中下部地壳拆离断层带演化中的褶皱作用:以辽南变质核杂岩为例
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摘要
作为变质核杂岩构造的重要组成部分,拆离断层带内广泛发育的褶皱构造与其寄主岩石一样记录了中下地壳拆离作用过程。选取辽南变质核杂岩金州拆离断层带内褶皱构造作为研究对象,基于叶理与褶皱构造关系分析,划分了褶皱期次与阶段性;通过形态组构分析、结晶学组构分析及石英古温度计等技术方法的应用,初步分析了拆离断层内褶皱的形成机制,为辽南地区拆离作用过程提供约束。根据褶皱形成与拆离作用的时间关系,将拆离带内褶皱分为拆离前褶皱、拆离同期褶皱和拆离后褶皱;拆离作用同期的褶皱按时间早晚分为早期(a1)阶段、中期(a2)阶段、晚期(a3)阶段。不同阶段褶皱的野外形态、叶理与褶皱关系等方面的差异,以及形态组构与结晶学组构的特征,为判断和恢复褶皱的形成机制提供了佐证,揭示出拆离断层带褶皱是在纵弯-压扁和顺层流变的共同作用下递进剪切变形的产物。在拆离作用过程中,a1阶段和a2阶段褶皱以纵弯、压扁褶皱作用为主,a3阶段褶皱以弯滑作用为主。褶皱作用记录了拆离断层一定温度范围内(主要集中在380～500℃)的变形特征,拆离作用从早期到晚期的演化整体处于相对稳定的应变状态下。对金州拆离断层带而言,在区域NW-SE向伸展过程中,还伴随着NE-SW向微弱的收缩。
Many fold structures are well-preserved in mid-lower crustal detachment fault zones owing to progressive shearing along the fault zone during exhumation of metamorphic core complexes.These fold structures,like host rocks,bear important information on the evolution of the detachment fault zone.In this paper,we studied the various fold structures from the Jinzhou detached fault zone of the Liaonan metamorphic core complex.Based on the relationship between mylonitic foliation and fold,the folds are subdivided into pre-,syn-,and post-shearing folds.The syn-shearing folds can be further grouped into early(a1),mid(a2)and late(a3)syn-shearing folds.The transition from early to late syn-shearing is ascribed to progressive shearing during the detachment faulting.By means of morphological and crystallographic fabric analysis and quartz paleothermometry,we performed preliminary examination on the formation mechanism of folds along the detachment fault to provide constraints to the detachment faulting process in southern Liaoning.Our study shows that differences in macroscopic characteristics or relationship between foliation and folds of different stages,as well as morphological and crystallographic fabric characteristics of quartz grains in the folded rocks,can provide corroborative evidence for determining and restoring formation mechanism of folds.We suggest that the folds from the detachment fault zone result from progressive shearing under the combined effects of buckling and rheological properties of folded layers.During progressive shearing,a1 and a2 stage folds are dominated by buckling,while a3 stage fold is attributed primarily to flexural slip.Folding mainly occurred at a temperature range of 500 to 380 ℃.The detachment fault zone evolution maintained a relatively steady strain state overall from the early to late stage,while a weak contraction occurred in the NE-SW direction during the regional NW-SE extension in the Jinzhou detachment fault zone.
