Mesozoic thrusts and extensional structures in the Daqingshan orogen, Inner Mongolia, and their temporal and spatial relationship

Three large-scale thrusts developed in the Daqingshan orogen, Inner Mongolia, with a northeast-east trending from Louhuashan to Suletu are described in this paper. These northwest-directed thrusts, together with the four tectonic belts (or tectonic sheets) separated by these faults, formed a typical thrusting system. The originally defined Hohhot metamorphic core complex may be a tectonic sheet, making the uppermost tectonic unit of the thrusting system and truncated by the Daqingshan detachment fault on top. The existing tectono-chronological studies showed that the thrusting of this region possibly happened at the same time as the extension along the top detachment fault. This presents that the contraction and extension in Daqingshan orogen were probably simultaneous. The structural pattern of the Daqingshan orogen can be correlated to the Himalayan orogen, and models for simultaneous thrusting and detachment in Himalaya may give a hint for explaining the development of the Daqingshan orogen.     

Middle-Miocene transformation of tectonic regime in the Himalayan orogen

Understanding the multiple tectonic transformations during the Himalayan orogeny is significant in evaluating the evolution of Himalayan orogen.In the Gyirong area in south Tibet,deformed leucogranitic veins in the biotite-plagioclase gneisses of Greater Himalayan crystalline complex(GHC) constitute south-vergent asymmetric folds.The reconstruction of the veins shows that they experienced two generations of deformation under different tectonic regimes:an earlier top-to-north extension and a later top-to-south thrusting,implying a tectonic transformation from N-S extension to N-S shortening.Zircons LA-ICP-MS U-Pb dating of the leucogranite shows that it was emplaced during 21.03-18.7 Ma.The data suggest that the tectonic transformation occurred after 18.7 Ma.The chronological data of South Tibet detachment system(STDS) and North-South trending rift(NSTR) from Gyirong and other areas indicate that the Himalayan orogeny was in a period of tectonic transformation from N-S extension to N-S shortening during 19-13 Ma.The transformation of tectonic regime was probably controlled by the India-Asia convergence rate.An increase in the convergence rate resulted in N-S shortening of the orogen,thrusting and folding,with coeval formation of the NSTR in Tibet.A decrease in the convergence rate led to N-S extension and reactivation of the STDS.     

Structures, kinematics, thermochronology and tectonic evolution of the Ramba gneiss dome in the northern Himalaya

The Ramba gneiss dome, one of the north Himalayan gneiss domes, is composed of three tectono-lithologic units separated by an upper and a lower detachment fault. Low-grade metamorphic Tethyan Himalayan sedimentary sequence formed the upper unit above the brittle upper detachment fault. Mylonitic gneiss and a leucogranite pluton made up the lower unit beneath the ductile lower detachment fault. Mylonitic middle-grade garnet-, staurolite- and andalusite-schist constituted the middle unit between the two faults, which may be that the basal part of the upper unit experienced detachment shear. The Ramba dome underwent three episodes of deformation in its tectonic evolution. The first episode was a top-down-to-north-northwest sliding possibly related to the activity of the south Tibetan detachment system （STDS）. The second episode was the dominant deformation related to a east west extension, which resulted in a unique top-down-to-east kinematics and the major tectonic features of the dome. The third episode was a collapse sliding toward the outsides of the dome. The Ramba gneiss dome is possibly a result of the east-west extension and magmatic diapir. The lower detachment fault is probably the main detachment fault separating the sedimentary sequence from the crystalline basement during the eas-west extension in the dominant deformation episode. The diapir of the leucogranite pluton formed the doming shape of the Ramba gneiss dome. This pluton intruded in the core of the dome in a late stage of the dominant deformation, and its Ar-Ar cooling ages are about 6 Myr. This indicates that the dominant deformation of the dome happened at the same time of the east west extension represented by the nort-south trending rifts throughout the northern Himalaya and southern Tibet. Therefore, the formation of the Ramba gneiss dome should be related to this east west extension.     

