共查询到20条相似文献,搜索用时 62 毫秒
1.
In the Sanandaj-Sirjan zone of metamorphic belt of Iran, the area south of Hamadan city comprises of metamorphic rocks, granitic
batholith with pegmatites and quartz veins. Alvand batholith is emplaced into metasediments of early Mesozoic age. Fluid inclusions
have been studied using microthermometry to evaluate the source of fluids from which quartz veins and pegmatites formed to
investigate the possible relation between host rocks of pegmatites and the fluid inclusion types. Host minerals of fluid inclusions
in pegmatites are quartz, andalusite and tourmaline. Fluid inclusions can be classified into four types. Type 1 inclusions
are high salinity aqueous fluids (NaCl eq >12 wt%). Type 2 inclusions are low to moderate salinity (NaCl eq <12 wt%) aqueous fluids. Type 3 and 4 inclusions are carbonic and mixed CO 2-H 2O fluid inclusions. The distribution of fluid inclusions indicate that type 1 and type 2 inclusions are present in the pegmatites
and quartz veins respectively in the Alvand batholith. This would imply that aqueous magmatic fluids with no detectable CO 2 were present during the crystallization of these pegmatites and quartz veins. Types 3 and 4 inclusions are common in quartz
veins and pegmatites in metamorphic rocks and are more abundant in the hornfelses. The distribution of the different types
of fluid inclusions suggests that CO 2 fluids generated during metamorphism and metamorphic fluids might also contribute to the formation of quartz veins and pegmatites
in metamorphic terrains. 相似文献
2.
The Naozhi Au–Cu deposit is located on the continental margin of Northeast China, forming part of the West Pacific porphyry–epithermal gold–copper metallogenic belt. In this paper, we systematically analyzed the compositions, homogenization temperatures, and salinity of fluid inclusions as well as their noble gas isotopic and Pb isotopic compositions from the deposit. These new data show that (1) five types of fluid inclusions were identified as pure gas inclusions (V-type), pure liquid inclusions (L-type), gas–liquid two-phase inclusions (W-type, as the main fluid inclusions (FIs)), CO2-bearing inclusions (C-type), and daughter-mineral-bearing polyphase inclusions (S-type); (2) W-type FIs in quartz crystals of early, main, and late stage are homogenized at temperatures of 324.7–406.7, 230–338.8, and 154.6–308 °C, with salinities of 2.40–7.01 wt% NaCleq, 1.73–9.47 wt% NaCleq, and 6.29 wt% NaCleq, respectively. S-type FIs in quartz crystals of early stage are homogenized at temperatures of 328.6–400 °C, with salinities of 39.96–46.00 wt% NaCleq; (3) Raman analysis results reveal that the vapor compositions of early ore-forming fluids consisted of CO2 and H2O, with H2O gradually increasing and CO2 being absent at the late mineralization stage; (4) fluid inclusions in pyrite and chalcopyrite have 3He/4He ratios of 0.03–0.104 Ra, 20Ne/22Ne ratios of 9.817–9.960, and 40Ar/36Ar ratios of 324–349. These results indicate that the percentage of radiogenic 40Ar* in fluid inclusions varies from 8.8 to 15.5 %, containing 84.5–91.2 % atmospheric 40Ar; (5) the 206Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios of sulfides are 18.1822–18.3979, 15.5215–15.5998, and 38.1313–38.3786, respectively. These data combined with stable isotope data and the chronology of diagenesis and metallogenesis enable us suppose that the ore-forming fluids originated from the melting of the lower crust, caused by the subduction of an oceanic slab, whereas the mineralized fluids were exsolved from the late crystallization stage and subsequently contaminated by crustal materials/fluids during ascent, including meteoric water, and the mineral precipitation occurred at a shallow crustal level. 相似文献
3.
