斑岩型Cu、Mo差异性成矿的岩浆—热液约束机制：以川滇乡城—中甸地区燕山期岩体和矿床为例

As the most important sources of global Cu and Mo resources, porphyry-type Cu and Mo deposit is attracting widespread interest. Nearly all of such porphyry-type deposits are related to granitic porphyries, thus how to recognize the granitic porphyries respectively associated with Cu or Mo mineralization and non mineralization is becoming an important problem. Previously, porphyry-relate Cu and Mo mineralization potentiality was evaluated by magmatic source or oxidation state. However, current study has shown that magmatic H2O and S contents, Cl/H2O ratio, emplacement depth and geochemical behavior of Cu and Mo in magmatic and hydrothermal systems also influence porphyry-type Cu and Mo mineralization. Thus using single index to define mineralization potentiality of granitic porphyry is incomplete, and more comprehensive research is needed. In this study, we will select two late-Yanshanian porphyry-type deposits (the Hongshan porphyry-type Cu deposit and the Tongchanggou porphyry-type Mo deposit) and related granitic porphyries and a contemporaneous non-mineralization granitic porphyry (Cilincuo pluton) in Xiangcheng-Zhongdian area as subject investigated. Using in-situ analysis technique, the elements and isotope compositions of both igneous accessory minerals and single fluid inclusions in deposits will be detected. The results can help us to better understand the different physical and chemical conditions between Cu-related and Mo-related magamtic and hydrothermal systems and different geochemical behavior of Cu and Mo during magmatic and hydrothermal evolution. The results can also provides us a clearer recognition on metallogenic specificity of granitic porphyry, which will be important for prospecting and exploration of porphyry-type Mo and Cu deposits .

斑岩型Cu、Mo矿床与花岗质斑岩有关，是全球铜、钼资源的主要来源。如何区分成铜矿、成钼矿与不成矿斑岩，备受国内外关注。以往多从斑岩的岩浆源区和氧逸度等单一指标评价其成矿潜力。实际上，岩浆具有高氧逸度、富水、富硫、较高的Cl/H2O和较浅的侵位深度等物化条件，均利于铜、钼自岩浆分异到热液而成矿，且Cu、Mo的差异性成矿与它们不同的地化行为有关。因此，若仅研究上述某个条件，很可能只会得到相对片面的结论。本项目选择乡城-中甸地区燕山期红山斑岩Cu矿、铜厂沟斑岩Mo矿和相关斑岩体及同期贫矿的茨林措斑岩体为对象，采用原位分析技术，系统研究斑岩中副矿物的元素-同位素以及矿床中单个流体包裹体的组成特征，确定岩浆源区、岩浆物理化学条件、成矿流体和Cu、Mo地化行为等因素对成矿的综合控制作用，揭示成铜矿、成钼矿和不成矿斑岩的异同。这些研究对正确辨析成矿（铜矿和钼矿）与不成矿斑岩、指导找矿勘探具有重要意义。

本项研究以义敦岛弧（中甸-甘孜段）若干成矿性不同的岩体（成Cu矿、成Mo矿和不成矿）为研究对象。对其中磷灰石、榍石、锆石等副矿物开展了原位微区分析。基于获得的副矿物元素-同位素地球化学成分，深入探讨了制约斑岩Cu、Mo成矿的岩浆机制。获得了以下成果： 1）证实Mo在岩浆中的富集不是决定斑岩Mo成矿的唯一关键因素，F对斑岩Mo成矿也起着重要作用。此外，尽管岩浆Cu的富集有利于成矿，但成Cu矿的岩浆不一定需要极高的Cu含量。2）明确了岩浆肥沃度的不同是导致义敦岛弧带斑岩Cu成矿潜力差异的主要原因。3）提出了岩浆氧逸度和含矿性不能单独用于判断斑岩成Cu矿或Mo矿。4）验证了副矿物在限定岩浆各类信息方面的有效性和优势性。总之，本项目获得的成果为揭示斑岩Cu、Mo成矿机制与规律、评判斑岩成矿潜力、指导找矿工作提供了新的思路，具有重要的理论和实践价值。