滇西北弥渡地区主要断裂晚新生代发育特征及其动力学机制

弥渡地区位于滇西北断陷带东南缘,红河断裂带尾端与程海断裂交汇部位,是揭示滇西北断陷带形成机制及其与红河断裂带间运动学关系的关键区域。综合利用遥感解译及野外调查发现,区内主要发育有北东向的毛栗坡断裂,北西—北北西向的凤仪-定西岭断裂、弥渡断裂、密祉断裂、寅街断裂。对断裂错动地质、地貌体及擦痕的统计分析结果表明,毛栗坡断裂第四纪以左旋走滑活动为主兼具有正断分量;弧形的弥渡断裂及北西向的寅街断裂第四纪期间均以正断活动为主;上新世期间凤仪-定西岭断裂以右旋走滑为主,密祉断裂主要为伸展正断,二者第四纪期间均无明显活动。据弥渡地区主要断裂的几何形态、运动学特征及红河断裂带晚新生代活动性变化过程推测,控制弥渡盆地展布的弥渡断裂、寅街断裂等主要第四纪活动断裂是在继承和改造红河断裂带原有断层行迹的基础上形成的。上新世或更早,弥渡地区及滇西北断陷带的断裂活动与地壳张扭变形可能与红河断裂带尾端伸展变形作用有关,但第四纪期间,程海断裂基本上完全控制了弥渡地区主要活动断裂的发育,这一时期区内张扭变形的动力可能来自于川滇内弧带的顺时针旋转以及周缘南汀河断裂、畹町断裂与理塘断裂等左旋走滑断裂引起的区域性走滑拉分的共同作用。      

滇西北宾川地区主要活动断裂及其活动构造体系

通过卫星遥感解译和地表调查,对滇西北宾川地区活动断层进行了相对全面的调查研究,并对该区活动构造体系提出了新认识。研究表明,该区发育以北东向正断层和走滑断层为主的活动断裂,并构成了典型的张扭性帚状构造,控制了宾川地区构造地貌的发育。该活动构造体系的主干活动断裂是近南北向程海—宾川断裂向南至宾川处分解后形成的2条分支断层,即近南北向以正断性质为主兼具左旋的宾川断裂(F1)和北东向左旋走滑的上沧—鱼棚断裂(F2)。宾川地区活动构造体系是在区域近东西向伸展和微地块顺时旋转的共同作用下形成的,反映了滇西北裂陷带在青藏高原整体瞬时旋转背景下的左旋拉分运动模式。同时,对宾川地区活动构造体系的研究也有助于更好地认识该区未来的强震危险性,对于其中主干断裂(F1、F2)的大震危险性应给予更多关注。     

江南东段地区NE-SW向断裂带断层滑移矢量反演及其大地构造意义

华南中-新生代构造演化受太平洋构造域和特提斯洋构造域的联合控制.以江南东段NE-SW向景德镇-歙县剪切带和球川-萧山断裂中发育的脆性断层为研究对象,利用野外交切关系和断层滑移矢量反演方法厘定了7期构造变形序列并反演了各期古构造应力场,讨论了断层活动的时代及其动力学.白垩纪至新生代研究区7期古构造应力场分别为:(1)早白垩世早期(136～125Ma)NW-SE向伸展;(2)早白垩世晚期(125～107Ma)N-S向挤压和E-W向伸展;(3)早白垩世末期至晚白垩世早期(105～86Ma)NW-SE向伸展;(4)白垩世中期(86～80Ma)NW-SE向挤压和NE-SW向伸展;(5)晚白垩世晚期至始新世末期(80～36Ma)N-S向伸展;(6)始新世末期至渐新世早期(36～30Ma)NE-SW向挤压和NW-SE向伸展;(7)渐新世早期至中新世中期(30～17Ma)NE-SW向伸展.结合区域地质研究表明,第1期至第4期古构造应力场与古太平洋构造域的板片后撤、俯冲以及微块体(菲律宾地块)间的碰撞作用有关;第5期伸展作用受控于新特提斯构造域俯冲板片后撤,而第6期和第7期古构造应力场主要与印-亚碰撞的远程效应有关.白垩纪至新生代,华南东部受伸展构造体制和走滑构造体制的交替控制.先存断裂的发育可能是导致华南晚中生代走滑构造体制的主要控制因素.     

