甘肃敦煌-阿克塞地区岩(矿)石磁化率特征分析及应用

各类岩(矿)石的磁性差异是进行航磁资料地质解释的物理基础.为全面、系统了解甘肃敦煌-阿克塞地区岩(矿)石的磁性特征,2015-2017年在该区开展了系统的岩(矿)石的磁化率调查工作,实测物性点320处,获得有效磁化率数据10154个.对实测资料进行了详细的分类统计,分析总结了区内沉积岩、侵入岩、火山岩、变质岩、矿石及围岩等各类岩矿(石)的磁性特征,沉积岩一般呈弱或无磁性;火山岩具有中等-强磁性,可引起一定走向的磁异常;基性-超基性岩多具有强磁性,可以引起一定强度、尖锋状或带状的磁异常;中、酸性侵入岩和变质岩磁化率变化范围较大,弱磁性的一般在磁场上无异常显示,中等-强磁性的一般在磁场上表现为带状或团块状异常区;磁铁矿、磁黄铁矿等磁性矿物含量的增多,不同类型矿石磁化率由中等磁性逐渐变为极强磁性.在此基础上将实测磁化率应用于磁性地层、侵入岩圈定,探讨了磁化率与矿产之间的联系.研究结果为该地区高精度航磁资料解释提供了基础资料和参考依据.

Analysis of magnetic susceptibility features of rocks and ores in Dunhuang-Akesai area and applications

The differences of magnetic property of rocks and ores are important physical basis of geological interpretation of aeromagnetic data. In order to fully understand the magnetic features of rocks and ores in Dunhuang-Akesai aera of Gansu, we carried out regional rock magnetic susceptibility investigation work in the region from 2015 to 2017 years, completed properties measurement work of 320 points,obtained 10154 effective magnetic susceptibility data. According to classified statistics in detail for the measured data, we analysis and summary the magnetic susceptibility features of sedimentary rocks, intrusive rocks, volcanic rocks, metamorphic rocks, ores and wall rocks. Sedimentary rocks are generally weakly-magnetic or non-magnetic. Volcanic rocks have medium-strong magnetism and can cause certain trend magnetic anomalies. Basic-ultrabasic rocks are mostly strong magnetic, which can cause peak or band magnetic anomalies of certain intensity. Intermediate-acid intrusive rocks and metamorphic rocks show no abnormality when their magnetic susceptibility is weak, or show banded or lumpy abnormal areas when their magnetic susceptibility is medium-strong. With the increasing content of the magnetic minerals likes magnetite, pyrrhotite, the magnetic susceptibility of different types of ores gradually changes from medium magnetism to extremely strong magnetism.Based on the magnetic susceptibility data, we define magnetic stratigraphy and intrusive rock boundary, and study the relationship between magnetic susceptibilities and ferromagnetic minerals. This research work can provide basic information and refernce for the aeromagnetic data interpretation.