Permo–Triassic and Liassic Tethyan Oceanic Tracts within the Pontide Belt Along the Southern Margin of Eurasia, Northern Anatolia

The Pontide belt in northern Turkey includes three major tectonic terranes,the Strandja Massif（Sj M）,and the Istanbul（ISZ）and Sakarya Zones（SZ）(Fig.1).We present new age and geochemical data from ophiolites and ophiolitic mélanges within the Sakarya Zone and show that these mafic–ultramafic rocks are the remnants of Tethyan oceanic lithosphere formed in different tectonic settings.The main ophiolite occurrences investigated in this study along the Karakaya Suture（KS）are associated with the latest Triassic Cimmeride orogeny,and in the Küre–Yusufeli ophiolite belt are part of the Alpide orogeny.The Karakaya Suture Zone ophiolites in northern west Turkey are comprised mainly of the Denizgoren（?anakkale）ophiolite,Bo?azk?y（Bursa）,Geyve（Sakarya）,Almac?k（Düzce）and?ele（Bolu）metaophiolites.The Denizg?ren ophiolite largely contains upper mantle peridotites,which are equivalents of the Permo–Triassic Lesvos peridotites and mélange units farther SW in the northern Aegean Sea.The Bo?azk?y ophiolite includes serpentinite and metagabbro,and the Almac?k and Geyve ophiolites display an almost complete Penrose–type sequence consisting of serpentinizeduppermantleperidotites,cumulate ultramafic–mafic rocks,isotropic gabbros,dolerite and plagiogranite dikes,and extrusive rocks.U–Pb zircon dating of plagiogranite dikes from?ele has revealed an igneous age of 260 Ma,and 255,235,227 Ma from Almac?k（Bozkurt et al.,2012a,b）.Consistent with the previouslypublished Permo–Triassic age,we obtained a 268.4±6.3 Ma U–Pb zircon age from a plagiogranite dike within the Almacik ophiolite to the west.This KS ophiolite belt containing the?ele,Almac?k,Geyve ophiolites within the SZ extends westward into the Armutlu Peninsula and then into the Biga Peninsula（i.e.Denizg?ren ophiolite）and most likely connects with the remnants of the Triassic Meliata–Meliac ocean basin（Stampfli and Borel,2002）in the Balkan Peninsula.The KS ophiolites also continue eastward within the Pontide Belt into the Elekda?ophiolite（eastern Kastamonu）and then to the Refahiye ophiolite in NE Anatolia.Triassic granites in the SZ represent a magmatic arc that formed as a result of the northward subduction of the Izmir–Ankara–Erzincan oceanic lithosphere existing during the late Paleozoic through Cretaceous（Sarifakioglu et al.,2014）beneath the Pontides.We obtained a U–Pb zircon age of 231±2 Ma from a metagranitic intrusion into the Variscan basement of the SZ in the Kastamonu region of the central Pontides.This metagranite is enriched in LILE（Rb:63 ppm;Ba:65 ppm;Sr:200 ppm）and depleted in HFSE（Y:12.58 ppm;Yb:1.26 ppm;Ti O2:0.2 wt.%;Nb:7.6 ppm;Hf:3.9 ppm）,characterizing it as subduction–related calc-alkaline pluton.Lead（3.9 ppm）,U（1.6 ppm）and Ce（59 ppm）contents are interpreted as evidence for contamination by continental crust.The Küre basin to the north opened during the late Triassic to Liassic,following a backarc rifting episode in the central Pontides.Metabasic dike intrusions in the Devrekani metamorphic massif represent the first magmatic stage of this backarc rifting event.Whole-rock 40Ar-39Ar dating ofthe metabasic dikes has yielded cooling ages of 160.5±1.2 Ma. We infer that this age was reset due to thermal heating during the emplacement of the Middle Jurassic granitoids as the Küre oceanic basin was closing. The Küre ophiolite contains upper mantle peridotites and oceanic crustal rocks composed mainly of pillow–massive–breccia basalts, dacitic and rhyolitic lavas–tuffs, diabase dyke swarms, massive gabbros and a limited extent mafic cumulates. We obtained 182.6±1.9 Ma as a whole-rock 40Ar-39 Ar age from a pillow basalt and a U–Pb zircon age of 171±1 Ma from the granitic intrusion cross-cutting the peridotites. The easternmost representatives of the Küre ophiolite occur in the Yusufeli（Artvin） area in the eastern part of the Pontide belt. Here, oceanic crustal rocks are tectonically related to metamorphic rocks of the Variscan basement of the SZ. The ophiolitic crustal rocks contain isotropic gabbro and mafic and felsic dikes. Serpentinized upper mantle peridotites are scarce. Pillow lava basalts are overlain by a thick metasandstone–metashale association with locally foliated meta–lava and some manganiferous chert and mudstone interlayers. We obtained a U–Pb zircon age of 172.5±1.4 Ma from the granitic intrusion cross-cutting the Yusufeli ophiolite and of 181.9±0.9 Ma from a felsic dike（plagiogranite） in the Yusufeli ophiolite. The Middle Jurassic granites are related to the closure of the Küre-Yusufeli marginal ocean basin. The Küre and Yusufeli ophiolites have been previously interpreted as the remnants of the Paleotethys or the Intra-Pontide Ocean. However, we posit that these ophiolites represent amarginal, short-lived（;0 Ma） ocean basin, which opened during the late Triassic through Liassic, and then closed in Dogger. This oceanic lithosphere is similar to the Evros ophiolite in the northeastern Greece in terms of its ages and geochemical characteristics.

