敦煌造山带岩石-构造组合特征及其构造环境
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摘要
敦煌地区位于北山造山带和祁连造山带之间,对其大地构造属性长期以来多存争议。对敦煌地区三危山—红柳峡一带的岩石-构造组合进行了研究,包括三危山—红柳峡北部地区和红柳峡南部地区2个构造单元。三危山—红柳峡北部地区,表现为变形强烈的变沉积岩以基质形式包裹不同类型、不同年龄的岩块和不同岩性的岩片相互堆叠,整体显示混杂带"blocksin-matrix"的岩石-构造组合特征。红柳峡南部地区,岩石的变质程度向南逐渐降低,北侧主要为云母石英片岩和长英质片麻岩组合,南端出露晚石炭世含煤岩系与碳酸盐岩沉积组合,可能形成于陆缘滨海环境,且被斜长角闪岩推覆体所覆盖;该区由北向南构造形式依次表现为倾向北的强剪切带→双冲构造→逆冲叠瓦扇,且变形强度呈逐渐减弱趋势,表现出前陆褶皱冲断带的岩石-构造组合特征。据此认为,敦煌地区自北向南存在三危山-红柳峡北部混杂带和红柳峡南部前陆褶皱冲断带两个大地构造单元,碰撞作用应发生于晚石炭世之后。
Located between the Beishan orogenic belt in the north and the Qilian orogenic belt in the south, the Dunhuang region possesses a crucial tectonic position. However, the geotectonic attribution of this region has long been controversial. In this paper,the authors investigated the characteristics of the rock-structure association of the Sanweishan-Hongliuxia area in the Dunhuang region,which includes the Sanweishan-Northern Hongliuxia Area(SNHA) and the Southern Hongliuxia Area(SHA). The observation in the SNHA shows that the intensively sheared metasedimentary rocks are well exposed as matrix which enclose the blocks with different lithological types and ages, and the structural slices with different lithological types are tectonically superimposed upon each other.This rock-structure association with the"blocks-in-matrix"fabric integrally shows the typical characteristics of mélange. In the SHA, the metamorphic grade of the exposed rocks decreases southward, and the northern part of the SHA is dominated by the micaquartz schist and felsic gneiss association, while the Late Carboniferous coal-bearing strata and carbonate succession regarded as being formed in a continental margin setting are exposed in the southern part of the SHA, which are overthrusted by the plagioclase amphibolite nappe. In the SHA, the structural forms from north to south are from the north dipping intense shear zone through the duplex to the imbricate thrust faults, accompanied by the southward decreasing deformation intensity. The characteristics of the rock-structure association of the SHA are consistent with those of the foreland fold-and-thrust belt. The authors thus hold that there exist two tectonic facies units, i.e., the Sanweishan-northern Hongliuxia mélange in the north and the Hongliuxia foreland fold-andthrust belt in the south of the Dunhuang region. The collision process within the Dunhuang orogenic belt should occur after the Late Carboniferous period.
Located between the Beishan orogenic belt in the north and the Qilian orogenic belt in the south, the Dunhuang region possesses a crucial tectonic position. However, the geotectonic attribution of this region has long been controversial. In this paper,the authors investigated the characteristics of the rock-structure association of the Sanweishan-Hongliuxia area in the Dunhuang region,which includes the Sanweishan-Northern Hongliuxia Area(SNHA) and the Southern Hongliuxia Area(SHA). The observation in the SNHA shows that the intensively sheared metasedimentary rocks are well exposed as matrix which enclose the blocks with different lithological types and ages, and the structural slices with different lithological types are tectonically superimposed upon each other.This rock-structure association with the"blocks-in-matrix"fabric integrally shows the typical characteristics of mélange. In the SHA, the metamorphic grade of the exposed rocks decreases southward, and the northern part of the SHA is dominated by the micaquartz schist and felsic gneiss association, while the Late Carboniferous coal-bearing strata and carbonate succession regarded as being formed in a continental margin setting are exposed in the southern part of the SHA, which are overthrusted by the plagioclase amphibolite nappe. In the SHA, the structural forms from north to south are from the north dipping intense shear zone through the duplex to the imbricate thrust faults, accompanied by the southward decreasing deformation intensity. The characteristics of the rock-structure association of the SHA are consistent with those of the foreland fold-and-thrust belt. The authors thus hold that there exist two tectonic facies units, i.e., the Sanweishan-northern Hongliuxia mélange in the north and the Hongliuxia foreland fold-andthrust belt in the south of the Dunhuang region. The collision process within the Dunhuang orogenic belt should occur after the Late Carboniferous period.
