毛北榴辉岩古地磁及岩石磁学初探

孟小红; 余钦范; 郭友钊; 周姚秀

毛北榴辉岩古地磁及岩石磁学初探

孟小红^{1, 2,},
余钦范^{1, 2},
郭友钊³,
周姚秀⁴

1.
地质过程与矿产资源国家重点实验室和地下信息探测技术与仪器教育部重点实验室, 北京 100083
2.
中国地质大学地球物理与信息技术学院, 北京 100083
3.
国土资源部地球物理地球化学勘探研究所, 河北廊坊 065000
4.
国土资源部航空物探遥感中心, 北京 100083

基金项目: 北京市重点学科“地球探测与信息技术(XK104910598)”资助

详细信息

作者简介:
孟小红(1958-), 女, 教授, 主要从事勘探地球物理学领域的教学和研究.E-mail: mxh@cugb.edu.cn

中图分类号: P631.2
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出版历程
- 收稿日期: 2007-04-12
- 刊出日期: 2007-07-25

A Pilot Study on Paleomagnetism and Rock Magnetism of Maobei Eclogite

1.
State Key Laboratory of Geological Processes and Mineral Resources; Geo-detection Laboratory of the Ministry of Education, Beijing 100083, China
2.
School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China
3.
Institute of Geophysical and Geochemical Exploration, CAGS, Langfang 065000, China
4.
China Aero Geophysical Survey and Remote Sensing Center for Land and Resources, Beijing 100083, China

摘要

摘要: 对中国大陆科学钻探孔区——江苏省东海县毛北地区的55块榴辉岩样品进行了古地磁研究, 并从中抽样测试了等温剩磁、磁滞迴线、磁组构、热磁化率以及电子探针和镜下分析, 结果表明, 毛北榴辉岩有两组稳定的剩磁, 即反向磁化和正向磁化, 稳定剩磁方向分别为: D=94.3°, I=-29.1°和D=273.7°, I=15.4°, 携带正向磁化与携带反向磁化样品的磁化强度和密度变化很大; 毛北榴辉岩的磁各向异性度非常弱, 最小轴方向很难确定; 等温剩磁和磁滞迴线显示磁铁矿可能是毛北榴辉岩的主要载磁矿物, 且在以M_r/M_s和H_cr/H_c的对数为纵、横坐标的图上落在视单畴(PSD)区域.根据磁性特征, 对毛北榴辉岩的磁性载体成因、剩磁获得机制及构造意义进行了讨论.
- 古地磁 /
- 岩石磁学 /
- 榴辉岩 /
- 超高压变质带
Abstract: In this paper, a pilot study of paleomagnetism and rock magnetism is done on 55 eclogite samples collected from Maobei area, Donghai County, Jiangsu Province. Synchronously, some of the samples are analyzed by electron-probe and scanning electric microscope, and tested for the isothermal remanence, hysteresis loop, magnetic fabric, thermal magnetic properties. The result indicates that there are two groups of stable remanence, i. e- the normal polarity and reversed polarity. The remanence orientations are: D=94. 3°, I=-29. 1° and D=273. 7°, I=15. 4° respectively. The magnetization and the density of the samples with normal polarities are very different from that of the samples with reversed polarities. The magnetic anisotropy is weak, and the minimum axis is hardly confirmed. The isothermal remanence and the hysteresis loop show that the magnetic carriers of the eclogite may be SD (single domain) and PSI) (pseudo-single domain) magnetite. According to the magnetic property, the cause of the formation of magnetic carrier, the causation of the remanence, and the significance for the geotectonic are discussed at the end of the paper.
- paleomagnetism /
- rock magnetism /
- eclogite /
- ultrahigh-pressure metamorphic zone.