滇西北永胜地区主要活动断裂与活动构造体系

位于滇西北断陷带东北部、程海-宾川断裂带北端的永胜地区上新世以来断裂活动强烈,构造地貌特征显著。永胜地区1:50000活动构造填图发现,区内共存在各类断裂14条。其中金官断裂（F₁）、永胜断裂（F₂）、木耳坪羊坪断裂（F₃）三者规模最大,活动性亦远超其他断裂,属于程海-宾川断裂带的一级分支断裂,其他断裂为程海-宾川断裂的二级分支断裂。构造地貌特征、错断地质体及擦痕统计等均指示区内断裂现今主要以伸展正断活动为主,根据活动性的差异可将其分为强、较强、中等、弱、极弱5类,其中金官断裂的活动性最强,垂向活动速率可达0.20~0.26 mm/a。对永胜地区主要断裂几何学、运动学特征的研究及动力学机制的讨论可知,永胜地区主要断裂在平面上构成向东突出的弧形旋扭构造体系,在剖面上表现为张扭性断裂常见的负花状构造;程海-宾川断裂带现今活动主要是在近南北向主压应力作用下产生的近东西向的伸展正断,并因为叠加了旋扭作用而具有一定左旋走滑。永胜地区的弧形旋扭构造体系及滇西北断陷带等均是在川滇内弧带顺时针旋转及南汀河断裂、畹町断裂与理塘断裂的走滑拉分共同作用下形成的。      

“伸展-走滑”复合作用下构造变形的物理模拟

新生代渤海湾盆地为典型的"伸展-走滑"复合盆地, NNW-SSE向伸展作用和NE-SW向走滑作用的复合效应导致盆地内部构造样式的复杂性和多样性。本文针对走滑作用方向与伸展作用方向垂直的情况,就不同"伸展-走滑"复合条件下的断裂发育特征与演化过程开展了3类13组构造物理模拟实验,结果表明:①在先伸展后走滑的条件下,早期发育的伸展断层被晚期走滑断层强烈切割、改造,平面上表现为雁列式组合或主走滑断层,剖面上发育花状构造;②先走滑后伸展的条件下,平面上表现为早期雁列式的R剪切复活,作为晚期伸展正断层的转换断层,剖面上表现为似花状构造;③伸展和走滑同时作用的情况下,伸展与走滑作用的强弱配比关系影响断裂的发育特征,可建立"走滑强于伸展"、"走滑伸展强度相近"和"伸展强于走滑"三类模式。实验结果在辽东湾坳陷得到了印证,可为渤海湾盆地及类似伸展-走滑复合盆地的构造解析及动力成因机制分析提供指导和借鉴。     

桂西北南丹-荔波地区中、新生代构造演化:来自古构造应力场的证据

桂西北南丹-荔波地区是我国重要的锡多金属矿床富集地,近年来油气勘探显示该区亦具有极大的海相页岩气成藏潜力。因此,深入探讨和认识该区中、新生代构造应力场特征及其构造演化是成矿规律研究和页岩气勘探过程中不可或缺的重要环节。本文以南丹-荔波地区广泛发育的褶皱、共轭节理和断层为研究对象,在详细野外观测的基础上,利用叠加褶皱、共轭节理分析以及断层滑动矢量等方法,反演了研究区中、新生代构造应力场变化。构造解析表明,该区中、新生代共经历了四期构造应力场的交替和演化,分别为NNE-SSW 向挤压、NW-SE 向挤压、NEE-SWW 向伸展和近E-W 向挤压。结合区域构造演化特征,推测NNE-SSW 向挤压应力场的形成可能与印支期华南大陆南北边缘与印支/华北板块碰撞闭合有关;NW-SE 向挤压应力场和NEE-SWW 向伸展应力场可能分别对应于燕山早期古太平洋板块向华南大陆之下的俯冲消减以及燕山晚期发生的弧后伸展作用;近E-W 向挤压应力场可能形成于喜山期印度?欧亚板块陆陆碰撞所产生远程效应的构造背景之下。     