Three different types of carbonatite magma may be recognized in the Cambrian Fen complex, S.E. Norway: (1) Peralkaline calcite carbonatite magma derived from ijolitic magma; (2) Alkaline magnesian calcite carbonatite magma which yielded biotite-amphibole søvite and dolomite carbonatite; and (3) ferrocarbonatite liquids, related to (2) and/or to alkaline lamprophyre magma (damjernite). Apatite formed during the pre-emplacement evolution of (2) contains inclusions of calcite and dolomite, devitrified mafic silicate glass and aqueous fluid. All of these inclusions have a magmatic origin, and were trapped during a mid-crustal fractionation event ( P4 kbars, T625° C), where apatite and carbonates precipitated from a carbonatite magma which coexisted with a mafic silicate melt. The fluid inclusions contain water, dissolved ionic species (mainly NaCl, with minor polyvalent metal salts) and in some cases CO 2. Two main groups of fluid inclusions are recognized: Type A: CO 2-bearing inclusions, of approximate molar composition H2O
88–90
CO
27-5
NaCl
5
( d=0.85–0.87 g/ cm 3). Type B: CO 2-free aqueous inclusions with salinities from 1 to 24 wt% NaCl eq and densities betwen 0.7 and 1.0 g/cm 3. More strongly saline type B inclusions (salinity ca. 35wt%, d=1.0 to 1.1 g/cm 3) contain solid halite at room temperature and occur in overgrowths on apatite. Type A inclusions probably contain the most primitive fluid, from which type B fluids have evolved during fractionation of the magmatic system. Type B inclusions define a continuous trend from low towards higher salinities and densities and formed as a result of cooling and partitioning of alkali chloride components in the carbonatite system into the fluid phase. Available petrological data on the carbonatites show that the fluid evolution in the Fen complex leads from a regime dominated by juvenile CO 2 + H 2O fluids during the magmatic stage, to groundwater-derived aqueous fluids during post-magmatic reequilibration. 相似文献
4.
The Shilu deposit is a world-class Fe–Co–Cu orebody located in the Changjiang area of the western part of Hainan Island, South China. The distribution of Fe, Co, and Cu orebodies is controlled by strata of the No. 6 Formation in the Shilu Group and the Beiyi synclinorium. Based on a petrological study of the host rocks and their alteration assemblages, and textural and structural features of the ores, four mineralization stages have been identified: (1) the sedimentary ore-forming period; (2) the metamorphic ore-forming period; (3) the hydrothermal mineralization comprising the skarn and quartz–sulfide stage; and (4) the supergene period. The fluid inclusions in sedimentary quartz and/or chert indicate low temperatures (ca. 160 °C) and low salinities from 0.7 to 3.1 wt.% NaCl eq, which corresponds to densities of 0.77 to 0.93 g/cm 3. CO 2-bearing or carbonic inclusions have been interpreted to result from regional metamorphism. Homogenization temperatures of fluid inclusions for the skarn stage have a wide range from 148 °C to 497 °C and the salinities of the fluid inclusions range from 1.2 to 22.3 wt.% NaCl eq, which corresponds to densities from 0.56 to 0.94 g/cm 3. Fluid inclusions of the quartz–sulfide stage yield homogenization temperatures of 151–356 °C and salinities from 0.9 to 8.1 wt.% NaCl eq, which equates to fluid densities from 0.63 to 0.96 g/cm 3.Sulfur isotopic compositions indicate that sulfur of the sedimentary anhydrite and Co-bearing pyrite, and the quartz–sulfide stage, was derived from seawater sulfate and thermochemical sulfate reduction of dissolved anhydrite at temperatures of 200 °C and 300 °C, respectively. H and O isotopic compositions of the skarn and quartz–sulfide stage demonstrate that the ore-forming fluids were largely derived from magmatic water, with minor inputs from metamorphic or meteoric water. The Shilu iron ore deposit has an exhalative sedimentary origin, but has been overprinted by regional deformation and metamorphism. The Shilu Co–Cu deposit has a hydrothermal origin and is temporally and genetically associated with Indosinian granitoid rocks. 相似文献
5.
