苏州西山震裂锥:太湖冲击坑又一新证据
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摘要
震裂锥已被公认为陨石冲击地球表面遗留的标志。研究及统计资料表明,震裂锥与陨石冲击形成的中、大型冲击坑有关。太湖西山震裂锥呈圆锥形,锥体表面有自锥顶向下辐射的锥纹,锥纹具有分叉的特征,这些特征与震裂锥的国际公认的定义和标准相符。此外,西山震裂锥还具有其特有的其他特征:碎裂岩化显著;气化—熔融现象发育;锥体表面具网状构造及波纹状、蜂窝状等多种气印。岩相学研究显示,震裂锥及含锥岩石中冲击变质现象明显,微页理(PDFs)、微裂隙(PFs)以及靶岩熔融现象发育。以上这些冲击变质的标志,可证明西山震裂锥是冲击成因,而非地表水风化淋溶石灰岩的喀斯特或风蚀成因的凤稜石。西山震裂锥的发现、太湖湖底冲击击变角砾岩"太湖石"的确定,为太湖冲击坑的研究增添了新的诊断性证据;加上早期研究确定的、冲击回落至太湖湖底淤泥层中的冲击溅射物,这些众多证据为确定"太湖冲击坑"或"太湖冲击事件"展示了美好前景。但是,要确定太湖冲击坑的具体位置、大小及构造模式等,尚需更多的深入研究。
The shatter cones have been recognized as a sign of meteorite impact on the earth's surface. Research and statistical data show that shatter cones are related to medium-or larger-scale impact craters. The shatter cones found in Xishan, Suzhou provides a diagnostic evidence for the existence of impact crater happened in Taihu Lake. The shatter cones are characterized by the conical shapes and coved with conical striations radiating downward from the top of the cones. The striation has been shown as the feature of bifurcation. The evidences are consistent with the international definition and standard for the shatter cone. In addition, special characteristics are also found in shatter cones in Xishan: remarkable cataclasis and the obvious melt-gasification phenomenon. On surface of cones, there are mesh—structure and the ripples-like, honeycomb-like gas imprint developed. Results of petrographic study show that shatter cones and cone-contained target rocks have visible impact metamorphism. Planar Deformation Features [PDFs], Planar Features [PFs] and target rock melting indicate the impact metamorphism happened. All of these show that shatter cones in Xishan are distinctly different from cone-sharp karst limestone formed by the surface water dissolution or ventifacts formed by eolian erosive action.The discovery of Xishan shatter cones and the breccias"Taihu stone" occurring at the bottom of the Taihu Lake has provided the new diagnostic evidence for the Taihu impact crater. There are also existed impact ejecta identified in earlier studies which fallen back into the silt layers under the Taihu Lake. Numerous evidences show a beautiful prospect for the determination of "Taihu impact crater" or"Taihu impact event". However, there is still much work to be done to determine the detailed locations, size and structural model of the impact crater in Taihu Lake.
The shatter cones have been recognized as a sign of meteorite impact on the earth's surface. Research and statistical data show that shatter cones are related to medium-or larger-scale impact craters. The shatter cones found in Xishan, Suzhou provides a diagnostic evidence for the existence of impact crater happened in Taihu Lake. The shatter cones are characterized by the conical shapes and coved with conical striations radiating downward from the top of the cones. The striation has been shown as the feature of bifurcation. The evidences are consistent with the international definition and standard for the shatter cone. In addition, special characteristics are also found in shatter cones in Xishan: remarkable cataclasis and the obvious melt-gasification phenomenon. On surface of cones, there are mesh—structure and the ripples-like, honeycomb-like gas imprint developed. Results of petrographic study show that shatter cones and cone-contained target rocks have visible impact metamorphism. Planar Deformation Features [PDFs], Planar Features [PFs] and target rock melting indicate the impact metamorphism happened. All of these show that shatter cones in Xishan are distinctly different from cone-sharp karst limestone formed by the surface water dissolution or ventifacts formed by eolian erosive action.The discovery of Xishan shatter cones and the breccias"Taihu stone" occurring at the bottom of the Taihu Lake has provided the new diagnostic evidence for the Taihu impact crater. There are also existed impact ejecta identified in earlier studies which fallen back into the silt layers under the Taihu Lake. Numerous evidences show a beautiful prospect for the determination of "Taihu impact crater" or"Taihu impact event". However, there is still much work to be done to determine the detailed locations, size and structural model of the impact crater in Taihu Lake.
