Characteristies and time-spatial analysis of epitharmal Au-Ag mineralization and acid-sulfate alteratin

针对岛弧地质环境中与年轻火山活动有关的浅成热液型金银矿床的成因和形成过程，在野外和实验室工作的基础上，从矿石地质、地球化学和岩石学等方面对其形成环境和富集过程进行了研究。为了提高化学分析的准确度，还进行了基础实验。研究了浅热和中热条件下低硫化型和高硫化型金矿化的矿石和蚀变矿物组合，确定了这两种类型的物化条件和时空关系。并将研究领域扩展到日本东北部和印度尼西亚的同类型地区进行比较研究。结论表明，高硫化型金矿化主要受岩浆流体的影响，而低硫化型金矿化主要受大气降水的影响。前者先于后者，且更靠近侵入岩。这两种类型的金矿化都与岩浆活动密切相关，形成的以硫化物配合物形式溶解各种金属的高温流体可能由于压力降低和/或与大气水混合而在浅层环境中产生冷却、氧化或稀释作用，从而有效地沉淀了金属。

On the genesis and formation process of the epithermal Au-Ag deposits related to young volcanic activities in the island arc geologic environ- ment, it is investigated to clarify the formation environment and con- centration process of the elements from the viewpoints of ore geology, geochemistry and petrology based on the field and laboratory works. Basic experiments are also conducted in order to improve and obtain high accuracy in chemical analyses.Both low- and high-sulfidation types of gold mineralizations in epi- and meso-thermal conditions are investigated on their assemblages of ore and alteration minerals to determine the physicochemical conditions and time-spatial relationships of the both types. Study fields are also extended to the same types in northeast Japan and Indonesia to make comparative study.As a concluding remarks, it is clarified that the high-sulfidation type gold mineralization is stongly affected by the magmatic fluids, but the low-sulfidations is by meteoric water. The former is prior to the latter and is located closer to the intrusive rock. Both types of gold mineralizations are strongly related to the magmatic acitivity, and the originated high temperature fluids dissolving various metals in the style of sulfide complexes might have effectively precipitated them due to the boiling by pressure decrease and/or mixing with meteoric water to cause cooling, oxidation or dilution in shallow environment.