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1.
河南省崤山地区金银矿床控矿构造特征与成矿模式 总被引：1，自引：0，他引：1
崤山位于华北陆块南缘,是河南省重要的有色金属成矿区。为进一步明确崤山地区控矿构造特征,分析探讨成矿就位机制,指导崤山地区中深部地质找矿工作,本文对崤山地区矿床地质特征、构造性质等要素进行了分析研究,将崤山地区控矿构造分为拆离断层控矿构造、韧性剪切带控矿构造和张扭性断裂控矿构造三类。①拆离断层沿太古界太华岩群的结晶基底与中元古界熊耳群盖层间发育,带内发育糜棱岩,崤山北部主要含矿石英脉多发育在紧靠拆离断层带下盘的太华岩群中,矿体就位于拆离剪切形成的拆离断层及其次级断裂带中;②韧性剪切带主要位于崤山中西部和北部,早期呈压扭特性,发育绿泥片岩质初糜棱岩、糜棱岩、花岗质超糜棱岩等,申家窑韧性剪切带晚期表现为张性特征,在其下盘发育有多组与其走向一致的羽列状次级断裂构造,矿体就位于韧性剪切带及其下盘羽状次级断裂带中;③张扭性断裂多发育于崤山中东部,断裂内充填有含金石英脉条带,围岩中多具绿泥石化、绿帘石化、钾化、黄铁矿化等,矿体就位于张扭性断裂带中。按照岩体、构造对成矿的作用关系,建立了崤山地区以深源岩浆为流体、以构造侵位为空间的"双控"成矿模式,指出韧性剪切带、拆离断层带中深部及其次级断裂带是寻找脉型金银矿床的有利地段,燕山期中酸性侵入岩体周缘有斑岩型铜钼矿成矿潜力。 相似文献
2.
Damage surrounding the core of faults is represented by deformation on a range of scales from microfracturing of the rock matrix to macroscopic fracture networks. The spatial distribution and geometric characterization of damage at various scales can help to predict fault growth processes, subsequent mechanics, bulk hydraulic and seismological properties of a fault zone. Within the excellently exposed Atacama fault system, northern Chile, micro- and macroscale fracture densities and orientation surrounding strike-slip faults with well-constrained displacements ranging over nearly 5 orders of magnitude (0.12 m–5000 m) have been analyzed. Faults have been studied that cut granodiorite and have been passively exhumed from 6 to 10 km depth. This allows direct comparison of the damage surrounding faults of different displacements. The faults consist of a fault core and associated damage zone. Macrofractures in the damage zone are predominantly shear fractures orientated at high angles to the faults studied. They have a reasonably well-defined exponential decrease with distance from the fault core. Microfractures are a combination of open, healed, partially healed and fluid inclusion planes (FIPs). FIPs are the earliest set of fractures and show an exponential decrease in fracture density with perpendicular distance from the fault core. Later microfractures do not show a clear relationship of microfracture density with perpendicular distance from the fault core. Damage zone widths defined by the density of FIPs scale with fault displacement but appear to reach a maximum at a few km displacement. One fault, where damage was characterized on both sides of the fault core shows no damage asymmetry. All faults appear to have a critical microfracture density at the fault core/damage zone boundary that is independent of displacement. An empirical relationship for microfracture density distribution with displacement is presented. Preferred FIP orientations have a high angle to the fault close to the fault core and become more diffuse with distance. Models that predict off-fault damage such as a migrating process zone during fault formation, wear from geometrical irregularities and dynamic rupture are all consistent with our data. We conclude it is very difficult to distinguish between them on the basis of field data alone, at least within the limits of this study. 相似文献
3.