Many fold structures are well-preserved in mid-lower crustal detachment fault zones owing to progressive shearing along the fault zone during exhumation of metamorphic core complexes.These fold structures,like host rocks,bear important information on the evolution of the detachment fault zone.In this paper,we studied the various fold structures from the Jinzhou detached fault zone of the Liaonan metamorphic core complex.Based on the relationship between mylonitic foliation and fold,the folds are subdivided into pre-,syn-,and post-shearing folds.The syn-shearing folds can be further grouped into early(a1),mid(a2)and late(a3)syn-shearing folds.The transition from early to late syn-shearing is ascribed to progressive shearing during the detachment faulting.By means of morphological and crystallographic fabric analysis and quartz paleothermometry,we performed preliminary examination on the formation mechanism of folds along the detachment fault to provide constraints to the detachment faulting process in southern Liaoning.Our study shows that differences in macroscopic characteristics or relationship between foliation and folds of different stages,as well as morphological and crystallographic fabric characteristics of quartz grains in the folded rocks,can provide corroborative evidence for determining and restoring formation mechanism of folds.We suggest that the folds from the detachment fault zone result from progressive shearing under the combined effects of buckling and rheological properties of folded layers.During progressive shearing,a1 and a2 stage folds are dominated by buckling,while a3 stage fold is attributed primarily to flexural slip.Folding mainly occurred at a temperature range of 500 to 380 ℃.The detachment fault zone evolution maintained a relatively steady strain state overall from the early to late stage,while a weak contraction occurred in the NE-SW direction during the regional NW-SE extension in the Jinzhou detachment fault zone.
引文
[1]BERTHED,BRUN J P.Evolution of folds during progressive shear in the South Armorican shear zone,France[J].Journal of Structural Geology,1980,2(1):127-133.
[2]RAMSAY J G,Huber M I.Folds and fractures[M].London:Academic Press,1987.
[3]STUNITZ H.Folding and shear deformation in quartzites,inferred from crystallographic preferred orientation and shape fabrics[J].Journal of Structural Geology,1991,13(1):71-86.
[4]ABDUL M,SAYANDEEP B,DUTTAGUPTA C,et al.Progressive deformation across a ductile shear zone:an example from the Singhbhum Shear Zone,eastern India[J].International Geology Review,2012,54(3):290-301.
[5]GROSE L,LAURENT G,AILLERES L,et al.Structural data constraints for implicit modeling of folds[J].Journal of Structural Geology,2017,104:80-92.
[6]ZULAUF G,ZULAUF J,MAUL H.Quantification of the geometrical parameters of non-cylindrical folds[J].Journal of Structural Geology,2017,100:120-129.
[7]TREPMANN C A,STOCKHERT B.Microfabric of folded quartz veins in metagreywackes:dislocation creep and subgrain rotation at high stress[J].Journal of Metamorphic Geology,2009,27(8):555-570.
[8]WANG Z X,ZHANG J,LI T,et al.Structural traps in detachment folds:a case study from the‘Comb-and Troughlike’deformation zones,East Sichuan,China[J].Acta Geologica Sinica(English Edition),2012,86(4):828-841.
[9]ADAMUSZEK M,D BROWSKI M.Sheath fold development in monoclinic shear zones[J].Terra Nova,2017,29(6):356-362.
[10]DERIKVAND B,ALAVI S A,FARD I A,et al.Folding style of the Dezful embayment of Zagros belt:signatures of detachment horizons,deep-rooted faulting and syn-deformation deposition[J].Marine&Petroleum Geology,2018,91:501-518.
[11]RAMSAY J.Folding and fracturing of rock[M].Black lick:McGraw-Hill Companies,1968.
[12]傅昭仁,蔡学林.变质岩区构造地质学[M].北京:地质出版社,1996.
[13]LISTER G S,DAVIS G A.The origin of metamorphic core complexes and detachment faults formed during tertiary continental extension in the Northern Colorado River Region,USA[J].Journal of Structural Geology,1989,11(1):65-94.
[14]DAVIS G A,郑亚东.变质核杂岩的定义、类型及构造背景[J].地质通报,2002,21:185-192.
[15]楼法生,舒良树,王德滋.变质核杂岩研究进展[J].高校地质学报,2005,11(1):67-76.
[16]DAVIS G H,CONEY P J.Geologic development of the Cordilleran metamorphic core complexes[J].Geology,1979,7(3):120-124.
[17]CONEY P J.Cordilleran metamorphic core complexes:an overview[J].Geological Society of America Memoirs,1980,153:7-31.
[18]纪沫,胡玲,刘俊来,等.辽南变质核杂岩主拆离断层的波瓦状构造(corrugation)及其成因[J].地质科学,2008,43(1):12-22.
