Two Phases of Cenozoic Deformation in Northeastern Tibet: Thrusting Followed by Strike-Slip Faulting

TWO PHASES OF CENOZOIC DEFORMATION IN NORTHEASTERN TIBET: THRUSTING FOLLOWED BY STRIKE-SLIP FAULTING     

THREE-DIMENSIONAL DEFORMATION ALONG THE ALTYN TAGH FAULT ZONE AND UPLIFT OF THE ALTYN MOUNTAIN, NORTHERN TIBET

THREE-DIMENSIONAL DEFORMATION ALONG THE ALTYN TAGH FAULT ZONE AND UPLIFT OF THE ALTYN MOUNTAIN, NORTHERN TIBET     

THE CENTRAL PAMIR—AN ALPINE COLLISION ZONE

THE CENTRAL PAMIR—AN ALPINE COLLISION ZONE     

THE FORMATION AND EVOLUTION OF ALTYN TAGH FAULT SYSTEM AND ITS RELATIONSHIP TO THE GROWTH OF TIBETAN PLATEAU

THE FORMATION AND EVOLUTION OF ALTYN TAGH FAULT SYSTEM AND ITS RELATIONSHIP TO THE GROWTH OF TIBETAN PLATEAUtheNational(G19980 4 0 80 0 )andthefundofOpeningLaboratoriesofGeomechanics     

Structural evolution and sequence of thrusting in the High Himalayan, Tibetan—Tethys and Indus suture zones of Zanskar and Ladakh, Western Himalaya

The timing of motion on major thrusts in the Western Himalaya shows an extremely complex sequence that spans approximately 70 Ma from the latest Cretaceous throughout the Tertiary. Three major phases of thrusting can be distinguished. The earliest phase (T1) is associated with emplacement of Tethyan basin thrust sheets (Lamayuru sediments and Spontang ophiolite) south and south-westwards onto the submerged northern passive margin of India (75-60 Ma). Collision between India and Asia occurred at 50-36 Ma and was followed immediately by the major phase (T2) of crustal shortening involving large-scale south and south-westward directed thrusting of the complete Palaeozoic, Mesozoic and Late Tertiary Tibetan—Tethys zone rocks. Preliminary balanced cross-sections show a minimum shortening of 126 km of these rocks across the Zanskar Range. The late collision phase (T3) involved re-thrusting of the previously stacked pile (breaching or leap-frog thrusting) reversing the earlier stacking order in places, and widespread steepening, overturning and backthrusting along the whole northern margin of the Tibetan—Tethys zone and throughout the Indus suture zone.     

南大巴山冲断构造及其剪切挤压动力学机制

南大巴山是一个形成于T3－K1，滑脱深度小于8－10km 的扬于板块北缘薄皮冲断锲它主要由发育在显生宙地层中台阶状逆断层及断层相关褶皱构成的逆冲岩席、双重推覆体和冲起构造等组成。变形扩展以前列式为主。经平衡地质剖面制作，因冲断南大巴山地壳缩短率平均达49.3％。并以每年约1.28mm 的速率总体缩短约64km，它的成因受控于秦岭碰撞造山过程中扬于板块北缘A型俯冲所提供挤压应力，在向南扩展时，由于古大陆边缘形态不一所诱发的右旋剪切挤压动力学机制。     

晚上新世龙门山南段斜向逆冲作用和区域应力场转换

2008年汶川地震(Mw 7.9)同震滑移结果表明,今地壳缩短为近EW向,与龙门山褶皱冲断带斜交。这一斜向逆冲作用的准确起始时间一直未得到很好的约束。基于龙门山南段山前大邑背斜区三维地震解释和构造建模,结合野外地质调查和年代学数据,确定了晚新生代存在NE向和近NS向2期构造变形。120km长的NS向构造切割了NE向构造,表明近NS向构造形成时间较晚。山前大邑和邛西背斜区近NS向断层和褶皱的活动,均反映了龙门山南段局部或区域上水平最大主应力方向的转换过程,渐新世—早上新世的NW—SE向转变为晚上新世—全新世的近EW向。龙门山南段山前发育的NS向构造和汶川地震同震变形均反映出青藏高原东缘最新的EW向地壳缩短过程,为理解青藏高原东缘的隆升机制提供了新的视角。     

