柯坪塔格推覆构造几何学、运动学及其构造演化
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摘要
大量野外构造地质调查和深部构造解释表明柯坪塔格推覆构造由多组倒转复式背斜、复式箱状背斜构成的推覆体及其前缘逆冲断裂组成 ,由寒武系—第四系组成的推覆体由北向南逆—斜冲 ,平面上构成向南凸出的弧形推覆构造 ;普昌断裂由各不相连的逆冲斜冲断裂段组成 ,而不是完整的一条走滑断层 ,各推覆体前缘逆冲断裂与各推覆体的普昌断裂段共同构成统一的前缘逆冲斜冲逆冲断裂和推覆构造系统 ;普昌断裂段以西的推覆体具有向东抬升、向西倾覆的鼻状构造特征 ,普昌断裂段以东的推覆体具有向西抬升、向东倾覆的鼻状构造特征 ,普昌基底隆起带是巴楚隆起隐伏在柯坪塔格推覆构造之下的部分。各推覆体前缘断裂在深部均归并于统一的寒武系底部的滑脱面 ,其南浅北深 ,东浅西深 (普昌隆起带以西 )或西浅东深 (普昌隆起带以东 ) (6 10km ) ,埋深较大区发育多组滑脱面。柯坪塔格推覆构造的形成时期为晚第四纪 ,为现今活动的推覆构造系统。文中认为各推覆体向南西的倾覆端基底滑脱面和中新生界内部的滑脱面没有贯通 ,是未来 6级以上地震的发震构造部位。
In this paper we have discussed the stratigraphy, geometry, kinematics and tectonic evolution of Kepingtage thrust system based on a lot of outcrop geological surveys and comprehensive interpretation with seismic profiles, MT profiles and gravity data. Kepingtage thrust system consists of many arcuate thrust nappes thrusting-oblique thrusting from north to south with inversed multi-anticlines and their front thrust faults, which were formed by Cambrian—Quaternary sedimentary rocks. It is discovered that the Puchang fault was formed by unconnected thrusting-oblique thrusting segments divided by nappes rather than an integrate strike-slip fault. The front thrust faults of each nappe combined with the related segments of Puchang fault form the thrusting-oblique thrusting front faults of the nappes and the whole thrust system. The nappes to the west of Puchang basement uplift show the nose structures dipping to the west, and the nappes to the east of Puchang basement uplift show the nose structures dipping to the east. Puchang basement uplift is a part of Bachu uplift extending below the Kepingtage thrust system. The front faults of the nappes form an integrate detachment surface in the deep along the bottom of Cambrian with the shallower depth in the southeast and deeper depth in the northwest (for the region to the west of Puchang basement uplift) and with the shallower depth in the west and deeper depth in the east (for the region to the east of Puchang basement uplift)(6~10 km). Kepingtage thrust system was formed in Late Quaternary and is still active at present. We consider that the basement detachment and the inner Mesozoic—Cenozoic detachment faults could not have formed some integrate fault surfaces in the dipping end of nappes, so the earthquakes with the magnitude larger than 6 will occur in the near future in these area.
In this paper we have discussed the stratigraphy, geometry, kinematics and tectonic evolution of Kepingtage thrust system based on a lot of outcrop geological surveys and comprehensive interpretation with seismic profiles, MT profiles and gravity data. Kepingtage thrust system consists of many arcuate thrust nappes thrusting-oblique thrusting from north to south with inversed multi-anticlines and their front thrust faults, which were formed by Cambrian—Quaternary sedimentary rocks. It is discovered that the Puchang fault was formed by unconnected thrusting-oblique thrusting segments divided by nappes rather than an integrate strike-slip fault. The front thrust faults of each nappe combined with the related segments of Puchang fault form the thrusting-oblique thrusting front faults of the nappes and the whole thrust system. The nappes to the west of Puchang basement uplift show the nose structures dipping to the west, and the nappes to the east of Puchang basement uplift show the nose structures dipping to the east. Puchang basement uplift is a part of Bachu uplift extending below the Kepingtage thrust system. The front faults of the nappes form an integrate detachment surface in the deep along the bottom of Cambrian with the shallower depth in the southeast and deeper depth in the northwest (for the region to the west of Puchang basement uplift) and with the shallower depth in the west and deeper depth in the east (for the region to the east of Puchang basement uplift)(6~10 km). Kepingtage thrust system was formed in Late Quaternary and is still active at present. We consider that the basement detachment and the inner Mesozoic—Cenozoic detachment faults could not have formed some integrate fault surfaces in the dipping end of nappes, so the earthquakes with the magnitude larger than 6 will occur in the near future in these area.
引文
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[16] JIADong,LUHuafu,CAIDongs
[2] QUGuosheng,CHENJie,XUJiandong,etal.Back thrustingsystemsofAtushiBapanshuimoinTarimBasin[J].SeismologyandGeology,2001,23(1):114(inChinese). [曲国胜,陈杰,许建东,等.阿图什—八盘水磨塔里木盆地反冲构造系统研究[J].地震地质,2001,23(1):114.]