[19]LIU J,DAVIS G A,LIN Z,et al.The Liaonan metamorphic core complex,Southeastern Liaoning Province,North China:a likely contributor to Cretaceous rotation of Eastern Liaoning,Korea and contiguous areas[J].Tectonophysics,2005,407(1):65-80.
[20]杨进辉,吴福元.华北东部三叠纪岩浆作用与克拉通破坏[J].中国科学:地球科学,2009(7):910-921.
[21]许志琴,李海兵,王宗秀,等.辽南地壳的收缩作用及伸展作用[J].地质论评,1991,37(3):193-202.
[22]YANG J H,WU F Y,CHUNG S L,et al.Rapid exhumation and cooling of the Liaonan metamorphic core complex:inferences from40 Ar/39 Ar thermochronology and implications for Late Mesozoic extension in the eastern North China Craton[J].Geological Society of America Bulletin,2007,119(11/12):1405-1414.
[23]STIPP M,STUèNITZ H,HEILBRONNER R,et al.The eastern Tonale fault zone:a‘natural laboratory’for crystal plastic deformation of quartz over a temperature range from250to 700℃[J].Journal of Structural Geology,2002,24(12):1861-1884.
[24]PASSCHIER B,TROUW R A J.Microtectonics[M].Berlin,Heidelberg:Springer,2005.
[25]ZULAUF G.Structural style,deformation mechanisms and paleodifferential stress along an exposed crustal section:constraints on the rheology of quartzofeldspathic rocks at supra-and infrastructural levels(Bohemian Massif)[J].Tectonophysics,2001,332(1/2):211-237.
[26]FALEIROS F M,CAMPANHA G A D C,BELLO R M D S,et al.Quartz recrystallization regimes,c-axis texture transitions and fluid inclusion reequilibration in a prograde greenschist to amphibolite facies mylonite zone(Ribeira Shear Zone,SE Brazil)[J].Tectonophysics,2010,485(1):193-214.
[27]ZHENG Y,HAN X,GAO X,et al.Enrichment of iron ores by folding in the BIF-hosted deposit:a case study from the Archean Qian'an iron deposit,North China Craton[J].Geological Journal,2017,53(2):617-628.
[28]PANOZZO R H.Two-dimensional strain from the orientation of lines in a plane[J].Journal of Structural Geology,1984,6(1):215-221.
[29]PANOZZO R H.Two-dimensional analysis of shape-fabric using projections of digitized lines in a plane[J].Tectonophysics,1983,95(3):279-294.
[30]BURG J P.Quartz shape fabric variations and c-axis fabrics in a ribbon-mylonite:arguments for an oscillating foliation[J].Journal of Structural Geology,1986,8(2):123-131.
[31]LAUNEAU P.Mise enévidence desécoulements magmatiques par analysed images 2-D des distributions 3-D d'Orientations Préférentielles de Formes[J].Bulletin de la Societe Geologique de France,2004,175:331-350.
[32]DUYSTER J.DIAna V3manual[M].Witten:Universitatsstr,1991:105.
[33]刘俊来,曹淑云,邹运鑫,等.岩石电子背散射衍射(EBSD)组构分析及应用[J].地质通报,2008,27(10):1638-1645.
[34]夏浩然,刘俊来.石英结晶学优选与应用[J].地质通报,2011,30(1):58-70.
[35]TROUW R A J,PASSCHIER C W,WIERSMA D J.Atlas of mylonites and related microstructures[M].Berlin,Heidelberg:Springer,2009:47-72.
[36]GARCIA C A.C-axis and shape fabrics in quartz mylonites of Cap de Creus(Spain):their properties and development[M].Catalonia:Proefschrift,1983:130.
[37]甘浩男.中上地壳岩石流变与拆离断层作用[D].北京:中国地质大学(北京),2013:22-25.
[38]JONES K A.A petrofabric method of fold analysis[J].American Journal of Science,1959,257(2):138-143.
