郯庐断裂系研究的新进展——兼论东亚北东向走滑断裂系统

对郯庐断裂系研究的最新进展作了介绍。郯庐断裂是多期活动，性质多次转换的巨型断裂，最初的启动时间在晚三叠世末，与南北大陆的碰撞有着直接的关系，早期以走滑（左行）运动为主，伴随挤压和拉伸，范围限于华北地块内部，断裂纵向伸展的高峰期为白垩纪到早始新世，这一时期也是裂陷作用最强的时期，始新世以来以挤压作用为主，东亚走滑断裂系各组成断裂性质复杂，不能以中生代左行平移运动简单概括，走滑断裂系的发展和演化与同时     

青藏高原中部第四纪左旋剪切变形的地表地质证据

在青藏铁路的格尔木—拉萨段进行的活动断裂调查发现,在沱沱河—五道梁之间宽约150km的地段内发育了多条由北西西向次级断层左列分布构成的北西西向和北西向左旋张扭性断裂带,在断裂带之间则发育"S"型的北东向裂陷盆地和雁列分布的菱形裂陷盆地,盆地边界断裂也为左旋张扭性质。上述断裂带和裂陷带主要形成于第四纪,它们构成了宽约150km的不均匀的左旋简单剪切变形域,该变形域的整体活动性较弱,属于弱的不均匀剪切变形域。但其中的二道沟断陷盆地是个例外,该盆地边界断裂的垂直活动速率约为0 5mm/a,左旋活动速率介于0 8～1 0mm/a之间。而在整个左旋剪切变形带累计的左旋走滑速率不会超过6mm/a,它们所调节的昆仑山与唐古拉山之间的地壳南北缩短量也可能仅占总缩短量的15%～30%。上述弱剪切变形域与强烈左旋走滑的昆仑断裂系共同构成了高原中部的左旋剪切变形带,它们在印度板块与欧亚板块强烈碰撞的构造动力学背景下,起着调节青藏高原南北向缩短的重要作用。     

郯庐断裂带北段构造特征及构造演化序列

根据大量野外地质调查和盆地地震资料分析,认为郯庐断裂北段在中-新生代发生多期不同性质的活动,形成各具特色的构造变形现象。密山县知一镇敦密断裂韧性剪切带具有左旋走滑特征,其中黑云母~(40)Ar/~(36)Ar-~(39)Ar/~(36)Ar等时线年龄为161±3Ma,是郯庐断裂带被利用发生第二期左旋走滑运动并向北扩展到中国东北-俄罗斯远东地区的产物。四平市叶赫乡佳伊断裂带中负花状断裂形成于早白垩世早中期,是郯庐断裂北段在早白垩世遭受左旋走滑-拉张作用的典型代表。四平市石岭镇佳伊断裂大型走滑-逆冲断褶带、桦甸县敦密断裂"逆地堑"、沈阳-哈尔滨逆冲断裂形成于晚白垩世嫩江运动-晚白垩世末期,这一时期脆性右旋走滑-逆冲事件规模大,影响范围广,导致整个郯庐断裂北段遭受到强烈改造。佳伊断裂带和敦密断裂带中古近纪盆地在横剖面上呈不对称地堑,并且不对称地堑沿断裂带走向发生断、超方向左右变位,是郯庐断裂带北段在古近纪时受右旋走滑、伸展双重机制控制的产物。根据郯庐断裂带北段中-新生代不同地质时期变形特征,建立了郯庐断裂北段构造演化序列。即郯庐断裂北段构造演化分为左旋韧性剪切(J_2末期)、左旋张扭(K_1早中期)、右旋压扭(K_2晚期-末期)、右旋走滑断陷(E)和构造反转(E_3末期)五个阶段。其演化历史主要受控于环太平洋构造域的构造作用。     

Three-dimensional compressional deformations in the Zailiski Alatau mountains,Kazakstan