^40Ar／^39Ar dating of Daqingshan thrust

The Daqingshan thrust system is an important part of the western segment of the Mesozoic Yinshan-Yanshan orogenic belt. Therefore, much attention has been paid to the thrusts due also to their large-scale and entirely devel-oped structural elements and typical structural styles. Studies and progress have been concentrated on the ge-ometry, kinematics, dating and dynamic mechanism of the thrust and thrusting. To date, there have been no reliable published isotopic data, however, on the dating…     

黔东凯里—三都断裂结构及形成演化

通过宏观描述、地震解译、有限应变测量、显微构造分析及包裹体测温等方法对黔东凯里-三都断裂进行了研究。认为凯里-三都断裂是黔东南推覆体的前锋断裂,呈向NWW突出的弧形,总体表现为由数条断层组成的逆冲断裂带,主断裂倾向SEE,为黔南拗陷和雪峰古陆的分界线。断裂带以浅层脆性变形为主,断裂带上盘向NWW推覆的水平位移达12～15km,是多条断层多期挤压、拉张和平移剪切作用叠加的结果。断裂带经历了多期演化过程,燕山期以来的演化历史主要受太平洋构造域控制,早中燕山期为主挤压逆冲阶段、晚燕山期为拉张正滑阶段、喜马拉雅期为再次挤压-定型阶段。     

Mesozoic basin development and its indication of collisional orogeny in the Dabie orogen

The Dabie orogen underwent deep continental subduction, rapid exhumation, and the huge amount of erosion during the Mesozoic. Its tectonic evolution, especially how its evolution was recorded by sedimentary basins at the flanks of the Dabie orogen is one of the most important issues of the world’s attention. These years, newly studies of basin sedimentology, combined with structural geology, have shown a fundamental progress. The overall distribution of different basin types in the orogen indicates that shortening and thrusting at the margins of the orogen from the Late Triassic to the Early Cretaceous controlled the foreland basins, and extension, doming and rifting were initiated in the core of the orogen from the Jurassic to the Early Cretaceous and were expanded to the whole orogen after the Late Cretaceous. Therefore, The Dabie orogen records gradual transition from overall shortening and thrusting to dominantly extension and rift basin formation expanded from its core to its margins, although these shortening and extension overlapped in time from the Jurassic through Early Cretaceous at crustal levels. The unroofing ages of the ultra-high pressure (UHP) metamorphic rocks in the Dabie orogen change from Early Jurassic to Late Jurassic westward. The depth of exhumation increases eastwards. The sediment sources for the Hefei basin are mostly composed of the deeply exhumed, axial Dabie metamorphic complex, and the sediment sources for the Middle Yangtze basin are mostly from cover strata in the southern orogen and related strata with subjacent (i.e. subsequently overthrusted) Mianlue suture belt. Geodynamic analysis represents that continental collision between the North China Block and the South China Block along the Shangdan and Mianlue sutures, subsequently northwestward progradation of the Jiangnan fold and thrust belt, and the underthrusting of the North China Block along the Northern Boundary Fault of Qinling Range led to crustal thickening, gravitational spreading and balanced rebound of the resultant thick crustal welt, and multi-episodic exhumation of the HP/UHP metamorphic rocks. The future studies by the methods of tracing the Dabie orogeny through deposition in the marginal basins should focus on eastward extension of the Mianlue suture, thrust and overlap of the Dabie HP/UHP metamorphic block on different lithotectonic zones and basins along the northern South China Block, the structural framework of the source area of the basins in the syn-depositional stage, the basin lateral extension, huge amount of erosion and sediment transportation from the Dabie blanket and basement rocks, and recovery of subducted and re- moved structural units within the Dabie orogen, etc.     

