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1.
Ilya V. Veksler 《Chemical Geology》2004,210(1-4):7-31
Several types of fluid immiscibility may affect the evolution of volatile-rich magmatic systems at the magmatic–hydrothermal transition. The topology of silicate–salt–H2O systems implies that three-fluid immiscibility (silicate melt+hydrosaline melt+vapour) should be stable in a broad range of compositions and P–T conditions. The most important factor controlling the immiscibility appears to be the Coulombic properties (electric charges Z and ionic radii r) of the main network-modifying cations and the capacity for immiscibility appears to decrease in the following sequence: Mg>Ca>Sr>Ba>Li>Na>K. Liquid immiscibility is enhanced in peralkaline compositions and in the presence of nonsilicate anions such as F−, Cl−, CO32− and BO33−. In volatile-rich magmatic systems, the H2O is likely to react with the chloride, fluoride, borate and carbonate species and the chemical effects of high-temperature hydrolysis may be greatly enhanced by phase separation in systems with multiple immiscible fluid phases. Natural granitic magmas can thus exsolve a range of chemically and physically diverse hydrosaline liquids and the role of these fluid phases is likely to be especially significant in pegmatites and Li–F rare-metal granites. 相似文献
2.
SW Iberia is interpreted as an accretionary magmatic belt resulting from the collision between the South Portuguese Zone and the autochthonous Iberian terrane in Variscan times (350 to 330 Ma). In the South Portuguese Zone, pull-apart basins were filled with a thick sequence of siliciclastic sediments and bimodal volcanic rocks that host the giant massive sulphides of the Iberian Pyrite Belt. Massive sulphides precipitated in highly efficient geochemical traps where metal-rich but sulphur-depleted fluids of dominant basinal derivation mixed with sulphide-rich modified seawater. Massive sulphides formed either in porous/reactive volcanic rocks by sub-seafloor replacement, or in dark shale by replacement of mud or by exhalation within confined basins with high biogenic activity. Crustal thinning and magma intrusion were responsible for thermal maturation and dehydration of sedimentary rocks, while magmatic fluids probably had a minor influence on the observed geochemical signatures.The Ossa Morena Zone was a coeval calc-alkaline magmatic arc. It was the site for unusual mineralization, particularly magmatic Ni–(Cu) and hydrothermal Fe-oxide–Cu–Au ores (IOCG). Most magmatism and mineralization took place at local extensional zones along first-order strike-slip faults and thrusts. The source of magmas and IOCG and Ni–(Cu) deposits probably lay in a large mafic–ultramafic layered complex intruded along a detachment at the boundary between the upper and lower crust. Here, juvenile melts extensively interacted with low-grade metamorphic rocks, inducing widespread anatexis, magma contamination and further exsolution of hydrothermal fluids. Hypersaline fluids (δ18Ofluid > 5.4‰ to 12‰) were focused upward into thrusts and faults, leading to early magnetite mineralization associated with a high-temperature (> 500 °C) albite–actinolite–salite alteration and subsequent copper–gold-bearing vein mineralization at somewhat lower temperatures. Assimilation of sediments by magmas led in turn to the formation of immiscible sulphide and silicate melts that accumulated in the footwall of the layered igneous complex. Further injection of both basic and sulphide-rich magmas into the upper crust led to the formation of Ni–(Cu)-rich breccia pipes.Younger (330 to 280 Ma?) peraluminous granitoids probably reflect the slow ascent of relatively dry and viscous magmas formed by contact anatexis. These granitoids have W–(Sn)- and Pb–Zn-related mineralization that also shows geochemical evidence of major mantle–crust interaction. Late epithermal Hg–(Cu–Sb) and Pb–Zn–(Ag) mineralization was driven by convective hydrothermal cells resulting from the high geothermal gradients that were set up in the zone by intrusion of the layered igneous complex. In all cases, most of the sulphur seems to have been derived from leaching of the host sedimentary rocks (δ34S = 7‰ to 20‰) with only limited mixing with sulphur of magmatic derivation.The metallogenic characteristics of the two terranes are quite different. In the Ossa Morena Zone, juvenile magmatism played a major role as the source of metals, and controlled the styles of mineralization. In the South Portuguese Zone, magmas only acted as heat sources but seem to have had no major influence as sources of metals and fluids, which are dominated by crustal signatures. Most of the magmatic and tectonic features related to the Variscan subduction and collision seem to be masked by those resulting from transpressional deformation and deep mafic intrusion, which led to the development of a metallogenic belt with little resemblance to other accretionary magmatic arcs. 相似文献
3.
