闽西南多金属成矿带地质地球物理特征综合研究——以永定大排多金属矿区为例

Comprehensive study of the geological and geophysical characteristics of the metallogenic belt in Southwest Fujian——A case study in the Yongding-Dapai polymetallic ore deposit

闽西南地区位于福建武夷山成矿带西南部,自远古宙以来经历了多期次的构造演化.该区地处东南沿海构造-岩浆-成矿带上,为环太平洋大陆边缘多金属成矿带与南岭多金属成矿带复合部位,是我国重要的多金属矿产地.永定大排多金属矿区作为近年来武夷山成矿带新发现的大型多金属矿,区内叠加作用和控矿作用相对复杂,现有的地质地球物理工作程度不足以满足对该区域成矿规律的深入认识,一些基础地质问题亟待解决.因此,本文在深入收集永定大排矿区地质地球物理资料基础上,综合分析区域成矿背景与成矿构造,在重点区域布设综合地球物理勘探工作,包括1:1万高精度磁测、可控源音频大地电磁剖面及反射地震剖面.基于上述工作:1)开展了研究区航磁数据三维磁化率反演与分布特征分析与大地电磁二维电阻率反演与分布特征分析,开展了地震资料真地表深度偏移成像,获得了更加准确的地震剖面成像结果.2)结合推覆体控矿特征,地震剖面和电阻率剖面、航磁反演结果相互验证和约束,勾画了地下构造形态.地表地质剖面延伸和标定了构造形态的地质内涵,获得了从地表到3000m深度的构造解释结果.解释结果清晰地显示了与推覆相关的构造、控矿层位以及岩体信息,为三位一体的找矿思路提供了地球物理依据.

The Southwestern Fujian area locates in the southeastern coastal tectonic magma metallogenic belt which is the composite part between the Pacific continental margin polymetallic metallogenic belt and the Nanling polymetallic metallogenic belt.It is one of the important polymetallic ore orogens in our country.Along with the increase of difficulty in finding superficial mineral resources,the prospecting focus has shifted to the search for deep concealed deposits.Dapai is a large polymetallic ore area with complicated tectonic conditions found along the Wuyishan metallogenic belt in recent years.The existing geological and geophysical works in this area are not enough for the deep understanding of the metallogenic regularity of this region.And there exist some basic geological problems to be solved.In the work discussed in this paper,geological and geophysical data of this area are collected.The regional metallogenic setting has been analyzed based on these collected data.Moreover,some effective comprehensive geophysical works have also been conducted in this area,including the high-precision aeromagnetic,the controlled source audio frequency magnetotelluric（CSAMT）method and the reflection seismic method.Based on above mentioned works,1） Three dimensional magnetic susceptibility inversion and two dimensional magnetotelluric resistivity inversion have been carried out in the study area.Moreover,the physical characteristics have been analyzed based on the inversion results.The true depth migration of seismic data has been carried out,and more accurate seismic profile imaging results have been obtained.2）According to the ore control characteristics of the nappe structure,the seismic and resistivity profile and the aeromagnetic inversion results have been verified and constrained by each other.Meanwhile,the structure of the underground structure has been outlined.The surface geological section was extended and elucidated the geological connotations of the structural form.The result of structural interpretation depicted the structure in the depth from the surface to 3 kilometers.The interpretation results clearly show the structure,ore control strata,and rock mass information of the nappe,and provide geophysical basis for the thought of the trinity prospecting.