Study on the Seismic Source Mechanisms of the Tibetan Plateau

STUDY ON THE SEISMIC SOURCE MECHANISMS OF THE TIBETAN PLATEAU     

帕米尔东北部木吉断层晚第四纪运动性质和滑动速率的约束

帕米尔造山带是印度-欧亚大陆会聚带的西构造结。木吉断层作为中-西帕米尔与东帕米尔的最北部边界转换断层,其运动性质和滑动速率的准确限定对于理解帕米尔现今应力状态和运动学特征等具有重要意义。本文以木吉断层东段布拉克村北位错特征显著的冰碛台地（39.2020°N,74.3910°E）为研究对象,基于高分辨率卫星影像解译、野外地质地貌调查、差分GPS测量和冰川漂砾宇宙成因核素¹⁰Be暴露测年,获得布拉克北冰碛台地形成（16.8±3.5 ka）以来木吉断层的累积右旋位错量、垂直位错量、南北向拉张量以及最小速率分别为约190 m、105±12 m、34±12 m和11.3±2.4 mm/a、6.3±1.5 mm/a、2.0±0.8 mm/a;三者的比值约为6：3：1,水平向的总滑动速率为11.5±2.3 mm/a。与位于断层中部近乎纯走滑的阿克萨依处相比,木吉断层在布拉克北以右旋走滑为主的同时,具有明显的正断分量。断层在布拉克北的水平向总滑动速率11.5±2.3 mm/a与阿克萨依处右旋走滑速率的最大值（9.4±0.9 mm/a）大致相当;因此尽管断层沿走向的运动性质发生了显著变化,其水平向滑动速率大致保持恒定。

     

Deformation Characteristics and Tectonic Evolution of the Eastern Qinling Orogenic Belt

The Qinling Mountains separating the northern from the southern China plate is a key region for the study of structural evolution of eastern Asia. It is composed of the Palaeozoic fold belt in its northern part and the Variscan and Indosinian fold belts in its southern part. The evolution of the former is marked by the closure of a northward subducting oceanic basin in the early stage, followed by southward obduction of ophiolites and intracontinental thrusting during the Variscan; whereas that of the latter is represented by intracontinental, shallow crustal deformation on the basis of a large-scale detachment structure(with a horizontal slip of at least of 100 km). Since the late Palaeozoic, however, both of the belts have been cut by a series of east-west sinistral strike-slip faults.     

A discussion on the Genesis of the Jiama Copper-Polymetallic Deposit,Maizhokungger,Xizang

A DISCUSSION ON THE GENESIS OF THE JIAMA COPPER-POLYMETALLIC DEPOSIT, MAIZHOKUNGGER, XIZANG     

THE NORTHWARD PROPAGATION OF THE ARC TECTONICS OF THE NORTHEAST PAMIR AND NORTHWEST TARIM BASIN

THE NORTHWARD PROPAGATION OF THE ARC TECTONICS OF THE NORTHEAST PAMIR AND NORTHWEST TARIM BASINThisworkispartoftheresearchproject“themechanismofJiashistrongearthquakeswarmandprediction ofearthquakeriskinthenortheastPamir     

Seismological Evidences for the Multiple Incomplete Crustal Subductions in Himalaya and Southern Tibet

SEISMOLOGICAL EVIDENCES FOR THE MULTIPLE INCOMPLETE CRUSTAL SUBDUCTIONS IN HIMALAYA AND SOUTHERN TIBET     

藏北改则新生代早期逆冲推覆构造系统

藏北改则及邻区新生代早期发育大型逆冲推覆构造系统,由不同方向的逆冲断层、不同时代的构造岩片、不同规模的飞来峰和构造窗、不同类型的褶皱构造组成.羌塘中部发育羌中薄皮推覆构造,石炭系板岩和二叠系白云质灰岩自北向南逆冲推覆于上白垩统与古近系红层之上,形成大型逆冲岩席和弧形逆冲断层,原地系统古近纪红层下伏三叠系—侏罗系海相烃源岩.羌塘南部发育南羌塘薄皮推覆构造,导致班公—怒江蛇绿岩、三叠系—侏罗系海相地层及侏罗纪混杂岩自北向南逆冲推覆于古近纪红层与下白垩统海相沉积岩层之上,形成三条蛇绿岩片带、大量飞来峰和厚度较大的构造片岩.中新世早期火山岩层和湖相沉积呈角度不整合覆盖逆冲断层、褶皱构造和逆冲岩席,不整合面上覆火山岩年龄为23.7~19.1 Ma,指示中新世早期改则及邻区基本结束了强烈逆冲推覆构造运动.估算羌中逆冲推覆构造的推覆距离约100~115 km,南羌塘逆冲推覆构造的推覆距离约82~110 km;新生代早期改则逆冲推覆构造系统近南北方向逆冲推覆总距离为182~225 km,对应地壳缩短率为(50.3±2.7)%.     

白垩纪以来中国西部地体运动的古地磁证据和问题

地质证据表明中国西部各地体在白垩纪之前已经增生到欧亚大陆之上 ,但这些地体自白垩纪以来的古地磁极位置与稳定欧亚大陆的古地磁极位置存在较大差异 ,对其最可能的解释是发生在晚白垩世与古新世之交 (约 6 5Ma)印度板块和欧亚大陆之间的碰撞及其后印度板块的持续北向挤压 ,使得这些地体之间以及这些地体与稳定欧亚大陆之间发生了相对位移和地体内部的变形。文中利用现有的古地磁研究成果 ,计算了自白垩纪以来中国西部各地体与欧亚稳定大陆之间的南北向相对位移量。塔里木地块和柴达木地体的古地磁数据表明 ,阿尔金断裂至少经历了四期活动。在欧亚地区普遍存在的第三纪磁倾角偏缓现象 ,很可能反映了在该地区长期存在非偶极子场。     