引文
何永年,徐道一,陆德复,等.1990.太湖地区石英晶粒的冲击变形特征--太湖成因初探[J].科学通报,15:1163-1166.
黄钟瑾,沈修志,黄志诚,等.1991.下扬子区下古生物界找油气的靶区--太湖穹窿的发现和研究[J].南京大学学报(地球科学),3(1):13-22
秦伯强,胡行祥,陈伟民.2004.太湖水环境演化过程与机理[M].北京:科学出版社:2-313.
石火生.1992.机载雷达遥感应用试验研究(太湖地区雷达图像的地质构造分析)[M].北京:中国科学技术出版社:126-132.
沈自励.2003.火山喷爆与太湖成因[J].地球科学--中国地质大学学报,28:441-444.
孙顺才,黄漪平.1993.太湖[M].北京:海洋出版社:271.
陶奎元.2017.走进太湖西山三山旅游指南[J].南京:江苏凤凰科学技术出版社.
王尔康,朱政,张海样,等.1993.太湖蕨山岛发现震裂锥[J].科学通报,38:2265-2268.
王鹤年,谢志东,钱汉东.2009.太湖冲击坑溅射物的发现及其意义[J].高校地质学报,15(4):437-447.
王鹤年,钱汉东,黄钟瑾,等.2015.太湖西缘击变角砾岩的岩相学特征及其研究意义--太湖冲击成因又添新证据[J].南京大学学报(自然科学),51(1):87-98.
Baratoux D and Melosh H J.2003.The formation of shatter cones by shock wave interference during impacting[J].Earth and Planetary Science Letters,216(1):43-54.
Baratoux D and Reimold W U.2016.The current state of knowledge about shatter cones:Introduction to the special issue[J].Meteoritics&Planetary Science,51(8):1389-1434.
Chen M,Xiao W and Xie X.2010.Coesite and quartz characteristic of crystallization from shock-produced silica melt in the Xiuyan crater[J].Earth and Planetary Science Letters,397:306-314.
Dietz R S.1947.Meteorite impact suggested by the orientation of shatter cones at the Kentand,Indiana,disturbance[J].Science,105:42-76.
Dietz R S.1960.Meteorite impact suggested by shatter cones in rock[J].Science,131:1781-1784.
Dietz R S and Butler L.W.1964.Orientation of shatter cones at Sudbury Canada[J].Nature,204:280-281.
Elmar B and Martin S.2010.Steinheim suevite-A first report of melt-bearing impactites from the Steiheim Basin(SW Germany)[J].Meteoritics&Planetary Science,45(7):1093-1107.
Fackelman S P,Morrow J R,Koeberl C,et al.2008.Shatter cone and microscopic shock-alteration evidence for a post-Paleoproterozoic terrestrial impact structure near Santa Fe,New Mexico,USA[J].Earth and Planetary Science Letters,270(3):290-299.
Ferrière L and Osinski G R.2010.Shatter cones and associated shock-induced microdeformations in minerals-New investigations and implications for their formation[A].Lunar and Planetary Science Conference,41:1392.
Gay N C.1976.Spherules on shatter cone surfaces from the Vredefort structure,South Africa[J].Science,194:(4266):724-725.
Gay N C,Comins N R and Simposon C.1978.The Composition of spherules and other features on shatter cone surfaces from the Vredefort structure,South Africa[J].Earth Planet.Sci.Lett.,41:372-380.
Gibson H M and Spray J G.1998.Shock-induced melting and vaporization of shatter cones surfaces evidence from the Sudbury impact structure[J].Meteoritics&Planetary Science,33:329-336.
Guy-Bray J and Geological Staft.1966.Shatter cones at Sudbury[J].The Journal of Geology,74:243-245.
Kenkmann T,Hergarten S,Kuhn T,et al.2016.Formation of shatter cones by symmetric fracture bifurcation:Phenomenological modeling and validation[J].Meteoritics&Planetary Science,51(8):1519-1533.
