西秦岭北缘构造带新生代盆地南部边界断层带结构与构造变形演化

西秦岭北缘构造带是青藏高原东北缘的主要构造边界之一,北缘断层及其所控制的新生代沉积盆地是青藏高原东北缘新生代盆—山格局演化、高原扩展隆升与变形的地质记录。因此,西秦岭北缘构造带的断裂构造和断裂控制的沉积盆地研究对于理解青藏高原构造系统形成和高原隆升过程都具有重要的科学意义。本文通过对西秦岭北缘新生代盆地的南部边界断层F1断层结构分带、断层岩类型、几何学—运动学特征分析,获得如下认识:1) F1断层总体走向为290°～300°,倾向北北东,倾角60°～80°,发育近百米宽的由韧性、韧脆性和脆性断层岩等组成的结构复杂的断层带;2)构造分析揭示了F1断层至少经历了3期构造变形事件,第一期为韧性—韧脆性伸展正断层作用,第二期为脆性高角度挤压逆冲断层作用,第三期为近直立的脆性斜向左旋走滑作用;3)该断层近百米宽的断层带内形成于不同构造层次的韧性、韧脆性、脆性等变形现象叠加交织出现在现今地壳浅表层次,说明该断层带经历了从早期较深层次韧性变形域逐渐抬升而进入晚期较浅层次的脆韧性变形域到现今的脆性变形域的韧—脆性变形机制转换;4)根据F1断层对西秦岭北缘渐新统—中新统漳县含盐红层盆地的空间构造配置、控...     

高要—高明剥离拉伸体系对长坑金,银矿床的控制

高要－高明剥离拉伸体系，是印支运动以后产生的拉伸（伸展）构造，它由剥离断层、变质核杂岩、断陷盆地和脆性正断层系组成，是控制长坑金、银矿的区域构造。脆性正断层系中的一条上三叠统与下伏印支期褶皱基底之间的区域性滑覆断裂是长坑金、银矿床的容矿构造。滑覆断层沿着古Ｕ形谷滑覆时所产生的“构造洼斗”和与“构造洼斗”沟通的基底断裂是长坑大型矿床形成的重要条件。     

西天山查岗诺尔矿区构造变形研究:对阿吾拉勒成矿带构造控矿模式的启示

阿吾拉勒成矿带是西天山重要成矿带之一,经历了多期构造作用,并伴生多期成矿作用。本文对成矿带内查岗诺尔矿区及邻区构造变形特征以及变形序列精细解析,探讨构造变形对铁矿的成矿作用以及后期改造作用的影响,为西天山地区铁矿床成因和找矿方向提供新启示。野外构造观察发现,研究区断裂构造主要分为NW-NWW向高角度韧性-韧脆性走滑断层及逆冲推覆断层,以近EW向、近SN向为主的高角度共轭脆(韧)性走滑断层和近SN向脆性右行走滑断层。年代学研究表明,断层分别形成于燕山晚期-喜马拉雅早期、喜马拉雅中期和喜马拉雅晚期,均为成矿期-成矿期后的构造记录。早期高角度韧性-韧脆性走滑断层是区域性控矿构造,而逆冲推覆断层是矿区主导控制性构造;中期共轭脆(韧)性走滑断层对矿体具有较为强烈的破坏和改造作用;晚期脆性右行走滑断层对矿体影响较小。查岗诺尔和智博矿区的断裂构造主要表现为对矿体的破坏和改造作用,而在松湖和塔尔塔格矿区,韧性-韧脆性剪切带是主要的控矿构造。主矿脉与构造密切伴生,具体表现为与成矿作用密切相关的磁铁矿化、绿泥石绿帘石化、碳酸盐化等蚀变多沿构造裂隙发生。     

