上地幔三维S波速度结构与大别苏鲁超高压变质带俯冲折返机制探讨
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摘要
本文分析了中国东部的上地幔剪切波速度结构及其与超高压变质岩带之间关系的构造意义。结果表明,在华北块体下面150km深处的速度高于扬子块体的速度值。大别-苏鲁造山构造带下面存在着一条地震波速度变化带。苏鲁、山东半岛下面的速度分布与大别造山带下面的速度分布处于同一个速度等值区域上。横跨大别造山带的南北走向速度结构剖面上,在100km以上的地壳和上地幔区域,华北块体下与扬子块体下面的速度均略低平均值。100km以下,大别造山带南北两侧的扬子与华北块体下面的速度结构分布形态大相径庭。华北下面的波速高于扬子块体下面的波速。大别造山带下呈现速度异常,界线的南侧,有一个略低于零速度的负波速异常区,呈现由南向华北块体的下方斜冲形态,下冲角度大约为30°,其先端部位下冲深达300多公里,其外围零速度等值线的分布区,斜向下延伸超过400km。在速度结构变化分界线的北侧,一个零速度值的分布区带,呈现出从由100多公里深处从北向南朝地表面斜上冲形态。这些速度结构成像的几何形态可能意味着200Ma前大别超高压变质岩带的形成与演化的俯冲、折返的构造运动在上地幔和岩石圈中留下的“痕迹”。
Relations between ultrahigh-pressure metamorphosed belt and 3-D S wave velocity structure image in the upper mantle in the east continent of China were analyzed in present study. The results suggest that the velocity beneath the North China block is generally higher than that beneath the Yangtze block at 150 km depth. A velocity variation boundary belt appears beneath the Dabie-Sulu orogeny belt. Velocity values beneath Sulu region and the Shandong peninsula are in the identical contour line with that beneath the Dabie orogeny belt. In the vertical velocity structure profile crossing the Dabie mountain along near N-S direction, at the region shallower than 100 km depth, the velocities beneath the North China and the Yangtze blocks are lightly less than the average value. The velocity distributions beneath the Yangtze block at the region deeper than 100 km, however, quite differ from that beneath the North China block. The velocity beneath the Yangtze block is slower than that beneath North China block. A anomalous velocity zone lightly less than zero at the south side of velocity variation boundary beneath Dabie mountain thrusts downward greater than 300 km depth beneath the North China block from south to north, at dip angle of about 30 degrees. A near zero velocity zone north of the velocity boundary seems to thrust upward the surface of the Yangtze block from 100 km depth along the N-S direction beneath the North China block. Such geometries of the velocity structure images beneath the region crossing the Dabie orogeny belt imply that the zones thrusting down and upward might be related to the evidences of the "traces" for the subduction and exhumation process of ultrahigh-pressure metamorphosed belt beneath the Dabie mountain.
Relations between ultrahigh-pressure metamorphosed belt and 3-D S wave velocity structure image in the upper mantle in the east continent of China were analyzed in present study. The results suggest that the velocity beneath the North China block is generally higher than that beneath the Yangtze block at 150 km depth. A velocity variation boundary belt appears beneath the Dabie-Sulu orogeny belt. Velocity values beneath Sulu region and the Shandong peninsula are in the identical contour line with that beneath the Dabie orogeny belt. In the vertical velocity structure profile crossing the Dabie mountain along near N-S direction, at the region shallower than 100 km depth, the velocities beneath the North China and the Yangtze blocks are lightly less than the average value. The velocity distributions beneath the Yangtze block at the region deeper than 100 km, however, quite differ from that beneath the North China block. The velocity beneath the Yangtze block is slower than that beneath North China block. A anomalous velocity zone lightly less than zero at the south side of velocity variation boundary beneath Dabie mountain thrusts downward greater than 300 km depth beneath the North China block from south to north, at dip angle of about 30 degrees. A near zero velocity zone north of the velocity boundary seems to thrust upward the surface of the Yangtze block from 100 km depth along the N-S direction beneath the North China block. Such geometries of the velocity structure images beneath the region crossing the Dabie orogeny belt imply that the zones thrusting down and upward might be related to the evidences of the "traces" for the subduction and exhumation process of ultrahigh-pressure metamorphosed belt beneath the Dabie mountain.