[39]PRICE G P.Application of the photometric method to fabric mapping around folds[J].Tectonophysics,1981,78(1):85-100.
[40]HONGN F D,HIPPERTT J F.Quartz crystallographic and morphologic fabrics during folding/transposition in mylonites[J].Journal of Structural Geology,2001,23(1):81-92.
[41]GRUJIC D,MANCKTELOW N S.Folds with axes parallel to the extension direction:an experimental study[J].Journal of Structural Geology,1995,17(2):279-285.
[2]RAMSAY J G,Huber M I.Folds and fractures[M].London:Academic Press,1987.
[3]STUNITZ H.Folding and shear deformation in quartzites,inferred from crystallographic preferred orientation and shape fabrics[J].Journal of Structural Geology,1991,13(1):71-86.
[4]ABDUL M,SAYANDEEP B,DUTTAGUPTA C,et al.Progressive deformation across a ductile shear zone:an example from the Singhbhum Shear Zone,eastern India[J].International Geology Review,2012,54(3):290-301.
[5]GROSE L,LAURENT G,AILLERES L,et al.Structural data constraints for implicit modeling of folds[J].Journal of Structural Geology,2017,104:80-92.
[6]ZULAUF G,ZULAUF J,MAUL H.Quantification of the geometrical parameters of non-cylindrical folds[J].Journal of Structural Geology,2017,100:120-129.
[7]TREPMANN C A,STOCKHERT B.Microfabric of folded quartz veins in metagreywackes:dislocation creep and subgrain rotation at high stress[J].Journal of Metamorphic Geology,2009,27(8):555-570.
[8]WANG Z X,ZHANG J,LI T,et al.Structural traps in detachment folds:a case study from the‘Comb-and Troughlike’deformation zones,East Sichuan,China[J].Acta Geologica Sinica(English Edition),2012,86(4):828-841.
[9]ADAMUSZEK M,D BROWSKI M.Sheath fold development in monoclinic shear zones[J].Terra Nova,2017,29(6):356-362.
[10]DERIKVAND B,ALAVI S A,FARD I A,et al.Folding style of the Dezful embayment of Zagros belt:signatures of detachment horizons,deep-rooted faulting and syn-deformation deposition[J].Marine&Petroleum Geology,2018,91:501-518.
[11]RAMSAY J.Folding and fracturing of rock[M].Black lick:McGraw-Hill Companies,1968.
[12]傅昭仁,蔡学林.变质岩区构造地质学[M].北京:地质出版社,1996.
[13]LISTER G S,DAVIS G A.The origin of metamorphic core complexes and detachment faults formed during tertiary continental extension in the Northern Colorado River Region,USA[J].Journal of Structural Geology,1989,11(1):65-94.
[14]DAVIS G A,郑亚东.变质核杂岩的定义、类型及构造背景[J].地质通报,2002,21:185-192.
[15]楼法生,舒良树,王德滋.变质核杂岩研究进展[J].高校地质学报,2005,11(1):67-76.
[16]DAVIS G H,CONEY P J.Geologic development of the Cordilleran metamorphic core complexes[J].Geology,1979,7(3):120-124.
[17]CONEY P J.Cordilleran metamorphic core complexes:an overview[J].Geological Society of America Memoirs,1980,153:7-31.
[18]纪沫,胡玲,刘俊来,等.辽南变质核杂岩主拆离断层的波瓦状构造(corrugation)及其成因[J].地质科学,2008,43(1):12-22.
[19]LIU J,DAVIS G A,LIN Z,et al.The Liaonan metamorphic core complex,Southeastern Liaoning Province,North China:a likely contributor to Cretaceous rotation of Eastern Liaoning,Korea and contiguous areas[J].Tectonophysics,2005,407(1):65-80.
[20]杨进辉,吴福元.华北东部三叠纪岩浆作用与克拉通破坏[J].中国科学:地球科学,2009(7):910-921.
