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1.
A combined fluid inclusion and mineral thermobarometric study in groups of synchronous inclusions in quartz within weakly foliated granites from the Chottanagpur Gneissic Complex, India, reveals super dense carbonic (CO2 with minor CH4 and H2O) inclusions and hypersaline (H2O–NaCl ± NaHCO3) inclusions, with halite- and nahcolite daughter phases. This study documents the highest density (1.115 g cm− 3) CO2 fluids ever reported in granites. Fluid isochores, constructed from CO2 (± CH4) and halite-bearing inclusions, coupled with two-feldspar thermometry constrain the minimum P–T at 8 kbar/ 750 °C for fluid entrapment in granites. By contrast, the carbonic inclusions in quartz from granite-hosted metapelite enclaves contain substantial CH4 (up to 30 mol%), and the entrapment pressure ( 4.3 kbar/600 °C) is considerably lower compared to those in the granites. By implication, the sillimanite-free granites were not derived from the metapelitic enclaves, and instead were formed by partial melting of fluid-heterogeneous lower crustal protoliths, with fluid entrapment at magmatic conditions.  相似文献   

2.
Metamorphic conditions within arenaceous, calcareous and argillaceous supracrustal rocks of the Magondi Mobile Belt (Zimbabwe) range from greenschist to granulite facies. Within the high-grade segment, basement gneisses of early Proterozoic age and argillaceous rocks of the Mid-Proterozoic Piriwiri Group are intruded by charnockites and enderbites. Metamorphic mineral assemblages and thermobarometric data for enderbitic granulites of Nyaodza show temperatures of 700–800°C and pressures of 5–7 kbar for the peak of granulite-facies metamorphism. Microthermometry and Raman microspectroscopy reveal that CO2, associated with minor N2, has been the dominant fluid phase during granulite-facies metamorphism. The chronology of the CO2 inclusions and the development of microtextures and mineral assemblages in the enderbites indicates that isolated negative crystal shaped CO2 inclusions in quartz and plagioclase porphyroclasts entrap syn-metamorphic fluids of medium-high densities (0.88–0.90 g/cm3). Lower density (0.71–0.77 g/cm3) CO2 inclusions in trails and clusters within the same minerals were formed from local re-equilibration and re-entrapment of the former (near-) peak granulitic CO2 inclusions. As in many other granulites, syn-metamorphic CO2 is associated with intrusives emplaced near the peak of metamorphism.  相似文献   

3.
In order to identify and characterise fluids associated with metamorphic rocks from the Chaves region (North Portugal), fluid inclusions were studied in quartz veinlets, concordant with the main foliation, in graphitic-rich and nongraphitic-rich lithologies from areas with distinct metamorphic grade. The study indicates multiple fluid circulation events with a variety of compositions, broadly within the C–H–O–N–salt system. Primary fluid inclusions in quartz contain low salinity aqueous–carbonic, H2O–CH4–N2–NaCl fluids that were trapped near the peak of regional metamorphism, which occurred during or immediately after D2. The calculated P–T conditions for the western area of Chaves (CW) is P=300–350 MPa and T500 °C, and for the eastern area (CE), P=200–250 MPa and T=400–450 °C. A first generation of secondary fluid inclusions is restricted to discrete cracks at the grain boundaries of quartz and consists of low salinity aqueous–carbonic, H2O–CO2–CH4–N2–NaCl fluids. P–T conditions from the fluid inclusions indicate that they were trapped during a thermal event, probably related with the emplacement of the two-mica granites.

A second generation of secondary inclusions occurs in intergranular fractures and is characterised by two types of aqueous inclusions. One type is a low salinity, H2O–NaCl fluid and the second consists of a high salinity, H2O–NaCl–CaCl2 fluid. These fluid inclusions are not related to the metamorphic process and have been trapped after D3 at relatively low P (hydrostatic)–T conditions (P<100 MPa and T<300 °C).

Both the early H2O–CH4–N2–NaCl fluids in quartz from the graphitic-rich lithologies and the later H2O–CO2–CH4–N2–NaCl carbonic fluid in quartz from graphitic-rich and nongraphitic-rich lithologies seem to have a common origin and evolution. They have low salinity, probably resulting from connate waters that were diluted by the water released from mineral dehydration during metamorphism. Their main component is water, but the early H2O–CH4–N2–NaCl fluids are enriched in CH4 due to interaction with the C-rich host rocks.