引文
[1]黄汲清,任纪舜,姜春发,等.中国大地构造及其演化[M].北京:科学出版社,1980:1-124.
[2]梅华林.甘肃敦煌太古宙英云闪长岩:单颗粒锆石U-Pb年龄和Nd同位素[J].前寒武纪研究进展,1998,21(2):41-45.
[3]李志琛.敦煌地块变质岩系时代新认识[J].中国区域地质,1994,2:131-134.
[4]Long X,Yuan C,Sun M,et al.New geochemical and combined zircon U-Pb and Lu-Hf isotopic data of orthogneisses in the northern Altyn Tagh,northern margin of the Tibetan plateau:Implication for Archean evolution of the Dunhuang Block and crust formation in NW China[J].Lithos,2014,200:418-431.
[5]Zhang J,Gong J,Yu S.c.1.85Ga HP granulite-facies metamorphism in the Dunhuang block of the Tarim Craton,NW China:evidence from U-Pb zircon dating of mafic granulites[J].Journal of the Geological Society,2012,169(5):511-514.
[6]Zhang J,Yu S,Gong J,et al.The latest Neoarchean–Paleoproterozoic evolution of the Dunhuang block,eastern Tarim craton,northwestern China:evidence from zircon U-Pb dating and Hf isotopic analyses[J].Precambrian Research,2013,226:21-42.
[7]赵燕,孙勇,朱涛,等.甘肃敦煌水峡口地区前寒武纪岩石的锆石U-Pb年龄,Hf同位素组成及其地质意义[J].岩石学报,2013,29(5):1698-1712.
[8]赵燕,敖文昊,王洪亮,等.敦煌地块发现~3.06 Ga花岗闪长质片麻岩[J].科学通报,2015,60(1):75-87.
[9]张振法,李超英,牛颖智.阿拉善-敦煌陆块的性质、范围及其构造作用和意义[J].内蒙古地质,1997,(2):1-14.
[10]孟繁聪,张建新,相振群,等.塔里木盆地东北缘敦煌群的形成和演化:锆石U-Pb年代学和Lu-Hf同位素证据[J].岩石学报,2011,(1):59-76.
[11]Zong K Q,Zhang Z M,He Z Y,et al.Early Palaeozoic high-pressure granulites from the Dunhuang block,northeastern Tarim Craton:constraints on continental collision in the southern Central Asian Orogenic Belt[J].Journal of Metamorphic Geology,2012,30(8):753-768.
[12]He Z,Zhang Z,Zong K,et al.Metamorphic P-T-t evolution of mafic HP granulites in the northeastern segment of the Tarim Craton(Dunhuang block):Evidence for early Paleozoic continental subduction[J].Lithos,2014,196:1-13.
[13]彭涛,王浩,陈泓旭,等.甘肃敦煌观音沟地区变质作用初步研究[J].岩石学报,2014,30(2):503-511.
[14]Zhao Y,Sun Y,Diwu C,et al.The Dunhuang block is a Paleozoic orogenic belt and part of the Central Asian Orogenic Belt(CAOB),NW China[J].Gondwana Research,2016,30:207-223.
[15]Lu S,Li H,Zhang C,et al.Geological and geochronological evidence for the Precambrian evolution of the Tarim Craton and surrounding continental fragments[J].Precambrian Research,2008,160(1):94-107.
