赣西北大湖塘超大型钨矿床中单向固结结构对早期岩浆流体演化及钨成矿作用的指示

大湖塘钨矿床位于江南造山带东段，是江南古陆钨矿带中的超大型斑岩型钨铜钼多金属矿床，目前对成矿流体的研究主要集中于晚期成矿阶段，缺乏对早期岩浆流体物理化学性质、出溶和演化过程的研究，钨矿成因机制尚不明确。大湖塘矿区发育的记录早期岩浆流体出溶证据的单向固结结构，是研究早期岩浆流体性质的绝佳载体。似斑状花岗岩中石英斑晶和单向固结结构石英分别是岩浆晚期和岩浆-热液过渡期的岩浆流体产物，反映了两阶段的早期岩浆流体性质。本项目选取以上两类石英为研究对象，拟在详细的岩相学和石英阴极发光成像研究基础上，利用电子探针、离子探针、激光消融等离子质谱等原位分析技术，系统开展不同世代石英的原位氧同位素和原位微量元素分析，及熔体和流体包裹体显微测温、原位化学成分分析等，以期查明岩浆熔体和早期岩浆流体的物理化学性质，剖析早期成矿流体出溶机制和演化过程，阐明成矿元素分离机理和运移过程，揭示钨矿成矿机制和成矿过程。

Dahutang tungsten deposit, located in the eastern Jiangnan Orogen, is a giant porphyry W-Cu-Mo polymetallic ore deposit in the Jiangnan tungsten ore belt. The research on the ore-forming fluids is still weak at present. Previous studies mainly focused on the ore-forming fluids in the stages of mineralization, but they neglected the study on the primary magmatic fluids exsolution, especially on the physical and geochemical characteristics, as well as the exsolving and evolutionary process of the primary ore-forming fluids. Hence the metallogenic mechanism of tungsten in this field is still ambiguous. Two suites of unidirectional solidification textures (USTs) are recognized in the Dahutang tungsten deposit. They record the exsolving process of primary magmatic fluids and are the ideal carrier to research the nature of primary magmatic fluids. Quartz phenocrysts in the porphyritic granites and USTs quartz are product of magmatic fluids in the late magmatic stage and magma-hydrothermal transition stage, and represent the nature of early magmatic fluids in these two stages. The two types of quartz (quartz phenocrysts in the porphyritic granites and USTs quartz) are selected as the research objects in this program for in-situ microanalysis studies using the latest in-situ analysis techniques, such as electron microprobe analyzer (EPMA), SHRIMP ion microprobe, laser ablation plasma mass spectrometry (LA-ICPMS), etc. Before all the experiments, petrographic observations and cathodoluminescence imaging of quartz studies are used to distinguish the detailed generations of the two types of quartz. Subjects to be studied include: (1) characteristics of melt inclusions and fluid inclusions, such as their redox states, formation temperature, salinity, power of hydrogen, contents of metallogenic metal elements and trace elements compositions; (2) the trace elements contents and variations in the two types of quartz; and (3) oxygen isotopic geochemistry of quartz in different generations. The objectives of this program are to identify the physical and geochemical characteristics of magmatic melts and primary magmatic fluids, as well as to analyze the exsolving and evolutionary process of early ore-forming fluids. Also, we will clarify the separation mechanism and migration process of ore-forming elements and reveal the ore-forming mechanism of tungsten deposits.