斑岩型钼矿:新类型的识别及成矿控制因素

Porphyry Mo Deposits: New Sub-Types and Ore-Controlling Factors

本文介绍了我国学者识别的斑岩钼矿新类型——碰撞型,并简述了其成矿控制因素。碰撞型斑岩钼矿形成于同碰撞-后碰撞环境,成矿岩体主要源自中-下地壳的部分熔融,成矿流体富CO_(2),可出现特征的多子晶富CO_(2)包裹体,围岩蚀变钾化、碳酸盐化、萤石化强烈,绢英岩化、青磐岩化相对较弱。研究揭示,在富钼地质背景下,长期、多次的钼金属预富集导致秦岭燕山期爆发式成矿。汇总了已有熔体/流体包裹体数据,揭示成矿岩浆中钼含量并不高,形成斑岩型钼矿需要高通量的熔体、大规模的岩浆房;钼金属的预富集、大规模的岩浆房和高氧逸度的岩浆有利于成矿,但单一因素不足以控制斑岩型钼矿的形成。最后展望了斑岩钼矿未来研究方向。

In this contribution, the newly-recognized subtype of porphyry Mo deposit, i.e. the Collision type that developed in syn-to post-collision settings, has been introduced and the ore-controlling factors of porphyry Mo deposit have been briefly described. In case of the collision-type porphyry Mo deposits, the ore-causative magma was mainly sourced from lower to middle continental crust, with ore-forming fluids featured by CO_(2)-rich. There is a kind of specific fluid inclusion that contains CO_(2) as well as multiple daughter minerals. The hydrothermal alterations are dominated by potassic, carbonate and fluorite alterations, with relatively weak phyllic and propylitic alterations. Such features distinguish them from the ever-known continental arc-and back-arc rift-type counterparts. It is proposed that the regional-scale Mo-rich background and long-term and several episodes of Mo pre-enrichment contributed to the Yanshannian explosive Mo mineralization in the Qinling area. A review of available melt/fluid inclusion data suggests that the formation of an economic porphyry Mo deposit need high flux melt and large scale magma chamber, though the Mo content of ore-causative magma of was not very high. The pre-enrichment of Mo metal, large scale magma chamber, and high oxygen fugacity of the magma are favorable for porphyry Mo mineralization, albeit none of them can be the sole factor controlling the mineralization potential. Finally, a preliminary prospects on the research trend of porphyry Mo deposit has also been carried out in this paper.