下地壳麻粒岩包体波速测定及其地质意义
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摘要
下地壳岩石的波速测定可以提供有关下地壳物质组成及物理性质的重要信息。但是,由于下地壳难于直接采样,因此常常利用目前出露地表的古老麻粒岩地体样品来代表下地壳,但所获结果常常与实际情况不符。由新生代玄武岩携带到地表的下地壳包体则为我们提供有关下地壳的直接信息。本文对采自河北汉诺坝玄武岩中的下地壳包体进行了密度和高温高压波速测定。下地壳由不同类型的麻粒岩相岩石组成,其密度和波速有较大的差异,因此所获波速不能直接与地震测深得到的下地壳波速进行对比,而需要进行波速的温度、压力校正,并进行具体的分析。本文得到下地壳包体的原地波速6.13～6.90km/s,与该区地震资料得到的结果十分接近,并探讨了下地壳低速层的可能成因。
The measurements of the elastic wave velocity of lower crustal rocks may provide valuable information on the composition and physical properties of the lower crust. The samples from old granulite terrane cropped out on the earth surface are often taken as the representatives of the lower crust, because of the difficulty of directly sampling the lower crust. The obtained results, however, are often in compatible with the actual conditions, as the old granulite terrane had experienced long period of multi-stage deformation and metamorphic processes. In Contrast, the lower crustal xenoliths brought up by Cenozoic basalts onto the surface may provide us with direct information of the lower crust. The measurements of density and elastic wave velocity of lower crustal xenoliths from Hanuoba basalts, Hebei Province, China under high temperature and pressure conditions are presented in this paper. The study shows that the lower crust of the area consists of various types of granulite facies rocks. Their density and velocity are different significantly from each others. The measured velocity of lower crustal xenoliths, therefore, can not be directly compared with the velocity structures of the lower crust obtained from deep seismic sounding, without temperature and pressure corrections. An in-situ velocity of lower crust of 6. 13 - 6. 90 km/s is obtained from this study, which is comparable well to the seismic data from the studied area. In addition, the origin of the low velocity layer is discussed as well.
The measurements of the elastic wave velocity of lower crustal rocks may provide valuable information on the composition and physical properties of the lower crust. The samples from old granulite terrane cropped out on the earth surface are often taken as the representatives of the lower crust, because of the difficulty of directly sampling the lower crust. The obtained results, however, are often in compatible with the actual conditions, as the old granulite terrane had experienced long period of multi-stage deformation and metamorphic processes. In Contrast, the lower crustal xenoliths brought up by Cenozoic basalts onto the surface may provide us with direct information of the lower crust. The measurements of density and elastic wave velocity of lower crustal xenoliths from Hanuoba basalts, Hebei Province, China under high temperature and pressure conditions are presented in this paper. The study shows that the lower crust of the area consists of various types of granulite facies rocks. Their density and velocity are different significantly from each others. The measured velocity of lower crustal xenoliths, therefore, can not be directly compared with the velocity structures of the lower crust obtained from deep seismic sounding, without temperature and pressure corrections. An in-situ velocity of lower crust of 6. 13 - 6. 90 km/s is obtained from this study, which is comparable well to the seismic data from the studied area. In addition, the origin of the low velocity layer is discussed as well.
引文
董树文.1989． 长江中下游地壳物质的构造动力调整作用.地质学报,63(2) :97～110．
樊祺诚,刘若新,李惠民,等.1998． 汉诺坝捕虏体麻粒岩锆石年代学与稀土元素地球化学.科学通报,43(2) :133～137．
冯锐,黄桂芳,郑书真,王均,严惠芬,张若水.1989． 华北地区地壳构造与地震活动.地质学报,63(2) :111～124．
顾芷娟,郭才华,李彪,等.1995． 壳内低速高导层成因初步探讨.中国科学(B辑),25(1) :108～112．
林传勇,史兰斌,陈孝德,等.1999． 福建明溪上地幔热结构及流变学特征.地质论评,45(4) :352～360．
史兰斌,林传勇,陈孝德,等.2000． 由包体推导的河北汉诺坝下地壳-上地幔地温线及其地质意义.地震地质,22(1) :37～46．
王懋基,程振炎.1982． 均衡异常与地壳结构.地质学报,56(1) :51～61．
王若华.1980． 地壳和地幔分界面性质的评述.地质论评,26(1) :60～66．
徐常芳.1996． 地壳内高导层成因:高温高压下卤水物态及其电导率(二).地震学报,18(3) :352～35．
岳石.1988． 对地壳应力分布规律的初步分析.地质论评,34(3) :248～253．
张荣华,胡书敏.1998． 地壳深部流体-NaCl-H_2O的高温高压实验观测及其科学意义.科学通报,43(22) :2451～2456．
张先康,祝志平,张成科,等.1998． 张家口-渤海地震带及其两侧地壳上地幔构造与速度结构研究.“活动断裂研究”6． 北京:地震出版社,1～16．
张友南,马瑾.1997． 深部地壳镁铁质岩石波速的研究.地球物理学报,40(2) :221～230．
张友南,孙君秀.1998． 华北地壳岩石波速类型及其地质意义.地震地质,20(1) :73～80．
张友南,孙君秀.1999． 华北北部克拉通地壳岩石的波速特征与地壳物质组成.地震地质,21(2) :147～154．
赵靖,钱祥麟.1998． 晋冀内蒙古交界区出露的太古宙下地壳剖面研究的问题和展望.地质学报(英文版),72(1) :1～13．
Christensen N I, Mooney W D. 1995． Seismic velocity structure and composition of the continental crust: a global view. Jour. Geophys. Res., 100(B7) : 9761～9788．
Dong Shuwen. 1989． Crustal material adjustment by tectonodynamics in the middle and lower reaches of the Changjiang (Yangtze) River. Acta Geologica Sinica, 63(2) : 97～110 (in Chinese with English abstract).
