相山铀矿田地球物理场特征浅析及其找矿意义

PRELIMINARY ANALYSIS FOR GEOPHYSICAL FIELD CHARACTERISTICS IN XIANGSHAN URANIUM ORE FIELD AND ITS PROSPECTING SIGNIFICANCE

相山钿矿田的地球物理场,区域特征表现为区域重力异常梯度带范围内的重力低与相对降低磁场配套,地面伽玛高背景场与航空伽玛能谱铀偏高晕复合,这是受区域深断裂和火山喷发带控制的具低密度、弱磁性、富铀酸性火山塌陷盆地的标志。矿床定位的局部地球物理场特征是重、磁二次微商场局部异常边缘等值线密集带或零值线附近与地面伽玛偏高场、航空伽玛能谱铀高值晕对应,这是断裂构造、岩石接触界面控制矿床产出的标志。根据区域标志提出了矿田“五位一体”的区域地球物理场——地质组合模式,深入讨论这一模式和应用这些标志对于建立矿田成矿模型、找矿模式、指导区域找矿、寻找隐伏矿床和富矿部位是有一定意义的。

Regional characteristies for the geophysical fields in Xiangshan uranium ore field is expres- sed as follows:(1) gravity low within the gradient zone of regional gravity anomaly is coincident with relatively low magnetie field; (2) the surface high gamma background is accordant with airborne gamma spectrometrie higher uranium halo. Above distinguishing indications are all reflected in a uranium-rich collapsed basin with low density and weak magnetism which is controlled by regional deep faults and volcanic eruption zone. Local geophysical characteri-stics for localization of uranium deposits are that dense zones of local anomalous marginal isopleth or zero lines nearby of second derivative field correspond to surface gamma higher field and higher halo of airborne gamma spectrometry. These indications show that occurren- ce of deposits are always limited by faulted structures or rock contact zones. According to the indications, an assemblage model of geophysical fields (regional) and geological terrains is presented which is known as “five factors within one body”. Further discussing this model and applying this indications is of significance in establishing metallogenic and prospecting patterns in the ore field guiding regional prospection and finding concealed deposits and their enrichment portions.