南秦岭安康汉中地区岩石物性特征及应用

Physical property characteristics of rocks in Hanzhong and Ankang areas at the southern foot of Qinling Mountains and their application

物性参数是地球物理与地质之间的纽带,也是地球物理解释和推断反演合理性的关键。为系统掌握南秦岭安康汉中地区岩(矿)石物性特征,提高解释准确性,服务基础地质研究和矿产资源调查评价,本次工作深入南秦岭安康汉中腹地,野外实测岩石物性点458处,采集磁化率数据13740个、能谱数据458组,根据岩石地层年代及岩性对岩石物性进行分类统计。磁化率数据统计结果表明:古元古代基性及部分中性岩体在研究区内属于强磁性地质体,磁化率均值达4000×10^(-5)SI以上,其中辉长岩为最强;区内最主要的磁性地层为震旦系耀岭河组凝灰岩、古元古界西乡群,磁化率均值多接近1000×10^(-5)SI,高值者达2000×10^(-5)SI以上测量单位。经实验室测定,区内大多数磁性地质体以感磁为主,少数凝灰岩、辉长岩及含磁铁辉长岩具有较强的剩磁,在异常反演中必须加以考虑。能谱参数物性分析表明区内古生界和震旦系变质岩放射性较高,其中黑色岩石(含炭质)普遍放射性较高。通过庙坝村西和石泉县东南两处示例说明了磁、放物性参数在磁放资料解释中的重要作用,建立了航空磁放信息与地质信息之间的连接,提高了解释可靠性。

Physical property parameters are the link between geophysics and geology and are crucial to the rational inversion of geophysical interpretation and inference.To systematically grasp the physical properties of rocks(minerals)in Hanzhong and Ankang areas to the south of the Qinling Mountains,improve interpretation accuracy,and serve basic geological research and the surveys and evaluation of mineral resources,this study collected 458 physical property points of rocks,13740 pieces of susceptibility data,and 458 sets of energy spectrum data in the hinterland of the Hanzhong and Ankang areas at the southern foot of the Qinling Mountains.Then,this study classified and made statistics of the physical properties of rocks.The results of magnetic susceptibility data show that the Paleoproterozoic basic and partial intermediate rock masses are ferromagnetic geological bodies in the study area,with an average magnetic susceptibility of greater than 4000×10^(-5)SI,and gabbro has the highest magnetic susceptibility;the dominant magnetic strata in the area are the Paleoproterozoic Xixiang Group and the tuff in the Sinian Yaolinghe Formation,which have average magnetic susceptibility of mostly close to 1000×10^(-5)SI,and the high magnetic susceptibility can reach more than 2000×10^(-5)SI.According to laboratory testing,most of the magnetic geological bodies in the study area have induced magnetism,and a few tuffs,gabbros,and magnetite-bearing gabbros in the study area have strong remanence,which must be considered in the anomaly inversion.The physical property analysis based on energy spectrum parameters shows that the Paleozoic and Sinian metamorphic rocks in the study area have high radioactivity and highly variable content,among which black rocks(carbonaceous)generally have high radioactivity.As indicated by two examples of western Miaoba Village and the southeastern Shiquan County,magnetic,radioactive,and physical-property parameters are important for the interpretation of magnetic and radioactive data,and they establish a link between aerial magnetic and radioactive information and geological information,improving the reliability of interpretation.