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1.
Triangle zones,generally found in foreland fold-and-thrust belts,serve as favorable objects of petroleum exploration.Taking the Dabashan foreland belt as an example,we studied the formation and development of triangle zones,and investigated the effect of decollements and the mechanical contrast of lithology by employing the method of physical modeling.Four experimental models were conducted in the work.The results showed that ’sand wedges’ grew episodically,recorded by deformational length,height and slope angle.The height versus shortening rate presented an S-shape curve,and uplifting occurred successively in the direction of the foreland belt.During the formation of the triangle zone,layer-parallel shortening took place at the outset;deformation decoupling then occurred between the upper and lower brittle layers,divided by a middle-embedded silicone polymers layer.The upper brittle layers deformed mainly by folding,while the lower sand layers by thrusting. As shortening continued,the geometry of a triangle zone was altered.We consider that the triangle zone in the Dabashan foreland belt was modified from an early one based on available seismic profiles and the experimental results.In addition,decollements and mechanical contrast impose significant influence on structural development,which can directly give rise to structural discrepancies.More decollements and obvious mechanical contrast between brittle layers can promote the coupling between the upper and lower brittle layers.Basal decollement controls the whole deformation and decreases the slope angle of the wedge,while roof decollement determines whether a triangle zone can be formed. 相似文献
2.
准噶尔盆地南缘褶皱-逆冲断层带分析 总被引：13，自引：0，他引：13
讨论了与准噶尔盆地南缘褶皱-逆冲断层带有关的4个问题。(1)准噶尔盆地南缘褶皱-逆冲断层带具有纵向分带、横向分段和垂向构造分层的特征:纵向上由南至北可分为逆冲推覆构造带、基底卷入褶皱-冲断带和滑脱型褶皱-冲断带三个带;横向上,基底卷入褶皱-冲断带从西至东按横向调节带分为5个段,构造特征表现为反冲断层从不发育到向南反冲的位移逐渐增大、反冲断层所滑脱的层位亦逐渐加深;滑脱型褶皱-冲断带以红车断裂为界划分为西段和东段,西段构造运动弱,构造变形具双层结构;东段构造运动较强,发育大型冲向后陆的反向逆冲断层,构造变形多具有3层结构。(2)逆冲断层-褶皱类型按其形成机制分为基底卷入型冲断-褶皱、滑脱型冲断-褶皱以及基底卷入-滑脱混合型冲断-褶皱3大类,其中,基底卷入型冲断-褶皱的特征是褶皱作用发生在逆冲断裂之前,而滑脱型冲断-褶皱以冲断和褶皱同时或冲断层先于褶皱形成为特征。(3)本区存在横向和纵向传递带。横向调节带一般分布于基底卷入型褶皱-冲断带,主要为左旋走滑断层;纵向传递带分布于滑脱型褶皱-冲断带,以逆冲断层系斜列分布和位移纵向斜列传递为特征。(4)褶皱-冲断带形成的主控因素主要有:近南北向的水平挤压作用,上新世末—早更新世末和晚侏罗世末发生的构造变形以及古近系、下白垩统和下—中侏罗统发育的三套异常高压泥岩层相关的滑脱作用。 相似文献
3.
构造三角带通常发育于褶皱冲断带中,是油气勘探的重要目标。构造三角带具有多种几何形态和命名,其中,阿尔伯达型构造三角带具有普遍意义。近年来,国内外对构造三角带的研究工作取得了重要进展。利用物理模拟和数值模拟并结合实际地质情况,许多学者对构造三角带的演化提出了多种运动学模型和成因解释,本文介绍了2个运动学模型和单斜推进模式。影响构造三角带形成与发展的因素包括滑脱层、地层能干性差异、同构造沉积、剥蚀等。由于其内部构造的复杂性,三角带的地震剖面品质一般较差。而利用地震模拟和生长地层的方法可以在地震剖面上帮助识别出构造三角带。国内的地震勘探表明,中国西部挤压盆地中广泛发育三角带构造。文中列举了中国西部盆地中发育的构造三角带的实例。 相似文献
4.