ABSTRACT Despite the close association with volcanic activity, the source of metals and ligands in the epithermal ore deposits is still controversial. In order to explore the magmatic–hydrothermal connection further, silicate melt, saline- and water-rich fluids, and CO2 vapours are documented that are trapped as inclusions in quartz phenocrysts from dacitic dykes associated with epithermal gold/base metal mineralization in the Shila district (Peru). Melt inclusion characteristics, and microthermometric and laser Raman fluid inclusion data are presented. The investigation of melt and fluid inclusions reveals that the volatile phase of magmas might represent the precursors to the early chlorine-rich ore-forming epithermal solutions. Microthermometric investigations in magmatic quartz crystals and data on quartz mineralized veins suggest that the fluid evolution and ore deposition may be the result of several processes including: release of an evolving magmatic fluid, and/or boiling, and/or mixing. 相似文献
4.
《Ore Geology Reviews》2003,22(1-2):61-90
Quantitative laser ablation (LA)-ICP-MS analyses of fluid inclusions, trace element chemistry of sulfides, stable isotope (S), and Pb isotopes have been used to discriminate the formation of two contrasting mineralization styles and to evaluate the origin of the Cu and Au at Mt Morgan.The Mt Morgan Au–Cu deposit is hosted by Devonian felsic volcanic rocks that have been intruded by multiple phases of the Mt Morgan Tonalite, a low-K, low-Al2O3 tonalite–trondhjemite–dacite (TTD) complex. An early, barren massive sulfide mineralization with stringer veins is conforming to VHMS sub-seafloor replacement processes, whereas the high-grade Au–Cu ore is associated with a later quartz–chalcopyrite–pyrite stockwork mineralization that is related to intrusive phases of the Tonalite complex. LA-ICP-MS fluid inclusion analyses reveal high As (avg. 8850 ppm) and Sb (avg. 140 ppm) for the Au–Cu mineralization and 5 to 10 times higher Cu concentration than in the fluids associated with the massive pyrite mineralization. Overall, the hydrothermal system of Mt Morgan is characterized by low average fluid salinities in both mineralization styles (45–80% seawater salinity) and temperatures of 210 to 270 °C estimated from fluid inclusions. Laser Raman Spectroscopic analysis indicates a consistent and uniform array of CO2-bearing fluids. Comparison with active submarine hydrothermal vents shows an enrichment of the Mt Morgan fluids in base metals. Therefore, a seawater-dominated fluid is assumed for the barren massive sulfide mineralization, whereas magmatic volatile contributions are implied for the intrusive related mineralization. Condensation of magmatic vapor into a seawater-dominated environment explains the CO2 occurrence, the low salinities, and the enriched base and precious metal fluid composition that is associated with the Au–Cu mineralization. The sulfur isotope signature of pyrite and chalcopyrite is composed of fractionated Devonian seawater and oxidized magmatic fluids or remobilized sulfur from existing sulfides. Pb isotopes indicate that Au and Cu originated from the Mt Morgan intrusions and a particular volcanic strata that shows elevated Cu background. 相似文献
5.
岩浆是将地球内部物质传送到表层系统的主要载体,并造成显著的资源聚集和环境效应。岩浆动力学是研究岩浆的迁移、储存、演化、就位以及喷发过程,侧重物理机制。这些岩浆过程主要发生在岩浆通道系统中,包括岩浆储库和岩浆管道。本文对目前国际岩浆动力学领域一些热点和前沿进行了介绍,这包括从岩浆房到岩浆储库概念的转变、岩浆储库的生长和动力学演化过程、岩浆过程的时间尺度以及岩浆中晶体的生长。然后阐述了岩浆中挥发分的种类和溶解度、获取天然岩浆挥发分含量的方法、一些典型镁铁质岩浆中的挥发分含量、岩浆去气的化学和物理机制,并简要梳理了热液金属矿床的形成过程和岩浆挥发分进入地表圈层系统引发的环境气候效应。最后列举了一些岩浆动力学有关的重要科学问题并建议了进一步的研究方向。 相似文献
6.
