Abstract: The gold deposits of Axi area in Yining county of xinjiang indicate those which con trolled by Tulasu volcanic basin in the north part of west Tianshan, including Axi, Xier-mande, Qiabukandangta etc. Based on Caledonides in west Tianshan, the Tulasu volcanic basin was formed in pull-apart environment in Late Palaeozoic, with E-Wextension, the length of 80km and the width of 20km approrimately. The basement of the basin had two lager structure of pre -Sinian crystalline rock series and Lower palaeozoic unmetamorphic sedimentary series. The basin was separated from Yili basin and Sailimu uplifting by thelarge faults on south and north boundaries respectively. The geological body related to gold deposit include continental intermediate -acid volcanic eruptive rock series of Dahalajunshan formation (C₁) and corresponding subvolcanic body which belong to calc-alkalic-alkalic series association; sedementary rock of Aqialehe formation (C₁) and K-feldspar porphyry rock body (C₂). The basin can be divided into three grades volcanic structure; the ist grade is volcanic basin which controlled gold ore belt;the 2 nd is S-N striking fault belt which controlled gold orefield; the 3rd is volcanic mechanism which controlled gold ore. The main types of gold deposit are as follows:① adular -sericite type of epithermal system (e.g. Axi) and silicified rock type (e.g. Yiermade); ②porphyry type (e. g. Tawuerbieke);③gold -bearing breccia type. The metallogenic epoch of the 1st type is Early Carboniferous (324.4-338.2 Ma), the adular-sericite type appeared as vein orebody and controlled by volcanic mechanism, and the silicified rock type appeared as plane orebody, with lower grade, far away from volcanic mechanism and controlled by volcanic cycle and rock series.
The discovery of Axi and Yiermande etc. gold deposits indicate that important breakthrough in gold ore prospecting have been realized in west Tianshan and mean that a new gold producing base will set up in the west of China. In metallogenic epoch and metallogenic environment, this kind of epithermal gold deposit is different from the former one which oc-cured in Cenozoic island arc area, and also different from the one which occured in Mesozoic superimposed volcanic basin of intraplate crystalline basement in east of China, while similar to the one which occured in volcanic basin of Palaeozoic orogenic belt. Therefore, this paper has great significance in expanding the prospecting area of epithermal deposit and improving the study on regional metallogenics of Eurasian continent.