蒙古国苏赫巴托尔-乌兰巴托-达兰扎达嘎德剖面岩石物性基本特征

摘要

为了深入认识与理解南北地震带北段和蒙古中部大陆强震孕育与发生的深部构造环境，在南北纵贯蒙古国全境的苏赫巴托尔-乌兰巴托-达兰扎达嘎德剖面上开展了大规模重磁测量及岩石样品采集。笔者系统地分析与总结了剖面上585块岩石样品的密度、磁化率和天然剩余磁化强度等物性参数。结果表明，整个剖面以火成岩为主，沉积岩为辅，仅有少量变质岩出露，且各岩石大类、类和亚类以及各年代地层之间，均存在着不同程度的密度与磁性差异。火成岩磁化率和天然剩余磁化强度分别具有3～5个数量级差异，密度变化范围较大；而沉积岩磁化率和天然剩余磁化强度相对较弱。一方面，物性差异为利用重磁测量开展剖面地壳结构的反演与研究奠定了基础；另一方面，这些物性参数为相关地球物理测量数据的反演与解释提供了重要约束。%To well understand the deep structure environment and mechanism of strong earthquakes occurred in the Tianshan-Mongolia-Lake Baikal seismic belt, an integrated geomagnetic and gravity survey was conducted along the profile from Suhbaatar to Ulaanbaatar to Dalandzadgad in Mongolia. In this paper, petrophysical parameters ( bulk density, magnetic susceptibility, intensity of natural rema-nent magnetization, and Köenigsberger ratio) of 585 rock samples collected from this profile are summarized. Results indicate that sig-nificant density contrast of different rocks would result in variable gravity anomalies along the profile. Magnetic susceptibility and natural remanent magnetization of all rocks are variable, covering 3~5 orders of magnitude, which would make a variable induced magnetiza-tion and further links to complex magnetic anomalies in ground surface. These petrophysical parameters provide essential constraints on the interpretation of geophysical data and to calibrate geophysical parameters.