矽卡岩矿床钨-铜共生分离机理：以鄂东矿集区阮家湾和铜山口为例

Tungsten has different geochemical characteristics with copper; however, the phenomenon of W and Cu paragensis is common in the skarn deposits. Consequently, it is an important issue need to be addressed about the mechanisms of W-Cu parageneis and separation. This proposal will take the representative Ruanjiawan Cu-baring skarn W deposit and Tongshankou W-bearing skarn Cu deposit as two examples. Firstly, in-situ Sr-Nd isotope for the magmatic apatite, zircon Hf-O isotope, and major, trace elements and REE geochemistry of the magmatic apatite, biotite, amphibole and zircon will be systematically conducted; these data are used to ascertain the magma source, differentiation index, pressure and oxygen fugacity of these intrusions associated with Cu and W mineralization. Secondly, physical and chemical conditions, and compositions of melt-fluid and fluid inclusions in the transparent minerals within the intrusion and pegmatite, as well as scheelite, quartz and garnet during different hydrothermal stages will be documented, and then confirming the nature and evolution path of the ore-bearing fluids. Finally, integrated studies of scheelite and chalcopyrite with Sr-Nd-He-Ar isotope characteristics of the scheelite and chalcopyrite will reveal the source of ore-forming fluids and metals. Based on above, we will try to discuss partition coefficient, transfer and precipitate difference between tungsten and copper during magmatic to hydrothermal evolution, and reveal the crucial factors controlling the W-Cu parageneis and separation. The implementation of the project not only may contribute to extend knowledge of skarn deposit theory, but also help to provide some significance for skarn deposit exploration in the area.

钨和铜元素具有不同的地球化学特征，但矽卡岩矿床中钨与铜共伴生现象多处可见，它们的共生分离机理是有待查明的重要科学问题。本项目以鄂东矿集区有代表性的阮家湾含铜矽卡岩钨矿和铜山口含钨矽卡岩铜矿为研究对象，通过对岩浆成因磷灰石原位Sr-Nd同位素、锆石Hf-O同位素及磷灰石、黑云母、角闪石和锆石主量和微量元素的研究，厘定含铜和含钨岩体的源区、分异演化程度、压力和氧逸度；分析含矿岩体、伟晶岩中石英和热液阶段石榴子石、白钨矿、石英等矿物的熔-流体和流体包裹体的物理化学条件和成分，确定流体性质和演化过程；开展白钨矿和黄铜矿的Sr-Nd-He-Ar同位素的研究，确定含矿流体和成矿元素的来源。综合以上成果，讨论钨和铜元素的分配、迁移、沉淀过程，揭示矽卡岩矿床钨-铜共生分离机理，进一步丰富矽卡岩矿床的成矿理论，也为区域上矽卡岩矿勘查提供理论指导和借鉴。

钨与铜具有不同的地球化学特征，暗示铜与钨似乎不可能共伴生。但全球多处矽卡岩铜矿共伴生钨矿化，矽卡岩钨矿共伴生铜矿化，其独特的铜钨共生分离机理是未解决的关键科学问题。长江中下游成矿带是全球重要的矽卡岩铜多金属矿成矿带，其西部的鄂东矿集区探明了3个大中型含铜矽卡岩钨矿床，近年来在铜山口矽卡岩铜矿深部发现厚大的钨矿体和钨铜共生矿体。因此，鄂东矿集区的矽卡岩型钨矿和铜矿是破解矽卡岩矿床铜钨共生分离机理的理想对象。.本项目选择阮家湾和付家山含铜矽卡岩钨矿及铜山口含钨矽卡岩铜矿为研究对象，通过系统的矿物学、岩石学和地球化学研究，主要取得以下3个方面的重要进展：（1）确认这些矽卡岩矿床均为氧化性钨矿或含钨铜矿，矿床具有明显的上铜下钨的分带规律，其白钨矿具有复杂的结构和多世代的特征，铜钨矿中白钨矿的钼含量高于钨铜矿，指示热液阶段氧化还原条件的不同是造成同时代矽卡岩矿床钨、铜成矿差异的主要原因；（2）研究发现地层中有机碳含量不同是造成矽卡岩钨矿中矽卡岩矿物和白钨矿成分及硫化物矿物组合存在明显差异的主要原因，同时，还原性地层附近的矽卡岩钨矿规模大且品位高；（3）氧化性矽卡岩钨矿、铜矿的含矿岩体均为富集地幔混染下地壳的混合产物，但含矿岩浆氧逸度和Nd-Hf同位素存在明显的差异性，指示含矿岩浆性质的不同是造成同时代矽卡岩矿床钨、铜成矿差异的根本原因。因此，地层的有机碳含量和矿床所在地区基底性质的差异是造成矽卡岩矿床钨、铜成矿差异的两个决定性因素。目前为止，依托本项目发表有标注论文12篇，其中第一、二标注论文8篇论文，SCI论文9篇，EI论文1篇，开展多次国内外学术交流，培养3名博士生和2名硕士生，项目负责人获得国家杰出青年科学基金项目资助。本项目成果丰富了矽卡岩钨矿成矿理论，对钨铜共生分离机制进行初步解释。