郯庐断裂带渤海段的深部构造与动力学意义

郯庐断裂带渤海段的3条大地电磁测深剖面,揭示了断裂带丰富的深部结构信息。这些剖面显示,郯庐断裂带已切穿了整个地壳,并且向下延入上地幔;该段断裂带在深部显示为陡立的走滑构造,浅部为伸展断层及断陷盆地所叠加,最后又发生过一期明显的逆冲活动;该断裂带的走滑构造在渤海湾内继续存在,指示其早期的走滑活动中向北延入了渤海内;该断裂带内部及其旁侧,浅部的断陷盆地发育与深部的高导层(带)紧密伴生,反映断陷盆地发生时在地壳深部都出现了软弱拆离带,也指示了岩石圈减薄中地壳内所发生的深部过程。     

浙西北地区二叠系和三叠系的构造变形样式及其大地构造意义初步研究

浙西下三叠系统政棠组(T_1zh)发育有典型的鲍马序列,是一套深水相浊积岩建造;区域构造环境初步分析表明浙西北地区具被动大陆边缘沉积楔特征。下三叠系统政棠组(T_1zh)与二叠系协调变形,其构造变形样式总体上以向西北逆冲的冲褶席(duplex)~ 为特征,变形强度自南东向北西呈递减趋势。上三叠统乌灶组(T_3w)为含煤陆相磨拉石盆地建造,变形样式以宽缓褶皱和逆断层组合为主。该区大地构造相主要为前陆褶皱冲断带相,而土三叠统乌灶组(T_3w)为前陆磨拉石盆地相,二者对浙西北地区早中生代造山作用的研究具重要意义。     

Diachroneity of continental subduction and exhumation: Constraints from the Permian-Triassic HP metamorphic terrane in the Tongbai orogen, central China

High-pressure （HP） metamorphic terrane in the Tongbai orogen comprises two HP slices （I and II） and a tectonic m61ange zone in the northeast and a blueschist-greenschist zone in the southwest. HP slice I is represented by the northern and southern eclogite zones on the two sides of the Tongbaishan antiform. HP slice II is represented by retrograded eclogite-bearing metamorphic en- claves in Cretaceous gneissic granites in the Tongbai Complex. U-Pb, Lu-Hf, Rb-Sr and 4Ar/39Ar multichronometric data indi- cate that the peak metamorphism of HP slice I took place at -255 Ma, whereas the metamorphic ages of HP slice II are as young as 232-220 Ma. By contrast, the tectonic melange zone near the suture was metamorphosed at -256 Ma. Such a diachroneity of dif- ferent slices across the direction of the orogen in the Hong＇an-Dabie-Sulu HP/UHP terrane is ubiquitous, and it can be interpreted by a syn-subduction detachment/exhumation model. Furthermore, the metamorphic age of HP slice I in the Tongbai orogen is older than that of the equivalent HP slice in the Hong＇an orogen by ~15 Ma, suggesting that the diachroneity may have also ex- isted along the direction of the orogen. A seesaw-type subduction/exhumation model is proposed to explain this age disparity and the subduction of the South China Block becomimg shallower towards the west.     

吐哈盆地哈密坳陷逆断层活动性及演化

在构造解释及断层受力机制分析的基础上,根据逆断层两盘剥蚀与沉积的关系,将哈密坳陷逆断层活动的地质模型归纳为单向逆冲型、逆冲生长型和基底抬升型,并提出针对这3种类型逆断层活动量的计算方法,对主要断层在印支期、燕山期和喜山期的活动强度进行研究。结果表明:火石镇凹陷内的断层在印支期活动最为强烈,燕山期断层活动变弱,喜山期只有南部边界断层活动增强;三堡凹陷内的断层在印支期开始活动,燕山期断层活动最为强烈,喜山期断层基本停止活动;断层活动的差异性直接影响着各凹陷构造格局的形成与演化,火石镇凹陷构造格局早在印支运动就基本定型,而三堡凹陷的构造格局在晚燕山运动后才最终定型。     

