还原性斑岩型Cu与Mo-Cu矿特征与形成机制

Characteristics and formation mechanism of reduced porphyry Cu and Mo-Cu deposits

还原性斑岩型Cu矿是近年新识别的一类斑岩型矿床,以岩浆阶段发育大量磁黄铁矿和成矿流体富CH4为主要特征。成因上,还原性斑岩型Cu矿与钛铁矿系列I型花岗岩伴生,形成于俯冲环境或者后碰撞环境。成矿流体为岩浆流体。岩浆阶段磁黄铁矿的结晶沉淀将导致岩浆中成矿元素Cu进入硫化物相而贫化,不利于成矿元素在流体中富集,结果导致还原性斑岩型Cu矿的矿化和蚀变规模较小。对比研究发现西准噶尔宏远Mo-Cu矿也具有还原性斑岩型矿床的特征,可能为还原性斑岩型矿床的新类型。

Reduced porphyry Cu deposits, that are recently recognized as a new type of porphyry Cu deposit, are characterized by widely occurrence of primary pyrrhotite at magmatie stages and CHa-bearing ore-forming fluids. Reduced porphyry Cu deposits are genetically related to ilmenite series, I-type granitoids, and suggested to be formed at subduction or post-subduction tectonic settings. The ore-forming fluids are magmatic. Crystallization and precipitation of magmatic pyrrhotite will cause the strong partition of copper content into the sulfide phase, resulting in decreasing of copper content in the melts. This process is not favour for enrichment of copper-rich fluids and formation of large class reduced porphyry Cu deposits. On the basis of definition of reduced porphyry Cu deposit, it is suggested that the Hongyuan Mo-Cu deposits in West Junggar is probably a new subtype of reduced porphyry deposit.