From the early H2O–CH4–N2–NaCl to the later aqueous–carbonic H2O–CO2–CH4–N2–NaCl fluids, there is an enrichment in CO2 that is more significant for the fluids associated with nongraphitic-rich lithologies.

The aqueous–carbonic fluids, enriched in H2O and CH4, are primarily associated with graphitic-rich lithologies. However, the aqueous–carbonic CO2-rich fluids were found in both graphitic and nongraphitic-rich units from both the CW and CE studied areas, which are of medium and low metamorphic grade, respectively.  相似文献   


4.
Minor granulites (believed to be pre-Triassic), surrounded by abundant amphibolite-facies orthogneiss, occur in the same region as the well-documented Triassic high- and ultrahigh-pressure (HP and UHP) eclogites in the Dabie–Sulu terranes, eastern China. Moreover, some eclogites and garnet clinopyroxenites have been metamorphosed at granulite- to amphibolite-facies conditions during exhumation. Granulitized HP eclogites/garnet clinopyroxenites at Huangweihe and Baizhangyan record estimated eclogite-facies metamorphic conditions of 775–805 °C and ≥15 kbar, followed by granulite- to amphibolite-facies overprint of ca. 750–800 °C and 6–11 kbar. The presence of (Na, Ca, Ba, Sr)-feldspars in garnet and omphacite corresponds to amphibolite-facies conditions. Metamorphic mineral assemblages and P–T estimates for felsic granulite at Huangtuling and mafic granulite at Huilanshan indicate peak conditions of 850 °C and 12 kbar for the granulite-facies metamorphism and 700 °C and 6 kbar for amphibolite-facies retrograde metamorphism. Cordierite–orthopyroxene and ferropargasite–plagioclase coronas and symplectites around garnet record a strong, rapid decompression, possibly contemporaneous with the uplift of neighbouring HP/UHP eclogites.

Carbonic fluid (CO2-rich) inclusions are predominant in both HP granulites and granulitized HP/UHP eclogites/garnet clinopyroxenites. They have low densities, having been reset during decompression. Minor amounts of CH4 and/or N2 as well as carbonate are present. In the granulitized HP/UHP eclogites/garnet clinopyroxenites, early fluids are high-salinity brines with minor N2, whereas low-salinity fluids formed during retrogression. Syn-granulite-facies carbonic fluid inclusions occur either in quartz rods in clinopyroxene (granulitized HP garnet clinopyxeronite) or in quartz blebs in garnet and quartz matrices (UHP eclogite). For HP granulites, a limited number of primary CO2 and mixed H2O–CO2(liquid) inclusions have also been observed in undeformed quartz inclusions within garnet, orthopyroxene, and plagioclase which contain abundant, low-density CO2±carbonate inclusions. It is suggested that the primary fluid in the HP granulites was high-density CO2, mixed with a significant quantity of water. The water was consumed by retrograde metamorphic mineral reactions and may also have been responsible for metasomatic reactions (“giant myrmekites”) occurring at quartz–feldspar boundaries. Compared with the UHP eclogites in this region, the granulites were exhumed in the presence of massive, externally derived carbonic fluids and subsequently limited low-salinity aqueous fluids, probably derived from the surrounding gneisses.  相似文献   


5.
In this paper the first fluid-inclusion data are presented from Late Archaean Scourian granulites of the Lewisian complex of mainland northwest Scotland. Pure CO2 or CO2-dominated fluid inclusions are moderately abundant in pristine granulites. These inclusions show homogenization temperatures ranging from − 54 to + 10 °C with a very prominent histogram peak at − 16 to − 32 °C. Isochores corresponding to this main histogram peak agree with P-T estimates for granulite-facies recrystallization during the Badcallian (750–800 °C, 7–8 kbar) as well as with Inverian P-T conditions (550–600 °C, 5 kbar). The maximum densities encountered could correspond to fluids trapped during an early, higher P-T phase of the Badcallian metamorphism (900–1000 °C, 11–12 kbar). Homogenization temperatures substantially higher than the main histogram peak may represent Laxfordian reworking (≤ 500 °C, < 4 kbar). In the pristine granulites, aqueous fluid inclusions are of very subordinate importance and occur only along late secondary healed fractures. In rocks which have been retrograded to amphibolite facies from Inverian and/or Laxfordian shear zones, CO2 inclusions are conspicuously absent; only secondary aqueous inclusions are present, presumably related to post-granulite hydration processes. These data illustrate the importance of CO2-rich fluids for the petrogenesis of Late Archaean granulites, and demonstrate that early fluid inclusions may survive subsequent metamorphic processes as long as no new fluid is introduced into the system.  相似文献   

