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1.
北京西山房山岩体岩浆底辟构造及其地质意义 总被引：16，自引：0，他引：16
运用底辟构造的理论和模型, 通过对北京西山房山岩体边缘围岩构造、变形和应变的研究, 厘定出岩体边缘的高温剪切带、周缘向斜、呈穹状分布陡倾的线理和面理, 并结合对西山区域构造事件分析后提出房山岩体为典型的岩浆底辟构造(HotStokesDiapir).这项研究成果不仅在世界上首次证实了岩浆底辟的存在, 而且对理清北京西山地区的地质构造格架和演化序列具有十分重要的意义.研究认为房山地区可能不存在变质核杂岩; 房山岩体边缘的关坻太古宙杂岩是基底岩石随岩体底辟流动上升带到地壳上部的; 原先确定的一些印支期“剥离断层”是房山岩体岩浆底辟的刺穿构造或围岩高温剪切作用造成的地层缺失; 太平山和凤凰山等向斜是岩体底辟过程中在围岩拖曳下形成的周缘向斜. 相似文献
2.
D. H. W. Hutton 《Geological Journal》1977,12(2):99-112
Seven phases of deformation are recognised in Dalradian metasediments within the NW aureole of the Main Donegal Granite. Major NW facing F2 folds (the Aghla Anticline and Errigal Syncline) refold an originally NW facing slaty cleavage, which is usually parallel to bedding. D3 structures cross-cut the major F2 folds and verge and face to the SE on their normal limbs. A fourth phase of deformation intensifies towards the granite contact and is shown to be broadly coeval with intrusion and responsible for a major structure in the aureole. Three later phases are variably developed throughout the aureole. The kinematics of F4 folds in relation to the granite intrusion are briefly discussed. 相似文献
3.
Structural mapping of the Pasupugallu pluton, an elliptical intrusive gabbro-anorthosite body, emplaced into the western contact zone between the Eastern Ghats Mobile Belt and the Archaean East Dharwar Craton, along the east coast of India, reveals concentric, helicoidal and inward dipping magmatic and/or tectonic foliations. We identify a <1 km-wide structural aureole characterized by pronounced deflection of regional structures into margin parallel direction, mylonitic foliations with S-C fabrics, sigmoidal clasts, moderately plunging stretching lineations, non-cylindrical intrafolial folds, and stretched elliptical mafic enclaves in the aureole rocks. Our results suggest that the pluton emplacement is syn-tectonic with respect to the regional ductile deformation associated with the terrane boundary shear zone at the western margin of the Eastern Ghats. We present a tectonic model for the emplacement of the pluton invoking shear-related ductile deformation, rotation and a minor component of lateral expansion of magma. The intrusive activity (1450-800 Ma) along the western margin of the Eastern Ghats can be correlated with the significant event of recurring mafic, alkaline and granitic magmatism throughout the global Grenvillian orogens associated with the continent-continent collision tectonics possibly related to the amalgamation and the breakup of the supercontinent Rodinia. 相似文献
4.
V. J. Morand 《Australian Journal of Earth Sciences》2013,60(3):339-353
The Wyangala Batholith, in the Lachlan Fold Belt of New South Wales, is pre‐tectonic with respect to the deformation that caused the foliation in the granite, and was emplaced during a major thermal event, perhaps associated with dextral shearing, during the Late Silurian to Early Devonian Bowning Orogeny. This followed the first episode of folding in the enclosing Ordovician country rocks. Intrusion was facilitated by upward displacement of fault blocks, with local stoping. Weak magmatic flow fabrics are present. After crystallization of the granite, a swarm of mafic dykes intruded both the granite and country rock, possibly being derived from the same tectonic regime responsible for emplacement of the Wyangala Batholith. A contact aureole surrounding the granite contains cordierite‐biotite and cordierite‐andalusite assemblages. Slaty cleavage produced in the first deformation was largely obliterated by recrystallization in the contact aureole. Postdating granite emplacement and basic dyke intrusion, a second regional deformation was accompanied by regional metamorphism ranging from lower greenschist to albite‐epidote‐amphibolite facies, and produced tectonic foliations, termed S and C, in the granite, and a foliation, S2, in the country rocks. Contact metamorphic rocks underwent retrogressive regional metamorphism at this time. S formed under east‐west shortening and vertical extension, concurrently with S2. C surfaces probably formed concurrently with S and indicate reverse fault motion on west‐dipping ductile shear surfaces. The second deformation may be related to Devonian or Early Carboniferous movement on the Copperhannia Thrust east of the Wyangala Batholith. 相似文献
5.
