大中条地区重磁场特征及其断裂分布与构造单元

大中条地区是我国著名的铜、金、铁矿集区,区内各类矿床的分布与该区的构造演化有关,并受构造体系、岩浆活动等地质因素控制。因此,系统研究本区的断裂分布和构造单元是预测隐伏矿床的基础。本文通过对大中条地区重、磁场特征研究,系统推断了该区断裂分布并划分了构造单元。对重、磁场特征的研究表明,布格重力异常与化极磁力异常均呈现东西分带的特征,这是大中条地区前寒武纪、中生代和新生代三期构造演化的综合反映。研究中利用重、磁位场边缘识别技术推断出11条断裂,对断裂的研究表明,大中条地区断裂以NE向和NW向为主,大多形成于元古代和中生代,多数断裂表现出多期活动的特点。综合重、磁场特征,构造演化特征及断裂分布,大中条地区可划分为4个一级构造单元和7个二级构造单元,构造单元控制了矿床的成因和分布。上述研究成果对大中条地区构造划分和矿产资源勘查提供了地球物理依据。

Distribution of faults and division of tectonic units in the Great Zhongtiao area of southern Shanxi Province derived from gravity and magnetic anomaly data

The Great Zhongtiao area of southern Shanxi Province is an important locality for copper, gold and iron deposits in China. The distribution of these deposits is related to the tectonic evolution and controlled by the tectonic system and magmatic activity in this area. Therefore, systematic study of the distribution of faults and tectonic units is the basis for the prediction of concealed ore deposits. In this work, we delineated the distribution of faults and divided the tectonic units based on the characteristics of gravity and magnetic fields in this area. Our research shows that the Bouguer gravity anomalies and magnetic anomalies reduced to the pole in the study area trend in NE or NNE directions dominantly, that may reflect the basement structure associated with the tectonic evolution of three periods, i.e. Precambrian, Mesozoic and Cenozoic. In terms of these data, we inferred 11 faults by using edge recognition technique of the gravity and magnetic potential fields. The trending directions of these faults are dominated by NE and NW, which mostly formed in Proterozoic and Mesozoic. Most of them have the characteristics of multi-stage development. On the basis of characteristics of gravity and magnetic fields, features of tectonic evolution and distribution of faults, the Great Zhongtiao area can be divided into 4 first-order tectonic units and 7 secondary tectonic units. The genesis and distribution of deposits in the study area are mostly controlled by these structural units. These results provide geophysical evidence for regional tectonic division and mineral resource exploration in the study area.