| 鲁科一井上白垩统沉积岩岩石磁学和天然剩磁分析:兼论利用剩磁方向恢复钻孔岩芯原始方位的可行性 |
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| 引用本文： | 韩非, 秦华峰, 季强, 孙靖鹏, 邓成龙, 潘永信. 2017. 鲁科一井上白垩统沉积岩岩石磁学和天然剩磁分析:兼论利用剩磁方向恢复钻孔岩芯原始方位的可行性. 地球物理学报, 60(12): 4730-4740, doi: 10.6038/cjg20171215 |
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| 作者姓名： | 韩非 秦华峰 季强 孙靖鹏 邓成龙 潘永信 |
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| 作者单位： | 1. 中国科学院地质与地球物理研究所古地磁与年代学实验室, 北京 100029; 2. 中国科学院大学地球科学学院, 北京 100049; 3. 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029; 4. 中国地质科学院地质研究所, 北京 100037 |
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| 基金项目： | 国家自然科学基金（91414101）资助. |
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| 摘 要： | 本文对"鲁科一井"（CCSD-LK-Ⅰ）768.9~1112.3 m之间的上白垩统沉积岩样品进行了岩石磁学、磁化率各向异性（AMS）以及天然剩磁组分的研究.在此基础上，分析了利用特征剩磁（ChRM）和黏滞剩磁（VRM）方向恢复岩芯原始方位的可行性.三轴等温剩磁热退磁曲线、磁滞回线、反向场退磁曲线、一阶反转曲线等岩石磁学测量结果表明，沉积岩的主要载磁矿物为磁铁矿和赤铁矿.335块样品的AMS测量结果表明磁化率椭球主轴的最大轴K1和中间轴K2与水平面夹角较小，最小轴K3接近垂直于水平面分布，说明沉积岩保留了原始沉积磁组构特征.系统热退磁实验表明，多数样品在25~350℃和500~690℃温度段分别获得VRM和ChRM分量.利用ChRM偏角方向，并考虑构造旋转量校正，对VRM偏角方向进行恢复，Fisher统计得到DVRM=-1.3°，IVRM=59.6°，与当地现代地磁场方向（D=-6.7°，I=53.9°）基本一致.用ChRM偏角方向对磁化率主轴K1偏角方向进行校正，校正的结果为：Dch_K1=349.2°，Ich_K1=-0.7°.本文研究结果对于地质勘探中利用古地磁学方法恢复钻孔岩芯原始方位具有一定参考意义.
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| 关 键 词： | 鲁科一井 特征剩磁 黏滞剩磁 岩芯原始方位恢复 |
| 收稿时间： | 2016-12-30 |
| 修稿时间： | 2017-10-07 |
Rock magnetism and paleomagnetism of Late Cretaceous sedimentary rocks in borehole CCSD-LK-I (Shandong province) and implications for the feasibility of core orientation recovery using natural remanent magnetization |
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| HAN Fei, QIN Hua-Feng, JI Qiang, SUN Jing-Peng, DENG Cheng-Long, PAN Yong-Xin. 2017. Rock magnetism and paleomagnetism of Late Cretaceous sedimentary rocks in borehole CCSD-LK-I (Shandong province) and implications for the feasibility of core orientation recovery using natural remanent magnetization. Chinese Journal of Geophysics (in Chinese), 60(12): 4730-4740, doi: 10.6038/cjg20171215 |
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| Authors: | HAN Fei QIN Hua-Feng JI Qiang SUN Jing-Peng DENG Cheng-Long PAN Yong-Xin |
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| Affiliation: | 1. Paleomagnetism and Geochronology Lab, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 2. School of Earth Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; 3. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 4. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The paleomagnetic method has been commonly used to orient the un-oriented borehole core, but its feasibility and reliability remain unclear due to the complexity of remanence. This study investigated the feasibility of orientation of the Cretaceous Continent Scientific Drilling(CCSD) borehole LK-Ⅰ in the Jiaolai Basin, Shandong Province, using the characteristic remanent magnetization (ChRM) and viscous remanent magnetization (VRM). In total 335 sedimentary rock samples from CCSD LK-Ⅰ core (depth 768.9~1112.3 m) were measured, including stepwise thermal demagnetization of the natural remanent magnetization (NRM), anisotropy of magnetic susceptibility (AMS), progressive thermal demagnetization of three-component isothermal remanent magnetizations (IRM), hysteresis loops, backfield demagnetization curves and the first order reverse curves (FORCs). Results show that magnetite and hematite are the dominant magnetic minerals in the measured samples. The principal axes of AMS ellipsoid K1 and K2 are nearly parallel to the horizontal plane, while the K3 axes are perpendicular to the horizontal plane, which indicates the sedimentary rocks preserved primary fabrics. After being adjusted by the declination of ChRM (also considering local tectonic rotation), the mean direction of VRM is DVRM=-1.3°, IVRM=59.6° by Fisher statistics, which is in accordance with the present local geomagnetic field (D=-6.7°,I=53.9°). Using the same adjustment and statistic methods, the mean direction of K1 is Dch_K1=349.2°,Ich_K1=-0.7°. Collectively, this work suggested that the direction of ChRM can be used to recover the orientation the borehole core of CCSD-LK-I. |
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| Keywords: | CCSD-LK-Ⅰ ChRM VRM Core orientation recovery |
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