冲断构造带深层变形的空间分布规律——以库车坳陷克拉苏构造带为例

传统上认为前陆冲断带内部的背斜构造具有"成排成带分段"的特征,在表观认识和宏观尺度上讲,容易理解这一特征,并且通过"成排成带分段"的解剖,直接为含油气区带评价和地震解释方案的落实提供指导作用。随着前陆冲断带深层结构的精细解剖和三维空间内构造变形的准确刻画,发现前陆冲断带深层构造变形的分布并非成排成带分段的特征,褶皱构造的发育与分布明显受前陆冲断构造位移量及各个断层位移量的大小所控制,各个断层控制的逆冲岩席在垂向上相互叠置、侧向上交叉对接、走向上错落有致, 3D立体空间内由多个次级弧形体组成鳞片状分布。本文以中国天然气勘探最为成功、勘探资料最为详实的库车坳陷克拉苏构造带为例,通过地震剖面精细构造解释,揭示出构造变形的运动学特征及其构造位移量在传播过程中的分异和转换,进而控制冲断带内部构造岩席的生长发育和空间展布特征,并在3D立体空间内揭示冲断岩席受构造位移量的控制而成鳞片状分布的规律,控制这一分布规律的主控因素是冲断构造位移量与冲断岩席长度之间定量的几何关系。这一认识提升了油气藏评价和构造圈闭描述的精度。     

“承德逆掩片”之商榷——来自燕山地区中元古代长城系的沉积地质证据

外来岩片不但在构造变形上应具有显著的特征标志,而且在其卷入的各类地质体中也应该表现出与原地系统之间具有明显的差异.近年来,承德地区两条断裂之间所夹地质体,被部分学者认为是晚侏罗世时期从该地区南部向北推覆而来的"逆掩片",水平位移量超过40km.本文对比研究了"逆掩片"内部和"根带区"中元古代长城系原始沉积特征和相带展布以及其他证据,发现承德地区长城系各相带原始展布和格局与周边同期沉积并无显著差别,这表明晚侏罗世期间发生自南向北大规模水平位移(＞40km)的可能性很小,研究结果不支持"外来岩片"的认识.     

The Sumba enigma: Is Sumba a diapiric fore-arc nappe in process of formation?

The anomalous updomed morphological expression of Sumba island, its enigmatic lack of strong Neogene deformation and the northward morphological indentation of southern Sumbawa and Flores require explanation.The stratigraphy of Sumba may be correlated with the Cretaceous to Miocene part of the Timor allochthon. The sedimentary and eruptive rock succession in Sumba shows remarkable similarities with the allochthonous Palelo, Wiluba and Cablac deposits of Timor. In both islands the Cretaceous parts of these sequences are regarded as characteristic of fore-arc deposits built on thin continental crust.The Timor nappe is interpreted as a 5 km thick tectonic flake of the Banda fore-arc thrust onto the Australian continental margin in the mid-Pliocene collision. The postulated Sumba nappe has not yet been thrust onto the Australian margin which, in the Sumba region, has not yet converged as close to the arc as in the Timor area. The postulated Sumba nappe is interpreted as a diapiric elongated dome of the Sunda fore-arc that is being squeezed by the converging margin of Australia against the volcanic islands of Sumbawa and Flores.The absence of indications on the seismic reflection profiles for the presence of the thrust fault of the Sumba nappe may perhaps be explained by the thrusts being nearly horizontal within flat-lying strata.The Savu thrust is correlated with the probably older (pre-Late Pliocene) Wetar Suture as a major southward dipping lithospheric rupture. East of 124°E, this suture does not seem to have moved much since the mid-Pliocene collision that emplaced the nappes on Timor. However, microearthquake data suggest some activity is continuing.     

Horizontal frost heave thrust acting on buttress constructions

Frost heave thrust of soil varies with its water content. When the water content of the soil is less than its plastic limit, the horizontal frost heave thrust of soil does not appear. When the water content of the soil is greater than its plastic limit the frost heave thrust increases with increasing water content and when the water content is a little over its liquid limit, it reaches a maximum value.

Also, the horizontal frost heave thrust of soil varies with temperature. It increases as the negative temperature falls, until it reaches a maximum value at about −7°C.

