Prediction Of Gang Cha Gold Deposit In Gansu Province

Gangcha gold deposit is located in the Luqu-Chengxian thrust nappe tectoniczone of Qinling orogenic zone, and is a typical tectonic alteration rock type golddeposit. The surface of the mine has discovered and controlled the five oreveins,vertically extending and controlling over500m, and their proven reserves isnearly19tons. Among them,the third vein is the largest gold veins, trending almostnorth-south, with an outcropped length of more than1km, an average grade of2.99g/t, an average thickness of2.91m.Based on the investigation in the field, this paperconducts an analysis on the geochemistry multi-element and its correlation of the oreveins. Combined with the combination regularities of the general geochemicalprimary halo element and the distribution characteristics of the mine’s value ofsingle-element lining, it defines the characteristics of Au3elements combination as:Au+Ag+Pb+Zn as the near-ore hole elements combination； Hg+As as the front haloelements combination； Bi+Co+Cu+Ni as the rear halo elements combination。Basedon the above elements combination characteristics,the analysis of the primary halo ofthe third vein shows that the characteristics of the axial zonation and superposition isobvious, the mineralization of the vein has southwards characteristics,andsuperimposed halo has not yet closed in the extending direction. Based on the aboveanalysis results,the authors speculated that the good prospecting prospect may appearin the deep south of the mine.Portable X-ray fluorescence spectrum (PXRF) was used to hand specimencollected from Gang-cha gold deposit in Gansu Province，and the results arecompared with that of ICP-MS. The results show that As, Sb, Pb, Zn and Au areclosely related and the test results of both methods are highly consistent. Based on theuse of the mean-standard deviation method which is used to determine the anomalythreshold of As, Sb, Pb, Zn, and analysis of the abnormal lining elements aimed at theNo.3gold veins, we hold that primary halo has not yet closed under the2900melevation between the12th to the7th exploration line. All of these suggest that there isstill good prospecting potential in the deep.The rock ore、pyrite and veins from Gang Cha gold deposit were carried out by S, Pb isotopic analysis. The results showed that the forming fluids of δ34S is0.6‰-1.1‰; In addition，the206Pb/204Pb，207Pb/204Pb and208Pb/204Pb ratios of pyrite are in theranges of17.935-18.6(mean value is18.0)，15.567-15.58(mean value is15.57) and38.093-38.27(mean value is38.19).According to the above sulfur and lead isotopesof judgment, post bifurcated gold mineralization fluids and minerals mainly frommixing with the West Qinling orogenic related mantle and crust, and with a deepsource characteristics.