黔东北地区构造作用对萤石成矿的控制与影响

黔东北地区与黔中隆起相邻，受黔中隆起影响与控制，该区自古生代以来经历了郁南运动、都匀运动、广西运动和燕山运动。早古生代早期发育在奥陶系下统红花园组(O₁h)和桐梓组(O₁t)脆性灰岩中的NW向裂隙是黔东北萤石矿床的容矿构造，而NE向断层属于导矿构造。本文通过区域构造研究，典型矿区的构造解析，面理、线理、节理等统计与赤平投影分析，对黔东北地区构造变形与萤石矿床的成因关系开展了研究。结果表明，寒武纪末-早奥陶世早期的郁南运动、晚奥陶世-早志留世都匀运动形成了容矿与导矿构造。早古生代末期的广西运动使得黔东北长期(石炭纪-二叠纪)处于隆升暴露，在此期间，在下古生界形成了以正断层为特点的断层组合，发育了地垒式、地堑式、阶梯状、放射状、羽裂状等多种断层组合，这些组合断层在上覆上古生界的地层中不发育。同时，下古生界还发育了切割寒武系-志留系地层的NW向断层，这些NW断层不是控矿断层，在上述研究基础上，拟定了该区控矿和不控矿的NW向断层的特征。燕山运动在黔东北形成隔槽式褶皱组合，早期断层在此期间大多反转或平移，少数继承性再活动切穿上覆二叠系-三叠系地层。总体...     

西秦岭北缘构造带新生代盆地南部边界断层带结构与构造变形演化

西秦岭北缘构造带是青藏高原东北缘的主要构造边界之一,北缘断层及其所控制的新生代沉积盆地是青藏高原东北缘新生代盆—山格局演化、高原扩展隆升与变形的地质记录。因此,西秦岭北缘构造带的断裂构造和断裂控制的沉积盆地研究对于理解青藏高原构造系统形成和高原隆升过程都具有重要的科学意义。本文通过对西秦岭北缘新生代盆地的南部边界断层F1断层结构分带、断层岩类型、几何学—运动学特征分析,获得如下认识：1）F1断层总体走向为290°～300°,倾向北北东,倾角60°～80°,发育近百米宽的由韧性、韧脆性和脆性断层岩等组成的结构复杂的断层带;2）构造分析揭示了F1断层至少经历了 3期构造变形事件,第一期为韧性—韧脆性伸展正断层作用,第二期为脆性高角度挤压逆冲断层作用,第三期为近直立的脆性斜向左旋走滑作用;3）该断层近百米宽的断层带内形成于不同构造层次的韧性、韧脆性、脆性等变形现象叠加交织出现在现今地壳浅表层次,说明该断层带经历了从早期较深层次韧性变形域逐渐抬升而进入晚期较浅层次的脆韧性变形域到现今的脆性变形域的韧—脆性变形机制转换;4）根据F1断层对西秦岭北缘渐新统—中新统漳县含盐红层盆地的空间构造配置、控制和改造以及新生代区域构造变形演化历史分析,认为第一期韧性—韧脆性伸展正断层作用与渐新世—中新世断陷盆地形成相匹配,活动时代为晚渐新世—晚中新世;第二期脆性高角度挤压逆冲作用与渐新世—中新世地层翘起、褶皱和底部抬升剥蚀及上新世磨拉石盆地充填相对应,活动时代应该始于中新世末期或上新世早期,持续至第四纪早期;第三期斜向左旋走滑则与西秦岭北缘断层带第四纪以来广泛发育的左旋走滑作用相对应。综上所述,西秦岭北缘新生代漳县盆地南部边界断层F1,虽然仅是北缘构造带中一条断层,但作为构造敏感带,其多期变形历史应该代表了青藏高原东北缘新生代以来的构造变形演化及构造体制转换过程。如果这一新生代沉积盆地边界断层F1在渐新世—中新世一直处于伸展正断作用,那么西秦岭北缘在这个阶段应该处于地壳伸展拉张状态,渐新世—中新世漳县盆地只能是伸展断陷盆地而不可能是挤压挠曲前陆盆地或压陷盆地。因此,我们认为印度—欧亚板块碰撞汇聚产生的构造挤压缩短和地壳隆升效应在中新世尚未波及到西秦岭北缘区域。F1断层在中新世末—上新世初的构造反转挤压冲断和上新世具有再生前陆磨拉石堆积出现才标志着西秦岭北缘卷入青藏高原挤压构造动力学系统。     