Migmatitic rocks near Grenville, Quebec, preserve features indicative of reactions at the onset of granulite facies metamorphism. In this area, metapelites and metacarbonates of the classic Grenville Series are spatially associated with granitic gneiss and metabasite, and flank a Paleozoic, Fe-rich syenite stock. Near this intrusion, the metapelite is diatexitic and nearly devoid of biotite, indicating the involvement of biotite during melting in the contact aureole of this intrusion. Outside of the contact aureole, metapelites and associated rocks contain biotite and are metatexitic. These features suggest two episodes of migmatization, the earlier predating the syenite, the later, synchronous with this intrusion.
Hornblende-rich metabasites near the syenite contain a two-part neosome consisting of coarse-grained leucosome veins and patches that are enclosed by fine-grained, pyroxene-rich envelopes. Migmatization is attributed to dehydration melting in the presence of CO2-rich fluids possibly derived from nearby carbonate rocks prior to and/or during emplacement of the syenite. The occurrence of isolated mafic clots in the mesosome and rarity of melanosome seams on leucosomes suggest that some melts were mobile on an outcrop scale. These observations suggest that the leucosomes formed by the segregation of melts, which, coupled with CO2 flux, dehydrated the wallrock along narrow margins, forming the pyroxene-rich neosomes. Back-reaction with residual fluids led to the local scapolitization of plagioclase and the concomitant formation of coronal garnet on pyroxene in neosomes. Thermobarometry of corona structures within the contact aureole generates diffusional Mg-Fe blocking temperatures ( 550 °C at 5.5 kbar). Extrapolated up-temperature, P-sensitive equilibria for the coronas yield similar pressures (8–9 kbar) as texturally-equilibrated assemblages for which high temperatures ( 750 ± 50 °C; XCO2 = 0.90−0.95) were determined for rocks sampled inside and outside of the contact aureole. This suggests that the Grenville migmatites had not been substantially decompressed by the time that the syenite was emplaced. 相似文献
6.
Roger H. Mitchell 《Contributions to Mineralogy and Petrology》1978,67(4):341-347
Garnet lherzolite xenoliths of similar petrography and mineralogy are found in the Elwin Bay, Nanorluk, and Amayersuk kimberlites. The xenoliths are either coarse equant to coarse tabular or porphyroclastic in texture. Compositions of coexisting pyroxenes indicates equilibration at 1000–1270° C at 34–41 kb (Wood-Banno/Wood method) or 865–1200° C at 29–36 kb (Wells/Wood method). No simple correlation exists between textural types and equilibration temperature. A primary spinel-bearing garnet lherzolite has equilibrated at 840° C at 21 kb (Wells/Wood) and provides the only known example of a xenolith with relatively high Cr/Cr+Al which has equilibrated at the spinel to garnet lherzolite transition along the continental geotherm. The pressure and temperature estimates for the xenoliths lie above those of the steady state geotherm and indicate that a perturbed geotherm existed in this region at the time of kimberlite intrusion. The formation of perturbed geotherms is discussed and it is considered that the upper high temperature limbs of inflected geotherms are transient pseudogeotherms generated in response to a thermal aureole about a rising mantle diapir and that the lherzolites which define such a geotherm represent a telescoped section of the mantle and include xenoliths derived from above and below the point of kimberlite liquid segregation. The lower temperature limbs of inflected geotherms are considered to be representative of the steady state geotherm and are sampled by the kimberlite which after segregation from the diapir rises at a much faster rate than the parent diapir and passes through material which is unaffected by the diapir thermal aureole. 相似文献
7.
