岩石磁性与低温流体成矿作用关系探讨

A PRELIMINARY STUDY ON THE RELATIONSHIP BETWEEN ROCK MAGNETIC PROPERTIES AND MINERALIZATION OF LOW TEMPERATURE FLUIDS

大量研究表明 ,低温流体通过改变岩石中磁性矿物的组成而改变了岩石的磁化率和剩磁等磁性参数 ,利用岩石磁学和古地磁学的方法能够帮助区分不同时期和类型的流体事件。笔者认为流体对围岩的影响受岩石组织类型的控制 ,通过研究岩石组织类型可望了解磁性矿物转变和重磁化的机制。文章通过金矿围岩地球化学和磁性参数对比的实例分析 ,提出岩石组织内部磁场也可能对流体的成矿作用发生重要影响。流体在萃取围岩中有用元素或发生成矿物质聚集的同时也可能导致新的磁性矿物形成。在此过程中 ,磁性矿物的晶体生长以化学剩磁的方式记录下环境磁场 ,由此可以研究流体运移轨迹。

Multidisciplinary studies have demonstrated that low temperature fluids may cause alteration of magnetic minerals and hence are responsible for their remagnetization and susceptibility changes. Rock magnetic and paleomagnetic data can thus provide important information on the timing and nature of fluid event. The authors propose that rock texture plays the most important role for fluid migration and magnetic mineral alteration. Distinguishing the type and the rank of the rock texture will be helpful to understand the mechanism of the fluid-associated remagnetization. Based on the comparison between Au geochemical and rock magnetic data from a mineralized area in northeast China, we suggested that the environmental magnetic field may affect the mineralization process in rock texture. Alternatively, when fluid extracted Au from the host rock, authigenic magnetic minerals formed and their chemical remanent magnetization (CRM) recorded the environmental magnetic field. The CRM is useful to trace the path of fluid migration.