It should be noted that the distribution of the horizontal frost heave thrust along the lateral surface of the structure is not always uniform: its value is greatest at the middle, less at the bottom, and least at the top. The maximum value generally appears at the place where the depth is about 60–80% of the depth of frost penetration.

According to laboratory data and engineering practice, the values of horizontal frost heave thrust vary greatly, but its maximum value is generally about 4.1–4.2 kg/cm².     

辽宁绥中永安堡构造窗的识别及其地质意义

为更好理解燕山带的构造,作者在燕山地区开展了构造填图.在近年的构造填图中于辽宁省绥中县永安堡地区识别出大型的构造窗,其原始的逆掩推覆构造系统上盘由太古宇片麻岩及上覆岩系组成,而下盘由强烈韧性变形的张家口组火山岩系组成.填图结果表明,永安堡地区并不是一个张家口组岩层形成的宽缓向斜,也不是大型古火山机构.燕山地区在早白垩世张家口组火山岩喷发之后仍然存在强烈的区域挤压变形作用.基于野外观察和填图工作,我们认为国内已发表的地质图件未能真实反映燕山带的区域构造基本特征.     

The Gangdese thrust: a phantom structure that did not raise Tibet

Detailed field investigations do not support the existence of a ‘Gangdese thrust’ along the Yarlung Tsangpo suture zone in southern Tibet. A relationship where Lhasa terrane rocks are thrust southwards over components of this zone was not observed over 2000 km of the suture. On the contrary, at the type locality of this ‘Gangdese thrust’, Miocene conglomerates unconformably overlie an eroded surface of Lhasa terrane rocks. Interpretations that invoke Late Oligocene – Early Miocene south‐directed thrusting on a ‘Gangdese thrust’ as a mechanism for uplift of the Tibetan Plateau must therefore be reassessed.     

帕米尔突刺东缘冲断带构造形成机制:物理模拟及讨论

利用物理模拟实验,建立了两个不同边界条件的模型分别模拟帕米尔突刺东缘柯克亚-和田褶皱冲断带和喀什-叶城转换断层带的逆冲走滑构造演化过程,进而分析和讨论了研究区构造变形特征和变形机制。物理模拟实验结果表明:(1)帕米尔突刺东缘的柯克亚-和田褶皱冲断带和喀什-叶城转换断层带均形成于压扭应力场作用下,发育明显断层走滑现象,前者逆冲前缘断层兼具左行走滑特征,后者逆冲前缘断层则具右行走滑特征,但前者总体走滑量明显小于后者;(2)帕米尔突刺东缘的柯克亚-和田褶皱冲断带和喀什-叶城转换断层带走滑作用均主要位于山前边界断层带,越靠近逆冲前缘(盆地内部),走滑效应越微弱,挤压效应越明显;(3)在边界走滑断层前缘(往盆地方向),弧形断裂由挤压方向向前依次产生,并且斜向相交,验证了帕米尔东缘冲断带构造演化符合自南向北依次变新的规律;(4)在斜向压扭作用过程中,走滑断层构造带不一定发育明显的高角度甚至直立的断层,也可能表现为逆冲叠瓦构造楔样式,形成走滑逆断层,故在进行帕米尔突刺东缘(如塔西南山前)地震剖面构造解析时应充分关注这种构造类型。     

土压平衡盾构施工的顶进推力模型试验研究

在盾构的掘削过程中,千斤顶顶进推力是一个重要的施工参数,它不仅决定着施工速度,而且还影响着刀盘的切削扭矩、转动速度等其他参量。但是,目前对千斤顶顶进推力的变化规律,尤其是土体与盾壳之间摩擦阻力的研究还不够深入。以上海地区粉砂地层为参照原型,借助于模型试验方法,通过对盾构机工作参数和地层特性参数进行不同的组合试验,研究了土压平衡盾构推进过程中顶进推力变化的规律,以及土体与盾壳之间摩擦作用的机理及其影响因素。在此基础上推导了盾构千斤顶顶进推力的计算公式。     