The Jinman Cu polymetallic deposit is located within Middle Jurassic sandstone and slate units in the Lanping Basin of southwestern China. The Cu mineralization occurs mainly as sulfide‐bearing quartz–carbonate veins in faults and fractures, controlled by a Cenozoic thrust–nappe system. A detailed study of fluid inclusions from the Jinman deposit distinguishes three types of fluid inclusions in syn‐ore quartz and post‐ore calcite: aqueous water (type A), CO 2–H 2O (type B), and CO 2‐dominated (type C) fluid inclusions. The homogenization temperatures of CO 2–H 2O inclusions vary from 208°C to 329°C, with corresponding salinities from 0.6 to 4.6 wt.% NaCl equivalent. The homogenization temperatures of the aqueous fluid inclusions mainly range from 164°C to 249°C, with salinities from 7.2 to 20.2 wt.% NaCl equivalent. These characteristics of fluid inclusions are significantly different from those of basinal mineralization systems, but similar to those of orogenic or magmatic mineralization systems. The H and O isotope compositions suggest that the ore‐forming fluid is predominantly derived from magmatic water, with the participation of basinal brine. The δ34S values are widely variable between ?9.7 ‰ and 9.7 ‰, with a mode distribution around zero, which may be interpreted by the variation in physico‐chemical conditions or by compositional variation of the sources. The mixing of a deeply sourced CO 2‐rich fluid with basinal brine was the key mechanism responsible for the mineralization of the Jinman deposit. 相似文献
6.
四川雪宝顶钨锡铍矿床产于花岗岩体与三叠系地层大理岩的接触带,赋矿石英脉受大理岩中的劈理破碎带控制。绿柱石与白钨矿中的包裹体可分为熔融包裹体、流体熔融包裹体和流体包裹体3类。流体包裹体又可分为H2O包裹体、CO2包裹体和CO2-H2O包裹体,其中,绿柱石中以富含CO2-H2O包裹体为显著特征。加热时,富H2O相CO2-H2O包裹体完全均一至H2O相,富CO2相CO2-H2O包裹体完全均一至CO2相,而二者的完全均一温度和均一压力一致,表明它们是同期捕获的CO2-低盐水不混溶包裹体组合。与绿柱石相比,白钨矿中CO2-H2O包裹体数量明显减少,H2O包裹体数量增多,成矿压力与成矿温度均有所降低。含CO2流体在花岗岩体与大理岩接触带附近发生流体不混溶和相分离,CO2的出溶使成矿流体中pH值升高,f(O2)降低,导致钨的溶解度降低而沉淀,这是形成白钨矿的主要原因。 相似文献
7.
Beryl crystals from the stockscheider pegmatite in the apical portion of the Li-F granite of the Orlovka Massif in the Khangilay complex, a tantalum deposit, contain an assemblage of melt and fluid inclusions containing two different and mutually immiscible silicate melts, plus an aqueous CO 2-rich supercritical fluid. Pure H 2O and CO 2 inclusions are subordinate. Using the terminology of Thomas R, Webster JD, Heinrich W. Contrib Mineral Petrol 139:394–401 ( 2000) the melt inclusions can be classified as (i) water-poor type-A and (ii) water-rich type-B inclusions. Generally the primary trapped melt droplets have crystallized to several different mineral phases plus a vapor bubble. However, type-B melt inclusions which are not crystallized also occur, and at room temperature they contain four different phases: a silicate glass, a water-rich solution, and liquid and gaseous CO 2. The primary fluid inclusions represent an aqueous CO 2-rich supercritical fluid which contained elemental sulfur. Such fluids are extremely corrosive and reactive and were supersaturated with respect to Ta and Zn. From the phase compositions and relations we can show that the primary mineral-forming, volatile-rich melt had an extremely low density and viscosity and that melt-melt-fluid immiscibility was characteristic during the crystallization of beryl. The coexistence of different primary inclusion types in single growth zones underlines the existence of at least three mutually immiscible phases in the melt in which the large beryl crystals formed. Moreover, we show that the inclusions do not represent an anomalous boundary layer. 相似文献
8.