6.
Abstract Andalusite-bearing veins formed during contact metamorphism in the aureole of the Vedrette di Ries tonalite. In the veins, quartz crystals that are completely armoured by andalusite or that occur in strain shadow areas contain three generations of fluid inclusions: low-salinity H2O-CO2-CH4 mixtures with CH4/(CO2+ CH4) ± 0.35 (type A); low-salinity aqueous fluids (type B); H2O-free, CO2-CH4 fluids with the same carbonic speciation as A (type C). Carbonic types A and C typically have a dark appearance, which is attributed to graphite coatings on inclusion walls. Microstructural analysis of the host quartz and calculated densities indicate that type A inclusions were likely trapped during vein formation. These inclusions underwent strain-assisted re-equilibration during cooling that resulted in density increases without change of composition. After the rocks had cooled below about 350 ° C, type C inclusions appear to have formed from one of the immiscible fractions after unmixing of the H2O-CO2-CH4 fluid mixtures. Aqueous type B inclusions, apparently trapped between 225 and 350 ° C, could represent an independent fluid, or could be the H2O-rich fraction of unmixed type A fluids. Taking account of the uncertainties, the composition and density of the complex type A inclusion fluids are in good agreement with the properties of primary fluids calculated from the petrological data. The fluid inclusion data support the model of vein formation by hydrofracturing as a result of dehydration of graphitic metapelites. These new results also demonstrate the importance of considering strain in the interpretation of metamorphic fluid inclusions.  相似文献   

7.
Although hydrocarbon-bearing fluids have been known from the alkaline igneous rocks of the Khibiny intrusion for many years, their origin remains enigmatic. A recently proposed model of post-magmatic hydrocarbon (HC) generation through Fischer-Tropsch (FT) type reactions suggests the hydration of Fe-bearing phases and release of H2 which reacts with magmatically derived CO2 to form CH4 and higher HCs. However, new petrographic, microthermometric, laser Raman, bulk gas and isotope data are presented and discussed in the context of previously published work in order to reassess models of HC generation. The gas phase is dominated by CH4 with only minor proportions of higher hydrocarbons. No remnants of the proposed primary CO2-rich fluid are found in the complex. The majority of the fluid inclusions are of secondary nature and trapped in healed microfractures. This indicates a high fluid flux after magma crystallisation. Entrapment conditions for fluid inclusions are 450–550 °C at 2.8–4.5 kbar. These temperatures are too high for hydrocarbon gas generation through the FT reaction. Chemical analyses of rims of Fe-rich phases suggest that they are not the result of alteration but instead represent changes in magma composition during crystallisation. Furthermore, there is no clear relationship between the presence of Fe-rich minerals and the abundance of fluid inclusion planes (FIPs) as reported elsewhere. δ13C values for methane range from − 22.4‰ to − 5.4‰, confirming a largely abiogenic origin for the gas. The presence of primary CH4-dominated fluid inclusions and melt inclusions, which contain a methane-rich gas phase, indicates a magmatic origin of the HCs. An increase in methane content, together with a decrease in δ13C isotope values towards the intrusion margin suggests that magmatically derived abiogenic hydrocarbons may have mixed with biogenic hydrocarbons derived from the surrounding country rocks.  相似文献   

8.
The Chinese Continental Scientific Drilling (CCSD) main drill hole (0–3000 m) in Donghai, southern Sulu orogen, consists of eclogite, paragneiss, orthogneiss, schist and garnet peridotite. Detailed investigations of Raman, cathodoluminescence, and microprobe analyses show that zircons from most eclogites, gneisses and schists have oscillatory zoned magmatic cores with low-pressure mineral inclusions of Qtz, Pl, Kf and Ap, and a metamorphic rim with relatively uniform luminescence and eclogite-facies mineral inclusions of Grt, Omp, Phn, Coe and Rt. The chemical compositions of the UHP metamorphic mineral inclusions in zircon are similar to those from the matrix of the host rocks. Similar UHP metamorphic P–T conditions of about 770 °C and 32 kbar were estimated from coexisting minerals in zircon and in the matrix. These observations suggest that all investigated lithologies experienced a joint in situ UHP metamorphism during continental deep subduction. In rare cases, magmatic cores of zircon contain coesite and omphacite inclusions and show patchy and irregular luminescence, implying that the cores have been largely altered possibly by fluid–mineral interaction during UHP metamorphism.