The Kostomuksha greenstone belt is the main iron district of Karelia. Gold, diamonds, and molybdenum mineralization have been found in this belt over the last two decades. The gold occurrences and deposits pertaining to the gold-sulfide and gold-quartz types were formed at the orogenic stage. The Taloveis deposit and the Faktorny and Berendei ore occurrences are located in the South Kostomuksha area and related to a complex of porphyritic diorite and granite porphyry. The West Ruvinvaara, Niemijarvi, Eastern, and Kurgelampi gold-sulfide and gold-sulfide-quartz occurrences are controlled by metasomatized shear zones and recrystallized sulfide ore hosted in the Shurlovaara and Ruvinvaara formations in the contact aureole of granite of the framework of the greenstone belt near its margin. The gold-arsenopyrite mineralization of the South Kostomuksha open pit is related to shear and metasomatic zones at the contact between the Kostomuksha Formation and helleflinta. Significant concentrations of gold are related to the complex of diorite and granite porphyry and the shear and metasomatic zones formed at the collision stage after emplacement of potassium granite. The small Taloveis deposit is located in the southern portion of the Kostomuksha greenstone belt and related to an intrusion of diorite and granite porphyry dated at 2720 Ma. The gold-sulfide mineral type in beresitized granite is combined with the gold-quartz type in shear zones trending at an azimuth of 20 NNE and coinciding in orientation with shear zones in the Kostomuksha belt. The Au grade varies from 0.5 to 60 g/t. 相似文献
8.
9.
马厂箐斑岩型铜钼金多金属矿床构造控岩控矿作用 总被引：5，自引：2，他引：3
滇西特提斯构造域存在一系列铜钼金铁多金属斑岩型矿床,这类矿床的成矿作用与本区富碱斑岩体(浆)的侵入、演化有关。以往的研究侧重于成矿物质的来源,但对岩浆侵入过程中形成的局部容矿构造的研究相对薄弱,这不利于提高矿床成因研究的整体水平,也阻碍了该区的地质找矿。本文旨在对马厂箐矿区容矿构造体系研究,揭示岩浆侵入接触构造体系对成矿的控制作用。该矿区是一个铜钼金铁多金属成矿集中区,成矿在时间、空间和物质组成上主要与喜马拉雅期的马厂箐富碱斑岩体有密切关系。由于岩浆侵位的方式、强度、规模等方面的原因,在岩体内、岩体与围岩内外接触带、近接触带围岩中的层间滑脱带和远接触带的围岩中的引张裂隙带等多种岩浆侵入接触构造样式,并为与岩浆作用成矿有关的成矿系列提供有利的成矿场所,分别控制着岩体内斑岩型铜钼矿、岩体与围岩接触带附近的接触交代型铜钼金磁铁矿和围岩地层中的石英脉型、破碎蚀变岩型的金、银、铅锌等矿化类型,并表现出从高温到低温的演化序列。岩浆侵入接触构造体系是该区主要的控岩控矿构造。 相似文献
10.
M. I. Holloway F. Bussy T. W. Vennemann 《Contributions to Mineralogy and Petrology》2008,155(1):111-121
Migmatites produced by low-pressure anatexis of basic dykes are found in a contact metamorphic aureole around a pyroxenite–gabbro
intrusion (PX2), on Fuerteventura. Dykes outside and inside the aureole record interaction with meteoric water, with low or
negative δ18O whole-rock values (+0.2 to −3.4‰), decreasing towards the contact. Recrystallised plagioclase, diopside, biotite and oxides,
from within the aureole, show a similar evolution with lowest δ18O values (−2.8, −4.2, −4.4 and −7.6‰, respectively) in the migmatite zone, close to the intrusion. Relict clinopyroxene phenocrysts
preserved in all dykes, retain typically magmatic δ18O values up to the anatectic zone, where the values are lower and more heterogeneous. Low δ18O values, decreasing towards the intrusion, can be ascribed to the advection of meteoric water during magma emplacement, with
increasing fluid/rock ratios (higher dyke intensities towards the intrusion acting as fluid-pathways) and higher temperatures
promoting increasing exchange during recrystallisation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Clement Ganino Nicholas T.Arndt Catherine Chauvel Alexandre Jean Charlotte Athurion 《地学前缘(英文版)》2013,4(5):535-546
