The Ore Deposit Geological Features And Genesis Study Of The Shizidong Copper Deposit In Wei Ning Country,Gui Zhou Province

Emeishan basalt is widely distributed in Sichuan, Yunnan and Guizhou provinces,and the one located in the Yunnan-Guizhou border area of the Permian basalt group iswidely developed in the native copper. The research object is located in theYunnan-Guizhou border region, through the outside observations, the indoor petrology,petrography, geochemistry, isotope geochemistry and fluid inclusion studies we canexplore the characteristics of natural deposits of copper deposits in this mining area.Through this study we can get a few achievements like these:（1） Explore the relationship between the Emeishan basalt and coppermineralization in this area. The Emeishan basalt in this area just outcrop the second tothe fourth paragraph, and with a higher Cu content, the average of the Cu contentcomes to287ug/g; the ore mineralization is mainly native copper and malachitemineralization, and widely development hydrothermal alteration, the mineralizationmajorly outputs in the upper part of the fourth paragraph and the third paragraph ofthe Permian basalt group, the ore shape likes a chicken coop or a massive.（2） Through the major elements study we can find that the basalt in this area aremainly the sub-alkaline—alkaline quartz tholeiite, the active elements Rb in the rockshow strongly negative anomalies, this indicates that the basalts was intense affectedby the hydrothermal alteration.（3） The lead isotope of the ore shows like this:²⁰⁶Pb/²⁰⁴Pb swings in the range of17.9652¹8.885,²⁰⁷Pb/²⁰⁴Pb swings in the range of15.497¹5.658,²⁰⁸Pb/²⁰⁴Pbswings in the range of38.321³9.18；and the lead isotope of the basalt shows like this:²⁰⁶Pb/²⁰⁴Pb swings in the range of18.228¹9.0915,²⁰⁷Pb/²⁰⁴Pb swings in the range of15.528¹5.672,²⁰⁸Pb/²⁰⁴Pb swings in the range of38.457³9.4112. Both lead isotopiccomposition is very similar to each other, this phenomenon shows that themetallogenic material probably come from leaching that hydrothermal leaching doingto the basalt.（4） By studying the organic matter’s carbon and oxygen isotopes that in thebasalt copper ore minerals and the ore minerals and gangue minerals’ carbon andoxygen isotopes of the ore, we found that the constitute of13δCPDBin ore are similarwith the constitute of biogenic13C in the nature, this conclusion shows that the carbonin the ore is organic causes. By further studies, it shows that it maybe come from thedehydroxylation of biological deposition, and different deposits’ carbon isotopic havethe similar composition, which suggest that the carbon of this area have the same source.（5） By the studying of the hydrogen and oxygen isotopes in the quartz andcalcite’s fluid inclusions in the ore, we can see that there is two stages to theore-forming fluids. To the first phase, the ore-forming fluids maybe consist ofmagmatic water and few amount of atmospheric precipitation water, which with ahigher temperature and to the second phase, the ore-forming fluids maybe consist ofhot brine mixing a small amount of the construction of water, which with a lowertemperature, and this phase there should have the organic fluid join in the ore-formingfluids, too. The hydrothermal fluids dissolved Cu from the basalt and deposited the Cuelement in the right position. In this progress, the organic matter can give a restoreenvironment to the ore-forming fluids and its adsorption can give a important hand tothe deposited of the Cu element.