Abundant H2O–CO2, H2O- or CO2-dominated fluid inclusions with low to medium salinities occur isolated or clustered in the magmatic cores of some zircons, coexisting with low-P mineral inclusions. These fluid inclusions should have been trapped during magmatic crystallization and thus as primary. Only few H2O- and/or CO2-dominated fluid inclusions were found to occur together with UHP mineral inclusions in zircons of metamorphic origin, indicating that UHP metamorphism occurred under relatively dry conditions. The diversity in fluid inclusion populations in UHP rocks from different depths suggests a closed fluid system, without large-scale fluid migration during subduction and exhumation.  相似文献   


9.
This work presents the results of a fluid inclusion study of an amphibolite-granulite facies transition in West Uusimaa, S.W. Finland. Early fluid-inclusions in the granulite facies area are characteristically carbonic (CO2), in contrast to predominantly aqueous early inclusions in the amphibolite facies area. These early inclusions can be related to peak metamorphic conditions (750-820°C and 3-5 kbar for peak granulite facies metamorphism). Relatively young CO2 inclusions with low densities (<0.8g/cm3) indicate that the first part of the cooling history of the rocks was characterized by a near isothermal uplift.
N2-CH4 inclusions, with compositions ranging between pure CH4 and pure N2 (Raman spectral analysis), were found in the whole area. They are probably syn- or even pre-early inclusions. Only nearly critical homogenizing inclusions have been found (low density). Pressure estimates, based on densities of early fluid inclusions, show that the rapid transition of amphibolite towards granulite facies metamorphism is virtually isobaric. Granulite facies metamorphism in West Uusimaa is a thermal event, probably induced by the influx of hot, CO2-bearing fluids.  相似文献   

10.
The Ditrău Alkaline Massif is an intrusion into the Bucovina nappe system that is part of the Mesozoic crystalline zone located in Transylvania, Romania, in the Eastern Carpathians. Nepheline syenites are the most abundant rocks in the central and eastern part of the Massif, and represent the last major intrusion of the complex. Fluid inclusions in nepheline, aegirine and albite were trapped at magmatic conditions on or below the H2O-saturated nepheline syenite solidus at about 400–600 °C and 2.5–5 kbars. Early nepheline, and to a lesser extent albite, were altered by highly saline fluids to produce cancrinite, sodalite and analcime, during this process cancrinite also trapped fluid inclusions. The fluids, in most cases, can be modeled by the H2O–NaCl system with varying salinity; however inclusions with more complex fluid composition (containing K, Ca, CO3, etc., in addition to NaCl) are common. Raman spectroscopic analyses of daughter minerals confirm the presence of alkali-carbonate fluids in some of the earliest inclusions in nepheline, aegirine and albite.

During crystallization, the melts exsolved a high salinity, carbonate-rich magmatic fluid that evolved to lower salinity as crystallization progressed. Phases that occur early in the paragenesis contain high-salinity inclusions while late phases contain low-salinity inclusions. The salinity trend is consistent with experimental data for the partitioning of chlorine between silicic melt and exsolved aqueous fluid at about 2.0 kbars. The activity of water (aH2O) in the melt increases during crystallization, resulting in the formation of hydrous phases during late-stage crystallization of the nepheline syenites.  相似文献   