Fluid inclusions were studied in quartz samples from early (stage I) gold-poor quartz veins and later (stage II) gold- and
sulphide-rich quartz veins from the Wenyu, Dongchuang, Qiangma, and Guijiayu mesothermal gold deposits in the Xiaoqinling
district, China. Fluid inclusion petrography, microthermometry, and bulk gas analyses show remarkably consistent fluid composition
in all studied deposits. Primary inclusions in quartz samples are dominated by mixed CO 2-H 2O inclusions, which have a wide range in CO 2 content and coexist with lesser primary CO 2-rich and aqueous inclusions. In addition, a few secondary aqueous inclusions are found along late-healed fractures. Microthermometry
and bulk gas analyses suggest hydrothermal fluids with typically 15–30 mol% CO 2 in stage I inclusions and 10–20 mol% CO 2 in stage II inclusions. Estimates of fluid salinity decrease from 7.4–9.2 equivalent wt.% NaCl to 5.7–7.4 equivalent wt.%
NaCl between stage I and II. Primary aqueous inclusions in both stages show consistent salinity with, but slightly lower Th
total than, their coexistent CO 2-H 2O inclusions. The coexisting CO 2-rich, CO 2-H 2O, and primary aqueous inclusions in both stage I and II quartz are interpreted to have been trapped during unmixing of a
homogeneous CO 2-H 2O parent fluid. The homogenisation temperatures of the primary aqueous inclusions give an estimate of trapping temperature
of the fluids. Trapping conditions are typically 300–370 °C and 2.2 kbar for stage I fluids and 250–320 °C and 1.6 kbar for
stage II fluids. The CO 2-H 2O stage I and II fluids are probably from a magmatic source, most likely devolatilizing Cretaceous Yanshanian granitoids.
The study demonstrates that gold is largely deposited as pressures and temperatures fall accompanying fluid immiscibility
in stage II veins.
Received: 15 May 1997 / Accepted: 10 June 1998 相似文献
9.
Synorogenic veins from the Proterozoic Eastern Mount Isa Fold Belt contain three different types of fluid inclusions: CO 2-rich, aqueous two-phase and rare multiphase. Inclusions of CO 2 without a visible H 2O phase are particularly common. The close association of CO 2-rich inclusions with aqueous two-phase, and possibly multiphase inclusions suggests that phase separation of low- to -moderate
salinity CO 2-rich hydrothermal fluids led to the selective entrapment of the CO 2. Microthermometric results indicate that CO 2-rich inclusions homogenize between –15.5 and +29.9 °C which corresponds to densities of 0.99 to 0.60 g.cm −3. The homogenization temperatures of the associated aqueous two-phase inclusions are 127–397 °C, with salinities of 0.5 to
18.1 wt.% NaCl equivalent. The rarely observed multiphase inclusions homogenize between 250 and 350 °C, and have salinities
ranging from 34.6 to 41.5 wt.% NaCl equivalent. Evidence used to support the presence of fluid immiscibility in this study
is mainly derived from observations of coexisting H 2O-rich and CO 2-rich inclusions in groups and along the same trail. In addition, these two presumably unmixed fluids are also found on adjacent
fractures where monophase CO 2-rich inclusions are closely related to H 2O-rich inclusions. Similar CO 2-rich inclusions are widespread in mineral deposits in this region, which are simply metal-enriched synorogenic veins. Therefore,
we argue that fluid immiscibility caused volatile species such as CO 2 and H 2S to be lost from liquid, thus triggering ore deposition by increasing the fluid pH and decreasing the availability of complexing
ligands.
Received: 28 April 1997 / Accepted: 4 January 1999 相似文献
10.