双排抗滑桩后侧推力分布物理模型试验

双排抗滑桩后侧滑坡推力分布是其设计中要考虑的关键要素之一。针对一大型基岩-覆盖层式滑坡,进行四组不同后排桩布设方式的双排桩加固滑坡的室内物理模型试验,通过采用坡体外注水,经过特定通道渗入滑带的方法来模拟强降雨条件对滑带的软化效应,测得不同工况下两排桩后侧滑坡推力分布特征,并通过FLAC3D数值模拟方法对试验结果进一步验证。试验结果表明,后、前排桩上坡体压力均呈两端小、中间大的抛物线型分布模式且峰值点相对靠近滑面位置;桩位不变时,后桩后侧坡体压力峰值随沉埋深度增大而减小且峰值点位置上移,前桩后侧坡体压力峰值随后桩沉埋深度增大而增大,但峰值点位置无明显变化;滑带软化效应并不改变双排桩上推力分布模式,但会增大前、后排桩后侧坡体压力,且相比桩顶和底部,桩身中间部分坡体压力增加幅度较大;注水软化前后,后、前排桩上坡体压力分别增大约14.3%～21.4%与17.9%～24.8%。     

基于地震与非地震联合约束下复杂冲断带构造建模:以西昆仑山前柯东构造带为例

柯东构造带是揭示西昆仑山前冲断带变形过程的关键区之一,也是当前油气勘探重要的目标区。由于该区构造变形 强、地层速度变化快以及地表条件复杂等因素,导致当前勘探面临着地震勘探资料品质差,构造建模多解性强等问题。文 章利用R型因子降维分析方法,通过对柯东构造带甫沙地区的重、磁、电反演成果进行降维分析,结果表明甫沙地区深部 发育断块构造,不存在地震剖面上显示的背斜构造;同时联合地震资料的综合解释,认为现今的甫沙地区发育的断块构造 是早期的完整背斜受早更新世山前右旋走滑断裂改造的结果。在柯东构造带的综合建模实践表明,通过地震与非地震方法 的联合约束可以为认识复杂冲断带的构造变形提供有效的手段。     

考虑水库岸坡特征的滑坡稳定性计算修正传递系数法

随着低碳能源的推行,大量水电站的兴建引发了大量库岸滑坡问题。库岸滑坡与普通滑坡有着显著区别,但在实际工程的稳定性计算过程中,工程人员常将二者归为一体,采用同样的思路和方法进行研究。为了更好地治理库岸滑坡,根据库岸自身的特点,在长期野外地质调查和室内文献调研的基础上,提出按结构面特征、坡体位置和滑体物质成分进行库岸斜坡分区的原则;针对库岸滑坡的特点,推导了被牵引段有推力+后缘拉裂面有剪力、被牵引段不存在推力+后缘拉裂面有剪力、被牵引段不存在推力+后缘拉裂面无剪力三种情况的水库岸坡滑坡稳定性计算公式;结合工程实例,验证基于水库岸坡特征滑坡稳定性计算修正传递系数法的正确性。     

Structural controls on fractured coal reservoirs in the southern Appalachian Black Warrior foreland basin

Coal is a nearly impermeable rock type for which the production of fluids requires the presence of open fractures. Basin-wide controls on the fractured coal reservoirs of the Black Warrior foreland basin are demonstrated by the variability of maximum production rates from coalbed methane wells. Reservoir behavior depends on distance from the thrust front. Far from the thrust front, normal faults are barriers to fluid migration and compartmentalize the reservoirs. Close to the thrust front, rates are enhanced along some normal faults, and a new trend is developed. The two trends have the geometry of conjugate strike-slip faults with the same σ₁ direction as the Appalachian fold-thrust belt and are inferred to be the result of late pure-shear deformation of the foreland. Face cleat causes significant permeability anisotropy in some shallow coal seams but does not produce a map-scale production trend.     

Mechanisms of thrust propagation: some examples and implications for the analysis of overthrust terranes

