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陕西省镇安县金龙山金矿是产于南秦岭印支褶皱带中的微细浸染型金矿,上泥盆统南羊山组(D3n)细碎屑岩-碳酸盐岩既是金龙山矿区的容矿地层,又是金等成矿物质的矿源层。金矿脉的产出主要受断裂构造控制,尤其NE向的断裂构造控制了金龙山金矿绝大多数的矿脉产出。在金龙山金矿区金龙山矿段106号金矿脉应用EH4连续电导率仪成功区分出了两种不同的岩性,并识别出了3条与成矿有关的断裂构造。测区内灰岩表现为高阻异常特征,页岩表现为低阻异常特征。近EW走向的断裂构造Fa为测区内规模最大的断裂构造,深部延伸较深;NE向的断裂构造Fb与Fc近平行产出,并且深部均与Fa交汇,其中Fb为106号金矿脉所处断裂构造,而Fc为测区内一条锑矿脉所处的断裂构造。Fa断裂与区域上EW走向的深大断裂倾向一致,为SN向推覆过程中形成的,在成矿过程中为成矿热液提供运移通道;NE向断裂Fb与Fc具有容矿条件,推测应为张性断裂。 相似文献
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湘中古台山金锑矿位于雪峰构造带西南段东北部,发育SN向金矿脉和NW向金锑矿脉2类矿脉。前人提出SN向和NW向断裂为容矿构造,并获得了印支期成矿的40Ar-39Ar同位素年龄,但对容矿断裂的性质、形成时代以及2类矿脉的时代关系缺乏研究和认识。鉴于此,文章通过地表和井下露头构造以及矿化蚀变的观测、解析,结合区域构造特征、区域构造演化和测年资料等,厘定了古台山金锑矿区构造变形序列及其时代、不同类型矿脉的成矿时代和构造背景,探讨了构造控矿规律及动力机制。主要认识如下：(1)研究区自早至晚经历了5期主要变形事件：志留纪晚期受到NWW向挤压,形成NNE向板劈理、NNE向褶皱(水车背斜)、SN向顺层断裂、逆冲剪切破裂和断裂;中三叠世晚期受到NNW向挤压,局部形成NEE向轴面劈理;晚三叠世受到SN向挤压,形成EW向褶皱、NW向—NNW向右行走滑断裂和剪切破裂、NNE向左行走滑断裂和剪切破裂、EW向逆冲剪切破裂等;中侏罗世晚期受到NWW向挤压,形成EW向右行剪切破裂和断裂;古近纪中晚期受到NE向—NNE向挤压,形成SN向—NNE向右行剪切破裂和断裂、EW向—N... 相似文献
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(一)区域地质特征 1.岩体产出的地质条件: 岩体位于阴山—天山纬向构造带,北山地区的旱山—凤尾山—小尘包山字型构造前弧东侧。在这里,近东西向展布的向西倾伏的背斜及切断背斜南翼的北东东向弧形大断裂与次一级北西向断裂交汇构成复杂的构造带。构造带内岩浆岩发育,含铷花岗岩位于北东东向弧形大断裂北侧,即北东东向弧形大断裂与次一级北西向断裂交汇处。区内发育有北西向压扭性和北东向张扭性两组小断裂,以及一组近南北向追踪断裂。前两组小断裂构成棋盘格子构造。小断裂中均充填有萤石矿脉和髓石—萤石矿脉,形成萤 相似文献
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安化廖家坪金矿床地质特征及成矿规律 总被引：1，自引：0，他引：1
廖家坪金矿床属江南地轴东南缘桃江－城步锑金多金属成矿带的一部分,以NE向桃江－城步深断裂为导矿构造,以长度＞2km,地层断距＞200m的矿区主干断裂为配矿构造,以早期NWW向剪切劈理带中叠加的长度＜1km,地层断距不明显的次级断裂破碎带为容矿构造,矿区38条金矿脉构成两个含矿带8个矿脉群,含矿带的分布与地层岩性有一定关系,矿脉群的分布与早期花岗斑岩脉关系密切,金矿脉主要有4组,NNE向组最发育,NWW向组规模最大,矿化富集与围岩蚀变种类及强度,矿脉交切部位及产状变化段关系密切,根据区域成矿地质条件,金矿床成矿规律,指出湘中地区有廖家坪、白云铺、三德堂矿区及外围和古台山地区4个廖家坪式金矿床找矿远景区。 相似文献
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河北峪耳崖金矿位于冀东NE向构造带中，矿区出露的地层为中元古界的一套沉积岩系，以高于庄组石灰岩为主，产于其中的峪耳崖岩株为主要岩浆岩，构造以断裂为主并较为发育，矿区90％的矿脉受其控制。利用地质力学的观点对其控矿规律进行了深入分析。按照断裂与矿脉的空间关系，可划分出成矿前、成矿期、成矿后3种类型。成矿期断裂一般与矿脉同时生成并对其具有控制作用，主要呈NE、近EW、NNE、NW向。矿脉一般赋存于NE、NNE向断裂中，在其转折处以及倾向上由陡变缓处矿体变富。另外，矿脉还具有等间距、沿倾向斜列排布及复合控矿等规律。利用上述控矿规律对矿区50—150m标高处金矿体的空间位置、赋存状态及富矿部位进行了初步预测。 相似文献
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该成矿区位于雪峰孤形构造带东北段,赋存在两条北东向断裂夹持并具矿源层特征的下奥陶统宁国组砂页岩中。矿脉呈中一陡倾斜柱板状产出,严格受断裂构造控制。成矿作用与构造活动同步,属动力变质热液矿床类型。 相似文献
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The Hyde-Macraes Shear Zone (HMSZ) is a regionally continuous, low-angle, NE dipping (~15°) late-metamorphic thrust zone in
the Mesozoic Otago Schist. The shear zone, which is host to large volumes of mineralised schist, consists of foliated fissile
schist with some massive schist pods. Two sets of quartz veins are found within the HMSZ: thrust-related, shallowly dipping
veins that were emplaced parallel or sub-parallel to the shears and swarms of steeply dipping extensional veins, which cut
across the metamorphic foliation. The latter are restricted to the massive schist pods. Mutual cross-cutting relationships
occur between steep extensional veins and shallow-dipping veins, suggesting that they formed contemporaneously. The co-existence
of these two vein types locally implies local rotation of the principal stress axes to produce extensional veins within a
regional thrust setting. The steep extensional veins are spatially related to lateral and oblique ramps within the HMSZ. Three-dimensional
mechanical models show that these lateral or oblique ramps can produce favourable conditions for extensional vein formation
when combined with a high fluid pressure and oblique convergence. Mechanical requirements include a reduced differential stress,
a positive volumetric strain and an increase in the horizontal shear stress. Our models show that under certain conditions,
it is possible for extension-related structures to form during shortening because of local changes in the stress state without
the need for a regional scale switch in the imposed stress field. The convergence direction across the HMSZ during formation
