| The Dihu-Jiuxing copper polymetallic deposit in southeastern Guizhou is located in the copper polymetallic metallogenic region of Congjiang County,Guizhou Province.The area is rich in metal minerals,and is a typical representative of mineralization at the southwestern end of the Jiangnan orogenic belt.In this paper,the geological investigation,classification of mineralization stages,and systematic analysis of trace and rare earth elements in ores and wall rocks at different mineralization stages,as well as in-situ elements of sulfide minerals LA-ICP-MS,have been conducted for the two representative copper polymetallic deposits in the region,Dihu and Jiuxing,and their geological characteristics and genesis have been discussed.The main understandings obtained are as follows:(1)The Dihu-Jiuxing copper polymetallic deposit is divided into four mineralization stages:S1 quartz magnetite-pyrite,S2 quartz copper sulfide,S3 quartz Pb-Zn sulfide,and S4 quartz with a slight amount of pyrite or magnetite.(2)The indication of the ore-forming environment of the samples Eu and Ce of the Dihu Jiuxing copper polymetallic deposit is basically consistent with Th/U,and the ore-forming environment of the deposit is reductive.Among them,the S2 stage Ce anomaly in the Dihu copper polymetallic deposit indicates the most obvious reduction environment at this stage;The Th/U ratio indicates that the reductivity of the S1 and S4 mineralization stages is relatively weak,with a trend towards an oxidizing environment.(3)In situ elemental analysis of sulphides indicates that the mineralization temperature of the Dihu Jiuxing copper polymetallic deposit should be dominated by medium temperature.In terms of spatial distribution,there are certain differences in height from the Dihu copper polymetallic deposit to the Jiuxing copper polymetallic deposit;In terms of time,from the early stage of mineralization to the late stage of mineralization,the mineralization temperature presents a gradually decreasing change.(4)Zn,As,Pb,and Cu mainly exist in pyrite in the form of mineral micro inclusions in the Dihu Jiuxing copper polymetallic deposit system.Cd and In mainly occur in the form of micro inclusions containing Zn(such as sphalerite).The enrichment of Pb and Cu has a certain genetic connection with the enrichment and mineralization of Ag,while the enrichment and mineralization of Pb and Cu have a certain genetic connection with Sb.The element content and enrichment index closely correspond to the mineralization stage.The Cu content and enrichment index in S2stage are the highest in the entire S1～S4 mineralization stage,indicating that Cu mineralization is the strongest in this mineralization stage.(5)The Co-Ni and Co/Sb-Se/As diagrams of pyrite at each stage of the Dihu-Jiuxing copper polymetallic deposit basically fall into the hydrothermal region.An examination of trace elements in the ore at each juncture reveals that the primary elements of ore-forming,such as Cu,Zn,and Pb,are introduced by the hydrothermal solution.The content changes of trace elements in ore and surrounding rock are basically similar,and although the values ofΣREE,LREE and HREE of ore and surrounding rock are quite different in each stage,the values ofΣLREE/ΣHREE,La _N/Yb _N,La _N/Sm _Nand Gd _N/Yb _Nare very similar.That is to say,REE enrichment forms and fractionation characteristics of ore and surrounding rock are similar at different stages.This indicates that the ore-forming materials mainly come from metamorphic hydrothermal fluids or metamorphic wall rocks,consistent with previous understanding that the ore-forming materials obtained from the study of H-O isotopes of associated quartz in ores originate from metamorphic hydrothermal fluids related to metamorphic wall rocks.Therefore,the deposit should belong to a mesothermal metamorphic hydrothermal deposit. |
