有机流体成矿作用与古油藏成藏作用相互耦合——以右江盆地微细浸染型金矿为例

Formation of Carlin-Type Gold Deposit by Hydrocarbon Fluid and its Correlation to Accumulation and Dispersion of Petroleum in Youjiang Basin, South China

右江盆地微细浸染型金矿与古油藏均产于二叠纪生物礁的核部或侧翼 .流体包裹体拉曼光谱分析和矿石抽提物色质谱分析均发现了大量的有机质官能团 ,暗示金矿成矿过程与古油藏的形成、演化密切相关 .金矿与古油藏的物质均来源于盆地裂陷期和凹陷早期的沉积地层 ,流体来源于沉积地层中封存的建造水 ,形成年龄 >172Ma .在随后约 40Ma(172～ 130Ma)的时间里 ,流体向盆地中生物礁及其他构造部位运移聚集 .由于盆地中烃源岩逐渐成熟 ,这一过程是油气运移成藏的过程 ,也是有机流体萃取成矿物质 ,最终演变为有机成矿流体并聚集的过程 .燕山运动是金矿成矿作用的主要构造营力 (130～ 46Ma) ,同时也是古油藏破坏的主要原因 .正是古油藏的破坏打破了流体的动态平衡 ,导致流体中成矿物质沉淀形成矿床 .

The genesis of the Carlin type gold deposits in the Youjiang basin, South China, has a close relationship with the evolution of the ancient oil reservoirs. Both Raman spectroscopy analysis of the fluid inclusions and gas chromatogram and mass spectrum analysis of the extractives from the ore indicate occurrences of abundant organic compounds. The gold deposits also have a consistent spatial distribution with the ancient oil reservoirs. Both of them occur in the core or on the flank of the Permian reef. According to the analyzed history of the Youjiang basin, the original fluid was formed during the rifting and early depression stage (>172 Ma) of the basin. In the following approximately 40 Ma (172-130 Ma), there exists no strong tectonic movement in the Youjiang basin. It is available for the original fluid to migrate into the core or flank of the carbonate platform and other similar reservoirs. The original fluid turned gradually into ore forming fluid during the migration. This process is also the migration of the hydrocarbon from the matured source rocks. The gold deposits were formed and the ancient oil reservoir was destroyed in Yenshan tectonic movement. It is the destroying of the ancient oil reservoir that caused the accumulation of the ore forming elements to form the ore deposits. Based on the above facts, this paper proposed that the gold deposits and the ancient oil pools were products of the same fluid in its different stages of evolution.