花岗质岩浆的起源、迁移及就位是研究大陆岩石圈流变学特性的重要方面。然而,板内伸展背景下同构造花岗岩体的岩浆来源、就位机制和岩浆流动与区域应力场的关系等问题缺乏系统性的总结。晚中生代期间华北板块东部逐渐变为区域伸展体制,同时中浅部地壳形成一系列的韧性剪切带、变质核杂岩和拆离断层,这些伸展构造往往伴有同剪切变形的花岗岩体。因此,华北东部是系统研究板内伸展背景下同构造花岗岩体的最佳区域。本文选取多个典型的同构造花岗岩体,进行综合分析。通过归纳总结这些同构造岩体的岩石地球化学和年代学资料,发现多数同构造岩体具有多个岩浆源区,且较早就位的中性岩席(单元)往往来自壳幔混合岩浆或新生下地壳的部分熔融,而较晚的酸性岩席(单元)则主要来源于古老下地壳的部分熔融。这一特点反映了同伸展岩体岩浆源区由深至浅的演化规律,也揭示了区域伸展背景下源自地幔的流体和热量是触发地壳部分熔融的重要因素。通过分析岩浆就位过程中围岩和岩体中形成的定向及变形组构,发现华北东部同伸展岩体的就位模式可分为三大类:以扁平岩床或岩基形式就位于中部地壳的水平韧性剪切带内;岩浆以近直立运移的方式形成长轴平行拆离断层的岩基,就位于变质核杂岩核部或拆离断层下盘;岩浆就位于再活化的先存断裂,通过膨胀作用、挤压围岩获得就位空间并使围岩变形,形成类似底辟作用的就位方式。剪切应力和浮力是影响岩浆运移方向的重要力学参数。岩浆自源区上升的过程中浮力起着主要控制作用,就位于韧性剪切带时剪切应力起着控制作用,就位于浅部地壳的脆-韧性过渡带时浮力的作用再次凸显。 相似文献
4.
已有研究实例阐明了蛇绿岩产出的构造环境及构造侵位机制的多样性 ,其中发育完整的蛇绿岩套具有与现代大洋岩石圈剖面相似的四层结构模式 ,它们形成于洋中脊扩张构造环境。由于构造运动使蛇绿岩套肢解 ,构造侵位于大陆造山带缝合线地带 ,沿断裂构造以构造岩片和构造混杂岩产出。蛇绿岩提供了洋壳形成和破坏的重要证据 ,蛇绿岩带或古缝合线是确定造山带中古洋盆存在及陆块边界的直接标志 相似文献
5.
Importance of fracturing during retro-metamorphism of eclogites 总被引：3，自引：0，他引：3
Presented textural and petrological data show that the deep to intermediate continental crust may fracture and that microfractures are the locus of fluid and mass transfer necessary for retrograde metamorphism. Kyanite eclogites from Ulsteinvik, Norway, underwent partial retrogression to granulite and amphibolite facies assemblages during near-isothermal exhumation from depths equivalent to more than 2.0 GPa at temperatures of 700–800 °C. Plagioclase-bearing assemblages, rich in hydrous phases, formed along margins of eclogite lenses and along mesoscopic fracture systems. Hydrated zones are from 1–50 cm thick, with adjacent wall-rock eclogite replaced by symplectites. At a low degree of reaction, the secondary minerals in the wall-rock are found along intra- and intergranular microfractures (typically 50–100 μm wide). Minerals filling the microfractures include orthopyroxene–plagioclase–spinel in garnet; plagioclase–sapphirine, plagioclase–corundum and plagioclase–spinel in kyanite; and diopside–plagioclase in omphacite. The microfractures are often arranged en echelon and are connected through microfaults. Releasing bends filled with amphibole and spinel form along microfaults in garnet. The faulting and fracturing caused localized chemical change in garnet: the damage zones close to faults are enriched in FeO and MnO with steep compositional gradients (8 wt% FeO over <20 μm). These FeO- and MnO-enriched zones form wedge-like structures around the tip of the faults (horsetail structures) and rose- or flame-like structures at sticking points along faults. They may represent examples of stress-induced chemical transport during fracture propagation. The change from dry to amphibole-bearing assemblages at the tip of the fracture, and fractures ending in splays of fluid inclusions trails, reflect the involvement of a fluid phase during fracture propagation. This suggests that the ‘dry’ granulite facies retrogression was also driven by fluid infiltration and that metamorphism at depth in collision zones may not be controlled by pressure and temperature alone. 相似文献
6.