11.
A detailed fluid inclusion study has been carried out on the hydrocarbon-bearing fluids found in the peralkaline complex, Lovozero. Petrographic, microthermometric, laser Raman and bulk gas data are presented and discussed in context with previously published data from Lovozero and similar hydrocarbon-bearing alkaline complexes in order to further understand the processes which have generated these hydrocarbons. CH4-dominated inclusions have been identified in all Lovozero samples. They occur predominantly as secondary inclusions trapped along cleavage planes and healed fractures together with rare H2O-dominant inclusions. They are consistently observed in close association with either arfvedsonite crystals, partially replaced by aegirine, aegirine crystals or areas of zeolitization. The majority of inclusions consist of a low-density fluid with CH4 homogenisation temperatures between −25 and −120 °C. Those in near-surface hand specimens contain CH4+H2 (up to 40 mol%)±higher hydrocarbons. However, inclusions in borehole samples contain CH4+higher hydrocarbons±H2 indicating that, at depth, higher hydrocarbons are more likely to form. Estimated entrapment temperatures and pressures for these inclusions are 350 °C and 0.2–0.7 kbar. A population of high-density, liquid, CH4-dominant inclusions have also been recorded, mainly in the borehole samples, homogenising between −78 and −99 °C. These consist of pure CH4, trapped between 1.2 and 2.1 kbar and may represent an early CH4-bearing fluid overprinted by the low-density population. The microthermometric and laser Raman data are in agreement with bulk gas data, which have recorded significant concentrations of H2 and higher hydrocarbons up to C6H12 in these samples. These data, combined with published isotopic data for the gases CH4, C2H6, H2, He and Ar indicate that these hydrocarbons have an abiogenic, crustal origin and were generated during postmagmatic, low temperature, alteration reactions of the mineral assemblage. This would suggest that these data favour a model for formation of hydrocarbons through Fischer–Tropsch type reactions involving an early CO2-rich fluid and H2 derived from alteration reactions. This is in contrast to the late-magmatic model suggested for the formation of hydrocarbons in the similar peralkaline intrusion, Ilímaussaq, at temperatures between 400 and 500 °C.  相似文献   

12.
Three types of fluid inclusions have been identified in olivine porphyroclasts in the spinel harzburgite and lherzolite xenoliths from Tenerife: pure CO2 (Type A); carbonate-rich CO2–SO2 mixtures (Type B); and polyphase inclusions dominated by silicate glass±fluid±sp±silicate±sulfide±carbonate (Type C). Type A inclusions commonly exhibit a “coating” (a few microns thick) consisting of an aggregate of a platy, hydrous Mg–Fe–Si phase, most likely talc, together with very small amounts of halite, dolomite and other phases. Larger crystals (e.g. (Na,K)Cl, dolomite, spinel, sulfide and phlogopite) may be found on either side of the “coating”, towards the wall of the host mineral or towards the inclusion center. These different fluids were formed through the immiscible separations and fluid–wall-rock reactions from a common, volatile-rich, siliceous, alkaline carbonatite melt infiltrating the upper mantle beneath the Tenerife. First, the original siliceous carbonatite melt is separated from a mixed CO2–H2O–NaCl fluid and a silicate/silicocarbonatite melt (preserved in Type A inclusions). The reaction of the carbonaceous silicate melt with the wall-rock minerals gave rise to large poikilitic orthopyroxene and clinopyroxene grains, and smaller neoblasts. During the metasomatic processes, the consumption of the silicate part of the melt produced carbonate-enriched Type B CO2–SO2 fluids which were trapped in exsolved orthopyroxene porphyroclasts. At the later stages, the interstitial silicate/silicocarbonatite fluids were trapped as Type C inclusions. At a temperature above 650 °C, the mixed CO2–H2O–NaCl fluid inside the Type A inclusions were separated into CO2-rich fluid and H2O–NaCl brine. At T<650 °C, the residual silicate melt reacted with the host olivine, forming a reaction rim or “coating” along the inclusion walls consisting of talc (or possibly serpentine) together with minute crystals of NaCl, KCl, carbonates and sulfides, leaving a residual CO2 fluid. The homogenization temperatures of +2 to +25 °C obtained from the Type A CO2 inclusions reflect the densities of the residual CO2 after its reactions with the olivine host, and are unrelated to the initial fluid density or the external pressure at the time of trapping. The latter are restricted by the estimated crystallization temperatures of 1000–1200 °C, and the spinel lherzolite phase assemblage of the xenolith, which is 0.7–1.7 GPa.  相似文献   

13.
哈西金矿位于新疆西准噶尔哈图—萨尔托海金成矿带的西延部分,是该成矿带内一个具有较大成矿潜力的金矿。为确定该金矿成矿流体的来源,本文对成矿阶段含明金石英脉中的流体包裹体及其氢氧同位素进行了研究,结果显示该成矿阶段石英中的包裹体数量众多,以气液两相包裹体为主,其次为富CO2三相包裹体,少量纯液相包裹体;成矿流体温度范围为226 ℃～325 ℃,盐度范围为2.24%～9.34%,密度范围为0.72～0.88 g/cm3;群体包裹体色谱分析显示,成矿流体液相成分富含Ca2+、SO42-、Cl-等离子,成矿流体气相成分主要为CO2,还有少量CH4、N2等气体。综合分析,哈西金矿成矿阶段的流体为一套中温、低盐度、低密度、受到了古大气水混入的岩浆后期热液,成矿后又伴随着多期次的热液叠加成矿。  相似文献   

