基于深部地球物理信息的构造变形岩相分类研究

“构造变形岩相”填图方法的创立和应用为老矿区深部及外围的找矿工作指明了方向,在实践中取得了显著的效果,需要大力推广和深入研究。对于构造变形岩相带的深部结构认识,需要依靠地球物理信息的解译。与地球物理场性质相类似,构造变形岩相带也是一个现存的地质体;物探工作目的是要探测和揭示构造变形岩相带的埋深、轮廓、内部结构构造等特征,为确定其形成时间和演化过程提供依据。由于地质与地球物理的复杂时空关系,如果仅以新鲜岩石标本物性参数的差异作为判别标志,难以提高地球物理方法的分辨率和有效性。结合构造变形岩相进行综合解译,更能提高解释推断成果的多学科融合性。作为终极勘探目标,需要紧密结合构造控矿级序,建立构造变形岩相带的三级分类标准,提取对应的地球物理信息:一级构造变形岩相带为目标物所处的构造单元及构造应力场,及其所对应的区域地球物理场特征,如隆凹构造相间的伸展构造域;二级构造变形岩相带为目标物所处的控矿构造体系,及其所对应的矿田地球物理场特征,如岩浆核杂岩隆起-拆离构造系统;三级构造变形岩相带为目标物所在的有利成矿构造部位,及其所对应于关键剖面的地球物理特征,如侵入岩体与围岩的接触带或者含矿断裂带等。选择国际流行的典型金属矿床类型,介绍了三级构造变形岩相带的地球物理组合信息特征及其分级利用操作流程,为有效应用地球物理勘探方法开展深部找矿预测提供了范例。

Classification of tectonic deformation lithofacies based on deep geophysical information

The establishment and application of “tectonic deformation lithofacies” mapping highlight the direction for deep and peripheral prospecting in old mining areas. In practice, this approach has achieved remarkable results and needs to be promoted and further studied. The understanding of the deep structure of tectonic deformation lithofacies zone depends on the interpretation of geophysical information. Similar to the properties of the geophysical field, the tectonic deformation lithofacies zone is also an existing geological body. The purpose of geophysical exploration is to explore and reveal the features of the burial depth, contour and internal structure of the tectonic deformation facies belt, so as to provide a basis for determining its formation time and evolutionary process. Due to the complex spatiotemporal correlation between geological and geophysical scales, it is difficult to improve the resolution and effectiveness of geophysical method if only the difference in physical parameters of fresh rock specimens is used as a discriminant marker. Therefore, it is necessary to combine tectonic deformation lithofacies into comprehensive interpretation, which can improve the multidisciplinary fusion of interpretation and deduction results. In searching the ultimate exploration targets, the structural ore-controlling factor is needed for setting up a three-level classification standard for tectonic deformation facies belt to extract the corresponding geophysical information. The first-level is the tectonic unit and tectonic stress field of the target object as well as the corresponding regional geophysical field characteristics, such as the extensional tectonic domain with alternative uplift and concave structures. The second-level refers to the ore-controlling structural system of the target object and the corresponding geophysical field characteristics of the ore field, such as the magmatic core complex uplift and detachment structural system. The third-level is the favorable metallogenic tectonic location of the target object and the geophysical characteristics corresponding to the key section, such as the contact zone between intrusive rock and surrounding rock or the ore-bearing fault zone. In this paper, the geophysical assemblage information characteristics and workflow of the three-level tectonic deformation lithofacies belt are introduced for selected typical metal deposit types prevalent in the world, providing an example for the effective application of geophysical exploration methods in deep prospecting prediction.