Simulation for the Controlling Factors of Structural Deformation in the Southern Margin of the Junggar Basin

According to the differences of structural deformation characteristics, the southern margin of the Junggar basin can be divided into two segments from east to west. Arcnate thrust-and-fold belts that protrude to the north are developed in the eastern segment. There are three rows of en echelon thrust-and-fold belts in the western segment. Thrust and fold structures of basement-involved styles are developed in the first row, and decollement fold structures are formed from the second row to the third row. In order to study the factors controlling the deformation of structures, sand-box experiments have been devised to simulate the evolution of plane and profile deformation. The planar simulation results indicate that the orthogonal compression coming from Bogeda Mountain and the oblique compression with an angle of 75° between the stress and the boundary originating from North Tianshan were responsible for the deformation differences between the eastern part and the western part. The Miquan-Uriimqi fault in the basement is the pre-existing condition for generating fragments from east to west. The profile simulation results show that the main factors controlling the deformation in the eastern part are related to the decollement of Jurassic coal beds alone, while those controlling the deformation in the western segment are related to both the Jurassic coal beds and the Eogene clay beds. The total amount of shortening from the Yaomoshan anticline to the Gumudi anticline in the eastern part is -19.57 km as estimated from the simulation results, and the shortening rate is about 36.46%; that from the Qingshuihe anticline to the Anjihai anticline in the western part is -22.01 km as estimated by the simulation results, with a shortening rate of about 32.48%. These estimated values obtained from the model results are very close to the values calculated by means of the balanced cross section.

塔里木盆地西北缘乌什西次凹的地层系统和构造特征

乌什西次凹位于塔里木盆地西北缘,隶属于库车坳陷的乌什凹陷。它位于南天山主山脉(哈尔克山)和塔里木盆地柯坪—温宿凸起之间。区域构造格局上,这里是塔里木克拉通向西北自然延伸的部分。次凹北缘的阿合奇断裂是南天山造山带和塔里木克拉通的分界。乌什西次凹内发育与柯坪—温宿凸起相似的晚前寒武纪—古生代地层系统,包括寒武系、奥陶系和石炭系的烃源岩。新近系—第四系碎屑岩建造直接不整合于变形的古生代被动大陆边缘碎屑岩—碳酸盐岩沉积建造之上;剖面上,向南天山方向加厚,向塔里木克拉通方向减薄,呈现典型的前陆盆地剖面结构特征。这是一个晚新生代陆内前陆盆地,叠加在晚海西期—燕山期古隆起之上。这里的构造变形主要有3期,分别是中海西期、晚海西期—印支期和晚喜山期。变形以厚皮冲断构造及其相关褶皱为主,薄皮构造不发育。平面上,主构造线走向NE-SW。剖面上,以南天山向塔里木冲断为主。