滇东南中三叠统个旧组震积岩的发现及意义

以往认为滇东南个旧地区中三叠统个旧组属台地相沉积,近期笔者在个旧组第三段中发现了大规模的震积岩,该震积岩分为脆性序列和液化序列,脆性序列震积岩主要由同沉积微断层、地裂缝、震碎角砾岩三种类型。同沉积微断层具有阶梯状、微地垒状、微地堑状构造样式组合特征。液化序列表现为形态、位态各异的手标本—露头尺度的顶厚翼薄褶曲。泥晶方解石脉、同沉积微断层伴随了个旧组第三段沉积的全过程。结合个旧组中发现夹有基性火山岩和滑塌角砾岩等,认为个旧组第三段震积岩是在强烈拉张构造背景下的产物。     

西秦岭北缘北西向断层特征和形成的构造机制及地质意义

西秦岭北缘构造带不仅发育一系列继承性多期活动或新生的近东西向断层,而且新生代地层中还发育与近东西向断层走向不一致且具有独特构造特征的北西向左旋走滑断层。这种北西向左旋走滑断层带不发育断层角砾岩、磨砾岩、碎粉岩、断层泥、摩擦镜面、擦痕线理、断层阶步等脆性断层中常见的构造现象,仅表现为地层旋转和剪切拉断形成的一定宽度的透镜化带,两条断层之间地层产状发生旋转形成了约1 km宽,平面上类似膝折构造几何形态地层扭折带。该北西向断层横切了渐新统—中新统地层,并被上新统砾岩覆盖和第四纪以来的近东西向左旋走滑断层斜切,指示了其形成于渐新世—中新世沉积地层形成之后,上新世砾岩沉积之前,即上新世早期。北西向断层带不发育脆性断层典型构造现象和断层左旋走滑作用在渐新统—中新统沉积地层中形成了类似膝折构造几何形态地层扭折带,说明其变形具有韧脆性过渡和缓慢剪切变形的特征,是西秦岭北缘一种新的断层类型。其形成机制为基底或中下地壳中大型左旋走滑韧性或韧脆性剪切带向上扩展延伸到上部沉积盖层中之结果,也就是说,新生代沉积盖层中这种北西向断层和地层扭折带是下部韧性剪切带的左旋走滑剪切在盖层中被动构造响应。这种基底或中下地壳北西向左旋韧性剪切带可能指示了上新世初期西秦岭北缘构造带深部韧性地壳物质向南东流变蠕动的构造标志,代表深部地壳缩短增厚向地壳韧性物质侧向扩展流动的转换过程。这种特殊的断层类型对理解青藏高原东北缘新生代构造变形体制转换和地壳隆升具有重要的科学意义。     

美国南阿帕拉契亚晚古生代上冲地体的复原再造

阿帕拉契亚造山带经历了早中古生代期间的增生历史,并伴有变形作用、变质作用和深成岩浆侵入作用。早中古生代期间形成的构造在二叠纪与非洲大陆碰撞期间,被阿勒格尼逆冲断层所切割。该逆冲断层从碰撞带下部的韧一脆性过渡带依次进入晚元古代和古生代裂谷边缘和地台,其上的构造迁移主要向北美内陆,但阿勒格尼走向滑移构造域也在包括主要为右行运动的内构造带中形成。有些地区(东部山麓)的右行位移明     

地震断层力学的多尺度问题

大量观察和研究结果证明,大陆浅源构造地震是由上地壳岩石的突发性剪切运动造成的,这种固体脆性破坏一般是在区域构造应力作用下沿原有断层面的快速滑动和破裂扩展,可称为地震断层作用(earthquake faulting),它的机制主要是固体力学过程,即岩石空间位置的变动。很多地震研究,如地震构造、地震机制、地震前兆等,都涉及地震断层力学问题,也是构造地质学的一个前沿研究领域。     

