基于先验信息约束的重磁三维交互反演建模技术——以铜陵矿集区为例

三维地质建模是实现深部矿产勘查突破的重要途径,其通过控矿地质体的三维建模,直观刻画控矿要素之间的空间、成因和演化关系,帮助理解成矿系统,开展深部找矿预测.当前三维建模主要采用地质资料构建,在缺少钻孔等已知资料的情况下,难于构建出可靠的三维地质模型.为了克服常规三维地质建模方法可信度低、精度差的缺点,本文将重磁交互反演技术引入到三维地质建模中,提出了基于先验信息约束,通过二度半剖面交互反演、三维物性反演联合修正的三维地质模型方法.采用该方法建立了铜陵矿集区的三维地质模型,并开展了深部找矿预测,取得以下主要认识:1)基于先验信息约束的重磁交互反演建模技术能大幅提高三维地质模型的可信度,是实现地下地质体"透明化"的重要途径;2)铜陵地区重要控矿地层(C-P-T2)主要分布于向斜区和火山岩覆盖区,深部岩浆岩条件优越,深部找矿工作应从传统的背斜隆起区转向向斜区和火山岩覆盖区以及部分凹陷区,这将极大拓展铜陵地区找矿空间;3)铜陵地区传统的五大矿田的侵入岩均具有复合岩体特征,特别是与辉石闪长岩共生的矿产以铁铜矿为主,而与金矿密切相关的侵入岩则多为中酸性岩体,这一推断如果成立,将对铜陵地区找矿突破产生重大影响;4)铜陵地区的推覆构造十分发育,木镇凹陷区的早古生代基底和南陵盆地北西缘的戴公山背斜就是一套区域性推覆构造的产物,三维地质模型还揭示铜陵地区侵入岩具有深、中、浅三重结构,这为铜陵隆起的推覆成因提供了证据,也指示了在铜陵之外再寻找类似铜陵矿集区的良好前景.

3D gravity and magnetic interactive inversion modeling based on prior information: A case study of the Tongling ore concentration area

Three-dimensional geological modeling is an important way to realize the breakthrough of deep mineral exploration. This method is based on the three-dimensional modeling of ore-controlling geological bodies, which can directly describe the spatial, genetic and evolutionary relationship between the ore controlling factors. At present, the 3D modeling mainly uses geological data; while in the absence of drilling and other known information, it is difficult to construct a reliable 3D geological model. In order to overcome the disadvantages of poor accuracy and low reliability of conventional 3D geological modeling, we propose an effective method based on the prior information. In this approach, a series of sections obtained by the 2.5D interactive inversion, combined with the sections of 3D physical property inversion, are employed to correct the process of building a 3D geological model. Using this method, the 3D geological model of the Tongling ore concentration area is successfully established, that objectively describes the 3D spatial characteristics of strata, fractures and rock mass. Through the interactive analysis of the 3D model, we draw the following conclusions. 1) The important ore-controlling formations (C-P-T₂) of the Tongling area are mainly distributed in the syncline and volcanic-covered area with intense deep magmatic activity, which will greatly expand the prospecting space in the Tongling area. 2)The traditional five orefield intrusive rocks are characterized by having a composite rock, especially with the pyroxene diorite symbiosis mineral iron copper-based, and the gold mines is closely related to the intermediate-acid intrusive rocks. This inference, if established, will have a significant impact on selection of the Tongling area prospecting target. 3)Nappe structure is well developed in the Tongling area, the early Paleozoic basement in the Muzhen sag region and the Daigongshan anticline in the NW edge of the Nanling basin are the product of a regional nappe structure. 3D physical property inversion reveals that the Tongling area intrusive rocks have deep-middle-shallow triple structure, which provides some evidence for the thrusting cause of the Tongling terrane, and also we can look for another "Tongling" outside the Tongling area.