Melt and fluid inclusions in minerals from the peralkaline granite intrusion and associated mineralized country rocks from the Yermakovka F–Be deposit were studied to characterize the behaviour of trace elements and exsolved fluids in the transition from magmatic to hydrothermal processes. Ore mineralization was mostly due to volatile release from a deep-seated pluton for which crystallization history and fluid exsolution can be tracked by three batches of magma (Gr1→Gr3) intruded at the level of the ore deposition to form the Yermakovka stock. Each batch of the sequential granite group is found to intrude at decreasing temperature (from 840 to 730 °C) and progressively increasing extent of crystallization of magma in the parental pluton. This resulted in the enrichment of the ascending melts in H2O (3.9 to 6.1 wt.%), F (2.6 to 4.1 wt.%) and some incompatible elements (Zr, Nb, Th, Rb, Pb). Although the earliest evidence for the exsolution of homogeneous fluoride–sulphate brine correlates with the final stage of the Gr2 ascent, the most intensive volatile(s) release from the emplaced magmas is shown to occur during their in situ crystallization, which was associated with the separation of exsolved fluid into immiscible phases, brine and low-salinity solution. Compositions of these fluid phases are determined using atomic emission spectroscopy of the appropriate fluid inclusions opened by a laser microprobe and EMPA and SEM–EDS analyses of daughter crystals. The brine phase is enriched in Mo, Mn, Be (up to 17, 8, and 0.3 g/kg, respectively) and contains perceptible abundances of Ce, La, Pb, Zn, whereas the low-salinity phase is enriched only in Be (up to 0.6 g/kg). The selective mobilization of the metals from the melt into fluids is considered to result from the oxidized state of the melt and fluids, peralkalinity of the melt during crystallization, and high F content of the melt. The immiscible fluid phases are shown to migrate together through the solidifying stock giving rise to the albitized granite that is enriched in molybdenite but devoid of Be minerals. In the country rocks, solutions similar to the brine and low-salinity phases of the magmatic fluid made up separate fluid flows, which produced Be and Mo mineralization and were issued predominantly from the parental pluton. Both types of mineralization are nearly monometallic which suggests that of the metals, jointly transported by the brine, only Mo and, in part, Ce and La precipitated separately at the level where the low-salinity solutions deposited Be ores. 相似文献
7.
The exsolution of magmatic hydrosaline chloride liquids 总被引：14，自引：0，他引：14
Hydrosaline liquid represents the most Cl-enriched volatile phase that occurs in magmas, and the exsolution of this phase has important consequences for processes of hydrothermal mineralization and for volcanic emission of Cl to the atmosphere. To understand the exsolution of hydrosaline liquids in felsic to mafic magmas, the volatile abundances and (Cl/H2O) ratios of more than 1000 silicate melt inclusions (MI) have been compared with predicted and experimentally determined solubilities of Cl and H2O and associated (Cl/H2O) ratios of silicate melts that were saturated in hydrosaline chloride liquid with or without aqueous vapor in hydrothermal experiments. This approach identifies the minimum volatile contents and the values of (Cl/H2O) at which a hydrosaline chloride liquid exsolves from any CO2- or SO2-poor silicate melt. Chlorine solubility is a strong function of melt composition, so it follows that Cl solubility in magmas varies with melt evolution. Computations show that the (Cl/H2O) ratio of residual melt in evolving silicate magmas either remains constant or increases to a small extent with fractional crystallization. Consequently, the initial (Cl/H2O) in melt that is established early during partial melting has important consequences for the exsolution of vapor, vapor plus hydrosaline liquid, or hydrosaline liquid later during the final stages of melt ascent, emplacement, and crystallization or eruption. It is demonstrated that the melt (Cl/H2O) controls the type of volatile phase that exsolves, whereas the volatile abundances in melt control the relative timing of volatile phase exsolution (i.e., the time of earliest volatile exsolution relative to the rate of magma ascent and crystallization history).
Comparing melt inclusion compositions with experimentally determined (Cl/H2O) ratios and corresponding volatile solubilities of hydrosaline liquid-saturated silicate melts suggests that some fractions of the eruptive, calc-alkaline dacitic magmas of the Bonnin and Izu arcs should have saturated in and exsolved hydrosaline liquid at pressures of 2000 bars. Application of these same melt inclusion data to the predicted volatile solubilities of Cu-, Au-, and Mo-mineralized, calc-alkaline porphyritic magmas suggests that the chemical evolution of dioritic magmas to more-evolved quartz monzonite compositions involves a dramatic reduction in Cl solubility that increases the probability of hydrosaline liquid exsolution. The prediction that quartz monzonite magmas should exsolve a hydrosaline chloride liquid, that is potentially mineralizing, is consistent with the general observation of metal-enriched, hypersaline fluid inclusions in the more felsic plutons of numerous porphyry copper systems. Moreover, comparing the volatile contents of melt inclusions from the potassic, alkaline magmas of Mt. Somma-Vesuvius with the predicted (Cl/H2O) ratios of hydrosaline liquid-saturated melts having compositions similar to those of the volatile-rich, alkaline magmas associated with the orthomagmatic gold–tellurium deposits of Cripple Creek, Colorado, suggests that hydrosaline chloride liquid should have exsolved at Cripple Creek as the magmas evolved to phonolite compositions. This prediction is consistent with the well-documented role of Cl-enriched, mineralizing hydrothermal fluids at this major gold-mining district. 相似文献
8.