[16]梅华林,左国朝.甘肃敦煌-北山早前寒武纪岩石组合-构造初步框架[J].前寒武纪研究进展,1997,20(4):47-54.
[17]于海峰,梅华林,李铨,等.甘肃敦煌地区太古宙孔慈岩系特征[J].前寒武纪研究进展,1998,21(1):19-25.
[18]Zong K,Liu Y,Zhang Z,et al.The generation and evolution of Archean continental crust in the Dunhuang block,northeastern Tarim craton,northwestern China[J].Precambrian Research,2013,235:251-263.
[19]张志诚,郭召杰,邹冠群,等.甘肃敦煌党河水库TTG地球化学特征,锆石SHRIMP U-Pb定年及其构造意义[J].岩石学报,2009,25(3):495-505.
[20]赵燕,朱涛,王洪亮,等.敦煌三危山地区晚泥盆世斜长花岗岩的发现及其地质意义[J].岩石学报,2015,31(7):1855-1869.
[21]甘肃省地质矿产局.甘肃省区域地质志[M].北京,地质出版社,1989.
[22]HsüK J.Principles of melanges and their bearing on the Franciscan-Knoxville paradox[J].Geological Society of America Bulletin,1968,79(8):1063-1074.
[23]李继亮.碰撞造山带大地构造相[C]//现代地质学研究文集(上).南京:南京大学出版社,1992.
[24]Wang Z M,Han C M,Su B X,et al.The meta sedimentary rocks from the eastern margin of the Tarim Craton:petrology,geochemistry,zircon U–Pb dating,Hf isotopes and tectonic implications[J].Lithos,2013,179:120-136.
[25]王忠梅,肖文交,韩春明,等.甘肃敦煌红柳峡地区石榴石斜长角闪岩的变质特征,锆石U-Pb年龄及地质意义[J].岩石学报,2013,29(5):1685-1697.
[26]李继亮.全球大地构造相刍议[J].地质通报,2009,28(10):1375-1381.
[27]Wang Z M,Han C M,Xiao W J,et al.Petrology and geochronology of Paleoproterozoic garnet-bearing amphibolites from the Dunhuang Block,Eastern Tarim Craton[J].Precambrian Research,2014,255:163-180.
[28]李继亮,孙枢,郝杰,等.碰撞造山带的碰撞事件时限的确定[J].岩石学报,1999,15(2):315-320.
[29]Xiao W J,Mao Q G,Windley B F,et al.Paleozoic multiple accretionary and collisional processes of the Beishan orogenic collage[J].American Journal of Science,2010,310(10):1553-1594.
[30]Liu X,Chen B,Jahn B,et al.Early Paleozoic(ca.465Ma)eclogites from Beishan(NW China)and their bearing on the tectonic evolution of the southern Central Asian Orogenic Belt[J].Journal of Asian Earth Sciences,2011,42(4):715-731.
[31]Qu J F,Xiao W J,Windley B F,et al.Ordovician eclogites from the Chinese Beishan:implications for the tectonic evolution of the southern Altaids[J].Journal of Metamorphic Geology,2011,29(8):803-820.
[32]毛启贵,肖文交,韩春明,等.北山柳园地区中志留世埃达克质花岗岩类及其地质意义[J].岩石学报,2010,(2):584-596.
[33]吕新彪,朱江,曹晓峰,等.北山南部柳园地区古生代—早中生代大陆地壳增生过程中的岩浆活动与成矿效应[J].地质科技情报,2012,(5):119-127.
[34]张文,吴泰然,贺元凯,等.甘肃北山西涧泉子富碱高钾花岗岩体的锆石LA-ICP-MS定年及其构造意义[J].岩石矿物学杂志,2010,29(6):719-731.
[35]张文,冯继承,郑荣国,等.甘肃北山音凹峡南花岗岩体的锆石LA-ICP MS定年及其构造意义[J].岩石学报,2011,27(6):1649-1661.