Fan Qicheng, Liu Ruoxin, Li Huimin, et al. 1998． Zircon chronology and REE geochemistry of granulite xenoliths of Hanuoba, Chinese Science Bull., 43(18) : 1510～1515 (in Chinese).
Feng Rui, Huang Guifang, Zheng Shuzhen, Wang Jun, Yan Huifen,Zhang Ruoshui. 1989． The crustal structure and earthquake activity in North China. Acta Geologica Sinica, 63(2) : 111～124(in Chinese with English abstract).
Gu Zhijuan, Guo Caihua, Li Biao, et al. 1995． Preliminary study on the origin of crustal low velocity-high conductivity layer. Science in China(B), 25(1) : 108～112 (in Chinese).
Holbrook W S, Mooney W D, Christensen N I. 1992． The seismic velocity structure of the continental crust. In: Fountain D M, Arculus R J, Kay R W, ed. The continental lower crust. Elsevier,Amsterdam, London, New York, Tokyo. 1～43．
Jackson I, Rudnick R L, O'Reilly S Y, Bezant C. 1990． Measured and calculated elastic wave velocities for the xenoliths from the lower crust and upper mantle. Tectonophysics, 173: 207～210．
Jones A G. 1992． Electrical properties of the lower continental crust.In: Fountain D M, Arculus R, Kay R W, ed. Continental lower crust. Elsevier, Amsterdam, London, New York, Tokyo. 81～144．
Lin Chuanyong, Shi Lanbin, Chen Xiaode, Han Xiuling. 1999． Thermal structures and rheology of the upper mantle beneath Mingxi,Fujian Province, China. Geological Review, 45(4) : 352～360(in Chinese with English abstract).
Meissner R. 1986． The continental crust-A geophysical approach. Orlando: Academic Press, 426．
O'Reilly S Y, Griffin W L. 1996． 4-D lithosphere mapping: methodology and examples. Tectonophys., 262: 3～18．
Parson T, Christensen N I, Wilshire H G. 1995． Velocities of Southern Basin and Range xenoliths: insight on the nature of lower crustal reflectivity and compositions. Geology, 23(2) : 129～132．
Rudnick R L. 1992． Xenoliths-samples of the lower continental crust. In: Fountain D M, Arculus R J, Kay R W, ed. The continental lower crust. Elsevier, Amsterdam, London, New York,Tokyo, 269～316．
Rudnick R L, Jackson I. 1995． Measured and calculated elastic wave speeds in partially equilibrated mafic granulite xenoliths: implications for the properties of an underplated lower continental crust.Jour. Geophys. Res., 100(B7) : 10211～10218．
Shi Lanbin, Lin Chuanyong, Chenxiaode, Han Xiuling. 2000． A xenolith-derived geotherm for the lower crust and upper mantle beneath Hanuoba area, Hebei Provimce, China. Seismology and Geology, 22(1) : 37～46 (in Chinese with English abstract).
Smithson S B, Brown S K. 1977． A model for lower continental crust. Earth Planet. Sci. Lett., 35: 134～144．
Smithson S B, Johnson R A, Wong Y K. 1981． Mean crustal velocity: a critical parameter for interpreting crustal structure and crustal growth. Earth Planet. Sci. Lett. 53: 323～332．
Wang Maoji, Cheng Zhen Zhenyan. 1982． Isostatic gravity anomaly and crustal structure. Acta Geologica Sinica, 56(1) : 51～61(in Chinese with English abstract).
Wang Ruohua. 1980． A review on the nature of the boundary surface between the crust and the mantle. Geological Review, 26(1) : 60～66 (in Chinese).