伊利石K-Ar/Ar-Ar年龄约束浅地表断层活动时间:原理和潜力

地壳脆性区断层的定年工作是地质学面临的一个重大瓶颈问题.尽管绝大多数脆性断层在活动时会产生可以用于放射性测年的自生/同运动学伊利石,但同时也会混入影响放射性年龄的碎屑矿物,如2M1多型伊利石或云母,从而使得自生/同运动学伊利石年龄数据受到质疑.随着伊利石年龄分析法及年龄牵引子法的提出,利用分离提纯的各粒级伊利石年龄与颗粒尺度的关系约束近地表脆性断层活动时间的方法逐渐变得可靠.首先介绍了伊利石定年的原理和假设,其次回顾了伊利石年龄限定断层活动时间的研究历史,并总结了关于伊利石年龄数据解释的2种方法及其原理和运用背景.然后评价了影响伊利石定年的可能因素,认为Ar损失在近地表脆性断层域中可以忽略不计,而2M1多型伊利石或云母是否自生对讨论断层泥伊利石年龄的地质意义至关重要.最后指出伊利石定年技术不仅仅局限于浅地表断层定年,还可以约束高应变褶皱及构造混杂岩的变形时间.另外,如果识别俯冲带中与俯冲、增生、剥蚀相关的各构造主控域并分别开展伊利石定年工作,将有助于从时空上对整个俯冲带循环过程(俯冲—增生—剥蚀)的还原.     

Reverse fault step at Engel Peaks,Antarctic Peninsula

A steep reverse fault at Engel Peaks, Antarctic Peninsula, cuts granophyre and overlying volcanic rocks and incorporates a lower angle zone or ‘fault step’. The reverse fault step differs from the more familiar thrust ramp in that it cuts down-section in the footwall in the direction of tectonic transport. Accommodation of the fault zone to this step and its associated sidewall are discussed with reference to kinematic models for pull-apart zones and for the movement of thrust sheets over non-planar surfaces.During movement on the main fault the step acted as a fault jog and pull-apart zone, preserving cataclasite, breccia and other structures demonstrating a brittle to ductile deformation history. Ultra-fine-grained rock in the step zone is the result of dynamic recrystallization of ultracataclasite. During episodes of brittle slip, the fault step acted as a dilational fault jog between the main steep reverse fault segments.Rotation of mylonite into the reverse fault step and its sidewall involved flexural flow parallel to foliation. Movement of material through the step zone resulted in shear parallel to the base of the step, enhancement of breccia layering, mixing of lithologies and cleavage formation; it also involved extension at a high angle to the main movement direction to accommodate the extra length of the fault zone. Late, steep, reverse fault zones propagating from the main fault folded the breccias in the step and crenulated the earlier cleavage. The fault step was a zone of brittle dilation, hydration, diffusive mass transfer and mineralization.     

Tectonic and lithological constraints on the evolution of the Karoo graben of northern Malawi (East Africa)

