Metallogenic Mechanism Of Laoshankou Fe-Cu-Au Deposit In Qinghe Country,Xinjiang

The northern margin of Junggar is one of the most important components ofXinjiang, has been found Halasu Cu deposit, Xilekuduke Mo-Cu deposit, KalatongkeCu-Ni deposit, Qiaoxiahala Fe-Cu-Au deposit, Suoerkuduke Cu-Mo deposit. TheLaoshankou deposit is located in the northern margin of East Junggar. Ore bodyproduce in the contact zone of diorite porphyrite and basaltic volcanic rock of MiddleDevonian Beitashan Formation. The host rocks is Basaltic volcanic breccia andandesitic volcanic breccia. Ore body and surrounding the skarn is univer developed,the genesis of the deposit is quite controversial. This thesis based on detailed fieldstudy of Laoshankou deposit, using some feasible methods such as EPMA,LA-ICP-MS zircon U-Pb dating, major and trace elements measuring, stable isotopemeasuring and inclusion homotemperature measuring, recognize its petrology,mineralogy, chronology and geochemistry characteristics, and then give a reasonableexplanation about its genesis is Skarn deposit. Some study results are as follows:1) The Fe-Cu-Au minerals mainly occur in the form of Massives, heterogeneousgobbets, Veinlets, Breccia and Veinlet-disseminated in the diorite porphyrite andbasaltic volcanic rock. The formation of deposit in the experience of skarns period、quartz-sulfide period and supergene oxidation period.2) After performance of LA-ICP-MS zircon U-Pb dating, we respectivelyobtained353.8±1.9Ma、366.3±1.9Ma、379.3±2.3Ma and379.7±3Ma for the diorite、syenite、biotitediorite and diorite porphyrite in Laoshankou ore district, are theproducts of The Middle Devonian in Island arc.3) Electron microprobe analyses show that the end member of garnet is mainlygrossularite and almandite, with the calculated end number dominated by andradite,The composition of pyroxene is mainly diopside, with asmall amount of augite. Theepidote is rich in Fe and Ca, all of them show the characteristics of calcic skarn.Magnetite is closely related to the retrogressive metamorphism of the skarn.4) The ore-forming fluids in early stage of skarn period is high-middletemperature, middle-low salinity and middle-low density, which is belong to H2O-NaCl system; The ore-forming fluids in retrogressive metamorphism stage ismiddle temperature, middle-low salinity and middle-low density, which is belong toH2O-NaCl system; The ore-forming fluids in quartz-sulfide stage is dominantlyH2O-NaCl-CO2system.5) Carbon and hydrogen and oxygen isotopes indicate that the ore-forming fluidis mainly a mixture of magmatic water and meteoric water. The sulfide isotopes andrare earth element data of rocks and ores suggest that the ore-forming materials ismainly derived from the dioritic magma.6) The Laoshankou deposit is belong to skarn type, and the mineralizationmechanism is Diorite porphyry magmatic hydrothermal interacting with MiddleDevonian Beitashan Formation volcanic, the formation of magnetite is related to theretrogressive metamorphism of the skarns. Copper and gold mineralization isformated in quartz-sulphide-carbonate period, and ultimately formate Fe-Cu-Audeposit.