The Hope Slide, which occurred on January 9, 1965, involved an estimated 47-Mm3 of meta-volcanics and intrusive rocks. Previous workers reported the presence of tectonic structures (faults and shear zones) along the failure surface at the Hope Slide. These tectonic features were investigated in detail to assess their effects on rock-mass quality and the related implications for slope stability. This paper integrates basic field and laboratory concepts from structural and engineering geology. Subdividing the failure area into structural domains allowed distinct discontinuity sets to be associated with specific tectonic structures. The Geological Strength Index (GSI) was used to estimate the rock-mass damage related to the tectonic structures. Low GSI values were seen to outline tectonic damage zones. Point-load tests were used to characterise the compressive strength of rocks adjacent to the tectonic structures. Strength anisotropy, tentatively attributed to damage caused by a large shear zone, was observed in greenstone samples. Seepage zones along the failure surface were observed preferentially along shallow discontinuities that dipped downslope and in rock masses of good quality (GSI > 40). An alternative morphology of the slope failure is proposed by distinguishing between the extent of the surficial damage due to the rock-slope failure and the zone of failed material (depletion zone). For the first time, a kinematic mechanism for the Hope Slide is proposed, based on a preliminary 3-dimensional block model. A pre-1965 DEM was produced from estimates of material lost and gained as reported by previous workers. The pre-1965 DEM revealed that the tectonic structures recognised during fieldwork bounded the material that failed in the 1965 event. 相似文献
7.
Michaél A Naylor 《Journal of Structural Geology》1982,4(1):1-18
The Cretaceous-Palaeocene Casanova Complex occurs in two thrust sheets of the eugeosynclinal Ligurids of the Northern Apennines. It is a sedimentary mélange with ophiolitic and quartzose turbidites or limestone-shale olistostrome (submarine debris flows) as matrix. Exotic blocks of ophiolite and granite, serpentinite breccias and lenticular ophiolitic breccias and olistostromes contribute to the mélange character of the complex. Deformational structures include soft-sediment slump folds (indicating a SW-dipping palaeoslope) and boudins, a gradational slumped top to the mélange, small-scale faults in chert blocks and deformation associated with the emplacement of the exotic slide blocks. The blocks were shed as rotational slides from submarine fault scarps and are surrounded by haloes of debris created by submarine weathering. The stacking pattern of the blocks, with the originally stratigraphically highest ophiolite lithologies lowest in the pile of blocks, is explained by a diverticulation model with progressively deeper erosion. Mechanical analysis shows that the blocks were stable when partly exposed resting on a soft sediment substratum. Criteria which distinguish the Casanova Complex from a tectonic mélange, and which may be of value in other mélanges, are discussed. Previous interpretations of the complex as a precursor olistostrome to northeastward nappe emplacement (the Bracco ridge model) are rejected. The mélange is believed to have formed on ocean crust as a result of turbidite and debris flow sedimentation, soft sediment deformation, block faulting, gravity sliding and submarine erosion at the distal edge of a uniformly SW-dipping continental margin. 相似文献
8.
Ridge axis deformation and coeval melt migration within layer 3 gabbros: evidence from the Lizard Complex,U.K. 总被引：1，自引：0，他引：1
Ridge-parallel extensional shear zones within the layer 3 gabbros of the Lizard ophiolite have recorded varied and numerous
chemical and mineralogical changes under a variety of P-T conditions. These changes accompany tectonic exhumation of lower crustal levels by a listric fault mechanism during amagmatic
extension at a slow-spreading centre. Deformation within the mid-crustal level of layer three resulted in the migration and
impregnation of an evolved iron-titanium-rich silica-poor melt along the shear zones. This syntectonic infiltration occurred
along the lowermost portions of listric faults which rooted in a partially molten zone beneath the ridge axis. Residual melt
was tapped from this underlying zone and tectonically redistributed about deforming gabbros situated immediately above the
partially molten zone. The occurrence of sub-solidus synkinematic assemblages within the shear zones, which were generated
at various temperatures and water : rock ratios, is explained in terms of their simultaneous development on listric fault
planes in the presence of a hydrothermal fluid phase. The sequential overprinting of pre-existing assemblages arises from
repeated block rotation during amagmatic episodes of extension within an oceanic slow-spreading environment.