McCall G J H.2009 Half a century of progress in research on terrestrial impact structures:A review[J].Earth-Science Reviews,92:99-116
Nicolaysen L O and Reimold U.1999.Vredefort shatter cones revisited[J].J.Geophys.Res(Solid Earth),104:4911-4930.
Oliveira G J G,Vasconcelos M A R,Crósta A P,et al.2014.Shatter cones and planar deformation features confirm Santa Marta in PiauíState,Brazil,as an impact structure[J].Meteoritics&Planetary Science,49(10):1915-1928.
Osinski G R and Spray J G.2001.Impact generated carbonate melts:evidence from the Haughton structure,Canada[J].Earth and Planetary Science letters,194:17-29.
Pittarello L,Nestola F,Viti C,et al.2015.Melting and cataclastic features in shatter cones in basalt from the Vista Alegre impact structure,Brazil[J].Meteoritics&Planetary Science,50(7):1228-1243.
Posges G.2016.First description of genuine shatter cones in upper Jurassic limestone clasts from the bunte breccia impactites of the Ries crater[J].Meteoritics&Planetary Science,51(S1):A521.
Qian H D,Wang H N and Xie Z D.2010.Discovery of impact breccia in the western of Taihu Lake in Jangsu province,China.New evidence for an impact origin[A].New York:73rd Annual Meteoritical Society Meeting,Jul 26-30.
Sagy A,Reches Z E and Fineberg J.2002.Dynamic fracture by large extraterrestrial impacts as the origin of shatter cones[J].Nature,418(6895):310-313.
Sharpton V L,Kennedy J W,Xu D Y,et al.1988.Searching for impact structure in China[J].EOS,69:391.
Wieland F and Reimold W U.2003.Field and laboratory studies on shatter cones in the Vredefort Dome,South Africa,and their genesis[J].Meteoritics and Planetary Science,S38:5016.
Wieland F,Reimold W U and Gibson R L.2006.New observations on shatter cones in the Vredefort impact structure,South Africa,and evaluation of current hypotheses for shatter cone formation[J].Meteoritics&Planetary Science,41(11):1737-1759.
Wilk J and Kenkmann T.2016.Formation of shatter cones in MEMIN impact experiments[J].Meteoritics&Planetary Science,51(8):1477-1496.
黄钟瑾,沈修志,黄志诚,等.1991.下扬子区下古生物界找油气的靶区--太湖穹窿的发现和研究[J].南京大学学报(地球科学),3(1):13-22
秦伯强,胡行祥,陈伟民.2004.太湖水环境演化过程与机理[M].北京:科学出版社:2-313.
石火生.1992.机载雷达遥感应用试验研究(太湖地区雷达图像的地质构造分析)[M].北京:中国科学技术出版社:126-132.
沈自励.2003.火山喷爆与太湖成因[J].地球科学--中国地质大学学报,28:441-444.
孙顺才,黄漪平.1993.太湖[M].北京:海洋出版社:271.
陶奎元.2017.走进太湖西山三山旅游指南[J].南京:江苏凤凰科学技术出版社.
王尔康,朱政,张海样,等.1993.太湖蕨山岛发现震裂锥[J].科学通报,38:2265-2268.
王鹤年,谢志东,钱汉东.2009.太湖冲击坑溅射物的发现及其意义[J].高校地质学报,15(4):437-447.
王鹤年,钱汉东,黄钟瑾,等.2015.太湖西缘击变角砾岩的岩相学特征及其研究意义--太湖冲击成因又添新证据[J].南京大学学报(自然科学),51(1):87-98.
Baratoux D and Melosh H J.2003.The formation of shatter cones by shock wave interference during impacting[J].Earth and Planetary Science Letters,216(1):43-54.
Baratoux D and Reimold W U.2016.The current state of knowledge about shatter cones:Introduction to the special issue[J].Meteoritics&Planetary Science,51(8):1389-1434.
Chen M,Xiao W and Xie X.2010.Coesite and quartz characteristic of crystallization from shock-produced silica melt in the Xiuyan crater[J].Earth and Planetary Science Letters,397:306-314.