14.
金路金矿床位于华北克拉通和中亚造山带的结合部位,矿体受北东向韧-脆性断裂控制,赋矿围岩为太古宇小塔子沟组变质岩和三叠纪片麻状二长花岗岩。以流体包裹体和电子探针分析为研究手段,讨论了成矿流体的特征、演化及其与金矿化的关系。其热液成矿过程可划分为乳白色石英阶段(Ⅰ阶段)、石英-黄铁矿阶段(Ⅱ阶段)、石英-多金属硫化物阶段(Ⅲ阶段)和碳酸盐阶段(Ⅳ阶段) 4个阶段,自然金主要产于Ⅲ阶段的石英和黄铁矿中,以粒间金、裂隙金和包体金的形式产出,成色较高。石英中原生包裹体主要有水溶液包裹体、含微量CO2水包裹体、含子矿物多相包裹体3种类型。Ⅰ阶段石英中以水溶液包裹体和含微量CO2水包裹体为主,均一温度较高,为365～405℃,盐度为7. 9%～11. 7%,密度为0. 61～0. 70 g/cm3;Ⅱ阶段石英中3种类型包裹体均发育,均一温度为335～390℃,盐度为4. 3%～36. 1%,密度为0. 62～0. 79 g/cm3;Ⅲ阶段(主阶段)石英中发育3种类型包裹体,均一温度为270～367℃,盐度为1. 7%～37. 8%,密度为0. 64～1. 1 g/cm3。成矿流体属H2O-Na Cl-CO2体系,成矿温度和流体盐度呈逐渐降低趋势,密度则呈现逐渐增大趋势。根据流体包裹体岩相学特征和矿床地质特征,认为流体沸腾作用和硫化作用是本矿区金沉淀成矿的主要机制。综合分析认为矿床成因类型为岩浆热液矿床。  相似文献   

15.
新华龙钼矿床位于中国东北地区吉林省东部,是一个新发现的斑岩型钼矿床。矿床产于花岗闪长斑岩中。矿床成矿阶段包括石英-浸染状辉钼矿、石英-网脉状辉钼矿、石英-黄铁矿-黄铜矿、石英-多金属硫化物和石英-碳酸盐化5个阶段。流体包裹体实验结果表明：流体包裹体的类型主要为气液两相包裹体,其次为纯气相和纯液相包裹体,还有少量含子矿物的多相包裹体。流体包裹体的均一温度为172～385 ℃,盐度(w(NaCl))为8.51%～45.44%。从早阶段到晚阶段成矿流体温度具有规律的演化,均一温度分别为360～390 ℃、270～350 ℃、250～260 ℃、220～230 ℃、170～190 ℃。其中:含子矿物多相包裹体均一温度为272～385 ℃,盐度为35.79％～45.44％,密度为1.07～1.08 g/cm3;气液两相包裹体均一温度为172～381 ℃,盐度为8.51％～23.36％,密度为0.70～0.99 g/cm3。激光拉曼光谱分析表明,包裹体的气体成分主要为CO2、H2O、N2和CH4。包裹体岩相学及测温表明,流体由早期的高温、高盐度、含二氧化碳的含矿流体在主成矿阶段发生流体包裹体的沸腾、CO2逸出、温度降低等过程,导致大量金属硫化物沉淀。结合氢氧同位素特征,初步确定该矿床的成矿流体主要以岩浆水为主,后期有大气水的加入。流体沸腾是新华龙钼矿床成矿的重要机制。  相似文献   

16.
海沟金矿流体包裹体为3种类型：富CO2三相、气液两相和纯气相。流体盐度集中在7.44％～8．67％NaCleqv,8.54％～8.94％NaCleqv和9.84％～10.87％NaCleqv三个区间;流体密度为0.54～0.88 g/cm3;成矿温度主要集中在298.4℃～313.5℃和258.2℃～264.6℃。研究表明成矿早期阶段流体为低盐度、富CO2的高温流体,且富CO2型和富气相包裹体共存。成矿中晚期阶段流体盐度和温度明显降低,CO2、H2O等气体能够大量逃逸,流体体系由封闭状态转化为较开放状态,大气降水、层间水等大量进入与岩浆流体发生混合,并引起流体内金络合物的溶解度减小而直接导致金和金属矿物的沉淀和富集。成矿压力范围为110～146 MPa,成矿深度为8.7～10.1 km。通过与典型的造山型金矿特征对比,该矿床成因类型为中成造山型金矿,动力学背景为早一中侏罗世华北板块与西伯利亚板块碰撞的持续汇聚力和古太平洋板块俯冲欧亚大陆的作用力引起的远程效应联合作用的结果。  相似文献   