准噶尔盆地南缘西部山前褶皱—冲断带构造分带特征及形成演化

准噶尔盆地南缘西部构造呈新的构造叠置特征和复杂的复合叠加构造样式,叠加构造在空间分布上具有明显的分带特征。根据野外地质调查和地震解释资料,采用平衡剖面恢复、楔型构造理论和构造地质学分析方法,研究复杂叠加构造变形差异及分带特征。结果表明:准噶尔盆地南缘西部发育受基底卷入与顺层滑脱联合与差异控制下的空间断褶体系,褶皱发育受断层控制,褶皱与断层相互叠加形成构造楔、双重构造、突发构造等复合构造样式,表现为多期活动特征。研究区按构造变形性质及变形差异可划分为山前逆冲推覆构造带、基底卷入型褶皱—冲断带、盖层滑脱型褶皱—冲断带3个构造带;其中,基底卷入型褶皱—冲断带与第一排断褶带重合,受控于基底卷入型断裂体系,发育基底卷入式大型构造楔、背形堆垛式双重构造与前倾双重构造,背斜轴线与断层线平面重合度高;盖层滑脱型褶皱—冲断带包括第二和第三排断褶带,受控于顺层滑脱型断裂体系,发育断展褶皱,背斜轴线与断层线平面重合度低,构造垂向上具有分层差异,构造变形程度自南向北表现为由强至弱。挤压应力作用的时期和强度、滑脱断层的向北滑脱、构造楔的楔入长度及推挤距离、滑脱层的厚度和上覆地层厚度,以及沉积时代、沉积速率和岩性差异等因素是引起研究区构造垂向分层、南北分带的原因。该结果对明确研究区构造发育及下一步油气地质勘探具有指导意义。

Deep structure at northern margin of Tarim Basin

In this paper, a 2D velocity structure of the crust and the upper mantle of the northern margin of the Tarim Basin (TB) has been obtained by ray tracing and theoretical seismogram calculation under the condition of 2D lateral inhomogeneous medium using the data of seismic wide angle reflection/refraction profile from Baicheng to Da Qaidam crossing the Kuqa Depression (KD) and Tabei Uplift (TU). And along the Baicheng to Da Qaidam profile, 4 of the 10 shot points are located in the northern margin of the TB. The results show that the character of the crust is uniform on the whole between the KD and TU, but the depth of the layers, thickness of the crust and the velocity obviously vary along the profile. Thereinto, the variation of the crust thickness mainly occurs in the middle and lower crust. The Moho has an uplifting trend near the Baicheng shot point in KD and Luntai shot point in TU, and the thickness of the crust reduces to 42 km and 47 km in these two areas, respectively. The transition zone between the KD and TU has a thickest crust, up to 52 km. In this transition zone, there are high velocity anoma-lies in the upper crust, and low velocity anomalies in the lower crust, these velocity anomalies zone is near vertical, and the sediment above them is thicker than the other areas. According to the velocity distributions, the profile can be divided into three sections:KD, TU and transition zone between them. Each section has a special velocity structural feature, the form of the crystalline basement and the relationship between the deep structure and the shallow one. The differences of velocity and tectonic between eastern and western profile in the northern margin of the Tarim Basin (NMTB) may suggest different speed and intensity of the subduction from the Tarim basin to the Tianshan orogenic belt (TOB).

生长地层及其在判断天山北缘前陆冲断褶皱带形成时间上的应用

新生代以来天山北缘前陆冲断褶皱带自南向北可分为山麓冲断褶皱带、霍尔果斯-玛纳斯-吐谷鲁冲断褶皱带、独山子-安集海冲断褶皱带3排构造带。在野外观察的基础上，结合地震剖面分析，确定了各排构造带生长地层发育层序；结合裂变径迹年龄证据，并根据现有磁性地层等年代学资料，确定了天山北缘晚新生代构造变形时间序列：第一排构造带形成于距今10Ma以来；第二排构造带形成于距今7～2．58Ma以来；第三排构造带形成于距今大约0．73Ma后。

