新疆东天山地区白山钼矿床的成因分析

白山钼矿床位于东天山觉罗塔格构造带的东部,赋矿围岩为下石炭统干墩组的黑云母长英质角岩,矿化石英网脉发育.文章测得含矿石英脉中的石英流体包裹体δ18OSMOW值为9.1%O～10.0‰,平均9.425‰,与石英相平衡的水δ18OH2O值为3.357‰～4.257‰,平均为3.682‰;δDSMOW值为-105‰～- 69%,平均-89.25‰.氢氧同位素组成显示白山钼矿床的成矿流体是岩浆水与发生了水-岩作用的大气降水的混合热液,含矿流体以岩浆水为主,演化大气降水的加入是成矿物质沉淀的重要因素.测得辉钼矿的Re-Os等时线年龄为(227.7±4.3)Ma(MSWD=0.32),指示白山钼矿床形成于中三叠世.矿床地质特征和地球化学特征指示白山钼矿床是斑岩型矿床,推测成矿物质主要来自于矿体下部的矿化花岗(斑)岩体.此外,作者还探讨了白山钼矿床的成矿背景,认为矿床形成于挤压的构造环境,是受到同时代古特提斯洋闭合的陆内远程效应影响而产生的成岩成矿作用.

A genetic analysis of Baishan molybdenum deposit in East Tianshan area, Xinjia ng

The Baishan molybdenum deposit is located in the eastern Juduotag tectonic belt of the East Tianshan Mountains. The wall rocks are biotite-felsic hornstone with well-developed mineralized quartz veins, belonging to Lower Carboniferous Gandun Formation (C_1g). The H, O compositions of the hydrothermal fluids in the quartz veins are as follows: δ~(18)O_(SMOW) values are 9.1‰～10.0‰ with an average of 9.425‰,δ~(18)O_(H_2O) balanced with quartz are 3.357‰～4. 257‰ with an average of 3. 682‰, and δD_(SMOW) are - 105‰～-69%, with an average of - 89.25‰. Characteristics of H, O isotopes indicate that the ore-forming hydrothermal fluid was dorninated by magmatic water with the participation of some evolutionary meteoric water that had experienced the water-rock in-teraction. The magmatic water supplied the main metaUogenic materials, and the evolutionary meteoric water served as an important factor for the precipitation of the metallogenic materials. The Re-Os isochronal age of molybdenites is (227.7± 4.3) Ma(MSWD=0.32), suggesting that the mineralization of the ore deposit took place in Middle Triassic. These geological and geochemical charac-eristics imply that the Baishan Mo deposit is a porphyry deposit, and its metallogenic materials mainly came from deep granitic rock. This paper deals with metallogenic background, and the authors hold that the Baishan molybdenum deposit was formed in a compres-sion environment after the post-collisional stage, and its mineralization was controlled by the distant effect of the Paleo-Tethys Ocean in Triassic. This paper has supplied a solid foundation for further researches on mineralization of granitoids which intruded into the same tectonic backgrotmd in Jueluotag block as well as in East Tianshan area.