Received: 8 February 1994/Accepted: 4 April 1995 相似文献
9.
Tectonic implications of damage zone-related fault-fracture networks revealed in drill core through the Nojima fault, Japan 总被引：1，自引：0，他引：1
1800 m of drill core through the Nojima fault zone, Japan, reveals subsidiary fault and fracture networks that developed in the fault zone that triggered the 1995 Ms 7.2 Kobe earthquake. The subsidiary fault zones contain a fault gouge of < 1 cm bounded by thin zones of foliated cataclasite or breccia. Fractures are filled with calcite veins, calcite-cemented breccias, clay, and iron-oxide and carbonate alternation of the granitic host rock. These features are typical of extensional fractures that form the conduit network for fluid flux close to a major fault zone. The zone of distributed deformation surrounding the main fault is 50 m in width, and the dip of the Nojima fault at > 1 km depth is 75°. The fault-fracture networks associated with the Nojima fault zone are coseismic and were filled with carbonate and fine-grained material during repeated seismic-related infiltration of the fault zone by carbonate-bearing subsurface water. This study shows that fault-related fracture networks plays an important role as fluid flow conduits within seismically active faults, and can change in character from zones of high permeability to low permeability due to cementation and/or pore collapse. 相似文献
10.
中国活动构造与地震活动 总被引：56，自引：3，他引：56
文中研究了中国活动构造与地震活动的关系 ,包括活动断裂、活动褶皱、活动盆地和活动块体与地震活动的关系。全部 8级、绝大部分 7～ 7.9级地震均发生在活动块体边界活动构造带内 ;但对内部有次级活动构造的块体而言 ,少数 7～ 7.9级地震和部分 6～ 6 .9级地震也可能发生在块体内部的活动构造带上。大地震与活动断裂、活动褶皱和活动盆地的关系十分紧密 ,70多次 7级以上地震的同震破裂带及其位移参数与活动构造完全一致 ,7～ 8级地震均发生在活动断裂、活动褶皱和活动盆地带内 ,仅个别地震由于发生在高原和高山区 ,情况不明 ,6～ 6 .9级地震则大约有 5 %～ 15 %发生在活动构造带外或者情况不明。由于中国各断块区应力环境的差别 ,各区活动构造变形和地震发震构造类型也有所不同 ,文中对不同构造区走滑型 ,逆断裂褶皱型和正断裂拉张型活动构造和地震发震构造模型作了讨论。 相似文献
11.
华北克拉通中部带中段古元古代构造格架与主要变形事件研究 总被引：2，自引：0，他引：2
古元古代是华北克拉通构造演化的关键时期,中部带的性质是近年来华北克拉通构造演化研究争论的焦点之一。文中根据古元古代韧性剪切带重新划分了中部带北段构造格架,即由近EW向朱家坊韧性剪切带、NEE向王家会韧性剪切带和NE向龙泉关韧性剪切带分割恒山、繁峙、五台和阜平地块。这些地块基底具有不同的前寒武纪变质杂岩组成、构造变形特征和构造演化历史,一般都具多期变质变形叠加的特征。研究表明华北克拉通中部构造带北段在古元古代末发生3次重要的构造变形事件：繁峙地块由SW向NE方向的构造挤入,挤入过程中导致五台地块变形并向南东方向逆冲(D1);以阜平地块为核部的大规模伸展抬升,阜平变质杂岩抬升至近地表,阜平地块与五台地块之间形成一系列低角度伸展型韧性剪切带(D2);最后一次构造事件是NE向拉伸导致的大量NW向基性岩墙群侵位(D3)。 相似文献
12.