引文
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Boschi L and Dziewonski A M. 1998． 'High ' and 'low ' resolution tomography of the Earths mantle. EOS Trans. Am. Geophys. Un. , 79(45) , Fall Mtg Suppl. , F656
David J. 2002． How old roots lose their bounce. Nature, 417(27) : 911
Ernst W G and Peacock S M. 2000． A Thermotectonic model for preservation of ultrahigh-pressure phases in metamorphosed continental crust, subduction top to bottom. In: Gray E. Bebout et al. , Editors. American Geophysical Union, pp 171-178
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Liu J H, Liu F T, Sun R M, Wu H and Wu D. 1995 Seismic tomography velocity structure in the Qinling-Dabie orogenic belt and its north and south edges. Chinese J. Geophys. , 38: 46-54 (in Chinese withEnglish abstract)
Liu F T, Xu P F, Liu J S. 2003． The crust velocity structure of thecontinental deep subduction belt: study on the eastern Dabie orogenby seismic wide-angle reflection/refraction. Chinese J. Geophys. ,46: 365-372(in Chinese with English abstract)
Liou J G, Zhang R Y. 1998． Petrogenesis of an ultrahigh-pressure garnet-bearing ultramafic body from Maowu, Dabie Mountains, east-centralChina. The Island Arc, 7:115-134
Maruyama S, Liou J G and Zhang R. 1994． Tectonic evolution of the
ultrahigh-pressure and high pressure metamorphic belts from centerChina. The Island Arc, 3: 112-121
Qian H, Jiang M and Su H P. 2002． Velocity structure in the ChineseContinent Science Drilling region, Donghai, Jangsu. Doctor Thesis
Riztwoller M H and Lavely E M. 1995． Three dimensional seismic modelsof the earth' s mantle. Rev. Geophys. , 33 : 1-65
Wang C R, Zhang X K and Chen B Y. 1997． The study on the curstalstructure of Dabie orogenic belt. Science in China (series D), 27:221-226
Widiyantoro S, Grobatov A, Kennnett N and Fukaao Y. 2000． Improvingglobal shear wave travel time tomography using three dimensional raytracing and interative inversion. Geophys. J. Inter. , 141: 747-758
Xu J R, Zhao Z X, Ishkawa Y and Oike K. 1988． Properties of the stressfield in and around West China, Derived from earthquake mechanismsolutions. Bulletin of the Disaster Prevention Research Institute,Kyoto University, 38:49-78
Xu J R, Zhao Z X and Oike K. 2002． Tectonic characteristics ofseismogenic stress field in east Asia. In : Fujinawa Y and Yoshida A(eds. ). Seismotectonics in Convergent Plate Boundary, Tokyo:TERRAPUB, pp.481-497
Xu J R and Yoshiteru K. 2002． Geometry of Slab, Intraslab stress fieldand its tectonic implication in the Nankai Trough, Japan. EarthPlanes and Space, 54: 733-742
Xu J R, Zhao Z X, Kono Y, Kinoshita H, 2003． Regional characteristicsof stress field and its dynamics in and around the Nankai Trough,Japan. Chinese J. Geophys. , 46: 488-494 ( in Chinese withEnglish abstract)
Xu JR and Zhao ZX. 2004． Regional structure characteristics of crustalroot of mountain beneath the Sulu orogenic belt. Acta PetrologicaSinica, 20(1) : 137-144 (in Chinese with English abstract)
Xu P F, Liu F T, Wang Q C. 2000． Seismic tomography beneath theDabie-Sulu collision orogen-3-D velocity structure of lithosphere.Chinese J. Geophys. , 43: 377-385 ( in Chinese with Englishabstract)
Xu, Z Q, Zhao Z X, Yang J S, Yuan X C and Jiang M. 2003． Tectonicsbeneath plates and mantle dynamics. Geological Bulletin of China,22: 149-159 (in Chinese with English abstract)
Xu Z Q, Yang W C, Cong B L. 1998． Drilling operations in the Dabie- Sulu UHPM belt, east China. A Propasal to ICDP.