Xu Changfang. 1996． Origin of the crustal conductive layer and conductivity of super-critical brine. Acta Seismologica Sinica, 9(3) :455～460．
Yue Shi. 1988． The regularity of distribution of stresses in the Earth's crust. Geological Review, 34(3) : 248～253 (in Chinese with English abstract).
Zhang Ronghua, Hu Shumin. 1998． Fluids in deep crust-high temperature and high pressure experimental observation of NaCl-H_2O and its scientific implications. Chinese Science Bulletin, 43(22) :2451～2456 (in Chinese).
Zhang Xiankang, Zhu Zhiping, Zhang Chengke, et al. 1998． Crust and upper mantle structure of the Zhangjiakou-Bohai Seismic zone. Research on active fault(6) . Beijing: Seismological Press,1～16 (in Chinese).
Zhang Younan, Ma Jin. 1997． Investigation of compressional wave velocities of mafic rocks in deep crust. Acta Geophysica Sinica, 40(2) : 221～231(in Chinese with English abstract).
Zhang Younan, Sun Junxiu. 1998． Rock wave velocity types in the crust of North China and its geological implications. Seismology and Geology, 20(1) : 73～81(in Chinese with English abstract).
Zhang Younan, Sun Junxiu. 1999． Characters of wave velocity and constitution structures of rocks of the craton crust in north part of North China. Seismology and Geology, 21(2) : 147～155 (in Chinese with English abstract).
Zhao Jing, Qian Xianglin. 1998． Exposed cross-section of the Archaean lower crust in the Shanxi-Hebei-Inner Mongolia border region: problems and prospects. Acta Geologica Sinica (English Edition), 72(1) : 1～13．
樊祺诚,刘若新,李惠民,等.1998． 汉诺坝捕虏体麻粒岩锆石年代学与稀土元素地球化学.科学通报,43(2) :133～137．
冯锐,黄桂芳,郑书真,王均,严惠芬,张若水.1989． 华北地区地壳构造与地震活动.地质学报,63(2) :111～124．
顾芷娟,郭才华,李彪,等.1995． 壳内低速高导层成因初步探讨.中国科学(B辑),25(1) :108～112．
林传勇,史兰斌,陈孝德,等.1999． 福建明溪上地幔热结构及流变学特征.地质论评,45(4) :352～360．
史兰斌,林传勇,陈孝德,等.2000． 由包体推导的河北汉诺坝下地壳-上地幔地温线及其地质意义.地震地质,22(1) :37～46．
王懋基,程振炎.1982． 均衡异常与地壳结构.地质学报,56(1) :51～61．
王若华.1980． 地壳和地幔分界面性质的评述.地质论评,26(1) :60～66．
徐常芳.1996． 地壳内高导层成因:高温高压下卤水物态及其电导率(二).地震学报,18(3) :352～35．
岳石.1988． 对地壳应力分布规律的初步分析.地质论评,34(3) :248～253．
张荣华,胡书敏.1998． 地壳深部流体-NaCl-H_2O的高温高压实验观测及其科学意义.科学通报,43(22) :2451～2456．
张先康,祝志平,张成科,等.1998． 张家口-渤海地震带及其两侧地壳上地幔构造与速度结构研究.“活动断裂研究”6． 北京:地震出版社,1～16．
张友南,马瑾.1997． 深部地壳镁铁质岩石波速的研究.地球物理学报,40(2) :221～230．
张友南,孙君秀.1998． 华北地壳岩石波速类型及其地质意义.地震地质,20(1) :73～80．
张友南,孙君秀.1999． 华北北部克拉通地壳岩石的波速特征与地壳物质组成.地震地质,21(2) :147～154．
赵靖,钱祥麟.1998． 晋冀内蒙古交界区出露的太古宙下地壳剖面研究的问题和展望.地质学报(英文版),72(1) :1～13．
Christensen N I, Mooney W D. 1995． Seismic velocity structure and composition of the continental crust: a global view. Jour. Geophys. Res., 100(B7) : 9761～9788．
Dong Shuwen. 1989． Crustal material adjustment by tectonodynamics in the middle and lower reaches of the Changjiang (Yangtze) River. Acta Geologica Sinica, 63(2) : 97～110 (in Chinese with English abstract).
Fan Qicheng, Liu Ruoxin, Li Huimin, et al. 1998． Zircon chronology and REE geochemistry of granulite xenoliths of Hanuoba, Chinese Science Bull., 43(18) : 1510～1515 (in Chinese).
Feng Rui, Huang Guifang, Zheng Shuzhen, Wang Jun, Yan Huifen,Zhang Ruoshui. 1989． The crustal structure and earthquake activity in North China. Acta Geologica Sinica, 63(2) : 111～124(in Chinese with English abstract).
