大别山千鹅冲斑岩型Mo矿床岩浆-热液演化过程：熔体和流体包裹体研究

Dabieshan area is one of the important metallogenic belts for porphyry Mo deposits in China. Most deposits from this belt show distinct characteristics from well-known Climax-type and Endako-type porphyry Mo deposits in the respects of tectonic setting, ore geology, ore-related intrusion and ore-forming fluid. Thus some researchers suggested these unique deposits could be classified as Dabie-type. To detect the metallogenic mechanism for this new type of deposit, this application proposes to analyze ore-forming metal and volatile concentrations in melt- and fluid inclusions hosted within quartz crystals from various ore-related intrusions or dykes and from different mineralization stages, using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), electron microprobe (EPMA) and other techniques. Based on the detailed investigations of field geology, petrography and ore microscopy, we can investigate how ore-forming metals evolved and got focused in the magma, and how ore-forming metals (Mo, Cu, Pb, Zn and Ag, etc.) selectively precipitated from fluids. Combining these two processes, a complete evolution of ore-forming metals and volatiles in this magmatic-hydrothermal system can thus be reconstructed, which can provide key insights into metallogenic mechanism for Dabie-type porphyry Mo deposit.

大别山地区是我国重要的斑岩Mo成矿带之一，带内大部分矿床在成矿构造背景和成矿地质特征等方面明显有别于已查明的Climax型和Endako型两类斑岩Mo矿床，部分学者建议将其划分为大别型斑岩Mo矿床。针对该类矿床成矿机制研究，本申请选取千鹅冲矿床为研究对象，拟在野外基础地质、室内岩相学、矿相学和包裹体热力学研究基础上，利用激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)和电子探针(EPMA)等技术对不同岩体/脉岩和不同成矿阶段石英矿物内熔体和流体包裹体进行成分分析，精确测定成矿岩浆和成矿流体中金属和挥发分含量，探讨金属在岩浆演化过程中迁移和聚集过程，以及在流体演化过程中成矿金属选择性富集沉淀机制，精细刻画成矿金属和挥发分在岩浆-热液体系中整个演化过程，为深入认识大别型斑岩Mo矿床成矿机制提供关键制约。

大别山地区是我国重要的斑岩Mo成矿带之一，是大别型斑岩Mo矿床重要分布区。针对该类矿床成矿机制研究，本项目选取千鹅冲矿床为研究对象，在野外基础地质、室内岩相学研究基础上，利用LA-ICP-MS和EPMA等技术对不同岩体/岩脉中石英矿物内熔体包裹体进行成分分析研究。取得的主要成果如下：（1）厘定脉岩和成矿斑岩侵位序列，识别深部存在另一期成矿斑岩；（2）限定成矿岩浆温-压条件，识别较深岩浆房的存在；（3）查明成矿岩浆经历结晶分异-晶粥活化-源区变化等演化过程；（4）千鹅冲成矿岩浆主要含2-8 ppm Mo，>5 wt. % H2O，较低的F (≤ 0.26 wt. %)，表明其成矿过程与成矿岩浆是否富集金属无关；（5）刻画成矿金属Mo岩浆-热液演化过程，发现多期流体出溶，该过程可能是大别型斑岩Mo矿床形成的关键；（6）初步认为构造转换可能是影响大别成矿带不同斑岩Mo矿化类型差异的主要因素。受本项目资助，共发表SCI论文2篇（另有1篇刚被Journal of Petrology录用；还有1篇正在审稿中）。