新疆西准噶尔成矿流体中还原性气体形成机理

摘要

西准噶尔是新疆重要的矿产开发区域,成矿潜力巨大,矿床类型丰富,主要包括斑岩型铜矿、斑岩型钼矿和造山带型金矿.区域上矿床成矿流体中普遍存在CH4等还原性气体,明显区别于典型的斑岩型矿床和造山带型金矿.通过对已发表的气相成分及碳同位素数据综合分析,结合地质作用中CH4等还原性气体的主要来源,认为新疆西准噶尔矿床中普遍存在的还原性气体与围岩中的含碳质地层密切相关,CH4等还原性气体主要来源于有机质热分解,也有少量还原性气体可能来源于深部岩浆或为非生物成因.由于还原性气体形成于岩浆上升末期或热液阶段,且斑岩型矿床成矿岩浆具有较高的氧逸度(高于镍-氧化镍(NNO)),所以西准噶尔在寻找斑岩型铜矿方面具有很大的潜力.%West Junggar is an important mineral exploitation region in Xinjiang.There are many types of deposits,including porphyry Cu deposit,porphyry Mo deposit and orogenic Au deposit. However,the mineralization fluid in these deposits always contain the reducing gas (such as CH4 and C2 H6 ),which conflict with the characteristics of the typical porphyry deposit and orogenic Au deposit around the world.According to the comprehensive analysis of gas composition,C isotope and source of the reducing gas in geological process,the reducing gas in the mineralization fluid associates with the wall rock containing carbonaceous material,and the reducing gas is produced by thermal decomposition of organic matter.However,a little reducing gas may come from hypomagma or abiogenic process. The reducing gas mainly forms at late magmatism or hydrothermal stage;meanwhile,the metallogenic magma has high oxygen fugacity (more than Ni-NiO (NNO)).Therefore,West Junggar has great potential to explore huge porphyry Cu deposits.