摘要
江西贵溪冷水坑矿床为一大型一超大型Ａｇ、Ｐｂ、Ｚｎ矿床，在矿床深部和矿化花岗斑岩体的中心部位有铜矿化现象，但未构成工业矿体。本文将冷水坑成矿体系作为一种含Ｈ_２Ｓ、ＣＯ_２以及Ｆｅ、Ｃｕ、Ｐｂ、Ｚｎ、Ａｇ、Ａｕ等金属元素的ＮａＣ１型降温成矿热液体系，根据矿床的矿物共生组合及其成矿物理化学条件，认为上述各金属元素在成矿热液中的饱和浓度应分别受黄铁矿或磁黄铁矿了黄铜矿、方铅矿、闪锌矿、辉银矿和自然金的溶解反应控制，并在假定模拟起始温度条件下各金属元素的浓度分别等于其饱和浓度的基础上，对上述金属元素在３６０－１７５℃温度区间内的迁移与沉淀过程进行了计算机数值模拟，在模拟过程中有４８种溶解类型参加了计算。其结果不仅与矿床的矿物生成序列基本一致，合理地解释了冷水坑矿床的矿化与蚀变分带，更重要的是，模拟结果还表明，冷水坑成矿热液中富含Ｃｕ，但由于其成矿体系的地球化学演化不利于Ｃｕ的沉淀和富集，因而未形成工业铜矿体，从而得出了富含金属元素的热液不一定成矿的结论。因此，就冷水坑矿床源区的成矿地球化学特征而言，完全有可能在适宜的地质和地球化学条件下形成具有较大经济价值的铜矿床。冷水坑矿床中缺少具有经济价值的金矿化则表明其矿源中?
Lengshuikeng ore deposit is known as a large scale Ag, Pb and Zn porphyry deposit,in which subeconomic chalcopyrite mineralization has also been found in the centre and the deep part of the mineralized granitic porphyry. In the deep part, the chalcopyrite associates with pyrrhotite and cubanite and formed at temperatures up to 360℃ while the chalcopyrite+ pyrite+Fe-chlorite assemblage disseminates the centre and the upper part of the granitic porphyry and is, in the revealed range,gradually disappeared as the granitic porphyry becomes thinner and thinner with depth. The distribution of this mineral assemblage disproves the argument that its formation temperature is higher than that of Ag, Pb and Zn mineralization and suggests that it is developed in less permeable wall rocks.In order to find out the factors controlling the geochemistry of Lengshuikeng deposit, an fluid geochemical numeric modelling of the ore-forming proccess from 360℃ to 175℃ is made, based on the assumption that Lengshuikeng ore-forming fluid is analogous to H_2S-CO_2-bearing NaCl hydrathermal solution, in which pyrrhotite,chalcopyrite, galena, sphalerite, argenite and gold are presumably saturated at 360℃. According to the mineral assemblage and the physico-chemical conditions of the ore-forming system, the solubilities of Fe, Cu, Pb, Zn, Ag and Au in the ore-forming fluid are, respectively, controlled by the dissolution reactions of pyrite (or pyrrhotite, depending on the js_2 of the fluid system), chalcopyryte, ganenla, sphalerite, argentite and nature gold. There are 48 chemical species concerned in the calculation which are considered to be dominate in the fluid system. The modelling result is in general consistent with the mineral formation sequence and provides a most resonable explanation for the mineral zonation of Lengshuikeng deposit. Moreo ver, it indicates that Lengshuikeng ore-forming fluid is rich in copper at 360℃, but its geochemical evolution is not favourable for copper deposition and accumulation,which would be the major cause accounting for the subeconomic metallization of copper in Lengshuikeng deposit. Therefore, as the geochemistry of its source is concerned, economic copper deposits would be expected to develop in suitable geological and geochemical enviorenments in this region. However, the absence of economic gold deposition in Lengshuikeng ore deposit suggests that its source would be Poor in gold of being easy to be mobilized.
出处
《地球化学》
CAS
CSCD
北大核心
1995年第C00期24-32,共9页
Geochimica
基金
国家自然科学基金