Evidence is presented for the existence of three fundamental mechanisms by which thrust sheets move. The mechanisms are: (1) failure of a stiff layer, to form ramp-flat geometry (‘imbricated’ thrust sheets); (2) detachment of a layer by folding (‘décollement” thrust sheets); (3) differential layer-parallel shortening (‘LPS’ thrust sheets). The mechanisms are independent but may operate interactively to form families of ‘hybrid” thrust sheets. Since LPS thrust sheets have not been previously described or documented, data from the New York plateau, deformed almost exclusively by differential LPS, is presented to demonstrate the physical characteristics of this thrust mechanism.Information from the plateau indicates that finite-strain behavior closely reflects the geometric boundary conditions and is independent of temperature and depth of burial. Finite-strain data are used to construct a set of iso-strain maps in both the deformed and undeformed states. The iso-strain maps are in turn used to determine the displacement field for the thrust sheet. The displacement field allows visualization of the effects of both Lagrangian and Eulerian transformations on an initially orthogonal grid.Utilizing sections from a number of overthrust belts, it is shown that the three mechanisms occur universally although in various proportions. LPS is regionally developed throughout the central and northern Appalachians. The presence of the LPS thrust sheets probably accounts for the failure of structural cross-sections to bed-length balance in these blind thrust terranes. Finally a series of examples drawn from the field as well as the literature are used to illustrate both the characteristics of hybrid thrust sheet families as well as to indicate how knowledge of their behavior can be utilized in developing strategies for the construction and balancing of structural cross-sections.     

Himalayan main central thrust and its implications for Himalayan inverted metamorphism

Within the scheme of south-directed orogenic polarity in the Himalayan region, the Main Central Thrust (MCT) developed at an intermediate stage between the collisional tectonics at the Indus-Tsangpo suture in the north and the latest underthrusting at the Main Boundary Thrust (MBT) in the south. The proposition that the MCT marks the base of the High Himalayan Central Crystalline zone against the Inner sedimentary belt of the Lower Himalayas creates confusion in its definition, and its location in Kashmir and especially in the Eastern Himalayas. The problem can be resolved by defining the MCT as the basal thrust of the crystalline nappe sequences either rooted at or detached as klippe from the Central Crystalline zone.Characteristically, the nappe sequences show inverted metamorphism which generally starts at the basal thrust, the redefined MCT, from the chlorite-biotite grades and reaches the kyanite-sillimanite grades with migmatites and anatectic granites in the highest tectonic levels. The metamorphic rank of both the substrate and the overthrust rock units in the vicinity of the MCT is generally low. The inverted metamorphism may be explained by intracontinental underthrusting and resultant downbowing of the isotherms. The redefined MCT does not appear to represent the thrust zone along which the continental underthrusting was initiated. It developed to the south of this zone as a possible sole thrust of the nappe stack of the crystalline rocks that overrode the parautochthonous sedimentary sequences of the Lower Himalayas.The sequence of events associated with the MCT would probably be repeated in the MBT.     

Deformation along a salient-transverse zone junction: An example from the Leamington transverse zone,Utah, Sevier fold-thrust belt (USA)

Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history of fold-thrust belts. The deformation history within these junctions is best preserved in areas where thrust sheets extend from a salient through an adjacent recess. We examine one such junction within the Sevier fold-thrust belt (western United States) along the Leamington transverse zone, northern Utah. The Canyon Range thrust sheet can be traced continuously from the Leamington transverse zone to its adjacent salient to the south, the Central Utah segment. Deformation within the Canyon Range thrust sheet took place by faulting and cataclastic flow. Analyses of these fault networks preserved throughout the Canyon Range thrust sheet are used to develop a kinematic history of the Leamington transverse zone. Field data is supplemented by analog sandbox experiments. This study suggests that, in detail, deformation within the overlying thrust sheet may not directly reflect the underlying basement structure. Moreover, these junctions may contain several types of accommodating structures that helped to maintain critical-taper and that serve as potential targets for natural resource exploration.     

构造平衡分析及其对前陆褶皱冲断带构造极性的制约:以浙西北地区为例

应用多级平衡恢复原则,对浙西北地区褶皱-冲断构造样式及其组合进行缩短量计算与分析,同时,对前陆褶皱冲断带的变形缩短量和前陆盆地的缩短量及其二者关系进行了探讨,表明后者包容于前者之中.平衡缩短量与构造样式空间展布关系的研究表明前陆褶皱冲断带蕴含了递进变形的复杂过程,记录了造山作用及其挤压变形从初始→发展→顶峰→尾声的连续过程.综合分析表明缩短量自南东向北西呈递减趋势,即向前陆方向缩短量减少,与应变状态向前陆方向减弱是协调一致的.构造平衡及其综合分析是浙西北前陆褶皱冲断带向北西的构造极性的主要制约因素之一.     