[21]许志琴,李海兵,王宗秀,等.辽南地壳的收缩作用及伸展作用[J].地质论评,1991,37(3):193-202.
[22]YANG J H,WU F Y,CHUNG S L,et al.Rapid exhumation and cooling of the Liaonan metamorphic core complex:inferences from40 Ar/39 Ar thermochronology and implications for Late Mesozoic extension in the eastern North China Craton[J].Geological Society of America Bulletin,2007,119(11/12):1405-1414.
[23]STIPP M,STUèNITZ H,HEILBRONNER R,et al.The eastern Tonale fault zone:a‘natural laboratory’for crystal plastic deformation of quartz over a temperature range from250to 700℃[J].Journal of Structural Geology,2002,24(12):1861-1884.
[24]PASSCHIER B,TROUW R A J.Microtectonics[M].Berlin,Heidelberg:Springer,2005.
[25]ZULAUF G.Structural style,deformation mechanisms and paleodifferential stress along an exposed crustal section:constraints on the rheology of quartzofeldspathic rocks at supra-and infrastructural levels(Bohemian Massif)[J].Tectonophysics,2001,332(1/2):211-237.
[26]FALEIROS F M,CAMPANHA G A D C,BELLO R M D S,et al.Quartz recrystallization regimes,c-axis texture transitions and fluid inclusion reequilibration in a prograde greenschist to amphibolite facies mylonite zone(Ribeira Shear Zone,SE Brazil)[J].Tectonophysics,2010,485(1):193-214.
[27]ZHENG Y,HAN X,GAO X,et al.Enrichment of iron ores by folding in the BIF-hosted deposit:a case study from the Archean Qian'an iron deposit,North China Craton[J].Geological Journal,2017,53(2):617-628.
[28]PANOZZO R H.Two-dimensional strain from the orientation of lines in a plane[J].Journal of Structural Geology,1984,6(1):215-221.
[29]PANOZZO R H.Two-dimensional analysis of shape-fabric using projections of digitized lines in a plane[J].Tectonophysics,1983,95(3):279-294.
[30]BURG J P.Quartz shape fabric variations and c-axis fabrics in a ribbon-mylonite:arguments for an oscillating foliation[J].Journal of Structural Geology,1986,8(2):123-131.
[31]LAUNEAU P.Mise enévidence desécoulements magmatiques par analysed images 2-D des distributions 3-D d'Orientations Préférentielles de Formes[J].Bulletin de la Societe Geologique de France,2004,175:331-350.
[32]DUYSTER J.DIAna V3manual[M].Witten:Universitatsstr,1991:105.
[33]刘俊来,曹淑云,邹运鑫,等.岩石电子背散射衍射(EBSD)组构分析及应用[J].地质通报,2008,27(10):1638-1645.
[34]夏浩然,刘俊来.石英结晶学优选与应用[J].地质通报,2011,30(1):58-70.
[35]TROUW R A J,PASSCHIER C W,WIERSMA D J.Atlas of mylonites and related microstructures[M].Berlin,Heidelberg:Springer,2009:47-72.
[36]GARCIA C A.C-axis and shape fabrics in quartz mylonites of Cap de Creus(Spain):their properties and development[M].Catalonia:Proefschrift,1983:130.
[37]甘浩男.中上地壳岩石流变与拆离断层作用[D].北京:中国地质大学(北京),2013:22-25.
[38]JONES K A.A petrofabric method of fold analysis[J].American Journal of Science,1959,257(2):138-143.
[39]PRICE G P.Application of the photometric method to fabric mapping around folds[J].Tectonophysics,1981,78(1):85-100.
[40]HONGN F D,HIPPERTT J F.Quartz crystallographic and morphologic fabrics during folding/transposition in mylonites[J].Journal of Structural Geology,2001,23(1):81-92.
[41]GRUJIC D,MANCKTELOW N S.Folds with axes parallel to the extension direction:an experimental study[J].Journal of Structural Geology,1995,17(2):279-285.
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