Investigation on evaluation for mineralization potential of magmatic hydrothermal systems

为了建立岩浆热液系统成矿潜力的评价方法，在几个重要的系统上研究了系统的演化和控制金属聚集的因素，重点讨论了系统的三维结构、沸腾带的分布和系统浅层的信息。主要地区包括莱潘托/FSE-Victoria、Kasuga、Hishikari、Kushikino、Fuke、Cibaliung、Iwami、昆士兰北部、Hoshino和Noya。结合一些实验工作，取得了以下重要成果。在Kushikino、Hoshino和Iwami2地区发现埃达克质火山岩。用裂变径迹、K-Ar和^&lt；40&gt；Ar/^&lt；39&gt；Ar方法对火山岩和矿石进行的年龄测定清楚地表明，在某一地区，热液活动在火山活动开始后约50万年开始，并持续约50万年，断续形成断裂。如果保存了系统的浅层部分，则可能存在烧结矿，而烧结矿中较高的金含量指示了可能的金矿化。水热蚀变分带构造了热液系统的区域热结构。以150-200摄氏度等温线为界的区域表示断裂系统，延伸3公里×4公里。沸腾带主要由片状方解石/石英、榴辉石和方解石的赋存状态以及流体包裹体特征指示。流通式高压灭菌器实验表明，在裂缝形成过程中，热水中的硅、铝和钙的浓度都是瞬时增加的。金在Al和Fe(III)氢氧化物上的吸附实验表明，金的沉积受吸附过程的强烈控制。

To develop the evaluation procedure for the mineralization potential of magmatic hydrothermal systems the evolution of systems and factors controlling concentration of metals were examined on several important systems, emphasizing three dimensional structures, distribution of the boiling zone and information of the shallow part of systems. Major areas include Lepanto/FSE-Victoria, Kasuga, Hishikari, Kushikino, Fuke, Cibaliung, Iwami, Northern Queensland, Hoshino and Noya. Together with some experimental works the following important results were obtained.1. Adakitic volcanic rocks were found in the areas of Kushikino, Hoshino and Iwami.2. Age determination using fission track, K-Ar and ^<40>Ar/^<39>Ar methods for volcanic rocks and ores clearly showed that in a certain area the hydrothermal activity starts about 500,000 years after the commencement of the volcanic activity, and continues about 500,000 years with intermittent fracture formation.3. If shallow part of a system is preserved, sinters may exist and the higher gold content of sinters indicates the possible gold mineralization.4. The regional thermal structure of a hydrothermal system is constructed by hydrothermal alteration zoning. The area bounded by 150-200 C isotherms indicates the fracture system and extends for 3 km by 4 km.5. Boiling zones are indicated by occurrence of bladed calcite/quartz, adularia and truscottite, and also by characteristics of fluid inclusions.6. Flow-through type autoclave experiments indicate that concentrations of Si, Al and Ca in hydrothermal waters increase transiently during fracture formation.7. Adsorption experiments of gold on Al and Fe(III) hydroxides suggest that deposition of gold is strongly controlled by adsorption process.