Abstract

The classical model of faulting predicts that slip planes occur in two conjugate sets. Theoretically, more sets can be contemporarily active if pre-existing structures are reactivated in a three-dimensional strain field. Four to six sets of faults have been active in the Holocene in the Zailiski Alatau mountain range, Kazakstan. Faults strike with the highest frequency ENE and ESE and show mostly left-lateral reverse and right-lateral reverse motions, respectively. These faults have a bimodal distribution of dips, forming four sets arranged in orthorhombic symmetry. Locally, NNW- to NNE- striking vertical faults have also been active in the Holocene and show right-lateral strike-slip and left-lateral strike-slip motions, respectively. All these fault sets accommodated the general three-dimensional deformation, given by N-S-directed horizontal shortening, vertical extension, and E-W-directed horizontal extension. Field evidence also shows that the reverse motions, even if with a minor strike-slip component, occurred on high-angle planes with inclination of 65°-85°. ENE- and ESE-striking faults reactivated older fracture zones, whereas the other sets are newly formed. Comparison of these field results with the structures obtained from published analogue models shows a strong similarity of fault geometry and kinematics.     

大型走滑断裂对青藏高原地体构架的改造

青藏高原的大型走滑断裂有13条,已确定的大型韧性走滑断裂主要形成于3个时期:早古生代、印支期和新生代以来.印度/亚洲碰撞(60～50Ma)以来形成的大型韧性走滑构造位于青藏高原的南部,而且主要在喜马拉雅山链的东、西两侧,如西侧的喀喇昆仑和恰曼韧性右行走滑断裂,东侧的鲜水河-小江和哀牢山-红河韧性左行走滑断裂、崇山-澜沧江、嘉黎-高黎贡山和萨盖韧性右行走滑断裂等.主要的变形特征表现为早期具有地壳深部的韧性走滑剪切带性质,在后期抬升过程中,由韧性→韧脆性→脆性应变转化;而在青藏高原北部,表现为古韧性走滑剪切带的再活动,如阿尔金-康西瓦、东昆仑左行走滑断裂,以及新生的脆性断裂,如海源左行走滑断裂等.本文在青藏高原13条大型走滑断裂研究及综合研究的基础上,阐述不同时期的大型走滑断裂,以及它们在青藏高原地体拼合及碰撞造山中的作用,包括走滑断裂与走滑型褶皱造山、走滑断裂与挤压/转换型造山、走滑断裂与挤压盆-山体系、走滑断裂与地体相对位移和走滑断裂与地体的侧向挤出,以及走滑断裂与构造结的形成.     

What is responsible for development of the Asian–Pacific transition zone: The geodynamics of oceanic plates or the Asian continent?

The main unusual feature of tectogenesis of the Asian–Pacific transition zone in the Mesozoic–Cenozoic consists in the formation of left-lateral strike-slip faults, which form the East Asian global shear zone with paragenesis of its constituent variously oriented fault systems. Paragenetic analysis has revealed that continental blocks of the Asian–Pacific transition zone were displaced along systems of transit left-lateral strike-slip faults of the East Asian global shear zone by hundreds of kilometers in the southerly to southwesterly direction due to tectonic activity of the Asian continent, which drifted southwestward. This process was accompanied by the formation of compression and extension structures. Otherwise, it is difficult to explain the structuring of the overhanging margin of the continent by subduction of oceanic lithospheric plates in the northerly to northwesterly direction opposite relative to the displacement of the continental crust as is usually thought.     