论述了西非被动大陆边缘下刚果盆地重力滑脱构造的发育特征及演化规律。下刚果盆地早白垩世至今的被动大陆边缘阶段主要发育重力滑脱构造,可分为上陆坡的重力滑脱伸展构造、中陆坡和下陆坡的重力滑脱底辟构造、下陆坡-深海平原转换区的重力滑脱冲断构造。一期完整的重力滑脱构造演化模式为从早到晚由陆向海逐渐发育的前展式发育模式,即最早发育高部位的重力滑脱伸展构造、其次发育中部的重力滑脱底辟构造、最后发育低部位的重力滑脱冲断构造。下刚果盆地总共发育两期重力滑脱构造,分别是早白垩世阿尔布期(Albian)-渐新世的第一期(早期)重力滑脱构造,中新世至今的第二期(晚期)重力滑脱构造。这两期重力滑脱构造之间呈现出从早到晚由陆向海发育的前展式结构,即晚期的重力滑脱构造位于早期重力滑脱构造的向海一侧。 相似文献
5.
鲁西地区沿寒武系/太古宇不整合面滑脱构造的主要特征及形成机制 总被引：12，自引：0，他引：12
郯庐断裂带以西的鲁西地区,寒武系/太古宇不整合面改造成为构造滑脱面,滑脱面上发育碎裂岩和动力变质岩。滑脱面上盘的寒武系底部产生强烈的构造变形,褶皱和破碎带发育;滑脱面之下的太古宇构造变形以劈理和裂缝为主,岩石破碎。构造滑动使露头区寒武系底部地层有不同程度的缺失,济阳坳陷南缘则出现地层重复现象。从地层缺失到褶皱产生再到地层重复是滑脱构造逐渐演化的结果。40Ar-39Ar、K-Ar、锆石和磷灰石裂变径迹数据分析表明:滑动的主要时期在早白垩世中-晚期(距今130~110Ma)和中始新世(距今43~37Ma)。各种构造指向标志表明滑动的方向以向北、北北西和北北东为主。滑脱构造是低角度的伸展构造,其机制与华北东部晚中生代的构造变革和新生代以来印度—欧亚板块碰撞、太平洋板块俯冲方向和速度的变化密切相关。 相似文献
6.
乌鲁木齐山前坳陷逆断裂-褶皱带及其形成机制 总被引：66，自引：9，他引：57
乌鲁木齐山前坳陷位于天山新生代再生造山带北侧,南以准噶尔南缘断裂与天山相隔,内部发育了几排逆断裂 背斜带,每一排构造带又由多个逆断裂 背斜组成。最南的齐古逆断裂 背斜带形成于中生代末,其北的玛纳斯逆断裂背斜带包含霍尔果斯、玛纳斯和吐谷鲁逆断裂背斜,形成于上新世末、早更新世初,受上、下２ 个滑脱面和断坡的控制,形成上、下２ 个背斜。再向北的独山子逆断裂背斜带由独山子、哈拉安德和安集海逆断裂背斜组成,形成于早、中更新世之间,主逆断裂向下在８ ～９ ｋｍ 深处的侏罗系中变为近水平滑脱面。此外,在独山子和吐谷鲁背斜的西北和东北还分别发育有正在形成之中的西湖和呼图壁隆起。研究了这些逆断裂 背斜带的地表和深部的构造特征、二维和三维几何学及运动学后指出,它们是在天山向准噶尔盆地扩展过程中发育于近水平滑脱面和不同断坡上的断展褶皱,独山子和安集海逆断裂 背斜的水平缩短量分别为２ ９００ ,１ ３５０ ｍ ,缩短速率分别为３９７ ,１８７ ｍ ｍ／ ａ。霍尔果斯、玛纳斯、吐谷鲁逆断裂 背斜的水平缩短量分别为５ ９００ ,６ ５００ ,６ ０００ ｍ ,相应的缩短速率分别为２０２,２２３ ,２０６ ｍ ｍ／ａ,准噶尔南缘断裂和乌鲁木齐山前坳陷第四纪? 相似文献
7.