Xu Z Q, Zhang Z M, Liu F L, Yang L S, Li H B, Yang T N, Qiu H J,Li T F, Meng F. C, Chen S Z, Tang Z M and Chen F Y. 2003． Exhumation structure and mechanism of the Sulu ultrahigh-pressuremetamorphic belt, Central China, 77:433-350
Yang J S, Wood J L, Wu C L, Liu F L, Xu Z Q, Shi R D and KatayamaI. 2003． Shrimp U-Pb, dating of cosite-bearing zircon from theUltrahigh-pressure metamorphic rocks, Su
Boschi L and Dziewonski A M. 1998． 'High ' and 'low ' resolution tomography of the Earths mantle. EOS Trans. Am. Geophys. Un. , 79(45) , Fall Mtg Suppl. , F656
David J. 2002． How old roots lose their bounce. Nature, 417(27) : 911
Ernst W G and Peacock S M. 2000． A Thermotectonic model for preservation of ultrahigh-pressure phases in metamorphosed continental crust, subduction top to bottom. In: Gray E. Bebout et al. , Editors. American Geophysical Union, pp 171-178
Ernst W G, Liu G J and Coleman R G. 1995． Comparative petrotectonic study of five Eurasia ultrahigh-pressure metamorphic complexs. Int. Geol. Rev. , 37:191-211
Liu J H, Liu F T, Sun R M, Wu H and Wu D. 1995 Seismic tomography velocity structure in the Qinling-Dabie orogenic belt and its north and south edges. Chinese J. Geophys. , 38: 46-54 (in Chinese withEnglish abstract)
Liu F T, Xu P F, Liu J S. 2003． The crust velocity structure of thecontinental deep subduction belt: study on the eastern Dabie orogenby seismic wide-angle reflection/refraction. Chinese J. Geophys. ,46: 365-372(in Chinese with English abstract)
Liou J G, Zhang R Y. 1998． Petrogenesis of an ultrahigh-pressure garnet-bearing ultramafic body from Maowu, Dabie Mountains, east-centralChina. The Island Arc, 7:115-134
Maruyama S, Liou J G and Zhang R. 1994． Tectonic evolution of the
ultrahigh-pressure and high pressure metamorphic belts from centerChina. The Island Arc, 3: 112-121
Qian H, Jiang M and Su H P. 2002． Velocity structure in the ChineseContinent Science Drilling region, Donghai, Jangsu. Doctor Thesis
Riztwoller M H and Lavely E M. 1995． Three dimensional seismic modelsof the earth' s mantle. Rev. Geophys. , 33 : 1-65
Wang C R, Zhang X K and Chen B Y. 1997． The study on the curstalstructure of Dabie orogenic belt. Science in China (series D), 27:221-226
Widiyantoro S, Grobatov A, Kennnett N and Fukaao Y. 2000． Improvingglobal shear wave travel time tomography using three dimensional raytracing and interative inversion. Geophys. J. Inter. , 141: 747-758
Xu J R, Zhao Z X, Ishkawa Y and Oike K. 1988． Properties of the stressfield in and around West China, Derived from earthquake mechanismsolutions. Bulletin of the Disaster Prevention Research Institute,Kyoto University, 38:49-78
Xu J R, Zhao Z X and Oike K. 2002． Tectonic characteristics ofseismogenic stress field in east Asia. In : Fujinawa Y and Yoshida A(eds. ). Seismotectonics in Convergent Plate Boundary, Tokyo:TERRAPUB, pp.481-497
Xu J R and Yoshiteru K. 2002． Geometry of Slab, Intraslab stress fieldand its tectonic implication in the Nankai Trough, Japan. EarthPlanes and Space, 54: 733-742
Xu J R, Zhao Z X, Kono Y, Kinoshita H, 2003． Regional characteristicsof stress field and its dynamics in and around the Nankai Trough,Japan. Chinese J. Geophys. , 46: 488-494 ( in Chinese withEnglish abstract)
Xu JR and Zhao ZX. 2004． Regional structure characteristics of crustalroot of mountain beneath the Sulu orogenic belt. Acta PetrologicaSinica, 20(1) : 137-144 (in Chinese with English abstract)
Xu P F, Liu F T, Wang Q C. 2000． Seismic tomography beneath theDabie-Sulu collision orogen-3-D velocity structure of lithosphere.Chinese J. Geophys. , 43: 377-385 ( in Chinese with Englishabstract)
Xu, Z Q, Zhao Z X, Yang J S, Yuan X C and Jiang M. 2003． Tectonicsbeneath plates and mantle dynamics. Geological Bulletin of China,22: 149-159 (in Chinese with English abstract)
Xu Z Q, Yang W C, Cong B L. 1998． Drilling operations in the Dabie- Sulu UHPM belt, east China. A Propasal to ICDP.
Xu Z Q, Zhang Z M, Liu F L, Yang L S, Li H B, Yang T N, Qiu H J,Li T F, Meng F. C, Chen S Z, Tang Z M and Chen F Y. 2003． Exhumation structure and mechanism of the Sulu ultrahigh-pressuremetamorphic belt, Central China, 77:433-350
Yang J S, Wood J L, Wu C L, Liu F L, Xu Z Q, Shi R D and KatayamaI. 2003． Shrimp U-Pb, dating of cosite-bearing zircon from theUltrahigh-pressure metamorphic rocks, Su
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