Oblique convergence during the Cimmerian collision: Evidence from the Triassic Aghdarband Basin,NE Iran

The Lower-Middle Triassic Aghdarband Basin, NE Iran, consists of a strongly deformed arc-related marine succession deposited along the southern margin of Eurasia in a highly mobile tectonic context. This basin is a key-area for the study of the Cimmerian events, as the Triassic units show severe deformations, which occurred short time after the collision of Iran with Eurasia, and were sealed by the Middle Jurassic succession. In this work, we document the structural setting and evolution of this area, based on detailed mesoscopic structural analyses of faults and folds, paleostress reconstruction and revision of the Triassic stratigraphy. The Triassic sequences are deeply involved in a N-verging thrust stack interacting with an important left-lateral transpressional fault zone characterized by strike-slip faults, vertical folds and high angle reverse faults generating intricate positive flowers. Systematic folds asymmetry indicates that they developed in a left-lateral transpressional zone coeval to thrust imbrication to the south, due to a marked strain partitioning.The extent of the transpressional zone shows that important left-lateral movements developed parallel to the belt during the Cimmerian collision, in response to oblique convergence between Iran and Eurasia. Inversion of Triassic syn-sedimentary faults, possibly inherited from Palaeozoic structures of the Kopeh Dagh basement and favouring strain partitioning, is suggested by unconformities, significant differences in the sedimentary successions, repeated olistoliths, scarp-related coarse breccias and rapid tectonic drowning, occurring especially along the northern tectonic boundary of the basin. Paleostress analyses point to a complex stress pattern showing a 45° rotation of the stress field along the left-lateral fault system, related to a complete deformation partitioning in two domains respectively characterized by pure reverse dip-slip and strike-slip motions. The main direction of compression, possibly oriented NE–SW in present days coordinates, favoured the development of large shear zones disrupting the eastern portion of the Cimmerian orogen.     

Seismic reflection imaging of active faults and their tectonic behavior in the Northern Moroccan margin. Is the Nekor fault a pure strike-slip fault?

The study of 1000-km seismic reflection profiles, along the Northern Moroccan margin, allowed browsing new imaging in detail about the regional geological structures and their functioning. To achieve this goal, we elaborated a high-resolution depth model and a global tectonic sketch. The influence of recent tectonic activity is manifested by normal and strike-slip faults, trending mainly 70° N and 125° N. In this segment, the Nekor strike-slip fault seems to be connected to a secondary major fault system that changes direction from 30° N to 70° N, and changing behavior to left-lateral strike-slip fault with normal component. Analysis of local seismic activity recorded from 1990 to 2014 with moderate magnitudes activity shows alignments in clear superposition with the detected active faults in seismic reflection lines.     

Deformation style in the damage zone of the Mondy fault: GPR evidence (Tunka basin,southern East Siberia)

The Mondy strike-slip fault connects the W-E Tunka and N-S Hovsgol basins on the southern flank of the Baikal rift system. Ground penetrating radar (GPR) surveys in its damage zone provide constraints on thicknesses, dips, and plunges of fault planes, as well as on the amount and sense of vertical slip. Strike-slip faulting in the southern segment of the Mondy fault within the territory of Russia bears a normal slip component of motion along the W-E and NW planes. These motions have produced negative flower structures in shallow crust appearing as grabens upon Pleistocene fluvioglacial terraces. The amount of normal slip estimated from the displacement of reflection events varies over the area and reaches its maximum of 3.4 m near Mondy Village. In the Kharadaban basin link, left-lateral strike slip displaces valleys of ephemeral streams to 22 m, while normal slip detected by GPR reaches 2.2 m; this normal-to-strike slip ratio corresponds to a direction of ~ 6° to the horizon. The angles of dips of faults are in the range 75°-79°; the thicknesses of fault planes marked by low- or high-frequency anomalies in GPR records vary from 2.5 to 17.0 m along strike and decrease with depth within a few meters below the surface, which is common to near-surface coseismic motions. Many ruptures fail to reach the surface but appear rather as sinkholes localized mainly in fault hanging walls. The deformation style in the damage zone of the Mondy fault bears impact of the NW Yaminshin fault lying between its two segments. According to photoelasticity, the stress field changes locally at the intersection of the two faults, under NE compression at 38°, till the inverse orientations of principal compression and extension stresses. This stress pattern leads to a combination of normal and left-lateral strike slip components.     

