东昆仑水闸东沟-黄龙沟金矿床硫化物矿物学特征对可见金形成条件的制约

Visible gold-forming environment evidenced by sulfide mineralogical characteristics of Shuizhadonggou-Huanglonggou gold deposit in eastern Kunlun orogen

东昆仑五龙沟地区水闸东沟-黄龙沟金矿床处于昆中断裂北部,受NW向构造控制,矿区出露中元古界小庙组和新元古界丘吉东沟组地层,岩浆岩以早古生代和早中生代侵入岩为主。围岩蚀变以绢云母化和硅化为主,矿体严格受NW向剪切带控制,赋矿岩石为早古生代正长花岗岩和新元古代丘吉东沟组板岩。综合野外地质特征、矿相学观察和电子探针测试结果,水闸东沟-黄龙沟金矿床可划分出4个成矿期:沉积期、热液Ⅰ期、热液Ⅱ期和表生期。新元古代沉积期属金的初步富集期;早古生代热液Ⅰ期可分为4个阶段,其中第一阶段(磁黄铁矿-毒砂-斜方砷铁矿-自然金阶段)是金的主成矿阶段;早中生代热液Ⅱ期金再次活化富集;表生期代表矿体暴露地表后的变化。热液Ⅰ期的磁黄铁矿-毒砂-斜方砷铁矿-自然金阶段,由早至晚体系温度和硫逸度升高,代表前进变质作用,变质条件达绿片岩相上限。斜方砷铁矿交代毒砂的结构中通常可以观察到可见金,说明该阶段是由不可见金向可见金转化的重要时期,可见金形成于绿片岩相上限的温度范围内。

The Shuizhadonggou-Huanglonggou gold deposit of eastern Kunlun orogen is located in the north of the Middle Kunlun fault and controlled by NW-trending structures. The Mesoproterozoic Xiaomiao Formation and Neoproterozoic Qiujidonggou Formation are exposed in the ore district, and Early Paleozoic and Early Mesozoic intrusions constitute the main magmatic rocks in the region. Alteration mainly includes sericitization and silicification. Ore bodies occur within Early Paleozoic syenogranite and Neoproterozoic slate and are strictly controlled by the NW-trending shear zone. On the basis of field work, ore microscopy and electron probe analyses, the authors recognized four metallogenic periods. The Neoproterozoic sedimentary period was a period of initial enrichment of gold. The Early Paleozoic hYdrothermal period could be further divided into four ore-forming stages, of which the first was the main gold ore-forming stage （pyrrhotite-arsenopyrite-loellingite-native Au stage）. Gold was activated and concentrated again during the third Early Mesozoic hydrothermal period. The fourth period represented a hypergene process. Temperature and sulfur fugacity increased during the pyrrhotite-arsenopyriteloellingite-native Au stage, which represented progressive metamorphism and attained the upper greenschist facies. Visible gold appears near the boundary between arsenopyrite and lolingite, which was probably related to the replacement of arsenopyrite by lollingited, and hence the visible gold must have been formed under the condition of the upper greenschist facies.