The Characteristics Of Cu-S Series Minerals And Genesis Study On Zijinshan Cu-Au Deposit

Several infrequent phenomena have been found in Zijinshan Cu-Au deposit which belongs to high sulfidation epithermal deposit.It has been confirmed that 8 kinds of Cu-S series minerals develop in this deposit and the vertical thickness of copper ore exceeding 1km.For the purpose of investigating the characteristics of Cu-S series minerals,revealing the genesis of giant thick copper ore,exploring the ending position of the copper ore and discussing if there is new deposit type under copper ore,some researches have been carried out based on detailed field geological investigation.After collecting typical samples,hand specimen observation,mineragraphy investigation,electron microprobe analysis,X-ray diffraction,microthermometry and Laser Raman analysis of fluid inclusions were carried out.Main results and recognitions are as follows:In this deposit,the primary Cu-S series minerals are covellite,anilite,digenite and djurleite,while yarrowite,spionkopite,geerite and chalcocite are rare.These minerals behave as vein or net vein mainly,also can be disseminated,filled,remnant.Their textures contain replacement texture and euhedral grain texture chiefly,while exsolution texture and poikilitic texture are minor.Composition characteristics show that these Cu-S series minerals are close to ideal minerals with few elements,such as Fe,Mo etc.And their results of X-ray study indicate that their cell parameters are identical to their theoretical characteristics generally.The morphologies of covellite and the assemblages of Cu-S series minerals are both changed with some rule in the space.From shallow to deep depth of this deposit,the morphologies of covellite change from fine needle and cotton fiber shape to plate column shape.And these covellite both replace digenite etc,it can be inferred that the Cu-S series minerals are the result of hydrothermal replacement from below to above.While the assemblages of Cu-S series minerals change from dominant in digenite to dominant in covellite.It indicates that the oxygen fugacity and sulfur fugacity are both higher in the deep depth of this deposit than in the shallow depth.The fluid inclusions can be classified into 4 types of liquid inclusion,gaseous inclusion,mineral-bearing inclusion and CO2 inclusion,which come from the mainmineralization stage of deep deposit.These inclusions are made up of CO2,H2O,CO32-etc,confirmed by Laser Raman analyses of inclusions.Microthermometry indicates that the homogenization temperatures concentrate in 200?260? and 300?360?,while the salinities range from 0.35%to 33.40%NaCl eqv.It can be inferred that the ore forming fluid is medium-high temperature,middle-low salinity and high salinity.The ore forming fluid can be considered as NaCl-H2O-CO2 system.It can be concluded that the metallogenic fluid are similar to epithermal deposit and porphyry deposit at the same time.It can be conjectured that the deep depth of Zijinshan Cu-Au deposit is a polygenetic deposit superposed by epithermal deposit and porphyry deposit,and there is prospecting potential of porphyry deposit below this deposit after comprehensive comparison analysis combined with the ore forming environment of high oxygen fugacity and high sulfur fugacity at the depth of this deposit.