The Panzhihua gabbroic intrusion,part of the plumbing system of the Emeishan large igneous province, intruded late-Proterozoic dolomites and marls about～263 Ma ago.The dolomites in the contact aureole were converted to brucite marbles and a diverse suite of forsterite,diopside and garnet skarns.The variation in mineralogy is explained in part by differences in the composition of the protolith,particularly the proportion of silica minerals and clay,and in part by transfer of elements from intruding magmas.The trace element compositions of most marbles and skarns are very similar to those of unmetamorphosed dolomites and marls,but some contain high Si,Ti,and Fe contents that are interpreted to have come from a magmatic source.Three brucite marbles sampled～10 m from the contact of the intrusion and named "enriched brucite marble" have trace element compositions very different from their dolomitic protolith:their rare earth elements are strongly enriched whereas levels of Nb-Ta,Zr-Hf and Ti are very low.These characteristics resemble those of carbonate liquid in equilibrium with silicate liquid or more probably with silicate minerals in the case of Panzhihua,a similarity we take to indicate that the sample underwent partial melting.Samples taken up to 300 m from the contact contain brucite indicating that high temperatures persisted well into the country rocks.However,other samples collected only tens of metres from the contact are only slightly recrystallized indicating that conditions in the aureole were highly variable.We suggest that temperatures within the aureole were controlled by conduction of heat from the main intrusion and by supply of additional heat from abundant small dykes within the aureole.Circulation of fluids derived from deeper levels in the aureole flushed the carbon dioxide from the dolomite,lowering temperature needed to partially melt carbonate to the temperatures attained near the intrusion.Irregular but extensive heating destabilized the carbonates of the aureole and decarbonation reactions associated with carbonate breakdown and melting emitted a large volume of CO2,with potential impact on global climate. 相似文献
12.
Arnaud Pecher Nicholas Arndt Alexander Jean Arthur Bauville Clement Ganino Charlotte Athurion 《地学前缘(英文版)》2013,4(5):571-581
The Panzhihua intrusion in southwest China is part of the Emeishan large igneous province and host of a large Fe-Ti-V ore deposit.In previous interpretations it was considered to be a layered,differentiated sill with the ore deposits at its base.New structural and petrological data suggest instead that the intrusion has an open S-shape,with two near-concordant segments joined by a discordant dyke-like segment. During emplacement of the main intrusion,multiple generations of mafic dykes invaded carbonate wall rocks,producing a large contact aureole.In the central segment,magmatic layering is oriented oblique to the walls of the intrusion.This layering cannot have formed by crystal settling or in-situ growth on the floor of the intrusion;instead we propose that it resulted from inward solidification of multiple,individually operating,convection cells.Ore formation was triggered by interaction of magma with carbonate wall rocks. 相似文献
13.
The Melechov pluton, Bohemian Massif, is interpreted as a mid-crustal nested granitic diapir with an apical part exposed at the present-day erosion level. The diapir head exhibits a concentric structure defined by lithologic zoning and by the anisotropy of magnetic susceptibility (AMS). In concert with theoretical models, outward-dipping margin-parallel magnetic foliations are associated with oblate shapes of the susceptibility ellipsoids and higher degree of anisotropy, passing inward into weaker triaxial to prolate fabric. By contrast, magnetic fabric in an inner granite unit is in places oriented at a high angle to internal contacts and is interpreted as recording an internal diapir circulation. We use inverse modeling to calculate strain variations across the diapir from the AMS data. The magnetic fabric parameters and calculated strains are in agreement with strain distribution in heads of model Newtonian diapirs traveling a distance of two body radii and suggest granitic magma ascent as a crystal-poor suspension followed by crystallization of fabric markers and their response to strain near the final emplacement level. The intrusive fabric thus formed late but, though generally weak, was still capable of recording incremental strain gradient in the granite diapir. 相似文献
14.