Gold mineralization of the Seolhwa mine occurs in a single stage of massive quartz veins which filled the north‐east‐trending fault shear zones in the Jurassic granitoid of 161 Ma within the Gyeonggi Massif. The vein quartz contains three main types of fluid inclusions at 25°C: (i) aqueous type I inclusions (0–15 wt.% NaCl) containing small amounts of CO 2; (ii) gas‐rich (more than 70 vol. %), vapor‐homogenizing, aqueous type II inclusions; and (iii) low‐salinity (less than 5 wt.% NaCl), liquid CO 2‐bearing, type III inclusions. The H 2O‐CO 2‐CH 4‐N 2‐NaCl inclusions represent immiscible fluids trapped earlier along the solvus curve in the temperature range 250–430°C at pressures of ~1 kb. Detailed fluid inclusion chronologies suggest a progressive decrease in pressure during the mineralization. Aqueous inclusion fluids represent either later fluids evolved through extensive fluid unmixing from a homogeneous H 2O‐CO 2‐CH 4‐N 2‐NaCl fluid due to decreases in temperature and pressure, or the influence of deep circulated meteoric waters. Initial fluids were homogeneous H 2O‐CO 2‐CH 4‐N 2‐NaCl fluids as follows: 250° to 430°C, 16–62 mol% CO 2, 5–14 mol% CH 4, 0.06–0.31 mol% N 2 and salinities of 0.4–4.9 wt.% NaCl. The T‐X data for the Seolhwa mine suggest that the hydrothermal system has been probably located nearer to the granitic melt, which facilitated the CH 4 formation and resulted in a reduced fluid state indicated by the predominance of pyrrhotite. Measured and calculated isotopic compositions of the hydrothermal fluids [δ 18O = 5.3–6.5‰; δD =?69 to ?84‰] provide evidence of the CH 4‐H 2O equilibria and further indicate that the auriferous fluids were magmatically derived. Both the dominance of δ 34S values of sulfides close to the meteoric reference (?0.6–1.4‰; δ 34S ΣS values of 0.3–1.1‰) and the available δ 13C data (?4‰) are consistent with their deep igneous source. The Seolhwa mine was probably formed by extensive fracturing and veining due to the thermal expansion of water derived from the Jurassic granitoid melt. 相似文献
11.
The Wangfeng gold deposit is located in Western Tian Shan and the central section of the Central Asian Orogenic Belt (CAOB). The deposit is mainly hosted in Precambrian metamorphic rocks and Caledonian granites and is structurally controlled by the Shenglidaban ductile shear zone. The gold orebodies consist of gold-bearing quartz veins and altered mylonite. The mineralization can be divided into three stages: quartz–pyrite veins in the early stage, sulfide–quartz veins in the middle stage, and quartz–carbonate veins or veinlets in the late stage. Ore minerals and native gold mainly formed in the middle stage. Four types of fluid inclusions were identified based on petrography and laser Raman spectroscopy: CO 2–H 2O inclusions (C-type), pure CO 2 inclusions (PC-type), NaCl–H 2O inclusions (W-type), and daughter mineral-bearing inclusions (S-type). The early-stage quartz contains only primary CO 2–H 2O fluid inclusions with salinities of 1.62 to 8.03 wt.% NaCl equivalent, bulk densities of 0.73 to 0.89 g/cm 3, and homogenization temperatures of 256 °C–390 °C. Vapor bubbles are composed of CO 2. The middle-stage quartz contains all four types of fluid inclusions, of which the CO 2–H 2O and NaCl–H 2O types yield homogenization temperatures of 210 °C–340 °C and 230 °C–300 °C, respectively. The CO 2–H 2O fluid inclusions have salinities of 0.83 to 9.59 wt.% NaCl equivalent and bulk densities of 0.77 to 0.95 g/cm 3, with vapor bubbles composed of CO 2, CH 4, and N 2. Fluid inclusions in the late-stage quartz are NaCl–H 2O solution with low salinities (0.35–3.87 wt.% NaCl equivalent) and low homogenization temperatures (122 °C–214 °C). The coexistence of inclusions of these four types in middle-stage quartz suggests that fluid boiling occurred in the middle-stage mineralization. Trapping pressures estimated from CO 2–H 2O inclusions are 110–300 MPa and 90–250 MPa for the early and middle stages, respectively, suggesting that gold mineralization mainly occurred at depths of about 10 km. In general, the Wangfeng gold deposit originated from a metamorphic fluid system characterized by low salinity, low density, and enrichment of CO 2. Depressurized fluid boiling caused gold precipitation. Given the regional geology, ore geology, fluid-inclusion features, and ore-forming age, the Wangfeng gold deposit can be classified as a hypozonal orogenic gold deposit. 相似文献
12.
