新疆金山沟金矿床地质特征和成因

新疆金山沟金矿床赋存在下石炭统巴塔玛依内山组火山岩中，受火山机构的环状、放射状断裂及叠加的NE向断裂裂隙控制.蚀变发育，分为线型和面型两类蚀变带，进一步划分出成矿期前、成矿期和成矿期后3期蚀变.流体包裹体及氢、氧、碳、硫、铅同位素特征表明，参与成矿的碳为岩浆源和地层的混合碳，硫、铅来源于地幔，金等成矿元素来自火山岩，成矿溶液为大气降水与岩浆水的混合溶液.矿床成因应属浅成中低温火山岩型金矿

GEOLOGICAL CHARACTERISTICS AND GENESIS OF THE JINSHANGOU GOLD DEPOSIT,XINJIANG

Located in the Laojunmiao area of Qitai County,Xinjiang,the Jinshangou gold deposit occurs in continental volcanic rocks of the Batamayineishan Formation.The ore zone and orebodies are controlled by circular and radial fractures of volcanic edifices and the late superimposed NE trending fracture fissure system.So far totally 13 orebodies have been found.These orebodies are from 200 to 480 meters in length and 2 5 to 5 8 meters in width.The grades of various orebodies vary from 0 92×10 6 to 17 80×10 6 .The mineralizing types include gold bearing welded tuff type,gold bearing altered rock type and gold bearing quartz vein type. There are many types of wall rock alteration. The gold mineralizations are associated with silicification and pyritization.The wall rock alteration zones are obviously divided into two types,i.e.linear type and areal type.The former distributes in contact and fracture belt,but the latter is controlled by volcanic apparatus and cross fracture.The alteration displays three epoch:premineral phase,mineralizing phase and post mineralizing phase.Following the evolation of time,the alteration are weak→strong→weak,while the alteration minerals are fewer→more→fewer. The temperatures of metallogenesis are of 220 to 316 ℃,pressures of 18～20 MPa,and depths of 500 to 600 meters.The pH values of mineralizing fluid are 6 93～8 58, E h values -0 67～-0 85 and lg f O 2 values -32 80 ～ -34 90 .Gas components of inclusions consist mainly of H 2O and CO 2,and also a little CO,N 2 and CH 4. In liguid phase cations are mainly Ca 2+ ,Na + and K +,whereas anions mainly SO 2 4 and Cl -. Isotopic geochemical studies show that δ 34 S values of pyrite and galena range from + 0.8 ‰ to + 3 8 ‰, peak values of δ 34 S +2 0‰ to +3 0‰.Sulfur isotopic data indicate that sulfur is associated with deep magmatism.Lead isotopic of ore is the same as that of volcanic rock of Batamayineishan group.The lead is derived from upper mantle.The δ 18 O and δ D values of quartz are +11 32‰ to 13 47‰ and -105 8‰ to -108 1‰,respectively.These data show that the metallogenic liquid is the mixture of magmatic and meteoric water.The δ 13 C values of calcite are -3 2‰ to +0.1‰,indicating that carbon came from magmatism and stratum. Based on the study of its geology,geochemistry and metallogenic epoch,the genesis of Jinshangou gold deposit is considered to be a typical shallow seated,low to medium temperature gold deposit related to volcanic rocks.