闽西南大排多金属矿区地球物理响应特征与找矿启示

大排多金属矿区位于闽西南坳陷大田—龙岩次级坳陷带南部,政和—大埔深大断裂西侧,是福建省较大的多金属矿产地之一.随着找矿勘查的不断深入,对在该矿区外围和深部寻找隐伏矿床提出了迫切需求,但研究区地表地形崎岖、植被茂密,以往很少进行高精度大比例尺的综合地球物理调查,因此对隐伏的控矿构造、赋矿层位和火成岩体分布的认识远不能满足深部找矿的需求.本文实施了反射地震、可控源音频大地电磁剖面测量和大比例尺航磁面积性测量,在成矿理论和找矿模型的指导下采用反射地震真地表偏移成像技术、可控源音频大地电磁二维带地形反演技术和航磁数据精细处理与三维反演技术,提取识别了剖面浅层逆冲推覆控矿构造和赋矿层位的反射地震特征,与成矿关系密切的燕山期火成岩体的地震、电磁特征,以及控矿构造和隐伏岩体平面分布的航磁异常特征.在地表地质和已知钻孔岩心及物性的约束下,构建了剖面的综合地球物理的地质解释模型,包括浅层推覆构造和控矿地层分布,推断解释大断裂6条,次级断裂16条和3处较大的隐伏岩体分布,为深入认识研究区的矿床成因和分布规律,指导在外围和深部找矿提供了地球物理有效响应特征.

Geophysical response characteristics of the Dapai polymetallic mining area in Southwestern Fujian Province and its prospecting implications

The Dapai polymetallic mining region,located in the south of the Datian-Longyan sub-depression belt in southwestern Fujian province,and on the west side of Zhenghe-Dapu deep fault zone,is considered as one of the largest polymetallic reserves in Fujian province.As exploration advances,finding the deeper and concealed deposits is urgently needed in this place and its adjacent areas.However,complex terrain and dense vegetation in Dapai deposit bring difficulties to geophysical investigations,especially for high-precision and large-scale surveys.Therefore,the understandings of the concealed ore-controlling structures,ore-bearing horizons and the distribution of igneous rocks are far from meeting the needs of deep prospecting.Under the guidance of metallogenic theory and prospecting model,the reflection seismic characteristics of the shallow thrust nappe ore-controlling structures and ore-bearing horizons have been extracted by using the reflection seismic method,2D inversion of controlled source audio frequency magnetotelluric method(CSAMT)data with terrain and 3D constrained inversion of aeromagnetic data.In addition,the seismic and electromagnetic characteristics of the Yanshanian igneous rocks that are closely associated with mineralization,and the aeromagnetic anomaly characteristics of the ore-controlling structures and the plane distribution of the concealed rock masses have also been obtained.Thereafter,a geological model,which contains shallow nappe structures and distribution of ore controlling strata,in a main section of this region have been established with the constraints from the geology and the physical properties of known drilling cores.Moreover,6 major faults,16 secondary faults and 3 large concealed rock masses have been deduced.All these results provide effective geophysical response characteristics for further understanding the genesis and distribution of ore deposits in the study area and guide prospecting in the periphery and deep spaces in this area.