新疆塔什库尔干县含稀有金属伟晶岩-碳酸岩的时代——对帕米尔构造结稀有金属成矿作用的启示

帕米尔构造结位于青藏高原北缘,记录了自新元古代晚期以来到新生代完整的特提斯构造演化过程。在长期的构造-岩浆演化过程中,发育了不同时代、不同类型的成矿事件。野外调查表明,在帕米尔北东段,发育了含绿柱石的伟晶岩及含氟碳铈矿的碳酸岩（碳酸岩-伟晶岩组合）。通过独居石及锆石U-Pb定年,识别出该区两期伟晶岩带（包括碳酸岩）,分别是新生代和中生代（19~18 Ma和200 Ma）,其中早期含绿柱石伟晶岩形成于古特提斯洋关闭后的伸展阶段,而新生代含氟碳铈矿碳酸岩-伟晶岩组合,与新生代陆内走滑伸展事件相关,表明帕米尔构造结伸展走滑启动的时间可能在19 Ma。结合区域地球化学异常特征,表明在帕米尔地区有望在稀有、轻稀土找矿上获得突破。     

新疆塔什库尔干县含稀有金属伟晶岩-碳酸岩的时代——对帕米尔构造结稀有金属成矿作用的启示

帕米尔构造结位于青藏高原北缘,记录了自新元古代晚期以来到新生代完整的特提斯构造演化过程。在长期的构造—岩浆演化过程中,发育了不同时代、不同类型的成矿事件。野外调查表明,在帕米尔北东段,发育了含绿柱石的伟晶岩及含氟碳铈矿的碳酸岩(碳酸岩—伟晶岩组合)。通过独居石及锆石U-Pb定年,识别出该区两期伟晶岩带(包括碳酸岩),分别是新生代和中生代(19～18 Ma和200 Ma),其中早期含绿柱石伟晶岩形成于古特提斯洋关闭后的伸展阶段,而新生代含氟碳铈矿碳酸岩—伟晶岩组合,与新生代陆内走滑伸展事件相关,表明帕米尔构造结伸展走滑启动的时间可能在19 Ma。结合区域地球化学异常特征,表明在帕米尔地区有望在稀有、轻稀土找矿上获得突破。     

冈底斯斑岩铜矿带东段早中新世剥蚀作用及对渐新世—中新世斑岩矿床时空分布的影响

冈底斯渐新世—中新世斑岩铜矿带是特提斯成矿域重要组成部分,已经发现了多处超大型-大型斑岩-矽卡岩型铜-钼-金矿床。然而,渐新世以来铜矿带所处的青藏高原经历了强烈抬升与剥蚀作用,在此背景下带内矿床是如何保存下来的尚未清楚,带内剥蚀作用的发育特征及对渐新世—中新世斑岩矿床的分布影响如何,控制机制有待解决。笔者通过泽当以北40km处冈底斯弧内部垂直剖面锆石和磷灰石（U-Th）/He定年,发现成矿带内部发育了早中新世（17.3～15.1 Ma）快速剥蚀作用,期间平均剥蚀速率＞1.82 km/Ma,剥蚀量为4.0 km,而后剥蚀速率降低至0.14～0.19 km/Ma,15.1 Ma至今剥蚀量~2.5 km。结合前人数据,笔者发现成矿带内早中新世强快速剥蚀区呈东—西向带状分布,且受谢通门-沃卡剪切带向南逆冲作用控制,其南、北两侧也发育同期剥蚀作用,强度明显低于剪切带活动区域,说明高原内部中新世以来的隆升与剥蚀作用具有差异性。冈底斯带渐、中新世斑岩矿床分别分布在早中新世强剥蚀区南、北两侧弱剥蚀区内,指示差异剥蚀作用是成矿带内已发现的渐新世—中新世矿床时空分布的重要影响因素。     

KINEMATICS OF QUATERNARY EXTENSION IN THE PAMIR

KINEMATICS OF QUATERNARY EXTENSION IN THE PAMIR1　BurtmanVS ,MolnarP .GeologicalandgeophysicalevidencefordeepsubductionofcontinentalcrustbeneaththePamir[J].SpecPapGeolSocAm ,1993,2 81:76 . 2　StreckerMR ,FrischW ,HamburgerMW ,etal.QuaternarydeformationintheEasternPamirs ,TadzhikistanandKyrgyzs tan[J].Tectonics,1995 ,14(5 ) :10 6 1～ 10 79.…     

晚白垩世后青藏高原和塔里木地块的整体北移

本文根据塔里木地块及其以南的昆仑、羌塘和拉萨地块晚中生代特别是晚白垩世古地磁数据,提出青藏高原自晚白垩世后北向移动两千余公里,主要并不是通过它本身的大规模地壳缩短来完成,而是与塔里木地块一起作大规模整体北移的结果。一种可能的解释是,在欧亚大陆北部稳定区和塔里木地块之间广大的中亚构造带,自晚白垩世后发生了大规模的地壳缩短。