[36]冯继承,张文,吴泰然,等.甘肃北山桥湾北花岗岩体的年代学,地球化学及其地质意义[J].北京大学学报:自然科学版,2012,48(1):61-70.
[37]姜洪颖,贺振宇,宗克清,等.北山造山带南缘北山杂岩的锆石U-Pb定年和Hf同位素研究[J].岩石学报,2013,29(11):3949-3967.
[2]梅华林.甘肃敦煌太古宙英云闪长岩:单颗粒锆石U-Pb年龄和Nd同位素[J].前寒武纪研究进展,1998,21(2):41-45.
[3]李志琛.敦煌地块变质岩系时代新认识[J].中国区域地质,1994,2:131-134.
[4]Long X,Yuan C,Sun M,et al.New geochemical and combined zircon U-Pb and Lu-Hf isotopic data of orthogneisses in the northern Altyn Tagh,northern margin of the Tibetan plateau:Implication for Archean evolution of the Dunhuang Block and crust formation in NW China[J].Lithos,2014,200:418-431.
[5]Zhang J,Gong J,Yu S.c.1.85Ga HP granulite-facies metamorphism in the Dunhuang block of the Tarim Craton,NW China:evidence from U-Pb zircon dating of mafic granulites[J].Journal of the Geological Society,2012,169(5):511-514.
[6]Zhang J,Yu S,Gong J,et al.The latest Neoarchean–Paleoproterozoic evolution of the Dunhuang block,eastern Tarim craton,northwestern China:evidence from zircon U-Pb dating and Hf isotopic analyses[J].Precambrian Research,2013,226:21-42.
[7]赵燕,孙勇,朱涛,等.甘肃敦煌水峡口地区前寒武纪岩石的锆石U-Pb年龄,Hf同位素组成及其地质意义[J].岩石学报,2013,29(5):1698-1712.
[8]赵燕,敖文昊,王洪亮,等.敦煌地块发现~3.06 Ga花岗闪长质片麻岩[J].科学通报,2015,60(1):75-87.
[9]张振法,李超英,牛颖智.阿拉善-敦煌陆块的性质、范围及其构造作用和意义[J].内蒙古地质,1997,(2):1-14.
[10]孟繁聪,张建新,相振群,等.塔里木盆地东北缘敦煌群的形成和演化:锆石U-Pb年代学和Lu-Hf同位素证据[J].岩石学报,2011,(1):59-76.
[11]Zong K Q,Zhang Z M,He Z Y,et al.Early Palaeozoic high-pressure granulites from the Dunhuang block,northeastern Tarim Craton:constraints on continental collision in the southern Central Asian Orogenic Belt[J].Journal of Metamorphic Geology,2012,30(8):753-768.
[12]He Z,Zhang Z,Zong K,et al.Metamorphic P-T-t evolution of mafic HP granulites in the northeastern segment of the Tarim Craton(Dunhuang block):Evidence for early Paleozoic continental subduction[J].Lithos,2014,196:1-13.
[13]彭涛,王浩,陈泓旭,等.甘肃敦煌观音沟地区变质作用初步研究[J].岩石学报,2014,30(2):503-511.
[14]Zhao Y,Sun Y,Diwu C,et al.The Dunhuang block is a Paleozoic orogenic belt and part of the Central Asian Orogenic Belt(CAOB),NW China[J].Gondwana Research,2016,30:207-223.
[15]Lu S,Li H,Zhang C,et al.Geological and geochronological evidence for the Precambrian evolution of the Tarim Craton and surrounding continental fragments[J].Precambrian Research,2008,160(1):94-107.
[16]梅华林,左国朝.甘肃敦煌-北山早前寒武纪岩石组合-构造初步框架[J].前寒武纪研究进展,1997,20(4):47-54.
[17]于海峰,梅华林,李铨,等.甘肃敦煌地区太古宙孔慈岩系特征[J].前寒武纪研究进展,1998,21(1):19-25.