of the steep extensional veins was ~WNW. 相似文献
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J. McMahon Moore 《Mineralium Deposita》1975,10(4):374-388
Geological plans and sections showing the traces of veins, faults and porphyry dykes associated with the Hercynian batholith, have been used to construct diagrams representing the trajectories of the minimum and intermediate principal stress axes as they were at the time of intrusion of the dykes and as the veinlode fissures formed. The dykes and veins were emplaced during a complicated series of events and the trajectory diagrams represent stress conditions during these overlapping periods of time towards the end of intrusion of the batholith. The mineralizing fluids emanated from the cores of plutons by means of pregranite faults, primary igneous joints, and structures created by intrusion, including faults and extension fissures. The trajectory diagrams indicate that the mapped configuration of veins and porphyry dykes results from fluid pressures, exerted by the mobile cores of granitic cupolas situated within a regional stress field. The stress models also indicate that fugitive dyke magma or hydrothermal fluids, emanating from a cupola, will make the mechanically easiest exit through the flanks of the intrusion. This explains the asymmetrical disposition of belts of mineralization which border the granite cupolas of southwest England. 相似文献
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岩脉的侵位机制对成矿作用的约束
———以内蒙古大井锡多金属矿床为例 总被引：2，自引：0，他引：2
[摘 要] 岩脉的侵位机制对理解岩脉和矿脉的侵位过程有着重要的意义。本文详细介绍了岩脉
的侵位机制,并以大井锡多金属矿床为例初步探讨了矿区内岩脉与矿脉的关系。研究表明,区域上主要
受NW-SE 向的挤压应力,在海西期向燕山期转变阶段,区域应力场并没有发生变化,只是林西断块发
生了顺时针转动的结果。矿区范围内,同样受NW-SE 向挤压应力作用,块体也发生了相应的变化,推测
矿区西南向北东方向挤压应力逐渐减小,隆升剥蚀量也随之减小。整体上,岩脉侵位于先存裂隙,矿脉
侵位于岩脉形成的构造空间,局部具有互相穿插的现象。通过岩脉和矿脉的侵位过程,认为矿区西部寻
找斑岩型矿床潜力较大。 相似文献
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滇西茅草坪脉状铜矿床脉体构造与成矿时代研究 总被引：2，自引：0，他引：2
西南三江造山带兰坪盆地西缘发育一条重要的脉状铜矿带,通常认为其成矿与盆地演化有关,而忽略了同处于盆地西缘的崇山剪切带和成矿的关系。茅草坪是近来在该带南段新发现的一例脉状铜矿床,本文通过详细野外工作厘定矿床地质特征,重点开展露头及镜下尺度的含矿脉体构造观察,在此基础上,分选成矿期热液白云母开展40 Ar/39 Ar定年,进而探讨成矿与剪切变形的关系。研究表明,矿床热液矿物以3种形式出现:热液蚀变晕、平行剪切面理的热液脉(A1脉)、横切剪切面理的热液脉(A2脉)。以上不同脉体中的矿物不仅有连续生长的特点,而且存在一定的交切关系,反映它们大致同期形成,但矿物沉淀顺序由早到晚变化。蚀变晕形成于早期,主要由电气石和石英组成,矿物呈强定向排列,长轴平行于剪切面理,为将挤压剪切应变下形成;A1脉形成略晚于蚀变晕,主要由电气石、石英、方解石、白云石、白云母、黄铜矿等组成,矿物弱定向排列,长轴近平行于剪切面理,为弱挤压剪切应变下形成;A2脉形成最晚,脉内矿物与A1脉相似,矿物无定向性、张性充填,反映形成时剪切变形已停止,可能为变形后应力松弛阶段形成的张性脉。因此,茅草坪矿床矿化形成在剪切作用由强变弱、直至停止的过程中,为剪切作用末期的产物。A1脉体中的白云母40 Ar/39 Ar坪年龄为20.34±0.19 Ma,可以代表矿床形成年龄,表明茅草坪地区的剪切作用结束于20Ma。综上表明,茅草坪矿床形成在崇山剪切带区域剪切走滑期间(末期),矿化受与剪切变形末期相关构造控制,是一个与崇山剪切带演化有关的脉状Cu矿床。因此,兰坪盆地西缘脉状铜矿带矿床成因应充分考虑与崇山剪切带演化的关系。 相似文献
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The subsolidus segregation of layer-parallel quartz-feldspar veins in greenschist to upper amphibolite facies metasediments 总被引：2，自引：0，他引：2
Abstract Layer-parallel (i.e. parallel to foliation or bedding) vein formation in the graywackes and pelites of the Quetico Metasedimentary Belt occurred during synchronous prograde metamorphism and regional (D2) compression. In a traverse across metasediments which change in metamorphic grade from greenschist to upper amphibolite (migmatite) facies, layer-parallel veins show the following trends: (1) an increase in thickness and internal complexity, the latter due to successive boudinage; (2) low-grade veins are parallel to planes of anisotropy due to the original sedimentary fabric of the host rocks, but at higher grades other sites are also used and (3) a systematic increase in plagioclase/quartz ratio in the veins towards higher grade, adjacent mafic selvedges first exhibit quartz depletion then, in the amphibolite facies, plagioclase depletion. Mineralogical zoning is often preserved in a single vein, older parts are more quartz-rich than younger. Mass balance