We present a structural analysis of serpentine-bearing faults and shear zones in the Koniambo Massif, one of the klippes of the Peridotite Nappe of New Caledonia. Three structural levels are recognized. The upper level is characterized by a dense network of fractures. Antigorite and polygonal serpentine form slickenfibers along fault planes with distinct kinematics. As a result, the upper level keeps the record of at least two deformation events, the first associated with the growth of antigorite (WNW-ESE extension), the second with the growth of polygonal serpentine (NW–SE compression). The lower level coincides with the ‘serpentine sole’ of the nappe, which consists of massive tectonic breccias overlying a layer of mylonitic serpentinites. The sole records pervasive tangential shear with top-to-SW kinematics and represents a décollement at the base of the nappe. The intermediate level is characterized by the presence of several meters-thick conjugate shear zones accommodating NE–SW shortening. Like the sole, these shear zones involve polygonal serpentine and magnesite as the main syn-kinematic mineral phases. The shear zones likely root into the basal décollement, either along its roof or, occasionally, around its base. Compared to top-to-SW shearing along the sole, the two deformation events recorded in the upper level are older.The three structural levels correlate well with previously recognized spatial variations in the degree of serpentinization. It is therefore tempting to consider that the intensity of serpentinization played a major role in the way deformation has been distributed across the Peridotite Nappe. However, even the least altered peridotites, in the upper level, contain so much serpentine that, according to theoretical and experimental work, they should be nearly as weak as pure serpentinite. Hence, no strong vertical gradient in strength due to variations in the degree of serpentinization is expected within the exposed part of the nappe. Our proposal is that strain localization along the serpentine sole results from the juxtaposition of the nappe, made of weak serpentinized peridotites, against the strong mafic rocks of its substratum. This interpretation is at odds with the intuitive view that would consider the nappe, made of peridotites, as stronger than its basement. 相似文献
8.
西非被动大陆边缘重力滑脱构造发育演化及成因机制 总被引：2，自引：1，他引：1
西非被动大陆边缘盆地在晚侏罗世伴随大西洋的裂开而形成,陆内裂陷构造旋回(晚侏罗世-早白垩世阿普特期(Aptian))主要发育陆内裂陷构造;过渡期构造旋回(阿普特期)沉积了一套潟湖相塑性层(盐岩);被动大陆边缘构造旋回(早白垩世阿尔布期(Albian)至今)共发育了两期重力滑脱构造,早白垩世阿尔布期-渐新世发育一期(早期)重力滑脱构造,中新世至今发育了另一期(晚期)重力滑脱构造。西非被动大陆边缘同一期重力滑脱构造具有从早到晚由陆向海的前展式发育规律,且多期重力滑脱构造具有从早到晚由陆向海迁移的进积叠加规律。西非被动大陆边缘重力滑脱构造发育的主要控制因素是大地构造背景、地层掀斜、滑脱面形态,其中大地构造背景控制重力滑脱构造体系类型,地层掀斜是引起地质体重力滑脱和变形的根本、控制构造变形的强度,滑脱面形态控制着重力滑脱构造类型和发育位置;次要控制因素是差异重力负载和塑性滑脱层等。并在此基础上建立了宽缓型凹面斜坡和窄陡型斜坡滑脱面下的西非被动大陆边缘重力滑脱构造成因发育模式。 相似文献
9.
Jonas B. Ruh 《地学学报》2017,29(3):202-210
Numerical experiments on evolving accretionary wedges usually implement predefined weak basal décollements and constant strength parameters for overlying compressed sequences, although fluid pressure ratio, and therefore brittle strength, can vary strongly in sedimentary basins. A two‐dimensional finite difference model with a visco‐elasto‐plastic rheology is used to investigate the influence of different simplified fluid pressure ratio distributions on the structural evolution of accretionary wedge systems. Results show that a linear increase in fluid pressure ratio towards the base leads to toeward‐verging thrust sheets and underplating of strata, while simulations with a predefined décollement form conjugate shear zones supporting box‐fold‐type frontal accretion. Surface tapers are in agreement with the critical wedge theory, which here is modified for cases of varying fluid pressure ratio. Furthermore, the numerical results resemble findings from natural examples of accretionary wedges. 相似文献
10.
