Typomorphic Studies Of Sphalerite In The Hutouya Pb-Zn Deposit From Qinghai

The Hutouya Pb—Zn deposit is one of the typical skarn—type polymetallic deposits in the Qimantage metallogenic belt, which is characterized by extensive magmatic activities, variable carbonate-bearing stratigraphic age and complicated ore-forming elements assemblage. Coupled with the field geological features, mineralogy and geochemistry, we used the genetic mineralogy to discuss the indication of sphalerite to the exploration.The metallogenic processes of the Hutouya Pb-Zn deposit can be divided into skarn stage, quartz—sulphide stage and hypergenesis stage. The sphalerite is classified into three types by its formation time. The colours turned from black into pale yellow from early to late, and the mineral assemblages of sphalerite—(galenite—halcopyrite)—pyrite—yrrhorite changed to Sphalerite—galenite—chalcopyrite—pyrite—(pyrrhorite). Sphalerite-galena-calcite or qua-rtz became late-stage mineral assemblage.In chemical composition, the early—stage sphalerite in the Hutouya Pb—Zn deposit exhibits enrichment of Fe and depletion of Zn, Cd. In contrast, late—staged sphalerite shows relatively depletion of Fe and enrichment of Zn, Cd. The decreasing contents of FeS in the spahlerite indicates a corresponding decrease of ore-forming temperature, namely262-258℃,260-200℃and248～148℃. The Hutouya lead and zinc deposit is reletively rich in Cd, Ga and Ge but barely contain In. All of the trace element abundance are much lower than the high tempreture sphalerite, and varies between the medium temperature sphalerite and the low temperature one. Ga/Ge ratio suggests solution tempreture of sphalerite ranges from174to218℃, everage196℃. The Hutouya Pb—Zn deposit is a mesothermal deposit.Texturally, the changes of Fe, Mn, Cd contents in sphalerite can result in the variation of the lattice parameters. The early-staged black sphalerite has the highest crystal lattice constant, the middle-staged aterrimus-sepia sphalerite lower, and the late-staged pale yellow sphalerite has the lowest. Crystal constant of sphalerite becomes smaller with the mineralization process getting late. The sphalerite in deep shows the highest constant, and the middle of the ore body takes the second. The crystal constant is lowest in the upper, including the lattice parameters of sphalerite become smaller from deep to shallow. Along the hydrothermal flow direction, sphalerite lattice parameters becomes smaller. In physical properties, the electrical characteristic of the lead and zinc ores mainly reflected the contents of iron-bearing mineral. High iron content strengthen the electrical conductivity and resistivity. The sesistivity variation trend of the ores shows obvious differences relative to other ore types. SIP can efficiently distinguish the sulfide-bearing ores, iron-bearing ores and carbon-bearing rocks.In summary, according to the spatial variation of typomorphic characteristic in different generation sphalerite and the occurrence of ore body, it is suggested that the flowing direction of the hydrothermal flux in this deposit is consistent with the strike of the ore body from NEE to SWW. The Zn, Fe, Mn contents and the cell parameters of sphalerite in the Hutouya Pb—Zn deposit shows similar characteristics to a typical skarn (magmatic hydrothermal) deposit and significantly differs from those of SEDEX deposits, stratabound deposits, hydrothermal and hot brine mixed zinc deposits. Combined with the geological characteristics and ore-forming processes, we propose that the Qinghai Hutouya Zn—Pb deposit is a mesothermal skarn-type one.