可靠地划分地震区可奠定地震预测与地震危险性评价的地质基础,具有十分重要的意义。笔者等通过研究分析指出板内孕震构造块体侧向边界可由区域性大断层或由区域性大断层与板块边界界定,底边界为康拉德面或低速高导层;板间孕震构造块体为俯冲板块,可由区域性大断层和(或)板块边界约束;在同一个孕震构造块体和同一轮地震周期的地震具有内在联系。因此,地震区可定义为代表相应孕震构造块体地震活动的区域,其可表征该块体内源自锁固段破裂的地震活动。基于笔者等提出的孕震构造块体和相应地震区边界确定原则,把全球两大地震带(环太平洋地震带和欧亚地震带)划分为62个地震区;每个地震区的分区方案均通过了多锁固段脆性破裂理论的检验,这说明方案可靠。进而,笔者等归纳总结了地震区划分方法。 相似文献
13.
14.
Igneous rocks in the Sistan suture zone have characteristics that can be correlated with important tectonic events. A Late Cretaceous ocean basin is recorded by ophiolites now exposed in numerous mélange zones. Subduction beneath the Afghan block is indicated by Late Cretaceous-Paleocene calc-alkaline volcanics. Collision of the Lut block with the subduction complex in the middle Eocene produced widespread deformation and was followed by the emplacement of late Eocene-early Oligocene calc-alkaline granitic batholiths that probably formed by widespread anatexis of marine sediments. A dominantly Oligocene magmatic event is represented by widespread alkaline volcanics and minor intrusions that appear to be related to major transcurrent faults. Miocene calc-alkaline activity was limited to sporadic volcanism in the north and minor intermediate intrusions farther south. These units are largely underformed and not related to any major faults. The youngest magmatic event is recorded by late Miocene-Pliocene mafic flows that are weakly alkaline, clearly related to right-lateral faults and probably were derived from a deep crustal or upper mantle source. 相似文献
15.
The Abitibi belt is one of the largest and most extensively studied Late Archean greenstone belts. The structural geology of the Abitibi belt consists of one generation of upright to slightly overturned, doubly plunging first-order folds with half-wavelengths of 20–60 km, and E–W-striking, steeply dipping fault zones that are parallel to the fold limbs. Two of the main fault zones are continuous for hundreds of kilometers. Previous tectonic models for the Abitibi belt interpret the fault zones to have formed as extensional growth faults bounding a volcanic-sedimentary basin, which were reactivated as thrusts during subsequent crustal shortening. Other models propose that the fault zones represent tectonic sutures, implying that the Abitibi belt is a collage of exotic terranes. However, distinct geological terranes have not been geologically demonstrated. We propose a new detachment fold model for the deformational history of the southern Abitibi belt, in Ontario, that explains the formation of the fault zones during the single, well-documented folding event that deformed the entire region. The internal structure of the fault zones, documented here with emphasis on the Porcupine–Destor fault zone, consists of isoclinally folded, strongly schistose, highly metamorphosed rock, cross-cut by numerous fault segments. We interpret that the upper crust (greenstones) was folded above a proposed detachment in the lower part of the volcanic stratigraphy. The fault zones would be, in essence, highly evolved detachment anticlines. Ultramafic metavolcanic rock that crops out within the fault zones would represent material from the detachment horizon that was emplaced in the cores of the detachment anticlines. The numerous segments that make up the mapped fault zones would be linked faults that formed within the isoclinal detachment anticlines to accommodate folding of the rheologically complex greenstones. The detachment fold model is compared to the results of analogue experiments designed to investigate crustal-scale folding, using viscous and frictional materials. Detachment folds are produced in the brittle upper crustal analogue on the limbs of folds formed in the ductile middle and lower crust analogues. The experimentally produced structures scale to the structures in the study area and indicate the detachment fold model for the southern Abitibi is mechanically viable. 相似文献
16.