陕甘川邻接区基于MAPGIS的金成矿远景区预测 总被引：9，自引：0，他引：9
陕甘川邻接区金矿床的展布与滑脱挤出构造、特别是不均匀滑脱关系非常密切。为了定量分析不均匀滑脱与金矿的关系 ,专门研制了自动追踪断裂求取弧形滑脱断裂曲率的计算机软件。经MAPGIS空间分析和多次实验证实 ,区内大中型以上金矿与曲率大于 4的点的密度区关系密切。用Grsip软件 ,对研究区进行断裂密度统计 ,再与金矿床进行MAPGIS空间分析 ,发现断裂密度在 10 0 2 40时 ,对金矿最有利。将研究区的印支—燕山期岩体依出露面积大小划分了大、中、小岩体和岩脉 4种规模的侵入岩。对侵入岩与金矿床MAPGIS空间分析 ,得出了中、小型岩体和岩脉的成矿有利区间分别为岩体边界向外扩展 70 ,6 0和 40个MAPGIS单位的环带。在进行MAPGIS空间分析过程中 ,还分析出研究区的金矿与该区应力异常区也有密切关系 ,但金矿与地层的关系不密切。最后 ,利用MAPGIS空间分析工具对陕甘川邻接区以上金成矿有利因素进行相交分析 ,圈定出 14个一级金矿远景区 ,19个二级金矿远景区和 11个三级金矿远景区。 相似文献
11.
《Journal of Structural Geology》1988,10(1):33-40
Two methods are introduced for identifying states of pervasive prefold strain in the total-strain field of large domes or basins. The first method relies on the symmetry rule and is restricted to structures in which the planes of effective symmetry of the total-strain field are non-coincident with those of the fold form. The second method seeks to demonstrate the existence of a strain-induced anisotropy (foliation or lineation) prior to upright folding, and utilizes narrow décollement zones within homogeneous rock units of domes or basins. The methods are applied to large oval structures in two Precambrian gneiss terranes of Ontario. 相似文献
12.
13.
Surface and subsurface data are integrated to characterize the structural architecture of the Marathon fold and thrust belt in west Texas. Multiple detachment levels are present within the thrust belt and result in distinct structural domains. In addition to the basal décollement, whose stratigraphic position varies along strike, we recognize a regionally extensive detachment zone in the late Mississippian to early Pennsylvanian lower Tesnus Formation. The Lower Tesnus Detachment forms a structural domain boundary that can be observed along strike in the surface data and at depth in the subsurface. The stratigraphic intervals above and below this detachment exhibit characteristic patterns of deformation. The Lower Tesnus Detachment is folded by imbrication and the formation of duplexes in the early Mississippian to Ordovician section, suggesting that the detachment may have initially formed as a perched décollement in the foreland that was subsequently exploited as a roof thrust in a duplex system as deformation progressed in a break-forward sequence and older strata were incorporated into the toe of the allochthonous wedge. The structural model presented here for the Marathon region may be applicable across much of the Ouachita orogenic system. 相似文献
14.
Jacob Geersen David Völker Jan H. Behrmann Dirk Kläschen Wilhelm Weinrebe Sebastian Krastel Christian Reichert 《地学学报》2013,25(6):472-477
Determining factors that limit coseismic rupture is important to evaluate the hazard of powerful subduction zone earthquakes such as the 2011 Tohoku‐Oki event (Mw = 9.0). In 1960 (Mw = 9.5) and 2010 (Mw = 8.8), Chile was hit by such powerful earthquakes, the boundary of which was the site of a giant submarine slope failure with chaotic debris subducted to seismogenic zone depth. Here, a continuous décollement is absent, whereas away from the slope failure, a continuous décollement is seismically imaged. We infer that underthrusting of inhomogeneous slide deposits prevents the development of a décollement, and thus the formation of a thin continuous slip zone necessary for earthquake rupture propagation. Thus, coseismic rupture during the 1960 and 2010 earthquakes seems to be limited by underthrusted upper plate mass‐wasting deposits. More generally, our results suggest that upper plate dynamics and resulting surface processes can play a key role for determining rupture size of subduction zone earthquakes. 相似文献
15.
In many cases, thrust wedges accreted at shallow crustal levels show an across‐strike rheological variability along the basal décollement, notably from brittle to ductile behaviour. In this paper, we illustrate the results of sandbox analogue modelling research devoted to studying the influence of convergence velocity on wedge architecture when laterally juxtaposed frictional and viscous materials occur along the basal décollement of accreting thrust wedges. Our results show that slow convergence favours a near symmetrical distribution of thrust vergence within wedge sectors accreted above viscous décollement material, whereas fast convergence favours vergence asymmetry. In particular, at fast convergence rates the hinterlandward extrusion of viscous décollement material at the toe of the frictional wedge is favoured and contributed to accommodate a significant amount of the total contraction. Terra Nova, 18, 241–247, 2006 相似文献
16.