[18]Zong K,Liu Y,Zhang Z,et al.The generation and evolution of Archean continental crust in the Dunhuang block,northeastern Tarim craton,northwestern China[J].Precambrian Research,2013,235:251-263.
[19]张志诚,郭召杰,邹冠群,等.甘肃敦煌党河水库TTG地球化学特征,锆石SHRIMP U-Pb定年及其构造意义[J].岩石学报,2009,25(3):495-505.
[20]赵燕,朱涛,王洪亮,等.敦煌三危山地区晚泥盆世斜长花岗岩的发现及其地质意义[J].岩石学报,2015,31(7):1855-1869.
[21]甘肃省地质矿产局.甘肃省区域地质志[M].北京,地质出版社,1989.
[22]HsüK J.Principles of melanges and their bearing on the Franciscan-Knoxville paradox[J].Geological Society of America Bulletin,1968,79(8):1063-1074.
[23]李继亮.碰撞造山带大地构造相[C]//现代地质学研究文集(上).南京:南京大学出版社,1992.
[24]Wang Z M,Han C M,Su B X,et al.The meta sedimentary rocks from the eastern margin of the Tarim Craton:petrology,geochemistry,zircon U–Pb dating,Hf isotopes and tectonic implications[J].Lithos,2013,179:120-136.
[25]王忠梅,肖文交,韩春明,等.甘肃敦煌红柳峡地区石榴石斜长角闪岩的变质特征,锆石U-Pb年龄及地质意义[J].岩石学报,2013,29(5):1685-1697.
[26]李继亮.全球大地构造相刍议[J].地质通报,2009,28(10):1375-1381.
[27]Wang Z M,Han C M,Xiao W J,et al.Petrology and geochronology of Paleoproterozoic garnet-bearing amphibolites from the Dunhuang Block,Eastern Tarim Craton[J].Precambrian Research,2014,255:163-180.
[28]李继亮,孙枢,郝杰,等.碰撞造山带的碰撞事件时限的确定[J].岩石学报,1999,15(2):315-320.
[29]Xiao W J,Mao Q G,Windley B F,et al.Paleozoic multiple accretionary and collisional processes of the Beishan orogenic collage[J].American Journal of Science,2010,310(10):1553-1594.
[30]Liu X,Chen B,Jahn B,et al.Early Paleozoic(ca.465Ma)eclogites from Beishan(NW China)and their bearing on the tectonic evolution of the southern Central Asian Orogenic Belt[J].Journal of Asian Earth Sciences,2011,42(4):715-731.
[31]Qu J F,Xiao W J,Windley B F,et al.Ordovician eclogites from the Chinese Beishan:implications for the tectonic evolution of the southern Altaids[J].Journal of Metamorphic Geology,2011,29(8):803-820.
[32]毛启贵,肖文交,韩春明,等.北山柳园地区中志留世埃达克质花岗岩类及其地质意义[J].岩石学报,2010,(2):584-596.
[33]吕新彪,朱江,曹晓峰,等.北山南部柳园地区古生代—早中生代大陆地壳增生过程中的岩浆活动与成矿效应[J].地质科技情报,2012,(5):119-127.
[34]张文,吴泰然,贺元凯,等.甘肃北山西涧泉子富碱高钾花岗岩体的锆石LA-ICP-MS定年及其构造意义[J].岩石矿物学杂志,2010,29(6):719-731.
[35]张文,冯继承,郑荣国,等.甘肃北山音凹峡南花岗岩体的锆石LA-ICP MS定年及其构造意义[J].岩石学报,2011,27(6):1649-1661.
[36]冯继承,张文,吴泰然,等.甘肃北山桥湾北花岗岩体的年代学,地球化学及其地质意义[J].北京大学学报:自然科学版,2012,48(1):61-70.
[37]姜洪颖,贺振宇,宗克清,等.北山造山带南缘北山杂岩的锆石U-Pb定年和Hf同位素研究[J].岩石学报,2013,29(11):3949-3967.