东天山镁铁质-超镁铁质岩带岩石特征及铜镍成矿作用 总被引：22，自引：2，他引：20
东天山地区分布有众多镁铁质-超镁铁质岩体,岩体成群成带状分布,从北向南可划分为7个区带,受区域性韧性剪切带和断裂构造控制。从岩相学来看,本区含矿岩体可分为多期次侵入的复式杂岩体和单期次侵入的超镁铁质单式杂岩体,显示出深源岩浆充分分异的特征。含矿岩体具有高镁、低碱、低钙、低铝、低钛特征,具有较高的Mg#、m/f和m/s比值,兼具岩浆硫化物熔离作用与岩浆结晶分异作用。根据TiO2-10P2O5-10MnO图判别出本区岩浆具有拉斑玄武岩到钙碱玄武岩过渡的性质,岩浆源具有钙碱性玄武岩浆特征,富含含水矿物,预示了早期俯冲洋壳对幔源岩浆的交代作用。岩体矿化分为3种成矿作用和5期成矿步骤,且岩浆成矿作用与热液作用几乎同时进行,岩浆分异作用提供热液来源,而热液作用促进硫化物的饱和与熔离,造成岩石的热液蚀变结构并对岩浆期成矿进行改造。晚期岩体隆升后,矿体出露地表遭受氧化淋滤作用,形成特有的地表氧化带找矿标志。 相似文献
15.
Structures within the aureole of the Acadian (Devonian) Victory Pluton suggest that movement along the Monroe Fault occurred during pluton intrusion. Pre- or syn-tectonic garnet textures, including discordant internal and external foliations, sigmoidal inclusion trails and deflection of the matrix foliation around garnet, are found along the Monroe Fault. In sillimanite+K-feldspar grade rocks, the matrix foliation, defined by biotite and fibrolitic sillimanite, wraps around garnet and sillimanite porphyroblasts. Granite dykes and sills near the pluton contact are folded and boundinaged, and leucosome fills garnet pressure shadows and shear bands. Away from the fault and pluton contact, microstructures indicate much less deformation during metamorphism, suggesting that deformation was partitioned into the fault or the pluton. Deformation ceased before crystallization of the main body of the Victory Pluton was complete. It is possible that magmatism facilitated deformation along the Monroe Fault, and/or that the magma was transported to the mid- to upper crust along the Monroe Fault. This study suggests that Acadian deformation in north-eastern Vermont occurred as late as 390–370 Ma. 相似文献
16.
本文通过区域地质背景、矿区地质特征概况、矿床地质特征的分析研究,总结矿区内银多金属矿床的成矿规律.结果表明,矿体展布主要受石英斑岩的断层破碎带构造控制;石英斑岩体为银矿体的主要矿源体;石英斑岩岩浆的侵入在粉砂岩、含泥粉砂岩与角闪黑云石英二长岩体沉积接触的地质界面中,这种封闭构造环境中利于富集形成高品位的银矿石;矿化富集用与不同构造的交叉、构造形变强度、岩石破碎强度以及蚀变交代强烈程度等因素密切相关.可将石英斑岩的断层破碎带及接触蚀变带作为银多金属矿找矿方向.石英斑岩断层破碎带中的硅化、黄铁矿化、褐铁矿化、绿泥石化蚀变,是该区银矿找矿的一种地表直接标志. 相似文献
17.
泥火山——天然气水合物存在的活证据 总被引：2，自引：0，他引：2
海底天然气水合物大多与通过切穿沉积盖层的断裂的上升烃类流体相关，这些高渗透带包括泥火山和底辟等侵入构造，所以泥火山、底辟和海底断裂等构造周围可能赋存水合物；实际钻探结果也证实，泥火山和水合物的形成与聚集有较为密切的关系。泥火山，它是地层内部圈闭气体由于压力释放上冲的结果，也是气体向上运移的通道。文章初步总结了泥火山与水合物的成矿关系，认为泥火山是水合物赋存的标志之一，是水合物存在的活证据。本文对我国泥火山与水合物的发育和赋存进行了分析预测，并对泥火山构造中水合物的成矿模式进行了初步探讨。 相似文献
18.