Dietz R S.1947.Meteorite impact suggested by the orientation of shatter cones at the Kentand,Indiana,disturbance[J].Science,105:42-76.
Dietz R S.1960.Meteorite impact suggested by shatter cones in rock[J].Science,131:1781-1784.
Dietz R S and Butler L.W.1964.Orientation of shatter cones at Sudbury Canada[J].Nature,204:280-281.
Elmar B and Martin S.2010.Steinheim suevite-A first report of melt-bearing impactites from the Steiheim Basin(SW Germany)[J].Meteoritics&Planetary Science,45(7):1093-1107.
Fackelman S P,Morrow J R,Koeberl C,et al.2008.Shatter cone and microscopic shock-alteration evidence for a post-Paleoproterozoic terrestrial impact structure near Santa Fe,New Mexico,USA[J].Earth and Planetary Science Letters,270(3):290-299.
Ferrière L and Osinski G R.2010.Shatter cones and associated shock-induced microdeformations in minerals-New investigations and implications for their formation[A].Lunar and Planetary Science Conference,41:1392.
Gay N C.1976.Spherules on shatter cone surfaces from the Vredefort structure,South Africa[J].Science,194:(4266):724-725.
Gay N C,Comins N R and Simposon C.1978.The Composition of spherules and other features on shatter cone surfaces from the Vredefort structure,South Africa[J].Earth Planet.Sci.Lett.,41:372-380.
Gibson H M and Spray J G.1998.Shock-induced melting and vaporization of shatter cones surfaces evidence from the Sudbury impact structure[J].Meteoritics&Planetary Science,33:329-336.
Guy-Bray J and Geological Staft.1966.Shatter cones at Sudbury[J].The Journal of Geology,74:243-245.
Kenkmann T,Hergarten S,Kuhn T,et al.2016.Formation of shatter cones by symmetric fracture bifurcation:Phenomenological modeling and validation[J].Meteoritics&Planetary Science,51(8):1519-1533.
McCall G J H.2009 Half a century of progress in research on terrestrial impact structures:A review[J].Earth-Science Reviews,92:99-116
Nicolaysen L O and Reimold U.1999.Vredefort shatter cones revisited[J].J.Geophys.Res(Solid Earth),104:4911-4930.
Oliveira G J G,Vasconcelos M A R,Crósta A P,et al.2014.Shatter cones and planar deformation features confirm Santa Marta in PiauíState,Brazil,as an impact structure[J].Meteoritics&Planetary Science,49(10):1915-1928.
Osinski G R and Spray J G.2001.Impact generated carbonate melts:evidence from the Haughton structure,Canada[J].Earth and Planetary Science letters,194:17-29.
Pittarello L,Nestola F,Viti C,et al.2015.Melting and cataclastic features in shatter cones in basalt from the Vista Alegre impact structure,Brazil[J].Meteoritics&Planetary Science,50(7):1228-1243.
Posges G.2016.First description of genuine shatter cones in upper Jurassic limestone clasts from the bunte breccia impactites of the Ries crater[J].Meteoritics&Planetary Science,51(S1):A521.
Qian H D,Wang H N and Xie Z D.2010.Discovery of impact breccia in the western of Taihu Lake in Jangsu province,China.New evidence for an impact origin[A].New York:73rd Annual Meteoritical Society Meeting,Jul 26-30.
Sagy A,Reches Z E and Fineberg J.2002.Dynamic fracture by large extraterrestrial impacts as the origin of shatter cones[J].Nature,418(6895):310-313.
Sharpton V L,Kennedy J W,Xu D Y,et al.1988.Searching for impact structure in China[J].EOS,69:391.
Wieland F and Reimold W U.2003.Field and laboratory studies on shatter cones in the Vredefort Dome,South Africa,and their genesis[J].Meteoritics and Planetary Science,S38:5016.
Wieland F,Reimold W U and Gibson R L.2006.New observations on shatter cones in the Vredefort impact structure,South Africa,and evaluation of current hypotheses for shatter cone formation[J].Meteoritics&Planetary Science,41(11):1737-1759.
Wilk J and Kenkmann T.2016.Formation of shatter cones in MEMIN impact experiments[J].Meteoritics&Planetary Science,51(8):1477-1496.