甘肃白银厂铜多金属矿田重磁异常及构造特征北大核心CSCD

甘肃白银厂铜多金属硫化物矿田是受陆缘弧环境火山机构及其同生断裂控制的典型火山岩赋矿块状硫化物矿床(VHMS)。为了进一步探讨该矿床重磁场特征及与构造和矿床的关系,通过对区内的重磁场异常数据进行位场分离、小波分析和基于张量数据的三维欧拉反褶积自动确定地质体位置和埋藏深度的定量反演计算。结果表明,研究区布格重力场具有西部高、东部低的特征,其磁场可划分为4个磁场区;局部异常按一定分布规律呈圆形或似圆形正负相间分布,不同尺度的重磁细节异常图在一定程度上反映出引起重磁异常的地质异常体具有一定的延深且分布稳定,而且这些地质异常体具有向深部复合的趋势。经位场分离后正负相间的剩余重磁异常分布范围和分布特征大致反映了白银厂奥陶纪中酸性火山岩建造构造为一个继承性的火山穹窿构造,东、西部不同的重磁异常特征说明东西部的火山喷发具有不同的基底、源区和喷发方式。发育NW向、NE向、近NS向、NEE向等4组断裂构造,近NS向断裂F3、F4、F5、F6、F7形成时间稍晚于NEE向断裂,其与NEE向断裂F1、F2共同形成了研究区棋盘网格状的构造分布特征,这两组断裂为研究区内主要的控岩、控矿断裂。火山机构的分布明显受断裂构造控制,火山口集中分布在深大断裂、大断裂或两组断裂的交汇处。矿田内各矿床及成矿有利地段均处于研究区中部低缓重磁异常场内正负磁异常变化的梯度带内。本次研究为控矿要素研究和开展找矿预测工作提供了丰富、翔实的地球物理资料。

Gravity-magnetic anomalies and tectonic characteristics of the Baiyinchang Cu-polymetallic ore field in Gansu Province

The Baiyinchang Cu-polymetallic sulfide field in Gansu Province is a typical volcanic-hosted massive sulphide deposit (VHMS) controlled by a volcanic edifices and its syngenetic fractures in a pericontinental arc environment. In order to further explore the characteristics of its gravity and magnetic field and its relationship with structures and deposits, quantitative inversion calculations to automatically determine the location of geological bodies and burial depth through potential field separation, wavelet analysis, and 3D Euler deconvolution based on tensor data on the gravity and magnetic field anomaly data in the area.The results show that the bouguer gravity field in the study area is high in the east and low in the west.The magnetic field can be divided into 4 magnetic fields; local anomalies are distributed in a circular or quasi-circular positive and negative phase according to a certain distribution law. The detailed anomaly maps of gravity and magnetic force of different scales reflect the geological anomaly that caused the gravity and magnetic anomaly to a certain extent. It has a certain extension and stable distribution, and these geological anomalies have a tendency to recombine to the deep. The distribution range and characteristics of residual gravity and magnetic anomalies between the positive and negative phases after the potential field separation roughly reflect that the Baiyinchang Ordovician intermediate-acid volcanic structure is an inherited volcanic dome structure.The different characteristics of gravity and magnetic anomalies in the east and west indicate that the volcanic eruptions in the east and west have different bases, source areas and eruption methods.Four groups of faults are developed in NW direction, NE direction, near NS direction, and NEE direction. Near NS direction faults F3, F4, F5, F6, F7 are formed slightly later than NEE direction faults, which are common with NEE direction faults F1 and F2. Formed the checkerboard grid structure distribution characteristics of the study area, these two groups of faults are the main rock-controlling and ore-controlling faults in the study area;The distribution of volcanic structures is obviously controlled by fault structures. Volcanic craters are concentrated in deep and large faults, large faults, or the intersection of two groups of faults; all deposits and favorable mineralization areas in the ore field are located in the middle of the study area in the low-gradient gravity and magnetic anomaly field, Within the gradient band of negative magnetic anomaly changes. It provides abundant and accurate geophysical data for the study of ore-controlling elements and the development of prospecting prediction.