郯庐断裂系研究的新进展─—兼论东亚北东向走滑断裂系统

对郯庐断裂系研究的最新进展作了介绍。郯庐断裂是多期活动、性质多次转换的巨型断裂。最初的启动时间在晚三叠世末，与南北大陆的碰撞有着直接的关系。早期以走滑（左行）运动为主，伴随挤压和拉伸，范围限于华北地块内部。断裂纵向伸展的高峰期为白垩纪到早始新世，这一时期也是裂陷作用最强的时期。始新世以来以挤压作用为主。东亚走滑断裂系各组成断裂性质复杂，不能以中生代左行平移运动简单概括。走滑断裂系的发展和演化与同时期大陆边缘所处的地球动力学环境，也就是与南北大陆的碰撞和古大洋板块的持续俯冲关系密切。新生代以来的构造事件使中生代的构造发生强烈变形变位改造。     

准噶尔盆地腹部两类走滑断裂带及其构造变形样式

走滑断裂带对中国西部压扭性叠合盆地大中型油气田形成与分布具有重要的控制作用,也是研究难点之一.基于高密度三维地震资料,本文采用多种地震构造解析技术,瞄准噶尔盆地腹部侏罗系开展了精细走滑断裂带解释和变形样式分析.在燕山Ⅱ幕构造活动期,侏罗系发育了NWW向左行压扭性和NE向左行张扭性两类走滑断裂带.它们都是由4组剪切断层复合而成,共同遵从左行简单剪切模式,但几何学特征和构造属性差异很大.NWW和NE向走滑断裂带不存在共轭剪切关系,而是在钝夹角区（135°左右）普遍具有弧形联合与归并趋势.在构造变形中,两类同期左行走滑断裂带弧形联合控制了变形区域旋扭形变和剪切破裂,构成了一个大尺度“面”状旋扭构造体系.旋扭构造变形样式对中亚陆内造山带研究具有一定借鉴意义,也为压扭盆地的油气勘探实践提供了新思路.     

Tectonic stress regimes,rift extension and transform motion: the South Iceland Seismic Zone

Abstract

The South Iceland Seismic Zone (SISZ) is located at the junction of three rift segments in southwestern Iceland. The presence of different types of faulting and of differently orientated subgroups in Upper Pliocene to Holocene formations indicate polyphase tectonism. We measured 736 minor faults at 25 sites. Two types of relationships between stress regimes are represented. The first type, named IDS (inhomogeneous data set), is characterized by the presence of two types of fault mechanisms, normal and strike-slip, consistent with a single direction of extension. The second type, named OSR (opposite stress regimes), is characterized by the presence of perpendicular directions of extensions for a single type (normal or strike-slip) of faulting. Because of contradictory chronological criteria, we infer that the OSR alternated during the brittle tectonic activity of the SISZ. Two stress regimes, primary and secondary, are characterized by directions of extension NW-SE and NE-SW, respectively. The general fracture pattern characterized for the primary stress regime in the SISZ includes NNE-SSW trending right-lateral strike-slip faults, conjugate ENE-WSW trending left-lateral faults and NE-SW normal faults. This distribution is quite consistent with a Riedel- type model of fault pattern in a left-lateral shear zone. The stress states characterized based on analysis of both the earthquake focal mechanisms and the recent faulting sow great similarity in terms of stress directions. The main difference is the larger ratio of strike-slip motions representing 71% of the total population in the case of earthquake focal mechanisms, whereas for the whole set of faults the proportion of strike-slip faulting was 50 %. We explain that a témpora evolution of the tectonic regime in the SISZ region, accompanied by a gradual change in stress field, starts with rift-type pure extension and progressively leads to development of preferentially strike-slip structures in the kinematic context of left- lateral transform motion. © Elsevier, Paris     

Evidences of Cenozoic strike-slip dislocations of the red river fault system in Paleozoic carbonate strata of Cat Ba Island (Northern Vietnam)

The structural researches of carbonate strata in the northeastern segment of the framework of the Red River Fault System (Cat Ba Island, Northern Vietnam) has been carried out. It was found that weakly deformed carbonate strata are cut by NW-trending (300–310°) strike-slip faults. Development of plicative and disjunctive dislocations occurred along predominantly sinistral strike-slip fault zones formed as a result of ENE regional compression (80°) during the Oligocene-Miocene phase of deformation. Late dislocations confined to the Pliocene-Quaternary phase of deformation (NNW regional compression 330–350°), are relatively less developed. Seismic monitoring data show that both plicative and disjunctive dislocations have continued to the present.     