内蒙古狼山地区新生代断层活动特征：对正断层生长的限定

阿拉善地块东北缘的狼山地区新生代发育有3期构造,分别为中新世NW-SE向挤压形成的逆断层,NNE向挤压形成的左行走滑断层以及晚新生代NW-SE向伸展形成的高角度正断层。结合阿拉善地块东缘的新生代构造,认为狼山地区新生代断层的活动与青藏高原东北缘的逐步扩展、应力场逐渐调整有关。狼山山前正断层目前是一条贯通的断层,其演化基本符合恒定长度断层生长模型,断层中间部位滑动速率最大,向断层两侧逐渐递减。从不同方法得出的滑动速率来看,进入全新世以来,断层滑动速率有逐渐变小的趋势。结合阿拉善地块内部及东缘断层震源机制解以及断层的几何学、运动学特征,认为河套—吉兰泰盆地和银川盆地属于两个性质不同的伸展盆地,两者通过构造转换带相连,转换区内断层表现为右行走滑。转换区5级以上地震可能是受区域性NE-SW向挤压,近南北向右行断层活动的表现。     

歧口凹陷新生代构造演化与油气

歧口凹陷是地壳拆离断层(NE-NNE向沧东断层)NW-SE向伸展作用和NNE向深断裂带走滑作用叠加的产物.新生代演化分为3个时期:始新世,由于NW-SE向区域伸展作用,凹陷是一个由沧东断层控制的断坡凹陷;渐新世,凹陷受NW-SE向区域伸展和NNE向深断裂带右旋走滑的共同作用;晚第三纪到第四纪,区域伸展作用基本停止,走滑作用仍在继续,由走滑作用导致的SN向局部伸展作用显得更加突出.构造演化对凹陷油气形成和分布有控制作用,凹陷西部和南部是有利的油气勘探区.     

Termit盆地构造变形的力学机制

Termit盆地是中西非裂谷系中典型的中-新生代裂谷盆地,形成于早白垩世大西洋张裂的构造背景下。在白垩纪至古近纪经历了"裂谷-坳陷-裂谷"的构造演化过程,且两期裂陷作用形成的断裂走向不同。依据Termit盆地的基础构造特征,运用弹性有限元数值模拟方法,从动力学角度讨论盆地构造演化模式,为盆地的构造演化研究提供动力学依据。模拟结果表明,在早白垩世,盆地受区域NE-SW向拉张作用,在盆地西部边界发育一系列NW-SE向早白垩世早期断层。在古近纪,盆地受近EW向拉张作用,在盆地西部受早期断层影响较大的Dinga断阶带和Yogou西斜坡地区,局部应力场使断层发育走向为NW-SE;受其影响较小的Araga地堑发育张扭性断层,沿早白垩世断层呈雁行排列;不受其影响的Fana低凸起和Moul凹陷发育NNW-SSE向断层。     

渤海海域渤南地区新生代断裂体系与盆地演化

利用现今丰富的三维地震资料,将地震剖面解释与相干切片分析相结合,对渤海海域渤南地区断裂发育与盆地结构 进行研究,明确了断裂体系及构造演化特征。结果表明：新生代郯庐断裂渤南段可分为东、中、西三支,并与受郯庐走滑 断裂影响的近EW向、NW向和NE向主干断裂体系共同组成了渤南地区网格状的构造格局;而区域应力背景的改变导致渤 南地区走滑和伸展作用的强弱发生了变化,使得构造演化可划分为左旋走滑-强伸展、右旋走滑-强伸展和弱走滑-弱伸展 三个阶段,第一阶段孔店组~沙四段郯庐断裂东支强烈活动,中支和西支活动微弱,NW向和近EW向大断裂活动形成了黄 河口凹陷和莱州湾凹陷的盆地格局;第二阶段沙三段~东营组走滑断裂三支及其他方向主干断裂均活动,NE向和近EW向 次级断裂开始发育,各盆地持续性伸展断陷;第三阶段馆陶组-明化镇组右旋走滑减弱,郯庐断裂中支和西支发育呈一系 列NE向雁列断层,东支及其他方向主干断裂附近次级小断层继续增多,各盆地转为了整体的坳陷。     

Successive Extensional Tectonic Regimes during the Mesozoic as Evidenced by Neptunian Dikes in the Pontide Magmatic Arc,Northeast Turkey