中国南天山西部冲断褶皱系前缘区的运动学特征

南天山冲断褶皱系是中—上新世以来形成的以薄皮滑脱为主的冲断构造 ,冲断作用导致了盆地内及周缘区古—新生界的碎屑岩和碳酸盐岩地层发主形变。本文对该冲断系前缘区 (巴音库鲁提北部至喀什地区 )的运动学特征进行了研究。南天山冲断褶皱系从平面上分出了六个冲断褶皱带。从剖面上划分出两种不同的冲断体系。冲断系的前锋为盲冲结构的构造三角带。冲断作用导致前锋区中新世以来层系变形、抬升并出露地表 ,本区有两个区域性的主滑脱面 ,冲断作用及断层相关褶皱的形成是冲断层沿主滑脱面向前陆方向逐渐推进的结果。同时发育的次级冲断层导致冲断褶皱带的复杂化。文章同时指出 ,南天山冲断褶皱系的冲断扩展顺序为逆序。这与塔里木盆地南缘西昆仑山前冲断带的活动方式相反 ,暗示着南天山构造带的运动学特征是独特的。利用平衡地质剖面的方法 ,在综合地质和地球物理资料的基础上 ,作出本区的构造横剖面图并进行了平衡恢复 ,从而得出南天山冲断褶皱系前缘区上新世以来的南北缩短率为30 % ,缩短量为 5 0km ,缩短速率为 9— 10mm/a。

塔里木盆地西部喀什地区的新生代冲断构造

利用新近获得的地球物理资料并结合前人的研究成果研究了塔里木盆地西部喀什地区的冲断构造特征。天山南缘冲断带西段 (巴什布拉克构造带 )以倾伏的短轴背斜为特征 ,东段 (乌恰—阿图什—喀什构造带 )以 3排枢纽近平行的线性背斜为特征。西昆仑北缘冲断带中褶皱相对不太发育 ,西北段 (肖尔布拉克构造带 )的前锋不是原来普遍认为的乌帕尔断层 ,而是其北部隐没在克孜勒苏河之下的一条无名逆冲断层。在乌恰以西 ,由于南天山与西昆仑相距较近 ,肖尔布拉克构造带的前锋与巴什布拉克构造带的前锋相互交切改造 ,不显示明显的早晚关系 ;在乌恰以东 ,南、北两条冲断带基本被喀什深洼陷阻隔。两个冲断带都在上新世中 晚期成型 ,第四纪以来仍受到强烈改造。西昆仑北缘冲断带主要以无序的方式扩展 ,天山南缘冲断带则主要以后展的方式扩展。冲断带的前锋断层主要是盲冲断层 ,这使得冲断带内 ,特别是南天山南缘冲断带内的背斜圈闭得以比较好地保存下来 ,对油气勘探具有重要意义。

塔里木盆地北缘—南天山造山带盆-山耦合和构造转换

文章探讨了塔里木盆地北缘和南天山造山带的盆-山耦合和构造转换过程。塔里木盆地属于典型的叠合盆地,经历了多期构造演化。研究表明,在地史时期中,塔里木盆地北缘和相邻南天山造山带经历了多期和复杂的盆山耦合和盆山转换过程,形成多种类型盆山耦合和转换方式。(1)按时间域可划分为:早古生代陆内裂陷盆地-早期伸展造山-晚期挤压造山耦合,晚古生代陆内裂陷盆地-弧后造山-晚期碰撞造山耦合,中生代陆内前陆盆地-挤压造山耦合,古近纪前陆盆地-挤压造山耦合,新近纪—第四纪再旋回前陆盆地-挤压造山耦合;(2)按深度域可划分为:深部地幔俯冲型盆-山耦合,地壳分层滑脱拆离型盆-山耦合,基底滑脱拆离型盆-山耦合,古生代伸展和逆冲推覆型盆-山耦合,中—新生代逆冲推覆型盆-山耦合;(3)按运动学和动力学可划分为:逆冲推覆型盆-山耦合和接触关系、重力滑脱型盆-山耦合和接触关系、走滑转换型盆山耦合和接触关系、深部岩浆上涌焊接型盆-山耦合和接触关系、鳄鱼嘴型盆-山耦合和接触关系。