Gu Zhijuan, Guo Caihua, Li Biao, et al. 1995． Preliminary study on the origin of crustal low velocity-high conductivity layer. Science in China(B), 25(1) : 108～112 (in Chinese).
Holbrook W S, Mooney W D, Christensen N I. 1992． The seismic velocity structure of the continental crust. In: Fountain D M, Arculus R J, Kay R W, ed. The continental lower crust. Elsevier,Amsterdam, London, New York, Tokyo. 1～43．
Jackson I, Rudnick R L, O'Reilly S Y, Bezant C. 1990． Measured and calculated elastic wave velocities for the xenoliths from the lower crust and upper mantle. Tectonophysics, 173: 207～210．
Jones A G. 1992． Electrical properties of the lower continental crust.In: Fountain D M, Arculus R, Kay R W, ed. Continental lower crust. Elsevier, Amsterdam, London, New York, Tokyo. 81～144．
Lin Chuanyong, Shi Lanbin, Chen Xiaode, Han Xiuling. 1999． Thermal structures and rheology of the upper mantle beneath Mingxi,Fujian Province, China. Geological Review, 45(4) : 352～360(in Chinese with English abstract).
Meissner R. 1986． The continental crust-A geophysical approach. Orlando: Academic Press, 426．
O'Reilly S Y, Griffin W L. 1996． 4-D lithosphere mapping: methodology and examples. Tectonophys., 262: 3～18．
Parson T, Christensen N I, Wilshire H G. 1995． Velocities of Southern Basin and Range xenoliths: insight on the nature of lower crustal reflectivity and compositions. Geology, 23(2) : 129～132．
Rudnick R L. 1992． Xenoliths-samples of the lower continental crust. In: Fountain D M, Arculus R J, Kay R W, ed. The continental lower crust. Elsevier, Amsterdam, London, New York,Tokyo, 269～316．
Rudnick R L, Jackson I. 1995． Measured and calculated elastic wave speeds in partially equilibrated mafic granulite xenoliths: implications for the properties of an underplated lower continental crust.Jour. Geophys. Res., 100(B7) : 10211～10218．
Shi Lanbin, Lin Chuanyong, Chenxiaode, Han Xiuling. 2000． A xenolith-derived geotherm for the lower crust and upper mantle beneath Hanuoba area, Hebei Provimce, China. Seismology and Geology, 22(1) : 37～46 (in Chinese with English abstract).
Smithson S B, Brown S K. 1977． A model for lower continental crust. Earth Planet. Sci. Lett., 35: 134～144．
Smithson S B, Johnson R A, Wong Y K. 1981． Mean crustal velocity: a critical parameter for interpreting crustal structure and crustal growth. Earth Planet. Sci. Lett. 53: 323～332．
Wang Maoji, Cheng Zhen Zhenyan. 1982． Isostatic gravity anomaly and crustal structure. Acta Geologica Sinica, 56(1) : 51～61(in Chinese with English abstract).
Wang Ruohua. 1980． A review on the nature of the boundary surface between the crust and the mantle. Geological Review, 26(1) : 60～66 (in Chinese).
Xu Changfang. 1996． Origin of the crustal conductive layer and conductivity of super-critical brine. Acta Seismologica Sinica, 9(3) :455～460．
Yue Shi. 1988． The regularity of distribution of stresses in the Earth's crust. Geological Review, 34(3) : 248～253 (in Chinese with English abstract).
Zhang Ronghua, Hu Shumin. 1998． Fluids in deep crust-high temperature and high pressure experimental observation of NaCl-H_2O and its scientific implications. Chinese Science Bulletin, 43(22) :2451～2456 (in Chinese).
Zhang Xiankang, Zhu Zhiping, Zhang Chengke, et al. 1998． Crust and upper mantle structure of the Zhangjiakou-Bohai Seismic zone. Research on active fault(6) . Beijing: Seismological Press,1～16 (in Chinese).
Zhang Younan, Ma Jin. 1997． Investigation of compressional wave velocities of mafic rocks in deep crust. Acta Geophysica Sinica, 40(2) : 221～231(in Chinese with English abstract).
Zhang Younan, Sun Junxiu. 1998． Rock wave velocity types in the crust of North China and its geological implications. Seismology and Geology, 20(1) : 73～81(in Chinese with English abstract).
Zhang Younan, Sun Junxiu. 1999． Characters of wave velocity and constitution structures of rocks of the craton crust in north part of North China. Seismology and Geology, 21(2) : 147～155 (in Chinese with English abstract).
Zhao Jing, Qian Xianglin. 1998． Exposed cross-section of the Archaean lower crust in the Shanxi-Hebei-Inner Mongolia border region: problems and prospects. Acta Geologica Sinica (English Edition), 72(1) : 1～13．
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