Characteristics and Formation Mechanism of Thrust Structures in the Eastern Margin of Pamir Salient: Insights from Analogue Modeling and DiscussionEI北大核心CSCD

Two models with different boundary conditions were carried out to simulate the structural evolution of the Kekeya-Hetian fold-and-thrust belt and Kashi-Yecheng strike-slip belt in the eastern margin of Pamir salient, respectively. The analogue modeling results show that: (1) Both of the Kekeya-Hetian fold-and-thrust belt and Kashi-Yecheng strike-slip belt in the eastern margin of Pamir salient were formed under compressive shearing. Strike-slip faults occurred within both of the belts, but the displacement of these strike-slip faults in the Kekeya-Hetian fold-and-thrust belt is less than that in the Kashi-Yecheng strike-slip belt; (2) The Kekeya-Hetian fold-and-thrust belt is mainly under the influence of compression stress with weaker shearing stress while the Kashi-Yecheng strike-slip belt is mainly under the influence of shearing stress with oblique compressive stress. The strike-slip faults are mainly located in the piedmont within these two belts. The effect of the strike-slip fault diminishes towards the front of the thrust belt (to the interior basin); (3) In the front of the boundary strike-slip faults (to the interior basin), the intersecting arc thrust faults occurred successively along the shortening direction. These structural features demonstrated that the structures evolved northwards in the eastern margin of Pamir salient; (4) The oblique compression does not necessarily result in high angle faults or vertical faults, whereas low-middle angle thrust faults with strike-slip displacement are also possible. Hence, more attention should be paid to such thrust faults during the structural analysis of seismic profiles in the eastern margin of Pamir salient (e.g. the structural belts in piedmont of western Tarim Basin). © 2017, Science Press. All right reserved.     

Thick- and thin-skinned tectonics in the Pyrenees

A comparison is made between the Gavarnie thrust and the Mérens Fault in the Axial zone of the Pyrenees. The former has a gentle dip and quite a large displacement (at least 12 km) but does not cut through either Hercynian or Alpine isograds. The latter has a smaller displacement (~ 5 km) but dips steeply and cuts through both Hercynian and Alpine isograds at a high angle. On this basis and on the basis of shear zone geometries immediately north of it, it is proposed that the Mérens Fault nucleated as a steeply (65°–80°) dipping structure, while the Gavarnie thrust nucleated with a shallow attitude. The Mérens Fault is not a backward-rotated thrust fault, nor is it the root zone for any major nappe structure. Similar steep ductile structures occur within the Gavarnie nappe and may reflect considerable internal strain in basement lithologies.The relationship between steep and shallow structures is not yet clear; the shear zones may pre-date the thrusting in which case they may be thick-skinned structures affecting the whole lithosphere, or they may be contemporary with thrusting reflecting only local thickening above a décollement.Rheological models can be used to test proposed geometrical and kinematic models for the lithosphere-scale evolution of the Pyrenees. Suggested models are dominated by a cool, rigid, high-level mantle wedge beneath the North Pyrenean zone which probably controlled the location of north-dipping thrust faults. Thick-skinned shortening is possible in thick crust in the Axial zone but is very unlikely in the North Pyrenean zone where steeply rooted structures would have to cut through the strongest part of the lithosphere.     

Structure and metamorphism of the Calliope Volcanic Assemblage: Implications for middle to Late Devonian orogeny in the northern New England Fold Belt

The Late Silurian to Middle Devonian Calliope Volcanic Assemblage in the Rockhampton region is deformed into a set of northwest‐trending gently plunging folds with steep axial plane cleavage. Folds become tighter and cleavage intensifies towards the bounding Yarrol Fault to the east. These folds and associated cleavage also deformed Carboniferous and Permian rocks, and the age of this deformation is Middle to Late Permian (Hunter‐Bowen Orogeny). In the Stanage Bay area, both the Calliope Volcanic Assemblage and younger strata generally have one cleavage, although here it strikes north to northeast. This cleavage is also considered to be of Hunter‐Bowen age. Metamorphic grade in the Calliope Volcanic Assemblage ranges from prehnite‐pumpellyite to greenschist facies, with higher grades in the more strongly cleaved rocks. In the Rockhampton region the Calliope Volcanic Assemblage is part of a west‐vergent fold and thrust belt, the Yarrol Fault representing a major thrust within this system.

A Late Devonian unconformity followed minor folding of the Calliope Volcanic Assemblage, but no cleavage was formed. The unconformity does not represent a collision between an exotic island arc and continental Australia as previously suggested.