桐柏—大别造山带内与脆性-韧性剪切带共生的假玄武玻璃的发现及意义
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摘要
在桐柏—大别造山带大河镇剪切带中首次发现与碎裂岩和糜棱岩共生的两种不同类型的假玄武玻璃。野外产状及显微结构的研究表明与碎裂岩共生的假玄武玻璃产出于以脆性破裂为主的断层浅部(<15km),而与糜棱岩共生的假玄武玻璃则产出于以韧性变形为主的断层深部(>15 km)。这两种类型的假玄武玻璃均含有熔解起源的自形微晶体,圆形或港湾状的碎片,流动结构和部分玻璃质基质。假玄武玻璃与碎裂岩和糜棱岩共生的现象说明在桐柏—大别造山带形成和隆起过程中同一断层剪切带内大地震重复发生。大河镇假玄武玻璃的研究可对大陆型大地震的发震机制及地壳浅部的脆性变形领域到深部的塑性变形领域的地震断层的破裂过程和力学性质的研究提供重要信息。
Two types of pseudotachylytes are observed in the Dahezhen ductile shear zone of the Tongbei-Dabie oro-genic belt, southwest Henan Province of China, one associated with the cataclasite cuts the foliation of mylonite and the other is interlayered and associated with the mylonite. The occurrences and microstructures suggest that the former type formed in the brittle regime (<15 km), and the latter was generated in the semi-ductile regime (15-25 km). Both pseudotachylytes display textures attesting of a melting origin: microlites, rounded and embayed clast, flow structures and glassy matrix. The coeval presence of the two types of pseudotachylytes indicates that cyclic seismic slips occurred in the same shear zone from brittle to semi-ductile regimes in the Tongbei-Dabie collisional erogenic belt.
Two types of pseudotachylytes are observed in the Dahezhen ductile shear zone of the Tongbei-Dabie oro-genic belt, southwest Henan Province of China, one associated with the cataclasite cuts the foliation of mylonite and the other is interlayered and associated with the mylonite. The occurrences and microstructures suggest that the former type formed in the brittle regime (<15 km), and the latter was generated in the semi-ductile regime (15-25 km). Both pseudotachylytes display textures attesting of a melting origin: microlites, rounded and embayed clast, flow structures and glassy matrix. The coeval presence of the two types of pseudotachylytes indicates that cyclic seismic slips occurred in the same shear zone from brittle to semi-ductile regimes in the Tongbei-Dabie collisional erogenic belt.
引文
刘国惠,张寿广,游振东,等.1993． 秦岭造山带主要变质岩群及变质演化.北京:地质出版社.
索书田,桑隆康,韩郁菁,等.1993． 大别山前寒武纪变质地体岩石学与构造学.武汉:中国地质大学出版社,259．
杨主恩.1984． 断层岩及其与地震的关系 地震地质论文集,天津科学技术出版社,99～122．
翟淳.1998． 桐柏北部韧性剪切带中假玄武玻璃的成因.地质论评,34(3) :203～213．
Allen A R. 1979． Mechanism of frictional fusion in fault zones. J. Struct. Geol., 1: 231～243．
Hobbs B E, Ord A, Teyssier C. 1986． Earthquakes in the ductile regime. Pure Appl. Geophys., 124: 309～336．
Kennedy G C, Wasserburg G J, Heard H C, Newton R C. 1962． The upper three-phase region in the system SiO_2-H_2O. Am. J. Sci., 260: 501～521．
Lin A. 1994a. Glassy pseudotachylyte veins from the Fuyun fault zone, northwest China. J. Struct. Geol., 16: 71～83．
Lin A. 1994b. Microlite morphology and chemistry in pseudotachylite, from the Fuyun fault zone, China. J. Geol., 102: 317～329．
Lin A. 1996． Injecion veins of crushing-originated pseudotachylites and fault gouge formed during seismic faulting. Engineering Geology, 43: 213～224．
Lin A. 1997． Fluidization and rapid injection of crushed fine-grained materials in fau1t zones during episodes of seismic faulting. Prec. 30 Int'l Cong., 14: 27～40．
Lin A. 1998． Selective melting processes as inferred from experimentally generated pseudotachylites. Journal of Asian Earth Sciences, 16 (5～6) : 533～545．
Lin A. 1999． Roundess of fragments in pseudotachylites as an indicator of frictional melting. J. Struct. Geol., 21: 473～478．
Liu G, Zhang S, Yao Z, et al. 1993． The major metamorphic groups and its evolutions in the Qinling orogenic belt. Beijing: Geological Publishing House (in Chinese).
Maddock R H. 1983． Melt origin of fault-generated pseudotachylites demonstrated by textures. Geology, 11: 105～108．
Magloughlin J F. 1992． Microstructural and chemical changes associated with cataclasis and frictional melting at shallow crustal levels: the cataclasite pseudotachylyte connection. Tectonophysics, 204: 243～260．
McNulty B A. 1995． Pseudotachylite generated in the semi-brittle and brittle regimes, Bench Canyon shear zone, central Sierra Nevada. J. Struct. Geol., 17: 1507～1521．
Philpotts A R. 1964． Origin of pseudotachylite. Am. J. Sci, 262: 1008～1035．
Sibson R H. 1975． Generation of pseudotachylite by ancient seismic faulting. Geophys. J. Royal. Astr. Soc., 43: 775～794．
Sibson R H. 1980． Transient discontinuities in ductile shear zone. J. Struct. Geol., 2: 165～174．
Suo S, Sang L, Han Y, et al. 1993． The Petrology and structure of Pre-Cambrian metamorphic terrane in the Dabie belt. Wuhan: China University of Geosciences Press, 259 (in Chinese).