The results of a lithostratigraphic, tectonic and kinematic study of the Karoo deposits of northern Malawi are reported. The objective of the lithostratigraphic study is to correlate the deposits of the Karoo basins of northern Malawi with the well-known deposits of southern Tanzania, thus establishing a stratigraphic framework through which the timing of faulting can be constrained. The kinematic analysis of faulting constrains the opening direction for the Karoo graben in this area and provides basic data to discuss the Karoo graben development within the regional tectonic framework of south-eastern Africa. The studied adults are defined by moderately to steeply dipping cataclastic zones with a width of up to 15 m and are characterized by an array of slickensided fault surfaces with different orientations and slip directions. In this study, small faults (offset < 10 m) and meso-scale faults (offset > 10 m, but generally not exceeding 30–40 m) have been distinguished. Methods used to analyse the kinematic data include the ‘pressure tension’ (PT) method, which estimates the principal axes for the bulk brittle strain, and the internal rotation axis (IRA) method, which estimates the axis of bulk internal rotation and the overall sense of slip at the faults. A mass balance calculation reveals a volume increase of up to 16% during cataclastic deformation in the fault zones. The PT method shows an approximately east trending extension direction for faults that occur only in the latest Carboniferous (?) and Early Permian strata, whereas the fault kinematics from faults that cut middle Permian to Early Triassic rocks is characterized by a ESE to SE trending extension direction. The small faults yield essentially the same kinematic results as the meso-scale faults. In a transport-parallel cross-sectional view, the principal extension axes are at an acute angle of approximately 60° to the major fault planes. Given the moderate fault density, the relatively high angle between the orientation of the principal extension axis and the fault planes suggest only a moderate amount of horizontal extension across the Karoo graben of northern Malawi. Riedel structures in the fault zones formed within two conjugate sets of localized shear zones; slip on one set was top to the W/NW and, on the other, top to the E/SE. The two conjugate sets of Riedel structures have an acute angle about the regional shortening axes, implying that no pronounced rotation of the strain axes occurred. The internal rotation axes for the Riedel structures reveal a largely bimodal distribution and inferred weakly monoclinic to orthorhombic symmetry. Therefore the overall deformation during Karoo rifting in northern Malawi is interpreted to be close to a coaxial deformation with a limited amount of horizontal extension.[/p]     

西藏洛扎地区拆离断层构造变形特征

西藏洛扎地区发育的拆离断层叠加在先期逆冲推覆构造之上,并被以脆性变形为特征的高角度北倾正断层改造,各阶段变形结构面交切关系清楚。拆离活动表现为韧性-韧脆性层间剪切,拆离体依次向北西(北北西)近水平左行滑断。与韧性拆离断层具有成生关系的淡色花岗岩产状特征及年代学研究表明,拆离断层变形时代为中新世中晚期。本文着重阐述拆离断层几何学及运动学特征,并根据地球物理场资料所反映的青藏高原深部结构特征讨论其成因。     

青海省活动断裂带分布发育特征研究

青海省活动断裂带在印度板块的推挤作用下具有各自不同的空间展布和运动学特征,通过对省内24条活动断裂带的研究,得出NNW向断裂带右旋走滑的同时还具有逆时针旋转的运动特性,柴达木盆地西南边缘的茫崖油沙山断裂的形成可能是阿尔金断裂带左旋走滑的压应力分量和持续板块推挤在青藏高原北部的一种响应,中更新世以来的构造运动决定了现今青海构造地貌的基本形态,现今高原北部的隆升主要集中在柴达木盆地西侧和祁连山地区,挤压应力分布表现为南北强于中部、东部强于西部。     

托莫尔日特金矿区韧脆性剪切带及其控矿作用

矿区位于近NW-NWW向展布的断裂带内,并严格受其控制.控矿断裂带为一条韧-脆性剪切带,其形成主要经历了早期韧性变形、晚期脆性变形及后期改造破坏3个阶段,叠加于早期韧性剪切带之上的晚期脆性破裂带,是矿脉的主要产出位置,成矿与断裂带的韧-脆性转换密切相关.矿体形成于韧-脆性剪切带的转换带附近,后期由于抬升剥蚀而出露地表.矿体分布可能具有"两层楼"式的垂直分带,上部为石英脉型金矿体,品位较高,但规模不大;下部为糜棱岩型金矿体,规模较大,但品位稍低.因此本区以后的找矿工作中应注意挖掘深部糜棱岩型金矿的潜力.     

Faults in crystalline rock and the estimation of their mechanical properties at the Olkiluoto site,western Finland

Brittle deformation zones at the Olkiluoto nuclear repository site in western Finland play critical roles in the strength and hydrology of the host rock mass. We present a procedure implemented there for incorporating information on deformation zones obtained through boreholes into quantitative engineering design. First, ductile and brittle deformation zones are classified based on their characteristics in drillhole cores as brittle joint clusters, brittle fault zones, or semi-brittle fault zones, with an awareness of the geologic processes that caused the zones to develop as they did. Next, it is shown that the mechanical properties of the brittle deformation zones can be calculated by one of several methods, each of which has advantages and disadvantages. The site geology must be kept in mind at all stages to arrive at meaningful estimates of the mechanical properties of the deformation zones.     