Carbon dioxide-rich fluid and carbonate-rich aluminosilicate melt inclusions in tantalite-(Mn) from the Alto do Giz pegmatite
in the Borborema Pegmatite Province, northeastern Brazil were investigated to constrain the formation of the host crystals.
The results demonstrate that in the Alto do Giz pegmatite, water- and alkaline carbonate-rich fluids and melts are responsible
for the transport and deposition of tantalite-(Mn) at temperatures around 600°C and about 4 kbar. Moreover, evidence is presented
to show that during crystallization of the tantalite-(Mn), three different components coexisted, which are now trapped as
separate inclusions: two immiscible silicate melts (types A and B melt inclusions) and a CO 2-rich aqueous fluid. We hypothesize that immiscible fluid separation may have been a critical factor in producing the water-
and alkaline carbonate-rich fluids and melts necessary for Ta and Nb transport. Since the tantalite-(Mn) crystallized during
pegmatite formation, this mechanism must also have implications for pegmatite genesis in general. 相似文献
13.
The Sanshandao gold deposit, with total resources of more than 60 t of gold, is located in the Jiaodong gold province, the most important gold province of China. The deposit is a typical highly fractured and altered, disseminated gold system, with high-grade, quartz-sulphide vein/veinlet stockworks that cut Mesozoic granodiorite. There are four stages of veins that developed in the following sequence: (1) quartz-K-feldspar-sericite; (2) quartz-pyrite±arsenopyrite; (3) quartz-base metal sulfide; and (4) quartz-carbonate. Fluid inclusions in quartz and calcite in vein/veinlet stockworks contain C-O-H fluids of three main types. The first type consists of dilute CO 2–H 2O fluids coeval with the early vein stage. Molar volumes of these CO 2–H 2O fluid inclusions, ranging from 50–60 cm 3/mol, yield estimated minimum trapping pressures of 3 kbar. Homogenization temperatures, obtained mainly from CO 2–H 2O inclusions with lower CO 2 concentration, range from 267–375 °C. The second inclusion type, with a CO 2–H 2O±CH 4 composition, was trapped during the main mineralizing stages. These fluids may reflect the CO 2–H 2O fluids that were modified by fluid/rock reactions with altered wallrocks. Isochores for CO 2-H 2O±CH 4 inclusions, with homogenization temperatures ranging from 204–325 °C and molar volumes from 55 to 70 cm 3/mol, provide an estimated minimum trapping pressure of 1.2 kbar. The third inclusion type, aqueous inclusions, trapped in cross-cutting microfractures in quartz and randomly in calcite, are post-mineralization, and have homogenization temperatures between 143–228 °C and salinities from 0.71–7.86 wt% NaCl equiv. Stable isotope data show that the metamorphic fluid contribution is minimal and that ore fluids are of magmatic origin, most likely sourced from 120–126 Ma mafic to intermediate dikes. This is consistent with the carbonic nature of the fluid, and the cross-cutting nature of those deposits relative to the host Mesozoic granitoid.Editorial handling: R.J. Goldfarb 相似文献
14.