准噶尔盆地南缘褶皱-冲断带变形特征及成因机制模拟

准噶尔盆地南缘褶皱-冲断带发育于北天山和博格达山北侧的准噶尔盆地南部的山前地区,构造变形具有明显的横向分带、纵向分段、垂向分层特征,其主控因素在于挤压应力的作用方式和滑脱层的空间分布规律。西段受北天山斜向挤压应力作用影响,发育北西西向四排雁列式褶皱-冲断带,构造变形样式为基底卷入式厚皮构造和盖层滑脱式薄皮构造,变形过程受侏罗系煤层和白垩系、古近系高塑性泥岩层等多滑脱层控制。滑脱层及其上覆岩层厚度决定变形的强度和应力向前传递的远近程度,厚度越大,褶皱变形强度越大。东段受博格达山正向楔冲挤压应力作用影响,发育近东西向向北凸出的弧形基底卷入式褶皱-冲断带,滑脱构造不发育。根据构造变形特征和相似理论,利用沙箱模拟实验分别对正向挤压和15°、30°、45°等斜向挤压平面变形进行了模拟,结果表明正向挤压和15°斜向挤压是形成东段和西段变形特征的主控应力条件,并设计了斜向和正向挤压组合边界平面模拟实验进行了验证,合理地解释了东、西段构造变形的差异。利用双滑脱层剖面模型实验对西段四排褶皱-冲断带的演化过程进行了模拟再现。

西昆仑—塔里木盆地盆-山结合带的中、新生代变形构造及其动力学

西昆仑—塔里木盆地盆-山结合带可划分为西昆仑北带和塔里木地块南缘拗陷带(塔南拗陷带)两个构造单元,后者由塔西南拗陷带和塔东南断陷带两部分组成。西昆北带分别以库地—喀什塔什断裂和西昆北冲断裂与西昆中带和塔里木地块南缘拗陷带相隔。盆-山构造经历了长期、叠次的形成、演化过程,但不同时期、不同层次的变形构造具有极大的统一性,总体表现为以西昆中断裂(其主体为库地—喀什塔什断裂)为根带,以北向逆冲扩展作用为主导,向北至塔南拗陷带腹部,逐渐转化为以垂直向上的构造伸展作用为主导。塔南拗陷带的逆冲断裂与具强烈深层流变组构的西昆北逆冲断裂属统一地球动力学系统中不同构造层次的成分,前者是后者向浅层脆性应变域扩展的产物。导致盆-山构造形成的驱动力来自昆仑构造带以南的持续、强烈的北向逆冲扩展作用,至少在塔南拗陷带的前早更新统地层分布区不存在塔里木地块自北向南俯冲的直接证据。西昆仑—塔里木盆地南缘的造盆、造山作用过程可简单地归纳为三个形成演化阶段:晚侏罗世—早白垩世的快速隆升和快速拗陷(沉降)期、晚白垩世—古近纪的深层拆离-缓慢隆升和均匀拗陷(沉降)期和新近纪至今的挤压-急剧隆升和强烈拗陷(沉降)期。造盆、造山作用的动力学过程表明,中—上新世是造盆造山作用机制发生重大转折时期,早更新世末的构造运动基本上奠定了西昆仑—塔里木盆地南缘的盆-山构造格架。

对新元古代湘桂海盆及邻区构造属性的探讨

新元古代的湘桂海盆夹持在中上扬子陆块的东南缘与华夏地块群之间,是古华南洋与下扬子陆块俯冲碰撞后在西南方向的残留海。东段古华南洋俯冲的地质记录发生在860～1034Ma间,为绍兴-江山-萍乡碰撞带,形成江南岛弧造山带;西段古华南洋与上扬子陆块俯冲的构造地质记录,推测在湖南的新化-城步至广西的三江一带,时间为850～820Ma,形成雪峰-四堡岛弧造山带,但无陆陆碰撞的记录。东、西两段构造活动有近1亿年至数十百万年的时间差,为湘桂海盆在停止扩张的洋底上提供了发育的空间,并转为弧前-深海盆地。由萍乡向南西方向至湖南茶陵-郴州为一结合带,西侧的沉积物属扬子沉积构造域和湘桂海盆,沉积了细屑浊积岩和硅泥质岩;东侧为华夏沉积构造域,包括赣、闽和粤北,充填了与热活动有关细碧岩、含铁石英岩和火山碎屑沉积岩;郴州至贺县间,有一东-西向的古南岭裂陷海与之相连,是分隔云开地块、粤东南地块与罗霄-武夷地块的深海槽。在早古生代构造旋回中,湘桂海盆、古南岭海槽以及华夏沉积构造域,分别转为不同构造走向的湘桂加里东褶皱带和华南加里东造山带。

中天山南缘乌瓦门地区发现蛇绿混杂岩

新发现的乌瓦门蛇绿混杂岩出露于中天山南缘断裂带中,主要表现为以变质粉砂岩为主的基质中混杂着大小不一、性质各异的块体。基质主要为泥盆纪绢云石英片岩、绢云绿泥石英片岩、二云石英片岩、千枚岩和变质粉砂岩,块体有肢解的蛇绿岩岩块、片麻岩岩块和大理岩岩块。肢解蛇绿岩岩块主要有含辉纯橄岩岩块、辉长岩岩块、基性火山岩岩块和硅质岩岩块。

