庐枞盆地正长岩的地球物理识别基础

    Basis for geophysical identification of syenites in the Luzong Basin

    • 摘要: 安徽庐枞地区的Fe-Cu-U矿化主要发育在正长岩岩体内部及其围岩的接触带上,地球物理勘查方法能否有效地圈定正长岩体,是该地区找矿突破急需解答的科学问题之一。根据取自庐枞深度达2 012 m的科学深钻ZK01孔的358个岩石物性样品,测得其密度、磁性(磁化率与剩磁强度)、电性(电阻率与极化率)、弹性波速度等综合岩石物性数据,通过研究分析得出,正长岩具有低密度、弱磁性特征,具备在该孔或类似的地质条件下,开展区分正长岩的重力勘探及磁法勘探的前提条件;钻孔中地层与正长—二长岩岩体电阻率均呈中—高阻特征,由于差异不显著,电法勘探难度较大;正长—二长岩岩体纵、横波速度均低于砖桥组火山岩地层,具备开展地震勘探区分地层与岩体的基础条件。

       

      Abstract: The Fe-Cu-U mineralization in the Luzong area in Anhui Province occurs primarily within the syenite mass and along its contact zone with surrounding rocks. Effectively delineating the syenite mass using geophysical exploration methods is a scientific issue that needs to be addressed urgently for mineral exploration breakthroughs in the Luzong area. Therefore, based on 358 rock samples from scientific drilling borehole ZK01 at a burial depth of 2 012 m in the Luzong area, this study measured their petrophysical properties, including density, magnetism (magnetic susceptibility and remanent magnetization intensity), electrical properties (resistivity and polarizability), and elastic wave velocity. The results indicate that syenites manifested low density and weak magnetic characteristics, providing prerequisites for syenite identification through gravity and magnetic explorations in borehole ZK01 or similar geological conditions. The strata and syenite-monzonite masses in the borehole exhibited medium-to-high resistivity characteristics with nonsignificant differences, increasing the difficulties in electrical prospecting. The syenite-monzonite masses displayed lower compressional and shear wave velocities compared to the volcanic layer in the Zhuanqiao Formation, laying a foundation for distinguishing strata from rock masses through seismic exploration.

       

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