Melt and fluid inclusions were investigated in minerals from igneous rocks and ore (Au-Ag-Pb-Zn) veins of the Stiavnica ore field in Central Slovakia. High H 2O (7.1–12.0 wt %) and Cl (0.32–0.46 wt %) contents were found in silicate melt inclusions (65–69 wt % SiO 2 and 5.2–5.6 wt % K 2O) in plagioclase phenocrysts ( An 68–36) from biotite-homblende andesites of the eastern part of the caldera. Similar high water contents are characteristic of magmatic melts (71–76 wt % SiO 2 and 3.7–5.1 wt % K 2O) forming the sanidine rhyolites of the Vyhne extrusive dome in the northwestern part of the Stiavnica caldera (up to 7.1 wt %) and the rhyolites of the Klotilda dike in the eastern part of the ore field (up to 11.5 wt %). The examination of primary inclusions in quartz and sanidine from the Vyhne rhyolites revealed high concentrations of N 2 and CO 2 in magmatic fluid (8.6 g/kg H 2O and 59 g/kg H 2O, respectively). Fluid pressure was estimated as 5.0 kbar on the basis of primary CO 2 fluid inclusions in plagioclase phenocrysts from the Kalvari basanites. This value corresponds to a depth of 18 km and may be indicative of a deep CO 2 source. Quartz from the granodiorites of the central part of the Stiavnica-Hodrusa complex crystallized from a melt with 4.2–6.1 wt % H 2O and 0.24–0.80 wt % Cl. Magmatic fluid cogenetic with this silicate melt was represented by a chloride brine with a salinity of no less than 77–80 wt % NaCl equiv. Secondary inclusions in quartz of the igneous rocks recorded a continuous trend of temperature, pressure, and solution salinity, from the parameters of magmatic fluids to the conditions of formation of ore veins. The gold mineralization of the Svyatozar vein system was formed from boiling low-salinity fluids (0.3–8.0 wt % NaCl equv.) at temperatures of 365–160°C and pressures of 160–60 bar. The Terezia, Bieber, Viliam, Spitaler, and Rozalia epithermal gold-silver-base metal veins were also formed from heterogeneous low-salinity fluids (0.3–12.1 wt %) at temperatures of 380–58°C and pressures of 240–10 bar. It was found that the salt components of the solutions were dominated by chlorides (high content of fluorine, up to 0.45 mol/kg H 2O, was also detected), and sulfate solutions appeared in the upper levels. The dissolved gas of ore-forming solutions was dominated by CO 2 (0.1–8.4 mol %, averaging 1.3 wt %) and contained minor nitrogen (0.00–0.85 mol %, averaging 0.05 mol %) and negligible methane admixtures (0.00–0.05 mol %, averaging 0.004 mol %). These data allowed us to conclude that the magmatic melts could be sources of H 2O, Cl, CO 2, and N 2. The formation of the epithermal mineralization of the Stiavnica ore field was associated with the mixing of magmatic fluid with low-concentration meteoric waters, and the fluid was in a heterogeneous state. 相似文献
15.
Heating and freezing studies on fluid inclusions in quartz from mineralized quartzfeldspar reef reveal the presence of type A CO 2-H 2O (H 2O>50% by volume), type B CO 2-H 2O (H 2O<50% by volume), type C pure CO 2 and type D pure aqueous inclusions. Types A, B and C are primary and/or psuedo-secondary inclusions while type D are secondary. Types A and B homogenize on heating into different phases at similar temperatures ranging between 307 and 476°C, indicating entrapment from boiling hydrothermal solutions. Type D inclusions homogenize into a liquid phase at temperatures between 88 and 196°C. Boiling of hydrothermal solutions led to the formation of a CO 2-rich phase of low density and salinity that coexisted with another dense and saline aqueous phase with very little CO 2 dissolved in it. Ore and gangue mineral assemblage of primary ores indicate that ore deposition was characterized by log f O 2=?34.4 to ?30.2 atm, log f S 2=?11.6 to ?8.8 atm and pH=4.5 to 6.5. 相似文献
16.