塔里木盆地西北缘柯坪冲断带构造变形特征

柯坪冲断带位于塔里木盆地西北缘，是新生代南天山褶皱冲断系的一部分。本文根据野外实际考察和地震剖面解释，总结了该冲断带的构造变形特征。它是发育于古生界中且以中寒武统膏盐层为主滑脱面的薄皮构造，是内部结构相对简单的叠瓦状冲断，因更新世才定型而具暴露式冲断前锋，有断层传播褶皱发育但已遭强烈剥蚀，前展式冲断。上新世晚期的冲断曾控制了磨拉石盆地发育（西域组砾岩），但该盆地已遭更新世的冲断推覆作用破坏。根据平衡剖面恢复，柯坪冲断带南部3排冲断层的总构造缩短量为29.1%～40.7%。

天山南麓库车晚新生代褶皱-冲断带

库车褶皱冲断带位于天山南麓,由近东西走向的多条构造带组成。三叠系暗色泥岩、侏罗系煤层、古近系库姆格列木组膏盐层和新近系吉迪克组膏盐层构成库车褶皱冲断带的区域性主滑脱面。褶皱冲断带底面由北向南逐渐抬高。褶皱冲断带主体发育盖层滑脱-冲断构造（薄皮构造）,基底卷入型冲断构造（厚皮构造）见于北缘的根带。新生界膏盐层之上构造变形以滑脱褶皱为特色,之下以冲断构造为特色。库车褶皱冲断带是印度-亚洲碰撞远程效应下,（南）天山晚新生代造山过程的产物。褶皱冲断带构造变形的动力来源主要是造山楔向塔里木盆地推进所形成的挤压构造应力。褶皱冲断带构造变形的起始时间为约23Ma,构造变形具有阶段式加速的特点,已经识别出约23Ma、约10Ma、5～2Ma和1～0Ma共4个变形加速期。褶皱冲断带的演化过程为前展式,褶皱冲断带前锋向南推进的同时,后缘持续变形。

南天山库车褶皱冲断带构造几何学和运动学

印度板块与欧亚大陆的汇聚作用和持续碰撞使中亚内陆沿天山、昆仑山、阿尔金山发生变形 ,山脉前沿发育褶皱冲断带。南天山库车褶皱冲断带中段库车河地区发育 3～4排东西走向的逆冲 (掩 )断层和相关褶皱 ,逆冲 (掩 )断层由北向南扩展 ,断层和褶皱的形成时代自北向南逐渐变新 ,北部山前带的变形发生于前中新世 ,南部秋立塔克背斜带和亚肯背斜带的变形时代为上新世 (5 2± 0 2Ma)。通过构造几何学和运动学分析 ,作者提出了库车褶皱冲断带的构造变形方式和演化模型。

天山南北前陆盆地冲断带沉积砂体对构造逆冲作用响应动力学

通过对中西部前陆盆地冲断带垂直隆升高度与水平挤压缩短的分析,认为前陆冲断带的构造逆冲作用是一种综合作用,是分别由垂直方向的隆升力和水平方向的前展力组成的矢量合力,两种力的联合作用控制了冲断带的沉积充填特征。垂直隆升作用产生逆冲型断层,形成垂向运动位移量,使冲断带山体隆升、盆地沉降、产生可容纳空间。水平前展作用产生走滑型断层,形成水平滑动位移量,使山体前移、物源前进。由此,将天山南北前陆盆地冲断带古近纪—新近纪的构造逆冲作用划分为5个阶段,分别对应着3套粗粒沉积物与2套细粒沉积物。①古近系底部砂砾岩是早喜马拉雅运动初始期逆冲推覆的标志,同时也是以水平前展力为主阶段(垂直隆升力为辅联合作用)陆源碎屑沉积充填的产物;②新近系底部发育的砾质粗碎屑沉积体是中喜马拉雅运动初始期逆冲推覆重新活动的标志,是冲断负载初期以水平前展力为主构造逆冲作用的结果;③新近系顶部库车组/独山子组底部砾质粗碎屑沉积体发育在中喜马拉雅运动晚期,是基底回弹抬升后期、水平前展力作用下大量沉积物供给、砂体进积的产物。古近系与新近系的2套湖相泥岩沉积,是在垂直隆升力为主作用阶段,山体抬升导致山前挠曲沉降加剧,致使湖平面上升而出现广泛沉积的结果。