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图 1 毛北榴辉岩及围岩退磁曲线

a₁，a₂，a₃为剩磁强度归一化衰减曲线；b₁，b₂，b₃为正交矢量投影图；C₁，C₂，C₃为退磁矢量赤平投影图

Fig. 1. The demagnetization curves of Maobei eclogite and its surrounding rocks

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图 2 毛北榴辉岩稳定剩磁方向赤平投影图

Fig. 2. Stereographic projection of the stable remanence orientations of Maobei eclogite

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图 3 (a) 磁化率与剩余磁化强度散点图; (b)磁化率与密度散点图

Fig. 3. (a)Scatter plot of susceptibility and remanence; (b)Scatter plot of susceptibility and density

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图 4 (a) 榴辉岩等温剩磁获得曲线及反向磁场退磁曲线; (b)围岩等温剩磁获得曲线及反向磁场退磁曲线; (c)磁滞廻线; (d)κ-t曲线

图 3c中H_r=236.4 mT, H_c=63.6 mT, H_r/H_c=3.71, M_r=2.35×10^-6A·m², M_s=6.91×10^-6A·m², M_r/M_s=0.34

Fig. 4. (a)The curve gotten from isothermal remanence and the demagnetization curves gotten from reversed polarities of the eclogite; (b)The curve gotten from isothermal remanence and the demagnetization curves gotten from reversed polarities of the surrounding rocks; (c)Hysteresis loop; (d)κ-t curve

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表 1 毛北榴辉岩样品磁组构测量结果

Table 1. The measured magnetic fabric of Maobei eclogite samples

参考文献(31)