《Journal of Structural Geology》2003,25(10):1623-1644
Duplexes are a common feature in thrust belts at many scales. Their geometries vary significantly from antiformal stacks with significant forethrusting in the cover (e.g. southern Pyrennes, Spain) to triangle zones (e.g. foreland Canadian Rockies) to low-displacement individually spaced ramp-anticlines (e.g. Sub-Andean thrust belt, Bolivia). We present a series of physical experiments demonstrating that the strength of the décollements relative to that of the intervening and overlying rock layers plays a significant role in controlling the duplex style. The models comprise brittle layers made of dry quartz sand and décollements made of two types of viscous silicone polymers. The strength of the décollements in the models is a function of the shortening rate applied to the model. The relative strength of the décollements and surrounding rocks affects the development of active- or passive-roof duplexes (triangle zones). It also affects the amount of translation of individual thrust blocks and the spacing of thrust ramps, which in turn determine if a duplex evolves into an antiformal stack or into individually spaced ramp-anticlines. Model results indicate that specific associations of structural features form systematically under similar rheological and boundary conditions. The presence of relatively strong décollements promotes local underthrusting of the cover, individual ramp-anticlines, internal deformation of thrust sheets, low early layer-parallel shortening, and sequential towards-the-foreland propagation of structures. Weak décollements promote forethrusting of the cover, antiformal stacks, coeval growth of structures, and low internal strain, with the exception of significant early layer-parallel shortening. No underthrusting at a regional scale occurred in any model. 相似文献
17.
The model of “Return-Flow in a Subduction Channel” (RFSC) is put to the test, by opposing key-assumptions of the model to an integrated review of field data, petrology, geochronology and structures of high-P mélanges of the Franciscan Subduction Complex (FSC), to which RFSC has been first applied. Key-assumptions are: (i) The subduction channel (SC) is a low-viscosity zone of finite width restrained by the rigid, subducted and overriding plates. (ii) Forced (return) flow in the SC is associated with formation and km-scale displacements of small tectonic blocks (< 1 km) in a highly deformable matrix. (iii) This results in apparently random distributions and close associations of blocks exhumed from different depths. Hence, the block-in-matrix structures and “exotic” blocks in high-P mélanges would reflect the structural state at depth of the SC. On the basis of the predictions ensuing from the key assumptions of the RFSC model on the rock record, it is detailed why the actual record of the high-P mélanges of the FSC does not comply with this perception. The record rather reflects recurring subduction, underplating-associated décollement, erosion and mingling of high-P rocks by sedimentary processes, in the trench, all occurring in an 80 m.y.-lasting period. Distributed deformation of the mélange matrix is unrelated to formation of apparently chaotic block-in-matrix structures since: (i) creation, subduction, ascent and cooling of “exotic” blocks on counterclockwise P-T paths predates deposition of the bulk of the metasediments constituting the matrix by ~ 20–40 m.y.; (ii) deformation of the matrix occurs during a second loop of high-P metamorphism postdating creation and ascent of the “exotic” blocks by at least ~ 20–40 m.y.; (iii) the magnitudes of distributed deformation of the matrix are too low to cause juxtaposition of blocks different in P-T paths against each other from km-scale vertical distances. Instead, narrow (few tens of metres-wide) fault/shear and décollement zones formed at locally high pore fluid pressures accumulate the major tectonic transport during high-P metamorphism. They bound several 100s of metres wide tabular tectonic bodies that are coherent. Sedimentary processes at the active continental margin formed the bulk of the mélanges. Tectonically formed block-in-matrix structures within the shear and décollement zones are unrelated to juxtaposition of “exotic” blocks. Universal diagnostic criteria are developed to identify return-RFSC as a mechanism that potentially amalgamates heterogeneous metamorphic terrains by using field data petrology and geochronology. 相似文献
18.