玉树断裂带左旋走滑活动标志及其几何学 与运动学特征

玉树断裂带位于甘孜-玉树断裂带北西段,是一条总体呈NWW向展布的左旋走滑活动断裂带.沿断裂带发育错断水系与冲沟、拉分盆地、地震地表破裂与断裂破碎带等一系列反映玉树断裂带左旋走滑活动的典型地质-地貌标志.在室内遥感解译的基础上,结合最新的野外实地调查成果,对沿玉树断裂带上反映其左旋走滑活动的地质-地貌标志进行了总结,并对断裂带的几何学与运动学特征进行了综合分析.结果表明,玉树断裂带总长约150km,总体走向120～130°,自西向东可划分为呈左阶雁列分布的陇蒙达-结隆段、结隆-结古段和结古-查那扣段3段.沿该断裂带发育的串珠状拉分断陷盆地规模的大小反映出玉树断裂带自西向东拉张效应逐渐减弱、挤压效应逐渐增强的特点.玉树2010年7.1级地震的宏观震中处于晚第四纪活动性最为显著的中段,而仪器震中恰好处于该断裂带的不连续部位,进一步证明雁列走滑活动断裂带上的不连续部位通常是强震活动的初始破裂区域.     

Opposed shear senses inferred from neotectonic mesofracture systems in the North Anatolian fault zone

The 1200-km long North Anatolian fault zone is a right-lateral, intracontinental transform boundary which was initiated in the Late Neogene. Sediments of Pliocene to Holocene age in basins between Cerkes and Erbaa, within the convex-northwards arc of the fault zone, are deformed by syn-sedimentary and post-depositional mesoscopic faults and joints. The mesofractures, which strike obliquely to the fault zone, include reverse faults, normal faults, normal shear joints, conjugate vertical joints and strike-slip faults. Each type of structure occurs in two geometrical groups, one comprises four systems of fractures, the other is made up of five systems. The directions of secondary compression and/or extension inferred from the first group of mesofractures, which are restricted to sediments of Pliocene to Early Pleistocene age, are interpreted as being related to left-lateral shear along the North Anatolian fault zone. The directions of compression and/or extension inferred from the second group of mesofractures, which cut sediments of Pliocene to late Holocene age, were generated during right-lateral shear.The presence of the second group of mesofractures is understandable because they are related to the shear sense which operates at the present-day, but those interpreted as being related to left-lateral shear are more puzzling: their development implies one or more reversals of the dominant sense of displacement. Several tentative models to explain such reversals are proposed, including regional and local influences, the latter related to mechanical constraints and/or the effects of other fault systems.     

