Analysis On The Geological Featur And Metallogenic Geological Conditions Of Yang Tianwo Arsenopyrite-gold District In Xiaojin, Sichuan

Yang Tianwo gold deposit is in the southern margin of Aba missif of the Songpan ~ Ganzi geosyncline fold zone. Sandwiched between Northeast Long Menshan deep fracture zone and Songpan—Jinchuan fault zone. This paper using the geochemical method and respectively discusses the elements characteristics of rock mass, wall rocks and ores. In order to study the source of metallogenic material. Combined with the field geological work we can research the metallogenic geological conditions. At the same time, we can also deeply realize this deposit, and instruct the gold prospecting.Currently we found six gold-bearing quartz vein orebodies in the mining area. They are mainly in the inner and outer contact zone of the quartz diorite and Sandstone、slate of Triassic Zhuwo Formation. The wall rock is mainly metamorphic quartz sandstone and hornfels. And the ore body cut through wall rock and rock mass. The vein are in different size, the thickness is 0.3~1.8m, and the length is 30~110m. It’s belongs to polymetallic sulfide quartz vein type. The main ore minerals in ore body are arsenopyrite, pyrite and chalcopyrite, with minor sphalerite. Limonite, malachite and magnetite content is minimal. Gangue minerals are mainly quartz. The ore bodies are double controlled by strata and structure. And has a close relationship with the shallow intrusive body quartz diorite.By analyzing the geochemistry datum of the ore bearing rock series, conclude that the average grade of Au in the ore is 4.7 g/t. And Au has a positive eorrelation with As、 Ag、 Sb etc element, the correlation coefficient is 0.83~1. As、Ag are obviously concentrated in the wall rock. Therefore the metallogenic minerals of Au main comes from sedimentary strata. The REE distribution patterns of the host rock and minerals have something in common: tilted to the right, negative Eu anomalies, weakly negative Ce anomalies. The ΣREE of ores is very low: 1.86~2.14×10-6, and the characteristic of REE distribution has a great similarity with the ones in the hornfels. At the same time, the content of metallogenic elements as Au、As、Cu in Sandstone、slate, hornfels and ores is in increasing order. this reflects that hornfels’ formation and mineralization of Au is consistent.By studying the geological feature in this area, metallogenic geological conditions of this area is superiority and has a good prospecting potential. The ore-forming conditions characters of this deposit were as follows: Ore bodies controlled by strata, Triassic Zhuwo Formation(T3zh)is the original mine-source straturm; The controlling structures are two NE-trending Compresso-shear faults as well as intralayered fractured belts formed by shear faults, and the ore body appears in shear en echelon vein-tapy; Calc-alkaline magmatic rocks were closely related to ore-forming, it not only provide heat, but also provide some fluid.