17.
成矿环境中的高密度碳质流体:以阿尔泰南缘为例   总被引：1，自引：0，他引：1       下载免费PDF全文
碳质流体(CO2-CH4-N2体系流体)常见于地幔橄榄岩和下地壳麻粒岩中。近期研究表明,阿尔泰南缘晚古生代成矿环境中的碳质流体极为丰富,不仅在造山型金矿中赋存大量与成矿有关的碳质流体,而且在VMS型矿床中也存在同造山期的变质碳质流体。由共生的富CO2包裹体(LCO2-LH2O型)和H2O-CO2包裹体(LH2O-LCO2型)的均一温度推测,造山型金矿的碳质流体捕获温度大于254～394.5℃,压力大于150～320MPa;VMS矿床的变质碳质流体捕获温度大于209～430℃,压力大于180～300MPa,两者具相似的捕获温度压力条件。碳质流体的捕获温度压力条件与变质相带相平衡计算的变质温度、压力范围相当。碳质流体源于区域变质作用,并参与了与造山型金矿有关的构造-变质-流体-成矿作用和对VMS型矿床的变质改造作用。  相似文献   

18.
辽宁五龙金矿床地质特征及成矿流体地球化学性质   总被引：3，自引：1，他引：2  
对五龙金矿床含金石英脉中发育的流体包裹体进行了系统的岩相学、显微测温及单个包裹体激光拉曼光谱成分分析,结果表明:含金石英脉中主要发育CO2±CH4、H2O-CO2±CH4及气液两相等3种类型的原生流体包裹体;H2O-CO2±CH4包裹体均一温度为287.8～382.5℃,盐度(w（NaCl）)为0.42%～4.87%;气液两相包裹体均一温度为198.5～338.4℃,w（NaCl）为2.24%～6.88%;包裹体气相成分以CO2、CH4为主,且含量变化较大。综合分析认为,形成五龙金矿含金石英脉的流体系来源于岩浆的中温、低盐度含CO2流体,在其运移汇集过程中经与围岩反应导致CH4不断加入,而最终演化成为富含CO2、CH4等挥发分的含矿热液。  相似文献   

19.
西秦岭地区矿产丰富,金资源储量巨大。国内学者对于该区域的众多金矿床开展了大量成矿流体性质及来源的研究工作,但是并没有形成统一的认识;此外,西秦岭礼(县)—岷(县)成矿带,合作—鹿儿坝—崖湾金、汞、锑多金属成矿亚带的成矿流体研究工作比较薄弱。鹿儿坝金矿床为该成矿带的一个代表性金矿床,其赋存于三叠统浊积岩建造中,属于微细粒浸染型金矿。主成矿阶段热液石英脉及方解石脉中流体包裹体主要为H2O气液两相包裹体,少见纯气相包裹体、纯液相包裹体、CO2-H2O三相包裹体。包裹体均一温度范围为81~247 ℃,盐度范围为1.23%~10.98%。流体包裹体气相成分以水为主,还有少量的CH4、CO2、H2等。氢、氧同位素实验数据表明,流体中δDV-SMOW值变化范围为-84.4‰~-96.0‰、δ18O值的变化范围为-4.20‰~6.45‰,表明成矿流体来源并非单一,可能为岩浆水与大气降水混合来源。此外,构造体制的转换造成流体沸腾,导致了大规模金等物质沉淀、聚集、成矿。  相似文献   

20.
Carbonic inclusions   总被引：17，自引：0，他引：17  
The paper gives an overview of the phase relations in carbonic fluid inclusions with pure, binary and ternary mixtures of the system CO2–CH4–N2, compositions, which are frequently found in geological materials. Phase transitions involving liquid, gas and solid phases in the temperature range between −192°C and 31°C are discussed and presented in phase diagrams (PT, TX and VX projections). These diagrams can be applied for the interpretation of microthermometry data in order to determine fluid composition and molar volume (or density).  相似文献   

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