calculations and whole-rock geochemistry based on veins, mafic selvedges and country rock are consistent with a closedsystem subsolidus segregation origin. The layerparallel veins are syntectonic, and migration of the mobile components required to form their mineralogy is a stress-induced mass transfer. The source of these components appears to be dominantly pressure solution of the same minerals in the host rocks, although metamorphic reactions may also have contributed. Veins nucleated first at those sites where initial sedimentary heterogeneites, such as fine-scale graded bedding, provided gradients of normal stress across grain boundaries, and hence of chemical potential, necessary to drive the subsolidus segregation process. The earliest veins are thus parallel to bedding. Later, nucleation of the veins could also occur along more randomly distributed sites within the metasediments, and these veins grew parallel to the schistosity rather than bedding, if the two were distinct. Once formed, the veins themselves, which are more competent than the surrounding rock, provide the stress heterogeneity required for their further growth. The increasing plagioclase/quartz ratio in the veins may be due to a temperature dependent increase in plagioclase component mobility relative to quartz. Alternatively, the increasing transfer distances for silica, resulting from prior quartz depletion in the inner parts of the mafic selvedge, may increase the relative mobility of plagioclase component. 相似文献
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透岩浆流体作用与矿田构造 总被引：1，自引：1，他引：0
从透岩浆流体成矿理论的角度对矿田构造进行了重新认识,提出矿田构造系统是一种复杂性动力系统的观点。根据这个模型,矿田构造是近场应力场与远场应力场强烈相互作用的产物。近场应力场由岩浆成矿系统而不是远场应力场派生,因而不能由矿田构造反演区域构造,但可以从区域构造限定矿田构造。矿田构造常有岩脉和热液脉充填,因而是可识别的。利用构造统计学方法,可以根据岩脉和/或热液脉的分布密度图(或等值线图)预测找矿靶区。 相似文献
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This paper presents a new approach to constrain paleoburial and subsequent uplift by folding in fold-thrust belts, combining differential stress estimates from mechanically-induced calcite twins with the assumption that stress in the upper crust is in frictional equilibrium. Calcite twin data were collected from pre-folding veins in late Cretaceous limestones from the Ionian zone in Albania in order to (1) determine Paleogene-Neogene stresses associated with the development of the major vein sets in the frontal anticlines of the Outer Albanides and (2) estimate paleoburial of the Cretaceous reservoir rocks during pre-folding flexural subsidence of the foreland. The first vein set (set I) trends N140 (± 20) and the second set (set II) is oriented N060 (± 20). Calcite twinning analysis from set I veins reveals a pre-folding N030° extension likely related to foreland flexure; a later pre-folding, NE-directed compression (LPS) is identified either from one or from both vein sets in the samples from the Saranda anticline; this NE compression is instead recorded by twinning in set II veins from the Kremenara anticline during late stage fold tightening. This NE compression well agrees with independent microtectonic data, regional transport direction and contemporary stress. The differential stress values related to this NE compression are combined with the hypothesis of crustal frictional stress equilibrium to derive first-order estimates of paleoburial of the Cretaceous limestones just before they were uplifted by folding. The ~ 4 km paleoburial of these limestones estimated in the Saranda anticline is consistent with independent paleoburial estimates from stratigraphy, maturity rank of organic matter, paleotemperature/paleogeothermal gradients from fluid inclusions and predictions of kinematic modelling of the Albanian foreland. Our results therefore place reliable constraints on the amount and rate of vertical uplift of these Cretaceous limestones and yield a promising methodology for better constraining paleoburial and therefore erosion and uplift in fold-thrust belts. 相似文献
