西藏拿若铜(金)矿床隐爆角砾岩流体包裹体研究

Fluid Inclusion Study of the Cryptoexplosive Breccias in the Naruo Cu(Au) Deposit of Tibet

隐爆角砾岩是西藏拿若矿床的重要组成部分,赋存厚大的铜矿体。笔者将隐爆角砾岩中流体分成两个主要期次,并对这两期流体开展包裹体研究。通过包裹体岩相学和显微测温认为：角砾中的石英（早期）包裹体形状均匀呈椭圆形,大小主要在2-5μm;胶结物中石英（晚期）包裹体形状可见椭圆状、长条状和近方形,大小主要在2-7μm。早期流体的包裹体可分为两个阶段,均一温度分别为早阶段280-368℃和晚阶段208-305℃,盐度分布为（4.65-12.73）%Na Cleq。晚期流体的包裹体同样可分为两个阶段,其均一温度分别为早阶段309-588℃和晚阶段232-335℃,盐度变化为（3.55-12.51）%Na Cleq,两个阶段的流体分别属于高温、中低盐度和中高温、中低盐度流体。L-V型包裹体激光拉曼分析显示：包裹体中气泡成分主要为气态H2O和少量CO2。拿若矿床至少经历两次隐爆作用,由晚期沸腾热液引起,并未成矿。成矿作用发生于隐爆角砾岩形成之后。

Cryptoexplosive breccia is an important part of the Naruo deposit,including a large copper ore body. We divide the fluid in this breccia into two main periods and carry out a detailed study on its fluid inclusions. Inclusion petrography and microthermometry suggest that the quartz from breccia（ early phrase） inclusion is of an oval shape and uniform,most of the sizes between 2 and 5μm. The shape of quartz from cement（ late phrase） inclusions is like oval,strip and square,most of the sizes between 2 and 7μm. The early inclusion is divided into two phases,of which homogenization temperatures280 - 368℃（ early phase） and 208 - 305℃（ late phase）,respectively,with salinity 4. 65 - 12. 73% NaC leq. The late inclusion is divided into two phases too,with homogenization temperatures 309 - 588℃（ early phase） and 232 - 335℃（ late phase）,and salinity 3. 55 - 12. 51% NaC leq. Two phases of late inclusions are respectively high temperature,medium- low salinity and medium- high temperatures,and medium- low salinity. Laser Raman of type L- V inclusions shows that the bubble components are mainly gaseous H2O and a little CO2. Concealed explosive occurred at least tow times at the Naruo deposit by late boiled fluid,which did not generate ore. Mineralization took place after the formation of cryptoexplosive breccia.