燕山褶断带晚三叠世都山复式岩基成因及侵位变形:华北北缘中生代早期构造背景的制约

对燕山褶断带内三叠纪都山花岗质岩基进行了详细野外观察,测量了岩体变形的构造要素,获得了锆石U-Pb定年、全岩主微量元素和锆石Lu-Hf同位素分析数据,用以揭示都山复式岩基的成因及构造背景。都山复式岩基包括南部变形较强的都山岩体和北部弱变形的大石柱岩体,锆石LA-ICP-MS分析表明都山岩体和大石柱岩体侵位时代在误差范围内一致,大石柱岩体并非晚二叠世岩体,而是与都山岩体近于同期侵位。都山复式岩基主要由花岗岩、石英二长岩及少量闪长岩组成,岩石具有高SiO2含量,低MgO含量的高钾钙碱性系列岩石,富集大离子亲石元素（如K、Ba、Sr）和轻稀土元素,亏损高场强元素（如Ti、Nb、Ta）和重稀土元素,并表现出埃达克质岩石的特征。锆石εHf（t）值介于-13.69~3.94。主微量元素和Hf同位素组成表明,都山复式岩基岩浆源区包括古老下地壳以及少量富集岩石圈地幔和亏损的软流圈地幔,母岩浆可能经历了岩浆混合。都山复式岩基南部岩体内片麻理具有环状分布特征,并且从岩体中心到边缘逐渐增强,岩体边部包裹大量片麻岩围岩团块。这些特征表明,岩体可能是在区域挤压构造应力场之下通过顶蚀-膨胀的方式主动侵位的。结合区域地质背景,都山花岗质复式岩基可能是在华北克拉通北缘中—晚三叠世岩石圈拆沉和减薄之后的板内伸展构造背景下软流圈上涌引起岩石圈地幔熔融底侵古老下地壳后形成的。中—晚三叠世之交,华北北缘进入板内伸展构造体制,岩石学证据表明,岩石圈经历了破坏和减薄,而上地壳岩石仍然记录了挤压构造变形。因此华北北缘中生代早期构造体制在时间和深度层次上存在解耦,岩石圈伸展的浅部响应存在明显的滞后性。

中天山东部南北两缘韧性剪切带变形特征

(1)中天山北缘韧性剪切带除右旋韧剪变形之外,还发育相对较弱的左旋韧剪变形,局部残留加里东晚期的逆冲推覆韧剪变形;右旋韧剪变形的变形温度环境为中-低温,左旋韧剪变形的变形温度环境为高温、中温、中低温及低温。(2)中天山南缘韧性剪切带以右旋韧剪变形为主,兼具左旋韧剪变形;右旋韧剪变形的变形温度环境为中温、中低温、低温,左旋韧剪变形的变形温度环境为高温、中温、中低温及低温。(3)东天山存在一系列右旋韧性剪切带,中天山南北两缘韧性剪切带的构造变形与辛格尔断裂、兴地断裂等右旋韧性剪切带的变形以及塔里木北缘东部晚震旦—早古生代地层的同劈理褶皱变形、南天山泥盆纪地层的变形可能具成因联系。

准噶尔盆地南缘褶皱冲断带断裂输导石油效率评价

为了评价准噶尔盆地南缘褶皱冲断带断裂输导原油效率,通过定义断裂输导系数和分析原油成藏过程有效性,建立了断裂输导石油效率评价方法。评价结果表明,断裂输导系数沿着褶皱冲断带呈带状分布,高效断裂输导区主要位于托斯台背斜、独山子背斜、安集海背斜、霍尔果斯背斜及其以南、吐谷鲁背斜、清水河断鼻和齐古背斜等地区。高效断裂输导区内,第一排构造带断裂输导效率最高,第二排构造带次之,第三排构造带相对最低。研究区独山子油田、霍尔果斯油田、吐谷鲁油田、齐古油田等均分布在高效断裂输导范围内,表明高效断裂输导是准南褶皱冲断带原油成藏的重要条件之一。