准噶尔盆地西北缘二叠纪古构造对层序地层建造及沉积体系的控制

准噶尔盆地西北缘二叠系是一套前陆盆地构造沉积组合.利用该区二叠系丰富的钻井、岩心和三维地震资料,按照构造层序分析的方法对该区二叠系层序地层和古构造对层序建造和沉积体系的控制作用进行了研究.研究表明,二叠系前陆盆地对应1个一级层序、4个与构造幕对应的超层序（二级层序）,超层序Ⅱ,Ⅲ,Ⅳ可识别出10个三级层序.二叠系前陆盆地的古构造格局不但控制了层序地层建造,而且控制了沉积体系和储层在平面上的展布.超层序Ⅱ盆地幕式逆冲挠曲沉降构造作用强烈,发育同沉积逆冲断裂挠曲坡折背景层序.湖扩展体系域发育的扇三角洲前缘砂体和碳酸盐岩（白云岩）储层物性良好,其分布受同沉积逆冲挠曲坡折及水下低隆起控制.超层序Ⅲ,Ⅳ盆地逆冲挠曲沉降构造作用减弱或停止,发育逆断裂坡折、隐伏断裂挠曲坡折背景及缓坡背景层序.逆断裂坡折、隐伏断裂坡折背景层序坡折向湖一侧低位域和湖扩展体系域辫状河道和三角洲前缘砂体是良好储层,其分布受逆断裂坡折和隐伏断裂坡折的控制.由于这些储层就分布在烃源岩内或有断裂与源岩沟通,成藏条件良好,是油气勘探的有利区带.     

河南熊耳山北坡西段的变质核杂岩和拆离断层

河南熊耳山北坡西段的变质核杂岩核部,由太华群深变质岩系组成结晶基底,熊耳群未变质的火山岩系和第三系红层组成盖层。二者之间的滑脱拆离带下拆离盘由韧性变形的糜棱岩组成,具有典型的糜棱岩类岩石的基本特征。上拆离盘以脆性变形为主。盖层中发育了拆离断层特有的铲形断层,局部见同构造的花岗斑岩侵入其中。第三系红层向拆离断层反倾。滑脱拆离断层控制了本区热液矿床的分布,尤其是大型低品位金矿的分布。     

Post-collisional extensional and thrust-nappe structures in northern part of Dabie Mountains

Thrust-nappe structures and extensional structures simultaneonsly occur in the northern part of the Dabie Mountains. The systematic structural study reveals that extensional structures along the Mozitan-Xiaotian fault and thrust-nappe structures that take the Jinzhai-Shucheng fault as their frontal thrust share the same shear sense, and display a transitional relationship from the ductile extensional structure of deep level in the south to the ductile-brittle and brittle thrust-nappe structure of shallow level in the north. The extensional and thrnst-nappe structures in the region are explained to result from post-collisional processes by the continuous subduction of the Yangtze continental block and the extension induced by the uplifting of the core part of the Dabie Mountains, which are components of the exteasional structures produced in the exhumation process of the ultrahigh pressure metamorphic rocks in the Dabie Mountains. Because of the frontal blocking in the process of the north-westward spreading, the extension and detachment of the low-grade metamorphic rocks along the Mozitan-Xiaotian fault was transformed into the northwestward thrustiag, resulting in the thrust-nappe structures. They developed in the period of 200-170 Ma, maybe last till the late Jurassic.     

负反转断裂主反转期和反转强度分析

以塔里木盆地北部隆起轮台断裂带为例,提出了非坪一坡式结构、具有多期道冲作用的负反转断裂演化模式。负反转断裂的发展演化可分为初始沉积阶段、早期冲断剥蚀阶段、同生冲断阶段和负反转阶段。早期的同生逆断层序和后期的负反转层序是识别负反转断裂的关键标志。位移一距离曲线上的“拐点”代表了断层由冲断活动向负反转活动转化的转折点,指示了主反转期。而“零点”则代表了断层上从净收缩转化为净引张的转折点。根据“零点”在同生逆断层序中的位置变化,可以确定断层的反转率或反转强度。同时,断层生长指数也反映了负反转强度的大小。对塔里木盆地北部隆起轮台断裂带进行的实例分析表明,轮台负反转断裂主反转期为中新世苏维依期一吉迪克期,反转率为０．８５～０．９８。     