Wallace R C. 1976． Partial fusion along the Alpine fault zone, New Zealand. Geol. Soc. Am. Bull., 87: 1225～1228．
Wenk H G. 1978． Are pseudotachylites preducts of fracture or fusion? Geol., 6: 507～511．
White J C. 1996． Transient diseontinuities revisited: Pseudotachylite, plastic instability and the influence of low pore fluid pressure on deformation processes in the mid-crust. J. Struct. Geol., 18: 1471～1486．
Yang Z. 1984． Fault rocks and its relationship with earthquake. In: Scientific Papers on Seismology and Geology. Tianjing: Tianjing Science and Technology Press, 99～122 (in Chinese).
Zhai C. 1988． Origin of pseudotachylites of the ductile shear zone in the northern part of Tongbai province. Geol. Rev., 34(3) : 203～213 (in Chinese with English abstract).
Zhang J, Liu S, Zheng Y, et al. 1998． Raman spectral analysis and genetic mechanism of pseudotachylite in Xiaoqinlig detachment fault. Science in China, 41 (3) : 242～247．
索书田,桑隆康,韩郁菁,等.1993． 大别山前寒武纪变质地体岩石学与构造学.武汉:中国地质大学出版社,259．
杨主恩.1984． 断层岩及其与地震的关系 地震地质论文集,天津科学技术出版社,99～122．
翟淳.1998． 桐柏北部韧性剪切带中假玄武玻璃的成因.地质论评,34(3) :203～213．
Allen A R. 1979． Mechanism of frictional fusion in fault zones. J. Struct. Geol., 1: 231～243．
Hobbs B E, Ord A, Teyssier C. 1986． Earthquakes in the ductile regime. Pure Appl. Geophys., 124: 309～336．
Kennedy G C, Wasserburg G J, Heard H C, Newton R C. 1962． The upper three-phase region in the system SiO_2-H_2O. Am. J. Sci., 260: 501～521．
Lin A. 1994a. Glassy pseudotachylyte veins from the Fuyun fault zone, northwest China. J. Struct. Geol., 16: 71～83．
Lin A. 1994b. Microlite morphology and chemistry in pseudotachylite, from the Fuyun fault zone, China. J. Geol., 102: 317～329．
Lin A. 1996． Injecion veins of crushing-originated pseudotachylites and fault gouge formed during seismic faulting. Engineering Geology, 43: 213～224．
Lin A. 1997． Fluidization and rapid injection of crushed fine-grained materials in fau1t zones during episodes of seismic faulting. Prec. 30 Int'l Cong., 14: 27～40．
Lin A. 1998． Selective melting processes as inferred from experimentally generated pseudotachylites. Journal of Asian Earth Sciences, 16 (5～6) : 533～545．
Lin A. 1999． Roundess of fragments in pseudotachylites as an indicator of frictional melting. J. Struct. Geol., 21: 473～478．
Liu G, Zhang S, Yao Z, et al. 1993． The major metamorphic groups and its evolutions in the Qinling orogenic belt. Beijing: Geological Publishing House (in Chinese).
Maddock R H. 1983． Melt origin of fault-generated pseudotachylites demonstrated by textures. Geology, 11: 105～108．
Magloughlin J F. 1992． Microstructural and chemical changes associated with cataclasis and frictional melting at shallow crustal levels: the cataclasite pseudotachylyte connection. Tectonophysics, 204: 243～260．
McNulty B A. 1995． Pseudotachylite generated in the semi-brittle and brittle regimes, Bench Canyon shear zone, central Sierra Nevada. J. Struct. Geol., 17: 1507～1521．
Philpotts A R. 1964． Origin of pseudotachylite. Am. J. Sci, 262: 1008～1035．
Sibson R H. 1975． Generation of pseudotachylite by ancient seismic faulting. Geophys. J. Royal. Astr. Soc., 43: 775～794．
Sibson R H. 1980． Transient discontinuities in ductile shear zone. J. Struct. Geol., 2: 165～174．
Suo S, Sang L, Han Y, et al. 1993． The Petrology and structure of Pre-Cambrian metamorphic terrane in the Dabie belt. Wuhan: China University of Geosciences Press, 259 (in Chinese).
Wallace R C. 1976． Partial fusion along the Alpine fault zone, New Zealand. Geol. Soc. Am. Bull., 87: 1225～1228．
Wenk H G. 1978． Are pseudotachylites preducts of fracture or fusion? Geol., 6: 507～511．
White J C. 1996． Transient diseontinuities revisited: Pseudotachylite, plastic instability and the influence of low pore fluid pressure on deformation processes in the mid-crust. J. Struct. Geol., 18: 1471～1486．
Yang Z. 1984． Fault rocks and its relationship with earthquake. In: Scientific Papers on Seismology and Geology. Tianjing: Tianjing Science and Technology Press, 99～122 (in Chinese).
Zhai C. 1988． Origin of pseudotachylites of the ductile shear zone in the northern part of Tongbai province. Geol. Rev., 34(3) : 203～213 (in Chinese with English abstract).
Zhang J, Liu S, Zheng Y, et al. 1998． Raman spectral analysis and genetic mechanism of pseudotachylite in Xiaoqinlig detachment fault. Science in China, 41 (3) : 242～247．
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