Lead isotope ratios of ores of the Candelaria-Punta del Cobre iron oxide Cu-Au deposits and associated Early Cretaceous volcanic and batholithic rocks have been determined. For the igneous rocks, a whole-rock acid attack technique based on the separate analyses of a leachate and the residual fraction of a sample was used. The lead isotope systematics of leachate–residue pairs are significantly different for unaltered and altered igneous rocks of the Candelaria-Punta del Cobre district. Residues of unaltered igneous rocks likely represent the common lead. In contrast, residues of all the altered igneous rocks except two samples have higher Pb isotope ratios than those of unaltered magmatic rocks and cannot represent common lead. We suggest that this is a result of the hydrothermal alteration suffered by these rocks and that the common lead composition of the altered igneous (volcanic and plutonic) rocks must have been similar to that of the unaltered batholith rocks. The conclusion that the altered volcanic rocks originally had a similar common lead isotope composition as the batholith is consistent with geological and geochemical arguments (e.g., setting, regional geologic evolution, ages and relative distribution of volcanic and intrusive rocks, magmatic affinities), which indicate that these rocks were derived from similar Early Cretaceous parent magmas. The modification of the leachate–residue pair lead isotope systematics of most altered igneous rocks is consistent with a selective removal of lead and uranium from these rocks by an oxidized hydrothermal fluid. The result of the hydrothermal leaching has been to alter magmatic rocks in a way that (1) their leachable fraction is presently a mix of common lead similar to that of the ore event and of radiogenic lead evolved from a source with a consistently high Th/U, and that (2) their residual fraction has less common lead than unaltered rocks. The outcrop area with altered volcanic rocks displaying anomalously high lead isotope ratios extends over 25 km along the eastern margin of the batholith. Since lead of the ores in the Candelaria-Punta del Cobre district has the same isotopic composition as the common lead of unaltered magmatic rocks of the area, the lead isotope data are consistent with a derivation of the ore lead (and by inference of other metals like Cu) both directly from a magmatic fluid exsolved during crystallization of the batholith and/or from hydrothermal leaching of the volcanic rocks originally having similar isotopic compositions as the batholith.Editorial handling: B. Lehmann 相似文献
9.
A quartz-monzodioritic dike associated with the porphyry-Cu mineralized stock at Santa Rita, NM, has been studied to constrain physico-chemical factors (P, T, fO2, and volatile content) responsible for mineralization. The dike contains a low-variance mineral assemblage of amphibole, plagioclase (An30–50), quartz, biotite, sphene, magnetite, and apatite, plus anhydrite and calcite preserved as primary inclusions within the major phenocryst phases. Petrographic relationships demonstrate that anhydrite originally was abundant in the form of phenocrysts (1–2 vol.%), but later was replaced by either quartz or calcite. Hornblende–plagioclase thermobarometry suggests that several magmas were involved in the formation of the quartz-monzodiorite, with one magma having ascended directly from ≥14 km depth. Rapid magma ascent is supported by the presence of intact calcite inclusions within quartz phenocrysts.
The assemblage quartz+sphene+magnetite+Mg-rich amphibole in the quartz-monzodiorite constrains magmatic oxygen fugacity at logfO2>NNO+1, in agreement with the presence of magmatic anhydrite and a lack of magmatic sulfides. The same reasoning generally applies for rocks hosting porphyry-Cu deposits, seemingly speaking against a major role of magmatic sulfides in the formation of such mineralizations. There is increasing evidence, however, that magmatic sulfides play an important role in earlier stages of porphyry-Cu evolution, the record of which is often obliterated by later processes. 相似文献
10.