西藏札达盆地构造与沉积特征

札达盆地位于青藏高原南西部,是发育于喜马拉雅山内部的盆地。盆地北东侧以阿依拉日居断裂为边界,该断裂属逆冲性质。西北边界为曲松断裂,为一拆离断层。盆地西南主边界为藏南拆离系（STDS）,是盆地主控构造。盆地内部沉积了巨厚的第三纪地层,可以分为上下2个部分,即上部的湖相沉积和下部的河湖交互相沉积。湖相沉积是以泥岩为主的巨厚沉积;河湖交互相沉积以砾岩层的出现为标志,可分为3个沉积旋回。札达盆地的主控构造为伸展构造,但同时经受了垂直于造山带的挤压作用。     

莫里青断陷西北缘走滑断裂带特征及油气地质意义

通过对莫里青断陷构造、沉积特征及油气成藏规律系统分析,总结出西北缘走滑断裂带演化特征及其对油气勘探的意义。研究结果表明:西北缘断裂成盆期为一条高角度的走滑张性断裂,新近系受挤压应力作用发生反转,形成了内部发育众多具走滑性质的次级逆冲断层、挤压褶皱、花状等构造的西北缘走滑逆冲断裂带;宏观来看西北缘断裂经历了早期走滑拉张和晚期走滑挤压2个演化阶段;西北缘走滑断裂对油气勘探具重要意义:深大断裂通过提供大坡度构造环境、有效物源及保存条件为湖泊水下扇有效储集体形成创造了有利条件,且水下扇中扇辫状水道微相上的油气产能较高;断裂带内部形成断褶皱等构造圈闭、具有挤压性质的逆冲断层封堵油气等因素为油气聚集提供了有效圈闭条件;各条件有效配置使得研究区西北缘走滑断裂带成为较有利的油气富集区带。     

造山带逆冲与前陆盆地沉降和沉积平衡关系的定量讨论——以库车陆内前陆盆地为例

造山带和克拉通之间的盆地称之为前陆盆地。近年来关于陆内(板内)造山的理论进一步拓宽了前陆盆地的含义。笔者建议将毗邻大陆板内造山带的拗陷盆地命名为陆内前陆盆地,并可以与典型前陆盆地类比。造山带向前陆区逆冲引起山麓带岩石圈的构造响应,形成前隆和前陆盆地。不同地区的前陆盆地具有明显的区域性特征,其演化阶段性也有许多差别。它们受岩石圈基底性质和大地构造位置,造山带隆升和剥蚀,前陆盆地沉积速度和开放程度等多种因素影响。最新的方法是采用校正的构造回剥曲线、时间段曲线、沉积速率等定量数值描述造山冲断楔和前陆盆地间的构造-沉积平衡关系,即山体隆升逆冲与盆地构造沉降的平衡,以及山体逆冲推移与盆地沉积间的平衡。南天山南麓库车陆内前陆盆地为典型的封闭系统,是理想的研究区。上述方法对库车陆内前陆盆地的分析表明,经过校正的回剥曲线反映逆冲和沉降更为精确。结合时间段曲线,沉积速率和区域地质资料能得出库车陆内前陆盆地生储盖组合与储油构造形成的主要时期和规律,为油气勘探提供佐证。     

SHRIMP U-Pb zircon geochronology of granulites at Rimana （Southern Tibet） in the central segment of Himalayan Orogen

TheCenozoicHimalayanorogenisimportantinun-derstandingcontinentaldynamicprocesses.Lowercrustal,high-grademetamorphicrockshaverecentlybeendiscov-eredinNamcheBarwaandParmir,i.e.therespectivere-gionsofeasternandwesternsyntaxisoftheorogen[1—4].Eclogitesthatunderwentgranulite-faciesmetamorphismhaverecentlybeenreportedintheCadaareatotheeastofMountEverestinthecentralsegmentoftheHimalayanorogen[5].WiththehelpofthegeologicalsurveyofDing-gyeCountyandChentangSheets(scale1︰250000),high-pressuremafic…     

方正断陷多期构造叠合构造解析及模式分析

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