Abstract The metamorphic history of the Archaean Superior Province crystalline basement in the Palaeoproterozoic Ungava Orogen attests to the importance of structural and geohydrological controls on a retrograde amphibolite-granulite transition. Two distinct metamorphic suites, separated in age by nearly one billion years, are recognized in extensively exposed tonalitic to dioritic metaplutonic gneisses. The older suite comprises c. 2.7-Ga granulite facies assemblages (orthopyroxene-clinopyroxene-hornblende-plagioclase-ilmenite ± biotite ± quartz) that record moderate pressures (±5 kbar) and high temperatures (±800° C). A younger, c. 1.8-Ga suite resulted from amphibolitization of the granulites and is characterized by regionally extensive amphibolite facies mineral zones that broadly parallel the basal décollement of the overlying Proterozoic Cape Smith Thrust Belt. Deformation/mineral growth relationships in the amphibolitized basement indicate that extensive hydration and re-equilibration of the Archaean granulites occurred during thrust belt deformation. The transition from granulite facies to amphibolite facies assemblages is characterized by the growth of garnet-hornblende-quartz ° Cummingtonite coronas between plagioclase and orthopyroxene-clinopyroxene, as well as titanite coronas on ilmenite. Multi-equilibrium thermobarometry on the coronitic assemblages documents re-equilibration of the granulitic gneiss to 7.7 kbar at 644° C in the south and 9.8 kbar at 700° C in the north. The variably deformed, amphibolite facies domain sandwiched between the coronitic garnet zone and the basal décollement is marked by significant metasomatic changes in major element concentrations within tonalite. These changes are compatible with equilibrium flow of an aqueous-chloride fluid down a temperature gradient. The source of fluids for basement hydration/metasomatism is interpreted to be dehydrating clastic rocks in the overlying thrust belt, with fluid flow probably focused along the basal décollement. 相似文献
19.
Dominique Frizon de Lamotte Jean-Claude Guézou Marie-Anne Albertini 《Geodinamica Acta》2013,26(4):267-281
AbstractThe Cenozoic westward motion of the Betic-Rif internal zone (“Alboran block”) between Iberia and Africa is constrained by paleogeographic considerations and by wrench faulting which affects both sides of the external zones. However, in the Alboran domain itself there was so far no evidence of significant internal deformation related to this westward displacement which was consequently consider as an en bloc” motion. Our work, in Eastern Andalucia, demonstrates that the main tectonic units building up the Betic zone should be regarded as large-scale tectonic sheets with a typical duplex style. The direction of the tectonic transport is to the West. At meso-scale, the major structures exhibit a combination of hindward and foreward dipping imbricates on the respective east and west sides of antiformal stacks or “rigid cores”. On a broader scale, the same geometric framework appears on both east and west sides of the Sierra Nevada window which we interpret as a tectonic culmination on the hangingwall of a Subbetic décollement zone. The development of this tectonics, in retrogressive metamorphic conditions, postdates the ductile deformation of the internal complexes. The morpho-tectonic relationships between the culmination of the metamorphic cores and the Neogene basins give a way to date the westward motion of the “Alboran System of Nappes” of the middle and upper Miocene. 相似文献
20.
板内扭压造山机制 总被引：5，自引：0，他引：5
据中国大陆板块内部构造特征提出两种扭压造山机制：（１） 扭压滑脱褶皱造山作用;（２） 扭压斜滑断裂岩浆造山作用。前者以扬子板块内的武陵山台褶带为例,后者以华北板块内的太行山断裂岩浆带为例。扭压滑脱褶皱造山作用表现为沉积盖层呈隔档式及隔槽式褶皱;结晶基底呈大型隆起和拗折,莫霍面下降,从而使地壳增厚,构成造山带。值得注意的是,这类滑脱褶皱带的整体形状呈Ｓ状展布,其中的次级褶皱呈雁行状斜列,表明这类造山带的形成除受水平挤压作用外,还伴有左行剪切作用。扭压斜滑断裂岩浆造山作用表现为沿断裂带有一系列花岗质深成岩体展布。这些断裂不仅深切地幔,而且导致下地壳局部融熔形成花岗岩浆,驱动岩浆斜向上升,并控制岩体侵位。与此同时地壳在平面上缩短,垂向上增厚,构成造山带。上述两种造山作用一致表明,东亚大陆在中生代时曾相对太平洋板块向南滑移 相似文献