玉龙斑岩铜(钼)矿床是亚洲最大的斑岩型铜矿床，包含多种矿化类型，成矿作用复杂。作为典型的斑岩型矿床，岩浆熔融体的性质在玉龙铜矿床的形成过程中起到了至关重要的作用。本文将分别从岩浆熔融体的物理和化学性质出发，解释玉龙矿床为何能成为玉龙成矿带中唯一一个超大型矿床的原因。在熔体演化方面，笔者主要通过对熔体密度、粘度的计算获得有关数据，以了解熔体运移、含矿流体分离的过程，以解释玉龙铜矿床为何能形成如此规模的矿床。 相似文献
11.
胶东青山群基性火山岩的Ar-Ar年代学和地球化学特征: 对华北克拉通破坏过程的启示 总被引：5，自引：3，他引：2
青山群火山岩是华北克拉通破坏期间最具代表性的地幔或地壳熔融产物,记录了华北深部地质演化的重要信息。本文对胶东青山群基性火山岩进行了40Ar/39Ar定年和岩石地球化学分析,结合前人报道的胶东青山群酸性火山岩资料,发现:(1)基性火山岩喷发年龄为122～113Ma,早于青山群酸性火山岩(110～98Ma);(2)基性和酸性火山岩显示了不同的元素和同位素地球化学特征。岩石成因分析表明,基性火山岩为交代富集地幔部分熔融作用的产物,而酸性火山岩为古老下地壳和中生代底侵岩浆的熔融产物(Ling et al.,2009)。因此,胶东地区青山群火山岩记录了岩浆熔融源区从地幔向下地壳的转变。这与长时间尺度的岩石圈减薄过程中热能由地幔向地壳传递过程相吻合,而不同于地壳拆沉作用所预测的岩浆演化趋势。 相似文献
12.
V.S. Kamenetsky V.B. Naumov P. Davidson E. van Achterbergh C.G. Ryan 《Chemical Geology》2004,210(1-4):73-90
Exsolution (unmixing) of the volatile element-rich phases from cooling and crystallising silicate magmas is critical for element transport from the Earth’s interior into the atmosphere, hydrosphere, crustal hydrothermal systems, and the formation of orthomagmatic ore deposits. Unmixing is an inherently fugitive phenomenon and melt inclusions (droplets of melt trapped by minerals) provide robust evidence of this process. In this study, melt inclusions in phenocrystic and miarolitic quartz were studied to better understand immiscibility in the final stages of cooling of, and volatile exsolution from, granitic magmas, using the tin-bearing Omsukchan Granite (NE Russia) as an example.
Primary magmatic inclusions in quartz phenocrysts demonstrate the coexistence of silicate melt and magma-derived Cl-rich fluids (brine and vapour), and emulsions of these, during crystallisation of the granite magma. Microthermometric experiments, in conjunction with PIXE and other analytical techniques, disclose extreme heterogeneity in the composition of the non-silicate phases, even in fluid globules within the same silicate melt inclusion. We suggest that the observed variability is a consequence of strong chemical heterogeneity in the residual silicate-melt/brine/vapour system on a local scale, owing to crystallisation, immiscibility and failure of individual phases to re-equilibrate. The possible evolution of non-silicate volatile magmatic phases into more typical “hydrothermal” chloride solutions was examined using inclusions in quartz from associated miarolitic cavities. 相似文献
13.
李文渊 《西安地质学院学报》2010,(1):15-23
从现代块状硫化物矿床成矿特征对比角度,总结分析了世界现代海底喷流的块状硫化物成矿堆积,综述了现代海底块状硫化物成矿主要形成于洋壳和岛弧环境的实际观察结果,突出强调了洋壳环境和岛弧或陆壳环境两种成矿环境对成矿类型分类的意义。对上地幔部分熔融岩浆来源与地壳物质可能带人、火山喷发岩浆系列的演化和对热液成矿作用的控制进行了讨论,对比分析了岩浆流体对成矿的重要贡献和控制作用,以及成矿热液循环体系形成的条件和模式。 相似文献
14.
Most magmatic-hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the hydrothermal system. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L’Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu?>?2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe–Ti oxide suggest that the surrounding lavas that host the Brothers hydrothermal system represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying hydrothermal system. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal–porphyry deposits. 相似文献
15.
