and the prediction of mineral production.The surrounding rock samples from the Duobaoshan deposit and the Tongshan deposit were selected for comparative analysis.The main and trace components of the epidote in the sample were analyzed by electron probe?EPMA?and laser ablation-plasma mass spectrometry?LA-ICP-MS?.The results showed that the epidote that developed in the Duobaoshan and Tongshan deposits are metamorphosed by hydrothermal fluids,but allanite are magmatic origins.The epidote in the phyllic alteration zone ore-bearing strata of the Duobaoshan copper deposit are richer in Al₂O₃and SiO₂,poor in FeO_T.In the low-grade ore-free samples of propylitic alteration zone,epidote is richer in TiO₂.In the Tongshan deposit,epidote in the propylitic alteration zone is rich in MnO and FeO_T,but the content of Al₂O₃ and SiO₂ is low.In terms of trace elements,all three are rich in LREE and LILE?Th,U,Sr,Sm?,but poor in HREE and HFSE?Nb,Zr,Hf?.The difference is that Duobaoshan epidote Eu anomaly is more obvious;while the Duobaoshan ore-bearing epidote has inhomogeneous REE and trace element contents,indicating that it has undergone many hydrothermal activities.Further study indicate that there is a negative correlation between Ps value of epidote and whether ore is contained in the samples.That is,the Ps?14³4?of the ore-bearing epidote are lower than the Ps?26³8?of the ore-less epidote,and the Ps value of the epidote in the propylitic alteration zone is between 26 and 34;and the average Cu content in ore-bearing epidote(3509.04×10^-6)was also significantly higher than that of the Cu-free epidote(4.04×10^-6 and 253.96×10^-6)which is far away from the metallogenic center.This paper argues that the altered characteristics of epidote in the porphyry copper deposit can reflect the characteristics of mineralized hydrothermal fluids and has the potential of becoming an indicator of mineralization.