矿田构造变形岩相带的地球物理资料解译与找矿应用

Geophysical data interpretation of the tectonic deformation lithofacies belts in the ore field:Application in ore prospecting

基于岩(矿)石物性参数和矿床成因类型建立的地球物理勘查模型,在深部找矿预测中出现了多解性的问题,急需找到地球物理方法能够高精度识别的地质体目标。多年的找矿实践表明,矿田构造变形岩相带就是一个重要的选项,业已取得显著的找矿效果。目前,大比例尺的矿区地球物理勘查工作较多,而中比例尺的矿田地球物理研究比较薄弱,且两者均缺乏分层次的战略指导。为了建立矿田构造变形岩相带的地球物理判别标志,需要厘清地质与地球物理的复杂时间-空间关系,加强地质力学与地球物理勘探方法的联系。文章提出分层次处理和解释地球物理信息的思路,即根据研究区构造形迹的“米字型”结构特征和构造体系阶段性发展的特点,从矿田、矿床2个层次解析不同尺度-维度的地球物理勘查资料,提取构造变形岩相带信息。具体操作流程为先在矿田范围内布置面积性物探,解译“米字型”断裂构造系统,选定张性和张扭性含矿断裂构造,预测找矿方向;再在含矿断裂带布置大深度物探剖面,分析剥蚀程度和埋藏深度,结合化探信息圈定找矿靶区位置。文中以内蒙古赤峰柴胡栏子金矿田为例,介绍该方法的找矿应用效果。首先从矿田地球物理资料中解译出新华夏构造体系“米字型”分布的构造形迹,然后在2个矿区内确认了北北西和北西西走向的构造变形岩相带是主要的含矿构造带,且两者之间存在时空上的先后关系,为深部找矿预测提供了依据。

Based on the physical parameters of the rocks(ores) and the genetic types of ore deposits, the geophysical exploration models have met issues of multiple solutions for deep prospecting prediction. It is necessary to find recognizable geological targets with high precision by geophysical methods. The ore prospecting practice over past years has demonstrated that the ore field tectonic deformation lithofacies belt is an outstanding target and significant prospecting results have been achieved. At present, the geophysical exploration work of large-scale mining area is heavy, while that of medium-scale ore field is limited, and both of them lack the strategic guidance at different levels. In order to establish the geophysical identification mark of the tectonic deformation lithofacies belt in ore field, it is necessary to clarify the complex time-space relationship between geology and geophysics, and strengthen the connection between geomechanics and geophysical exploration methods. In this paper, a method of processing and interpreting geophysical information at different levels is proposed. According to the “■-shaped” structural features of the tectonic traces in the study area and the characteristics of the periodic development of the tectonic system, the geophysical exploration data of different scales and dimensions are analyzed from the two levels of ore field and deposit, and the information of tectonic deformation lithofacies belts is extracted. The specific operation procedures are as follows:(1) Making an area geophysical exploration within the scope of the ore field, interpreting the “■-shaped” fault structure system, and then selecting the tensional and tension-torsional ore-bearing fault structures and predicting the prospecting direction;(2) Laying out large-deep geophysical profiles in the ore-bearing fault zone, analyzing the denudation degree and burial depth, and delineating the location of prospecting targets based on the geochemical exploration information. The application results of this method in the Chaihulanzi gold field in Chifeng, Inner Mongolia is introduced. The “■-shaped” distribution of structural traces of the Neocathaysian tectonic system are interpreted from the geophysical data of the ore field, and then it is confirmed that the NNW and NWW trending tectonic deformation lithofacies belts are the main ore-bearing structural belts and there is a spatio-temporal sequential relationship between them in the two mining areas. These findings, provides a basis for deep ore prospecting and prediction.