摘要：阐述了不同类型内生矿床的成矿深度和金属沉淀的垂直范围。热液成矿作用的深度下限可以下降到10000～12000m。不同类型矿床的成矿深度范围与成矿时的具体地质构造特征有关,且有很大的变化空间。金属矿床的形成深度受成矿母岩岩浆侵位深度的约束,而岩浆侵位的深度又与岩浆中挥发组分的数量、流体释放的时间、成矿元素的矿物/熔体和溶液/熔体分配系数等因素有关。据此可以解释斑岩铜－（钼）、斑岩钼-(铜)和斑岩钨矿床形成深度的差异。地温梯度和多孔岩石的渗透率也与成矿深度有关。CO2等挥发组分的溶解度对压力非常敏感,因此流体包裹体地质压力计对于成矿深度的确定有重要的应用价值。在开展深部成矿预测和找矿时,探寻隐伏岩体顶上带或岩钟是寻找深部与花岗岩有关的多金属矿床的捷径之一。 相似文献
16.
Maryannick Richard Herv Bellon RenC. Maury Eric Barrier Juang Wen-Shing 《Tectonophysics》1986,125(1-3)
K-Ar radiometric datings are presented for volcanic rocks from the Coastal Range of Taiwan and from Lanhsu and Lütao islands. The samples involved are basalts, andesites and dacites which show the main petrological and geochemical characteristics of island arc magmas. The K-Ar data show that volcanic activity occurred from Early Miocene to Early Pliocene times in the Coastal Range and in Lanhsu Island, and during Pliocene times (ca. 1.3–4.3 Ma) in Lütao Island. The geological significance of Early and Middle Miocene ages is discussed with respect to hydrothermal/metasomatic alterations which have affected most of the samples. A significant increase in incompatible elements (e.g., K and Sr) is shown to have occurred during Pliocene to Recent times, and is exemplified by the compositions of the Lanhsu, and Lütao volcanic rocks. The origin of these chemical variations is related to the magmatic effects of crustal thickening linked to the transition from subduction to collision regimes. 相似文献
17.
广东省博罗县横河钠长石矿构造岩浆演化及成矿机理 总被引：1，自引：1，他引：0
通过对广东省博罗县横河超大型钠长石矿床、锡铌钽矿化带和金矿化带野外勘查和室内微观分析,发现岩浆随着构造演化而分异自交代成矿的特殊新颖现象。研究表明该矿区在不同的构造旋回中构造应力场的主压应力方向不同,持续构造压应力作用下发生不同构造序次,岩浆也随构造应力场的演化而分异。燕山构造旋回控制的早期第三阶段岩浆,结晶分异和气液分异导致强烈岩浆自交代形成超大型钠长石矿床;燕山构造旋回控制的晚期岩浆,随着构造演化产生云英岩化、石榴子石化等岩浆自交代而锡铌钽矿物结晶富集成矿;燕山构造旋回最晚期的北北西向、北北东向、北西向断裂,控制岩浆热液期的金矿化带。即本矿区经构造岩浆演化分异,发生岩浆自交代至热液蚀变演化系列成矿机理。 相似文献
18.
矿床形成深度与深部成矿预测 总被引：5，自引：2，他引：5
阐述了不同类型内生矿床的成矿深度和金属沉淀的垂直范围。热液成矿作用的深度下限可以下降到10000～12000m。不同类型矿床的成矿深度范围与成矿时的具体地质构造特征有关,且有很大的变化空间。金属矿床的形成深度受成矿母岩岩浆侵位深度的约束,而岩浆侵位的深度又与岩浆中挥发组分的数量、流体释放的时间、成矿元素的矿物/熔体和溶液/熔体分配系数等因素有关。据此可以解释斑岩铜-(钼)、斑岩钼-(铜)和斑岩钨矿床形成深度的差异。地温梯度和多孔岩石的渗透率也与成矿深度有关。CO2等挥发组分的溶解度对压力非常敏感,因此流体包裹体地质压力计对于成矿深度的确定有重要的应用价值。在开展深部成矿预测和找矿时,探寻隐伏岩体顶上带或岩钟是寻找深部与花岗岩有关的多金属矿床的捷径之一。 相似文献
19.
本文依据区内金矿床地质特征、矿化与火山作用、矿物流体包裹体的研究,阐明区内金矿成矿条件:火山岩基底变质岩是金矿"原始矿源岩";中生代岩浆部分熔融了"原始矿源岩"所形成的后生矿源岩"为金矿成矿提供了物质来源;毛坦厂组形成时期的火山活动及与之有关的火山(次火山)热液使金发生活化、迁移,并在有利部位富集成矿;火山构造及与火山活动有关的断裂构造控制了矿化部位.流体包裹体和稳定同位素研究结果表明,成矿热液主要来自天水,少量来自岩浆.成矿物质是在低fO2、fS2,pH≈7的弱还原条件下沉淀的. 相似文献