青海鄂拉山断裂带晚第四纪构造活动及其所反映的青藏高原东北缘的变形机制

鄂拉山断裂带是分隔青海乌兰盆地 (柴达木盆地的一部分 )与茶卡—共和盆地的一条重要边界断裂 ,长约 2 0 7km ,由 6条规模较大的主要以右阶或左阶次级断裂段羽列而成 ,阶距约 1～ 3.5km。该断裂右旋走滑的起始时代为第四纪初期 ,约在 1.8～ 3.8MaB .P .期间 ,大的地质体累积断错约 9～12km。断裂新活动形成了一系列山脊、冲沟和阶地等的右旋断错及断层崖、断层陡坎等。晚更新世晚期以来 ,鄂拉山断裂带的平均水平滑动速率为 (4 .1± 0 .9)mm/a ,垂直滑动速率为 (0 .15± 0 .1)mm/a。鄂拉山地区的构造变形受区域NE向构造应力作用下的剪切压扁与鄂拉山断裂的右旋剪切和挤压的共同影响 ,共和—茶卡盆地和乌兰盆地均属于走滑挤压型盆地。青藏高原东北缘地区在区域性北东向挤压的作用之下 ,应变被分解为沿北西西向断裂的左旋走滑和沿北北西向断裂的右旋走滑运动 ,形成一对共轭的剪切断裂。鄂拉山断裂及其他北北西走向断裂的发展演化和变形机制表明青藏高原东北缘向东的挤出和逃逸是非常有限的。     

Tectonic interpretations of enigmatic structures in the North Anatolian fault zone

Two geometrically distinct groups of syn-sedimentary and post-depositional mesofaults and joints cut Neogene-Quaternary sediments in basins situated along the convex-northwards arc of the North Anatolian fault zone between Çerkes and Erbaa. One group comprises second-order fractures interpreted as having developed during episodes of right-lateral shear along the fault zone, while the morphologically identical fractures in the other group have been interpreted as secondary products of left-lateral shear; thus apparently implying one or more former episodes of eastwards motion of the Anatolian scholle. Because such a reversal of motion would be counter to the well-established westward escape of Anatolia the structures have been called anomalous or incompatible.Alternative hypotheses which have been advanced to explain the development of the anomalous mesofractures include: localized reversals related to displacements of rigid blocks acting as buttresses within basins; selective operation of intra-pull-apart strike-slip faults; stress release; the coincidence of the present western sector of the fault with an older left-lateral fault zone; and the influence of a North Turkish neotectonic stress regime.     

Late Quaternary and current deformation in the western Tunka system of basins: evidence from structural geomorphology and seismology

Integrated seismological and structural geomorphological studies of the western Tunka system of basins in the southwestern Baikal rift show that the historic seismicity reflects the general Late Quaternary evolution trend of structures. Crustal deformation occurs mainly as transpression. Compression follows block boundaries and the northern mountainous borders of basins, whereas extension acts upon basin inner parts which remain in “tectonic shadow” during left-lateral strike-slip motions on W-E faults. Principal stresses inferred from earthquake mechanisms are most often a combination of horizontal NW extension and oblique or vertical compression in the basins and vertical extension with horizontal NE compression in the bordering ridges and along block boundaries. The general deformation style in the region is dominated by strike-slip faulting, and compression (shortening) dominates over extension.     

Fault kinematics of the Magallanes-Fagnano fault system,southern Chile; an example of diffuse strain and sinistral transtension along a continental transform margin

A system of left-lateral faults that separates the South American and Scotia plates, known as the Magallanes-Fagnano fault system, defines the modern tectonic setting of the southernmost Andes and is superimposed on the Late Cretaceous – Paleogene Patagonian fold-thrust belt. Fault kinematic data and crosscutting relationships from populations of thrust, strike-slip and normal faults from Peninsula Brunswick adjacent to the Magallanes-Fagnano fault system, presented herein, show kinematic and temporal relationships between thrust faults and sets of younger strike-slip and normal faults. Thrust fault kinematics are homogeneous in the study area and record subhorizontal northeast-directed shortening. Strike-slip faults record east—northeast-directed horizontal shortening, west—northwest-directed horizontal extension and form Riedel and P-shear geometries compatible with left-lateral slip on the main splay of the Magallanes-Fagnano fault system. Normal faults record north-south trending extension that is compatible with the strike-slip faults. The study area occurs in a releasing step-over between overlapping segments of the Magallanes-Fagnano fault system, which localized on antecedent sutures between basement terranes with differing geological origin. Results are consistent with regional tectonic models that suggest sinistral shearing and transtension in the southernmost Andes was contemporaneous with the onset of seafloor spreading in the Western Scotia Sea during the Early Miocene.