[3] CHENJie,DINGGuoyu,BURBANKDW ,etal.LateCenozoictectonicsandseismicityinthesouthwesternTianshan,China[J].EarthquakeResearchinChina,2001,17(2):134155(inChinese). [陈杰,丁国瑜,BURBANKDW ,等.中国西南天山山前的晚新生代构造与地震活动[J].中国地震,2001,17(2):134155.]
[4] QUGuosheng,CANEROTJ,WANGZongqi,etal.Arctec tonicsinorogenicbelts[J].GeologicaSinica,1996,31(4):295307(inChinese). [曲国胜,CANEROTJ ,王宗起,等造山带弧形构造[J].地质科学,1996,31(4):295307.]
[5] QUGuosheng,CANEROTJ .ComparativestudiesofCenozoicandMesozoictectonicsandevolutionbetweenwestKunlun—Pamir(China)andPyrenees(France)[J].XIAOXuchang,LIUHefu.Proc30thInt lGeolCongr[C].1997,6:133140
[6] ZHANGXiankang,ZHAOJinren,ZHANGChengke,etal.CrustalstructureatthenortheastsideofthePamir[J].ChineseJournalofGeophysics,2002,45(5):665671(inChinese). [张先康,赵金仁,张成科,等.帕米尔东北侧地壳结构研究[J].地球物理学报,2002,45(5):665671.]
[7] LIUQiyuan,CHENJiuhui,LIShuncheng,etal.Passiveseis micexperimentinXinjiangJiashistrongearthquakeregionanddiscussiononitsseismicgenesis[J].ChineseJournalofGeo physics,2000,43(3):356365(inChinese). [刘启元,陈九辉,李顺成,等新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨[J].地球物理学报,2000,43(3):356365.]
[8] LAIYuangen,LIUQiyuan,CHENJiuhui,etal.FeaturesoftheS wavesplittingandstressfieldingintheXinjiangJiashistrongearthquakeregion[J].ChineseJournalofGeophysics,2002,45(1):8393(inChinese). [赖院根,刘启元,陈九辉,等.新疆伽师强震群区的横波分裂与应力场特征[J].地球物理学报,2002,45(1):8393.]
[9] WANGQi,DINGGuoyu,QIAOXuejun,etal.ResearchonpresentcrustaldeformationinthesouthernTianshan(Jiashi),ChinabyGPSgeodesy[J].ActaSeismologicaSinica,2000,22(3):263270(inChinese). [王琪,丁国瑜,乔学军,等.用GPS研究南天山(伽师)地区现今地壳变形[J].地震学报,2000,22(3):263270.]
[10] BureauofGeologyandMine.XinjiangAutonomousRegion,GeologicalMapofXinjiangAutonomousRegion(1∶2000000)[M ].Beijing:GeologicalPublishingHouse,1985(inChi nese). [新疆维吾尔自治区地质矿产局.新疆维吾尔自治区地质图(1∶2000000)[M ].北京:地质出版社,1985.]
[11] BureauofGeologyandMine,XinjiangAutonomousRe gionRegionalGeologyofXinjiangUygurAutonomousRegion[M].Beijing:GeologicalPublishingHouse,1993(inChinese). [新疆维吾尔自治区地质矿产局.新疆维吾尔自治区区域地质志[M ].北京:地质出版社,1993.]
[12] JIAChengzao,WEIGuoqi,YAOHuijun,etal.Tectonicevolu tionandregionalstructural geology[A ].BookSeriesonPetroleumintheTarimBasin[M ].Beijing:PetroleumIndustryPublishingHouse,1995(inChinese). [贾承造,魏国齐,姚慧君,等.盆地构造演化与区域构造地质[A].塔里木盆地油气勘探丛书[M ].北京:石油工业出版社,1995.]
[13] JIAChengzao.TectonicCharacteristicsandPetroleumofTarimBasin,China[M ].Beijing:PetroleumIndustryPublishingHouse,1997(inChinese). [贾承造.中国塔里木盆地构造特征与油气[M ].北京:石油工业出版社,1997.]
[14] CAIDongsheng,LUHuafu,JIADong,etal.ThedeformationanalysistoKalpinOrogenicBelt,northernwestmarginofTarimBasin[A].TONGXiaoguang,LIANGDigang,JIAChengzao.RecentProgressofTarimBasinPetroleumGeology[M ].Bei jing:SciencePress,1996.133138(inChinese). [蔡东升,卢华复,贾东,等.塔里木盆地西北缘柯坪造山带变形分析[A].童晓光,梁狄刚,贾承造.塔里木盆地石油地质研究新进展[M ].北京:科学出版社,1996.131138.]
[15] LUHuafu,JIADong,CAIDongsheng,etal.OntheKalpinTranspressiontectonicsofnorthwestTarim[J].GeologicalJour nalofChinaUniversities,1998,4(1):4958(inChinese). [卢华复,贾东,蔡东升,等塔西北柯坪剪切挤压构造[J].高校地质学报,1998,4(1):4958.]
[16] JIADong,LUHuafu,CAIDongs
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