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本文以广西龙水水政顶倾竖褶皱构造变形分析为基础,根据含金石英脉与非含金石英脉的变形差异,认为作用于岩层上的主剪切应力(σ_s)与主压缩应力(σ_p)随时间(t)的变化是导致岩层褶皱过程中石英脉多样性变形的主因;阐述了上述模型的动态应力场及其动力学过程;提出了构造变形的分解作用、水力压裂作用与裂开-愈合作用是石英脉形成的新构造机制。 相似文献
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Brittle fracture processes were hypothesized by several researches to cause a damage zone around an underground excavation in sulfate-rich clay rock when the stress exceeds the crack initiation threshold, and may promote swelling by crystal growth in newly formed fractures. In this study, laboratory experiments such as unconfined and confined compression tests with acoustic emission monitoring, and microstructural and mineralogical analyses are used to explain brittle fracture processes in sulfate-rich clay rock from the Gipskeuper formation in Switzerland. This rock type typically shows a heterogeneous rock fabric consisting of distinct clayey layers and stiff heterogeneities such as anhydrite layers, veins or nodules. The study showed that at low deviatoric stress, the failure behavior is dominated by the strength of the clayey matrix where microcracks are initiated. With increasing deviatoric stress or strain, growing microcracks eventually are arrested at anhydrite veins, and cracks develop either aligned with the interface between clayey layers and anhydrite veins, or penetrate anhydrite veins. These cracks often link micro-fractured regions in the specimen. This study also suggest that fracture localization in sulfate-rich clay rocks, which typically show a heterogeneous rock fabric, does not take place in the pre-peak range and renders unstable crack propagation less likely. Sulfate-rich clay rocks typically contain anhydrite veins at various scales. At the scale of a tunnel, anhydrite layers or veins may arrest growing fractures and prevent the disintegration of the rock mass. The rock mass may be damaged when the threshold stress for microcrack initiation is exceeded, thus promoting swelling by crystal growth in extension fractures, but the self-supporting capacity of the rock mass may be maintained rendering the possibility for rapidly propagating instability less likely. 相似文献
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Conspicuous, gently inclined, lenticular quartz–carbonate veins with fibre-textured infills dissect the steep, gold-bearing quartz veins in the Dolgellau Gold-Belt. Similar quartz veins fill the necks of boudin-like structures affecting the main gold-bearing veins at Clogau mine. They also dissect the post-mineralization ENE–WSW ‘Clogau Stone’ dykes. The uniformly oriented regional cleavage shows marked deflection around the gently inclined quartz veins. These late quartz veins were emplaced whilst the mudstones of the Clogau Formation, which host the steep gold-bearing quartz veins, were undergoing ductile deformation. The stretching involved in the late vein and boudin development requires these structures to be contemporaneous with some stage in the development of the regional sub-vertical cleavage and upright fold system. The earlier gold-bearing veins show evidence of brittle fracture and still retain some drusy space-filling textures. Cleavage is deflected adjacent to these early veins and in breccia clasts within the veins. The rare minor folds seen in the gold-bearing quartz veins have axial planar cleavages. It is concluded that the gold-bearing veins pre-date cleavage development. Thus they were forming when large amounts of water were still available in the sedimentary sequence, removing the severe source and transport problems that are implicit in the previous view that the veins were post-tectonic. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献