从油气运移探讨有机质在成矿中的作用

The Function of Organic matter in Ore-forming Processes:In View of the Oil Migration

本文从盆地中有机质热演化成烃、烃类物质经过初次运移和二次运移形成油气藏以及油气藏破坏的烃类运聚演化过程探讨了有机质在成矿中的作用。来自于盆地中沉积地层的烃类物质和成矿流体具有相同的输导体系,因而两者通常在同一种流体介质中运移。来自烃源岩的流体的盐度很低(20～30g/L),说明流体从烃源岩中萃取的成矿物质的量有限。在油气的二次运移阶段,烃类物质使流体保持酸性环境,从而加速了流体演变为成矿流体的速度。同时,有机质通过络合、还原和吸附作用参与了成矿物质的搬运,油气成藏的过程也是成矿流体聚集的过程。油藏(reservoir)的破坏使流体发生剧烈的物化条件改变,从而导致了矿质沉淀形成矿床。

The function of organic matter is a key point to understand the mineralization of ore-forming fluids. Organic matter and ore-forming fluids are both derived from basins and have the same conduits during their migration. Thus, organic matter migrates together with ore-forming fluids. The most effective way to understand its function is to see its changes during the migration and concentration of fluids. The original fluid and organic matter are from the source rock in the basin. The fluid salinity from the source rock is rather low, which means that there is a small amount of material concentrated from the source rock. This suggests that the function of the organic matter be rather small during the first migration of the oil. During the secondary migration of the fluid, the salinity is increasing, and the temperature is dropping down. The organic matter helps the concentration and transport of the ore-forming material by complexation, reduction, adsorption and supplying the fluid with acidic environment. The destruction of reservoirs can create great changes of physical and chemical properties of the fluid and is an important factor to cause the deposition of ore-forming material.