The eastern Pontide magmatic arc extends ～600 km in an E-W direction along the Black Sea coast and was disrupted by a series of fault systems trending NE-SW, NW-SE, E-W, and N-S. These fault systems are responsible for the formation of diachronous extensional basins, rift or pull-apart, in the northern, southern, and axial zones of the eastern Pontides during the Mesozoic. Successive extensional or transtensional tectonic regimes caused the abortive Liassic rift basins and the Albian and Campanian pull-apart basins with deep-spreading troughs in the southern and axial zones. Liassic, Albian, and Campanian neptunian dikes, which indicate extensional tectonic regimes, crop out within the Paleozoic granites near Kale, Gumushane, and the Malm–Lower Cretaceous platform carbonates in Amasya and Gumushane. These neptunian dikes correspond to extensional cracks that are filled and overlain by the fossiliferous red pelagic limestones. Multidirectional Liassic neptunian dikes are consistent with the general trend of the paleofaults (NE-SW, NW-SE, and E-W), and active dextral North Anatolian fault (NAF) and sinistral Northeast Anatolian fault (NEAF) systems. The Albian neptunian dikes in Amasya formed in the synthetic oblique left-lateral normal faults of the main fault zone that runs parallel to the active North Anatolian fault zone (NAFZ).

Kinematic interpretation of the Liassic and Albian neptunian dikes suggests N-S extensional stress or northward movement of the Pontides along the conjugate fracture zones parallel to the NAFZ and NEAFZ. This northward movement of the Pontides in Liassic and Albian times requires left-lateral and right-lateral slips along the conjugate NAFZ and Northeast Anatolian fault zones (NEAFZ), respectively, in contrast to the recent active tectonics that have been accommodated by N-S compressional stress. On the other hand, mutual relationships between the neptunian dikes and the associated main fault zone of Campanian age extending in an E-W direction in the Kale area, Gumushane suggest the existence of a main left-lateral transtensional wrench zone. This system might be accommodated by the counterclockwise convergence of the Turkish plate with the Afro-Arabian plate relative to the Eurasian plate, and the southward oblique subduction of Paleotethys beneath the eastern Pontide magmatic arc during the Mesozoic.     

Seismic and GPS evidence for the kinematics and the state of stress of active structures in south and south-central Tibetan Plateau

Since the middle Miocene, widely distributed N-S striking rifts or rift-depressions and NE-NW-striking strike-slip faults have developed as major structures in southern and south-central Tibet. Active structures, seismic mechanisms and directions and rates of movement determined from GPS data are different in south and south-central Tibetan Plateau. In southern Tibet, N-S striking normal faults and a few transtensional/transpressional faults are the main structures, but none of the GPS measurements show eastward movement. In south-central Tibet, NE- and NW-striking transpressional/transtensional faults and several large-scale E-W and WNW-striking dextral and sinistral strike-slip faults are the main structures, and are consistent with the movement direction indicated by the GPS data. On the other hand, the pattern of earthquake data from the south-central Tibetan Plateau, and especially from the eastern and western syntaxes, are very complicated. These structures may be produced by N-S contraction which has resulted in the N-S striking linear structures, parallel to the direction of maximum compressive stress, and conjugate NE- and NW-striking transpressional/transtensional faults on the southern side of the Qiangtang Block, and in the eastern and western syntaxes, but the deformation is not continuous from the south to the south-central Tibetan Plateau. Underthrusting of the Indian Plate under the southern Tibetan Plateau after the Middle Miocene may be the main cause of these structural features.     

