治岭头斑岩钼矿-浅成低温热液金银矿-脉状铅锌矿成矿系统流体演化研究

Connections between porphyry copper deposits and high-sulfidation epithermal gold deposits have long been proposed and intensively studied as one ore-forming system. However, the porphyry Mo mineralization to the low-sulfidation epithermal Au or vein-type Pb-Zn mineralization transitions are still in contention, especially for issues on the evolution of mineralizing fluids and the formation of metal zoning. Zhilingtou deposit is characterized by vertical metal zonation from the deep Mo mineralization to the shallow low-sulfidation epithermal Au-Ag and vein-type Pb-Zn mineralization. Thus, this deposit could serve as a perfect case study for investigating the controversial issues. This proposal intent to take the hydrothermal quartz-pyrite-calcite in Zhilingtou Mo-AuAg-PbZn mineralization as the research object. Fluid inclusion microthermometry, fluid compositions of gas/liquid phase, H-O-C-He-Ar isotopes, electronic probe microanalysis and single-inclusion microanalysis by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) will be applied to monitor the systemic changes of compositions and physical conditions of ore-forming fluids. Then by spatial and temporal comparisons of those data acquired, we could discuss the systematic evolution of hydrothermal fluids and the mechanism of metal zonation. Furthermore the Transition model between the porphyry Mo to epithermal Au-Ag/Pb-Zn mineralization in Zhilingtou deposit will be reconstructed. This study will be helpful to further understand the geological processes of the system evolving from porphyry Mo stage to epithermal Au-Ag/Pb-Zn-Ag stage, and provide important implications for the mineral prospect of similar hydrothermal system.

相比于环太平洋成矿带内斑岩铜矿-高硫型浅成低温热液金矿成矿系统，前人对斑岩钼矿与低硫型浅成低温热液型金银矿-脉状铅锌矿共生的成矿系统的研究较为薄弱，尤其缺乏对热液成矿过程和矿化分带机制等科学问题的深入剖析。浙江省治岭头多金属矿为空间分带清晰的斑岩钼矿-低硫型浅成低温热液型金银矿-脉状铅锌矿成矿系统，为本研究提供了典型案例。本申请拟选择治岭头钼矿、金银矿、铅锌矿三类矿化共有的石英-黄铁矿-方解石为研究对象，系统开展包裹体显微测温、气液相成分、H-O-C-He-Ar同位素组成研究，结合电子探针和LA-ICP-MS分析单个流体包裹体的金属元素含量及其成分变化，通过空间对比分析，精细刻画治岭头成矿流体的出溶-演化过程，讨论矿化分带机制，建立斑岩钼矿-浅成低温热液型金银矿-脉状铅锌矿成矿系统模型。本研究对丰富斑岩钼矿成矿系统的成矿过程具有重要的科学意义，并对同类型矿床的勘查具有重要的借鉴意义。

本项目按计划书进行了三年的研究工作，项目按年度工作计划进行并取得了超过预期的研究成果：（1）通过系统的流体包裹体及LA-ICP-MS的研究，首次建立了治岭头斑岩Mo-浅成低温热液Pb-Zn-Au-Ag成矿系统，丰富了斑岩钼矿的内涵和外延，对浅成低温热液型金银矿和铅锌矿深部找斑岩钼矿和斑岩钼矿外围找浅成低温热液型金银矿和铅锌矿提供了理论基础。（2）对华南钼矿省治岭头等白垩纪斑岩钼矿的系统总结，揭示了早白垩世两期斑岩钼矿以高F型斑岩钼矿为主，形成于古太平洋后撤诱发的伸展背景，指明区域具有重要的成矿潜力。（3）系统分析浙江省花岗岩的年代学和地球化学，识别晚侏罗世（170–145 Ma）、早白垩世早期（145–125 Ma）和早白垩世晚期（125–90 Ma）三期岩浆活动，并表现出自内陆向沿海逐渐年轻的趋势，推断与古太平洋板块俯冲、后撤有关。研究奠定了浙江省中生代斑岩钼矿的构造-岩浆背景。（4）本项目资助发表与研究有关的2篇国际SCI论文。