基于地球物理技术圈定沉积变质型富铁矿体:辽宁鞍山齐大山铁矿例析

Delineation of Sedimentary Metamorphic Rich Iron Ore Bodies Based on Geophysical Techniques:Case Analysis of Qidashan Iron Ore in Anshan,Liaoning

辽宁鞍山—本溪地区是中国北方最重要的铁矿资源基地之一,区内分布有数量不等的富铁矿体,长期以来对富铁矿成矿理论研究成果丰硕,但针对富铁矿找矿技术方面的研究则相对缺乏。本文以辽宁鞍山齐大山铁矿为研究对象,基于贫铁矿体和富铁矿体的物性参数差异,优选地面高精度磁法和高密度电阻率法,开展齐大山铁矿内富铁矿体的综合地球物理探测研究工作。研究结果显示,地面高精度磁法可以通过16000 nT以上的高磁场强度特征圈出贫铁矿磁异常场内的富铁矿体,而高密度电阻率法则可以精细刻画高磁异常范围内的富铁矿体形态特征和规模;磁铁矿富矿电阻率小于2200Ω·m,以此为约束条件构建地面磁法的正反演模型,可实现对贫铁矿层中富铁矿体的准确识别定位;齐大山铁矿NNW走向断层与NEE横向断层交汇处更易产出厚大富铁矿体。

Anshan-Benxi Area of Liaoning Province is one of the most important iron resource bases in Northern China.There are various iron-rich orebodies distributed in this area.The studies on the iron-rich ore metallogeny are fruitful for the past decades but the prospecting technology for iron-rich ores is relatively lacking.Based on the discrepancy of physical parameters between the iron-poor and-rich orebodies,we selected surface high-precision magnetic and high-density resistivity methods to perform the comprehensive geophysical exploration of the iron-rich orebodies in the Qidashan iron mine area in Anshan,Liaoning Province.The study results show that the high-precision magnetic method is able to delineate the spatial distribution range of the magnetic anomalies caused by the enriched iron bodies in the magnetic anomaly field with a poor iron grade through limiting the magnetic field intensity at>16,000 nT.The high-density resistivity method can accurately characterize the shape and scale of iron-rich bodies in the high magnetic anomaly field by limiting the resistivity at<2200Ω·m.This can be considered as a constraint threshold to build a forward and inverse models for the ground magnetic method as to identify and locate the iron-rich bodies in iron-poor ore layers.We also found that the intersection area of the NNW strike and NEE lateral fault in Qidashan iron mine area has a higher potential to form thick and enriched iron orebodies.