西秦岭地区东昆仑-秦岭断裂系晚新生代左旋走滑历史及其向东扩展

要通过在TM遥感图像解译和野外观测的基础上,描述了东昆仑断裂带东段活动形迹的组成和活动断层地貌特征,阐述了甘南高原西秦岭地区新近纪拉分盆地的沉积-构造特征,提出了该区东昆仑-秦岭断裂系晚新生代左旋走滑伸展-走滑挤压-走滑伸展的3个阶段的构造变形模式。指出,中新世晚期至上新世早期,东昆仑-秦岭断裂系以左旋走滑伸展活动为主,伴随着西秦岭地区拉分盆地的形成和超基性火山岩群的发育。这期左旋走滑伸展活动向东扩展导致了渭河盆地新近纪引张应力方向由早期的NE-SW向转变为晚期的NW—SE向。上新世晚期以来(约3．4Ma以前),东昆仑-秦岭断裂系以左旋走滑挤压活动为主,导致早期拉分盆地的轻微褶皱变形,走滑挤压活动主要集中在东昆仑东段玛沁-玛曲主断裂带上。该期构造变动持续到早更新世,它的向东扩展产生了广泛的地壳形变效应,包括青藏东缘岷山隆起带的快速崛起、华北地区汾-渭地堑系的形成和发展以及郯庐断裂带右旋走滑活动等。中、晚更新世时期,断裂系以走滑伸展变形为主,主要集中在东昆仑断裂带东段3个分支上,地块向东挤出伴随着顺时针旋转。     

Structural appraisal of the Gadag schist belt from gravity investigations

Semi-detailed gravity investigations were carried out over an area of approximately 2750 sq km with maximum N-S and E-W extents of 55 and 50 km respectively in the Gadag region in the Dharwar craton with a view to obtain a clearer perception of the structural configuration of the region. From qualitative analysis of the gravity data, several tectonic features are inferred: the high density Gadag schist belt is characterized by a gravity high and occurs in two discontinuous segments — the main N-S trending segment, and its thinner NW-SE trending extension, the two separated by a NE-SW trending deep seated fault. While the N-S trend of the Gadag schist belt is bounded on its east by the NW-SE trending Chitradurga thrust fault and on its west by another major NNWSSE trending fault, the NW-SE extension is likewise bounded by two other NW-SE major faults. Quantitative evaluation from forward modeling/inversion of five profiles in the region, assuming a density contrast of 0.29gm/cc of the anomalous schistose body with the gneissic host rocks indicated a synclinal structure plunging to the southeast along its axis for the Gadag schist belt. The maximum width and depth from surface of the schist belt are 22 km and 5.6 km respectively.     

En echelon fractures in a dextral shear zone - tectonic heritage for a hydrothermal cave (Budapest, Hungary)

Microtectonic study of brittle structures in the József Hill Cave, Budapest, highlights the connection between different phases of fracturing and cave formation. E-W trending dextral faults (second order Riedels) and NW-SE oriented tension fractures developed in a ENE-WSW trending dextral shear zone as a result of WNW-ESE directed compression. Ascending thermal water dissolved cave galleries and created barite veins along these fractures. The first stage of cave formation as inferred from timing of fracturation from the regional stress field was Oligocene-Early Miocene. Between the Middle Miocene and Quaternary new N-S to NE-SW trending normal faults were formed by ESE-WNW extension. Pleistocene differential uplift resulted in the reactivation and enlarging of fault zones, dominantly the E-W trending older Riedels. These recent tectonic events enhanced the original en echelon geometry of the older cave corridors.     

黔西北纳雍-水城一带构造变形特征及其演化

黔西北纳雍-水城一带位于扬子板块西南缘,区内断裂和褶皱极为发育。通过详细野外地质调查,并结合沉积地层接触关系,对区内构造行迹及其组合特征、构造变形期次和构造演化进行探讨。研究表明,震旦纪末至中侏罗世纳雍-水城一带经历了多次构造事件,特别是广西构造事件和印支期构造事件,导致明显的差异剥蚀,但均未造成地层褶皱变形,地层间表现为平行不整合接触。晚侏罗世以后的燕山构造期和喜山构造期才是区内发生构造变形的重要时期。纳雍-水城一带发育的NE-SW、NW-SE及近E-W向三组构造以及在NE-SW、NW-SE向两组构造交接转换部位发育的穹窿构造、构造盆地,均为侏罗纪晚期至早白垩世时期强烈构造事件的产物。其中NE-SW向褶皱及近E-W向断层先期形成,NW-SE向褶皱后期形成,并对先期形成的NE-SW向褶皱进行叠加改造。     