Roger Bateman 《Australian Journal of Earth Sciences》2013,60(3-4):253-265
The Bruinbun pluton is a small, massive, I‐type granitoid intruded into the meta‐sedimentary Hill End Trough, in eastern N.S.W. It is a multiple pluton representing two discrete magma pulses, the granodiorite core intruding the adamellite margin. A weak alignment of orthoclase megacrysts in the granitoids is best developed adjacent to both the internal and external intrusive contacts, and is considered by the writer to be a product of magmatic flow. Part of the northern contact and the southern and western contacts dip inward at moderate angles, whereas the eastern contact is vertical to outward‐dipping. The pluton is inferred to be mushroom‐shaped, and slightly tilted. The intensity of aureole deformation is low. The aureole has been flexed into concordancy with the pluton roof, and a rudimentary rim fold‐zone is present around lower levels of the pluton. Intrusion of the granitoid is inferred to be primarily by uplift of its roof and depression of its floor. The highest‐grade contact metamorphic parageneses developed are: cordierite‐K feldspar‐biotite‐quartzite ± andesine ± epidote in metapelites, and ferrohornblende‐biotite‐muscovite‐andesine‐epidote‐quartz in metavolcarenites. No intrusion‐related foliation or lineation was formed. 相似文献
19.
M. B. HOLNESS K. DANE R. SIDES C. RICHARDSON M. CADDICK 《Journal of Metamorphic Geology》2005,23(1):29-43
Contact metamorphism caused by the Glenmore plug in Ardnamurchan, a magma conduit active for 1 month, resulted in partial melting, with melt now preserved as glass. The pristine nature of much of the aureole provides a natural laboratory in which to investigate the distribution of melt. A simple thermal model, based on the first appearance of melt on quartz–feldspar grain boundaries, the first appearance of quartz paramorphs after tridymite and a plausible magma intrusion temperature, provides a time‐scale for melting. The onset of melting on quartz–feldspar grain boundaries was initially rapid, with an almost constant further increase in melt rim thickness at an average rate of 0.5–1.0 × 10?9 cm s?1. This rate was most probably controlled by the distribution of limited amounts of H2O on the grain boundaries and in the melt rims. The melt in the inner parts of the aureole formed an interconnected grain‐boundary scale network, and there is evidence for only limited melt movement and segregation. Layer‐parallel segregations and cross‐cutting veins occur within 0.6 m of the contact, where the melt volume exceeded 40%. The coincidence of the first appearance of these signs of the segregation of melt in parts of the aureole that attained the temperature at which melting in the Qtz–Ab–Or system could occur, suggests that internally generated overpressure consequent to fluid‐absent melting was instrumental in the onset of melt movement. 相似文献
20.
山东沂南金-铜-铁矿床成矿条件分析——兼论不整合面的控矿作用 总被引：3，自引：0，他引：3
山东沂南金-铜-铁矿床中与成矿有关的岩体为燕山期多期次浅成侵入的钙碱性杂岩体,岩性主要为闪长玢岩类和花岗斑岩类,属相对富含硅质、碱质和磁铁矿并通常与氧化型含金矽卡岩有关的侵入岩系列。新元古界一寒武系碳酸盐岩与碎屑岩的频繁互层,为含矿气水热液的运移和顺层交代提供了良好的围岩条件,在靠近岩体接触带部位形成了多层矽卡岩矿体。区域性断裂控制了含矿岩体的侵位,而接触带、捕虏体、层间破碎带以及不整合面等构造控制了矿体的空间定位。成矿在中低压力的中浅成至浅成条件下进行,主成矿阶段的含矿流体具有中高温、高盐度的特点,流体的沸腾可能是金-铜-铁等成矿物质大量沉淀的主要原因。接触带的矽卡岩型Au—Cu—Fe矿化与内接触带的斑岩型Cu—Mo矿化、外接触带的热液充填一交代型Au—Cu矿化,以及岩体边部的隐爆角砾岩型Au—Cu矿化一起,构成了一个中酸性岩浆-热液成矿系统。作为一种容易失稳的构造薄弱带和地球化学屏障,不整合面极易产生破碎和滑脱,从而有利于岩浆及其所分泌的含矿气水热液的贯入和成矿,这是沂南矿床中新发现的一种具有重要找矿前景的控矿构造类型。 相似文献