Tectonic evolution of a crustal-scale oblique ramp,Hellenides thrust belt,Greece

This study investigates the tectonic evolution of the Omalos transverse zone, which served as a crustal-scale oblique ramp in the External Hellenides thrust belt on Crete island. The Omalos oblique ramp developed above an inherited Mesozoic fault zone that strikes NE–SW, oblique to the regional SSW-directed tectonic transport. During the Early Miocene–Pleistocene evolution of the thrust belt, the oblique ramp was repeatedly reactivated localizing deformation above the inherited structure. Geological and structural mapping combined with kinematic analysis of ductile and brittle structures suggest that the Omalos oblique ramp generated a local kinematic field, which deviated significantly from the regional kinematic pattern in the thrust belt. The most conspicuous feature in the tectonic evolution of the oblique ramp is a change from a ductile wrench-dominated to a brittle, primarily reverse faulting regime across the brittle–ductile transition, followed by brittle wrench deformation after the final exhumation of high-pressure (HP) rocks. Deflections of transport and compression orientations from the regional pattern are attributed to buttressing against basement-cover offsets produced by the pre-existing fault zone, to oblique ramping, and to transfer faulting, respectively. Our findings are potentially applicable to other examples of crustal-scale oblique thrust ramps in various tectonic settings.     

西藏罗布莎豆荚状铬铁矿成矿演化的构造过程

摘要：通过对罗布莎铬铁矿区的构造解析,揭示出了豆荚状铬铁矿的成矿演化规律。由地幔韧性剪切带和脆－韧性剪切带组成的含铬剪切带是成矿期构造,被造山期发生的变形分解作用和脆性断裂作用改造,成矿演化经历了从上地幔到上地壳所发生的５个构造变形相的转换,即熔融流变变形相→地幔韧性剪切变形相→壳幔脆→韧性剪切变形相→塑性挤压变形相→脆性断裂变形相,可划分为中生代改造成矿和新生代矿床改造两个阶段,并概括为包含６个变形世代的构造成矿序列。     

胶东地区控矿剪切带脆性变形时代的Ar-Ar年代学及其对成矿的制约

胶东地区是典型的剪切带型金矿集中区,精确厘定该地区控矿剪切带的活动时代,可为探讨剪切带与金矿成因关系提供关键的时限约束,并且对矿床成矿模式的建立具有至关重要的意义。大量矿床地质证据显示胶东地区控矿剪切带中脆性变形活动对金矿体的形成具有直接影响,但其脆性变形时代尚不十分清楚。据此,本文在详细研究金矿体赋存特征的基础上,系统选取胶东焦家、玲珑、邓格庄、乳山这四个金矿区控矿剪切带断层泥中白云母进行⁴⁰Ar-³⁹Ar年代学研究。定年结果显示,胶东地区焦家剪切带、招平剪切带以及牟乳剪切带的脆性变形时代分别为110.3±1.5Ma、122.8±1.7Ma、119.6±1.2Ma~115.8±1.4Ma。其中焦家剪切带的脆性变形时代明显晚于招平和牟乳剪切带,可能代表了焦家蚀变岩型矿化形成后易遭受后期的构造叠加。综合胶东各金矿区控矿剪切带变形时代、岩体侵位时代、成矿时代及剪切带活动特征和矿体产出特征,本文认为在多期岩体侵位以及控矿剪切带递进变形过程中,剪切带韧性变形区中由高压流体作用产生的同期脆性破裂可形成脉型矿化,如乳山金矿;而在脆-韧性和脆性变形区中发生的大规模脆性变形可导致脉型和蚀变岩型矿化的形成,如玲珑、邓格庄和焦家金矿。但随着剪切带的递进变形和隆升剥蚀,后期多期次的脆性构造变形叠加,可导致多种矿化类型出现在同一构造部位,如焦家金矿中石英脉型和蚀变岩型矿化。