Seismic faults in the Aegean area

Reliable fault plane solutions of shallow earthquakes and information on surface fault traces in combination with other seismic, geomorphological and geological information have been used to determine the orientation and other properties of the seismic faults in the Aegean and surrounding area.Thrust faults having an about NW-SE strike occur in the outer seismic zone along western Albania-westernmost part of mainland of Greece-Ionian Sea-south of Crete-south of Rhodes.The inner part of the area is dominated by strike-slip and normal faulting. Strike-slip with an about NE-SW slip direction occurs in the inner part of the Hellenic arc along the line Peloponnesus-Cyclades-Dodecanese-southwest Turkey as well as along a zone which is associated with the northern Aegean trough and the northwesternmost part of Anatolia. All other regions in the inner part of the area are characterized by normal faulting. The slip direction of the normal faults has an about SW-NE direction in Crete (N38°E) and an about E-W direction (N81°E) in a zone which trends N-S in eastern Albania and its extension to western mainland of Greece. In all other regions (central Greece-southern Yugoslavia and Bulgaria, western Turkey) the slip of the normal faults has an about N-S direction.     

Qualitative analysis of mafic dyke swarms and kimberlites from morphological and geophysical signatures,NW of Proterozoic Cuddapah basin,Eastern Dharwar craton

Widespread distribution of mafic dykes and scanty occurrence of ultrabasic intrusives of kimberlitic affinity around Proterozoic Cuddapah basin, parts of Eastern Dharwar craton of south India has been the focus of attention since their discovery, to understand the structural fabric in relation to their emplacement in geological time. Satellite Imagery, geomorphological, geophysical and radiometric age data of Narayanpet area, northwest of Cuddappah basin, have clearly displayed the alignments and structures of geological significance, such as deep seated fault / fracture / shear zones, stratigraphic / lithological contacts, basic / ultrabasic intrusives and younger granites etc,. Based on the field observations such as emplacement of mafic dykes, their cross cutting relationship, study of morphological and geophysical signatures, inferred linears drawn from satellite imagery, aeromagnetic and gravity maps are arranged in a chronological order. A system of long, narrow and widely spaced dykes trending NW-SE direction conformable to gneissic foliation, typically associated with migmatites in the southwestern part of the study area are the oldest. Followed by E-W dykes, cut across by the sparsely distributed dykes associated with NW-SE and N-S features and in turn off set by dykes of NE-SW trends are the youngest. Kimberlites of Narayanpet area, belongs to hypabysal facies, which are essentially controlled by E-W to ENE-WSW deep seated fault / fracture zone, their intersection with NW-SE, NE-SW to N-S trends, which may have been reactivated during Proterozoic period as indicated by the intrusion of mafic dykes (～2270 to 1701 Ma) and emplacement of kimberlitic magmatism (～1300 to 1100 Ma) suggesting different intrusive episodes. Kimberlite pipes of Narayanpet field, falls in an ellipsoid form trending WNW-ESE direction in the northern part of the area, associated with radial drainage / topographic high and a gravity low. In addition, physical properties such as density and magnetic susceptibilities of mafic dykes and kimberlites, their geophysical signatures, emplacement of kimberlites at the close vicinity of mafic dykes or at their intersections have also been discussed.     

天水盆地晚新生代构造演化——对青藏高原北东向扩展的指示意义

天水盆地是一个位于青藏高原东北缘的晚新生代盆地,西秦岭北缘断裂穿盆而过。盆地内充填了较为完整的晚新生代地层,记录了该区晚新生代以来的构造变形历史,对研究青藏高原北东向扩展的构造响应具有重要意义。本文基于详细的野外构造变形分析与测量,结合已有的年代学与沉积学研究,初步提出天水盆地晚新生代以来构造变形序列与构造应力场,重建其晚新生代构造演化历史。详细研究表明,天水盆地晚新生代以来主要经历了3期构造演化:即中新世早-晚期NW-SE向构造伸展,沉积盆地发育,并伴随碱性超基性火山岩喷发和金刚石矿床形成;中新世晚期-早、中更新世NE-SW向挤压,盆地发生构造反转,其动力学背景可能源于晚新生代青藏高原的北东向扩展,指示高原物质扩散开始显著影响到西秦岭地区;晚更新世以来受近N-S向伸展作用控制,盆地发生向东有限挤出并伴随顺时针旋转,主要由于青藏高原向北东扩展过程中,区域构造挤压应力方向发生顺时针偏转所致。