隐性断裂带是区域或局部应力场、基底断裂体系活动、潜山块体扭动影响下在沉积盆地盖层中产生的断裂趋势带, 它是断裂带的一种类型, 与显性断裂伴生于沉积盆地, 但由于其不具有显性断裂的固有特征, 隐蔽性强而常常被忽略.可以通过以下7个方面有效识别隐性断裂带: ①小型显性构造(小断层、小褶皱、断块)呈雁列式、断续状、错位对称式反映的大型隐性断裂带; ②基底断裂体系活动在沉积盆地盖层中产生的隐性断裂带; ③潜山、凹陷分布形成的线状、调节型或者侧列式隐性断裂带; ④砂体分布反映的隐性断裂带; ⑤油藏排列、分布、走向反映的隐性断裂带; ⑥相干体切片显示的隐性断裂带; ⑦断层叠覆端、末端、深大断裂分段活动等局部应力场变化形成的隐性断裂带.应用上述方法开展渤海湾盆地隐性断裂带识别研究, 综合国内外的调研结果, 建立了隐性断裂带的类型划分方案体系并阐述了不同级别构造单元中隐性断裂带的类型特征.研究表明, 隐性断裂带具有多方面的地质意义, 可以作为调节构造带调节盆地不均匀伸展活动, 分隔凹陷、隆起等构造单元; 控制盆地沉积相带发育分布, 影响断陷湖盆砂体的展布范围; 控制圈闭组合排列、改造输导体系, 形成串珠状、带状油气富集区; 深断裂活动触发地震的过程中会在地表形成隐性断裂带, 因此, 隐性断裂带的识别和分析具有现实意义. 相似文献
17.
青藏高原东西向伸展及其地质意义 总被引：30，自引：4，他引：30
东西和南北向伸展是青藏高原最显著的地质特征之一。南北向伸展形成的东西走向伸展构造,主要包括藏南拆离系(STDS),和沿喀喇昆仑—嘉黎断裂带(KJFZ)发育的正断层体系。东西向伸展形成数目众多的南北走向伸展构造,它们切割青藏高原几乎所有的东西走向构造单元,包括羌塘地块、KJFZ和STDS等,说明东西向伸展以整体形式发生并同时波及整个青藏高原,而不是由以KJFZ和STDS为边界的不同地块的不均匀挤出所致。南北走向伸展构造在地表呈之字形,为南北向挤压形成的追踪张断裂;剖面上表现为被后期高角度正断层叠加的拆离断层,拆离断层形成于中-晚中新世而高角度正断层形成于上新世及以后。导致拆离断层的东西向伸展可能是南北向挤压的变形分解,后期高角度正断层作用可能是高原隆升后的垮塌所致。东西向伸展是控制青藏高原新生代浅色花岗岩和盆地形成的主要因素。 相似文献
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断裂带通常包括狭窄的断层核与宽阔的破碎带,并对岩石物理及其水力学、流体与渗透性具有重要作用。根据断裂破碎带结构的差异,将碳酸盐岩断层核划分为颗粒支撑、基质支撑与胶结支撑等3种类型,将碳酸盐岩破碎带划分碎裂带与裂缝带。不同类型碳酸盐岩断层核与破碎带形成多种类型组合,并造成断裂破碎带多种复杂的渗流结构。通过井—震资料的结合,可以判识沉积盆地内部较宽的碳酸盐岩断裂破碎带,其宽度—位移关系可以指示断裂破碎带的不同生长方式与机制。复杂内部结构、多期构造成岩作用与non-Andersonian破裂机制可能导致碳酸盐岩断裂破碎带的异常生长,也是碳酸盐岩断裂破碎带机理研究的重要方向。 相似文献
19.
20.
碳酸盐岩断裂破碎带结构、分布与发育机制 总被引：1，自引：0，他引：1
断裂带通常包括狭窄的断层核与宽阔的破碎带,并对岩石物理及其水力学、流体与渗透性具有重要作用。根据断裂破碎带结构的差异,将碳酸盐岩断层核划分为颗粒支撑、基质支撑与胶结支撑等3种类型,将碳酸盐岩破碎带划分碎裂带与裂缝带。不同类型碳酸盐岩断层核与破碎带形成多种类型组合,并造成断裂破碎带多种复杂的渗流结构。通过井一震资料的结合,可以判识沉积盆地内部较宽的碳酸盐岩断裂破碎带,其宽度一位移关系可以指示断裂破碎带的不同生长方式与机制。复杂内部结构、多期构造成岩作用与non-Andersonian破裂机制可能导致碳酸盐岩断裂破碎带的异常生长,也是碳酸盐岩断裂破碎带机理研究的重要方向。 相似文献