Chen, J.F., Xie, Z., Liu, S.S., et al., 1995. Cooling age of Dabie orogen, China, determined by ⁴⁰Ar-³⁹ Ar and fission track techniques. Science in China(Series B), 38(6): 749-757.
Cong, B.L., Wang, Q.C., 1994. Review of researches on ultrahigh-pressure metamorphic rocks in China. Chinese Science Bulletin, 39: 2068-2075.
Cong, B.L., Wang, Q.C., 1999. The Dabie-Sulu UHP rocks belt: Review and prospect. Chinese Science Bulletin, 44(12): 1074-1086. doi: 10.1007/BF02886130
Cong, B. L., Zhai, M.G., Carswell, D.A., et al., 1995. Petrogenesis of the ultrahigh-pressure rocks and their country rocks at Shuanghe in Dabieshan, Central China. European J. Mineralogy, 7: 119-138. doi: 10.1127/ejm/7/1/0119
Davies, J.H., Blanckenburg, V., 1995. Slab breakoff: A model of lithosphere detachment and its test in the magnatism and deformation of collisional orogens. Earth & planet. Sci. Lett. , 129: 85-120.
Ernst, W.G., Liu, J.G., Hanker, B.R., 1994. Petrotectonic significance of high-and ultrahigh-pressure metamorphic belts: Inference for subduction-zone histories. International Geology Review, 36: 213-317. doi: 10.1080/00206819409465457
Harland, W.B., Cox, A.V., Llewellyn, P.G., et al., 1982. A geologic time scale. Cambridge University Press.
Harley, S.L., Carswell, D.A., 1995. Ultradeep crustal metamorphism: A prospective view. J. Geophys. Res. , 100: 8367-8380. doi: 10.1029/94JB02421
Hrouda, K., 1982. Magnetic anisotropy of rocks and its application in geology and geophysics. Geophysical Surveys, 5: 37-82. doi: 10.1007/BF01450244
King, J., Banerjee, S.K., Marvin, J., et al., 1982. A comparison of different magnetic methods for determining the relative grain size of magnetic in natural material: Some results from lake sediments. Earth Planet. Sci. Lett. , 59: 404-419. doi: 10.1016/0012-821X(82)90142-X
Li, S., Jagoutz, E., Xiao, Y., et al., 1996. Chronology of ultrahigh-pressure metamorphism in the Dabie Mountains an Su-Lu terrane: I. Sm-Nd isotope system. Science in China(Series D), 39(6): 597-608.
Li, S., Li, H., Chen, Y., et al., 1997. Chronology of ultrahigh-pressure metamorphism in the Dabie Mountain and Su-Lu terrane: Ⅱ. U-Pb isotope system of zircon. Science in China(Series D), 27(3): 200-206. http://www.researchgate.net/publication/285341356_Chronology_of_ultrahigh-pressure_metamorphism_in_the_Dabie_Mountains_and_Su-Lu_terrene_II_U-Pb_isotope_system_of_zircon?ev=auth_pub
Liu, Q.S., Zhang, Z.M., Liu, Y.S., 1999. Magnetic structures of eclogites from ZK703 drill hole in the Donghai region, eastern China: Implications for deep geological processes. Geoscience, 13(Suppl. ): 45-50(in Chinese with English abstract).
Meng, X.H., Hu, C.S., Wang, W.M., et al., 2000. Magnetostratigraphic study of Meishan Permian-Triassic Section, Changxing, Zhejiang Province, China. Journal of China University of Geosciences, 11(3): 361-365.
Schreyer, W., 1995. Ultradeep metamorphic rocks: The retrospective viewpoint. J. Geophys. Res. , 100: 8353-8366. doi: 10.1029/94JB02912
Stacey, F.D., Banerjee, S.K., 1974. The physical principles of rock magnetism. Elsevier Scientific Publishing Company, Amsterdam, London, New York.
Wu, C.L., Zhang, S.W., Mao, X.P., et al., 2006. Geometry and kinematics of tectonic evolution in northern part of Sulu orogenic belt. Earth Science—Journal of China University of Geosciences, 31(6): 817-822 (in Chinese with English abstract).
Xu, Z.Q., Qi, X.X., Yang, J.S., et al., 2006. Deep subduction erosion model for continent-continent collision of the Sulu HP-UHP metamorphic terrain. Earth Science—Journal of China University of Geosciences, 31(4): 427-436(in Chinese with English abstract).
Yang, W.C., Yu, C.Q., 2001. Kinetics and dynamics of development of the Dabie-Sulu UHPM terranes based on geophysical evidences. Chinese Journal of Geophysics, 44(3): 346-359(in Chinese with English abstract).
Yang, W.C., 2003. Layered mantle reflectors in Dabie-Sulu areas and their interpretation. Chinese Journal of Geophysics, 46(2): 191-196(in Chinese with English abstract).
Yu, Q.F., Guo, Y.Z., Meng, X.H., et al., 2002. Petrophysical parameters at continental scientific drilling site in Subei, China. Chinese Journal of Geophysics, 45(1): 93-100(in Chinese with English abstract).
Zhu, R.X., Tschu, K.K., 2001. Studies on paleomagnetism and reversals of geomagnetic field in China. Science Press, Beijing.
Zhu, R.X., Yang, Z.Y., Wu, H.N., et al., 1998. Paleomagnetic constraints on the tectonic history of the major blocks of China during the Phanerozoic. Science in China(Series D), 28(Suppl. ): 1-16. (in Chinese)
丛柏林, 王清晨, 1999. 大别山-苏鲁超高压变质带研究的最新进展. 科学通报, 44(11): 1127-1140. doi: 10.3321/j.issn:0023-074X.1999.11.002
刘庆生, 张泽明, 刘勇胜, 1999. 江苏东海地区ZK703钻孔榴辉岩的磁性结构及其深部地质意义. 现代地质, 13(增刊): 45-50.
吴冲龙, 张善文, 毛小平, 等, 2006. 苏鲁造山带北侧构造演化的几何学运动学特征. 地球科学———中国地质大学学报, 31(6): 817-822. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200606009.htm
许志琴, 戚学祥, 杨经绥, 等, 2006. 苏鲁高压-超高压变质地体的陆-陆碰撞深俯冲剥蚀模式. 地球科学———中国地质大学学报, 31(4): 427-436. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200604000.htm
杨文采, 余长青, 2001. 根据地球物理资料分析大别-苏鲁超高压变质带演化的运动学与动力学. 地球物理学报, 44(3): 346-359. doi: 10.3321/j.issn:0001-5733.2001.03.007
杨文采, 2003. 大别苏鲁地区层状地幔反射体及其解释. 地球物理学报, 46(2): 191-196. doi: 10.3321/j.issn:0001-5733.2003.02.010
余钦范, 郭友钊, 孟小红, 等, 2002. 苏北大陆科学钻探靶区岩石物理性质. 地球物理学报, 45(1): 93-100. doi: 10.3321/j.issn:0001-5733.2002.01.012
朱日祥, 杨振宇, 吴汉宁, 等, 1998. 中国主要地块显生宙古地磁视极移曲线与地块运动. 中国科学(D), 28(增刊): 1-16. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK1998S1000.htm