Geochemical Characterisics And Prospecting Prediction Of Cu And Au Deposits In Boka, Yunnan Province

The ore deposits are located in polymetallic deposit-accumulated areaes of Dongchuan lying in the middle of the platform-fold belt in the East Yunnan and western edge of Yangtze paraplatform. It is in the East River Upheaval, a secondary upheaval in the east edge of north end of Xikang-Yunnan Axis, and at the east edge of north of Kunyang aulacogen. In recent years, many Au, Au-Cu and Cu ore bodies and occurrences have been found one after another in this area by general prospecting and exploration on the geochemistry abnormal area of soil. By study on the geochemistry characteristic of three typical mineral deposit (Au, Cu-Au and Cu), we have summarized ore-control factors, ore-hunting indicators, inherent relationship between Au and Cu deposit, and mechanism of deposit generation, and suggested prospecting model of the Au, Cu-Au and Cu deposits in this area.The study of geological background on rock in the diggings indicates that the content of normal elements in each stratum accords with lithology. Qinglongshan Formation is silicification because of SiO2content, and its content of CaO and MgO higher, content of other oxide lower. Its chemical ingredients accord with that of Cu ore of Renzhanshi. The oxide content of Au ore is the same with that of Yinming Formation and Heishan Formation, and the content of Na2O is more than that of K2O indicates that Au mineralization relates with albitization. Element of Au is enrichment in Yinming Formation, Luoxue Formation and Heishan Formation (6.6×10-9、18.0×10-9、4.0×10-9repectively). High variation coefficient indicates they are the source layers of Au in the diggings. Luoxue Formation, Qinglong Formation and Yinming Formation is the source layers of Au in the diggings because of their enrichment of Cu element (1140×10-6、113×10-6、60×10-6repectively) and high variation coefficient.The data of soil analysis indicates that content of Au, As and Sb is high in Yinming Formation, Luoxue Formation and Heishan Formation, and that of Cu is high in Luoxue Formation and Qinglongshan Formation. Their variation coefficient is high too. All those accord with the characteristic of rock geochemistry. Based on explanation of soil geochemistry abnormal, comparison and comprehensive analysis of geochemistry characteristics and factor analysis in the known ore deposits, we suggest regional planning.of "three zones, one ring and one point" for Cu-Au metallogenic prognosis in region. The "three zones" are (1) Xiamabozi-Liangshuipeng potential area of Au deposit,(2) Xinghuofang-Xiaoshuijing-Sutouliangzi-Botou potential area of Au(Cu) deposit, and (3) Shanghuangcao-Renzhanshi potential area of Cu(Au) deposit respectively; the "one ring" is Guizhoupeng-Baishiyan-Shangshuiping-Shuijingshan potential area of Au deposit; and the "one point" is potential Changdi Pb-Zn deposit.