Fluid inclusion measurements on quartz, scheelite, beryl, fluorite and calcite in the metamorphosed Felbertal scheelite deposit display two main types of fluid inclusions: - H2O-CO2 fluid inclusions are characterized by variable amounts of CO2 up to 18 wt.%. They show two or three phases at room temperature. The bulk homogenization temperatures for the inclusions range between +269 °C and +357 °C. The calculated salinities are between 2.2 and 7.8 wt.% NaCl equivalent. For the late CO2-bearing fluid inclusions a methane component is evident from microthermometrical data (Tmclath >10.0 °C combined with TmCO256.6 °C) and from Raman microprobe analyses.
- Aqueous, two-phase fluid inclusions with salinities in the range between 0 and 11 wt.% NaCl equivalent. Their homogenization temperatures are scattered between 100 °C and 360 °C.
Both types of fluid inclusions are of Alpine origin. They do not record the conditions of the original tungsten ore formation in pre-Alpine (Upper Proterozoic) time. However, it was possible to deduce a path for the fluid evolution and the combined ore redeposition during the retrograde Alpine metamorphism and tectonism from microthermometrical and petrographical studies. 相似文献
17.
Quartzitic pelites forms a part of Higher Himalayan Crystalline of higher geotectonic zone in Garhwal Himalaya. Quartzitic pelites (locally known as Pandukeshwar Quartzite) in Garhwal Himalaya is sandwiched between high grade metamorphic rocks of Central Crystallines and Badrinath Formation. Fluid inclusion studies are carried out on the detrital, and recrystallized quartz grains of quartzitic pelites to know about the fluid phases present during recrystallization processes at the time of maximum depth of burial. The quartzitic pelite (Pandukeshwar Quartzite) essentially consists of recrystallised quartz with accessory minerals like mica and feldspar. Fluid microthermometry study reveals the presence of three types of fluids: (i) high-salinity brine, (ii) CO 2-H 2O and (iii) H 2O-NaCl. These fluids were trapped during the development of grain and recrystallization processes. The high saline brine inclusions and CO 2-H 2O fluid with the density of 0.90 to 0.97 gm/cm 3 are remnants of provenance area. CO 2 density in detrital quartz grains characterise the protolith of the sandstone as granite or metamorphic rock. The H 2O-NaCl fluids involved in the recrystallization processes at temperature-pressure of 430-350°C; 4.8 to 0.5 Kbars as constrained by fluid isochores of CO 2-H 2O and H 2O-NaCl inclusions and bulging and subgrain development during recrystallization processes. The re-equilibration of the primary fluid due to elevated internal and confining pressure is evident from features like ‘C’ shaped cavities, stretching of the inclusions, their migration and decrepitation clusters. The observed inclusion morphology revealed that the rocks were exhumed along an isothermal decompression path. 相似文献
18.
The large, newly discovered Lijiagou pegmatite spodumene deposit, is located southeast of the Ke'eryin pegmatite ore field, in the central Songpan–Garze Fold Belt (SGFB), Eastern Tibet. The Lijiagou albite spodumene pegmatites are unzoned, granite‐pegmatites of the subtype LCT (Lithium, Cesium, and Tantalum) and consist of medium‐ to coarse‐grained spodumene, lepidolite, microcline, albite, quartz, muscovite, and accessory amounts of beryl, cassiterite, columbite–tantalite and zircon. Secondary fluid inclusions in quartz and spodumene include two‐phase aqueous inclusions (V + L), mono‐phase vapor inclusions (V); three‐phase CO 2‐rich CO 2–H 2O inclusions (CO 2 + V + L) and less abundant liquid inclusions (L). The homogenization temperature of the fluid inclusions are low (257.3 to 204.3°C in early stage, 250.3 to 199.6°C in middle stage, 218.7 to 200.6°C in late stage). Fluid inclusions were formed during the long cooling period from the temperature of the pegmatite emplacement. Liquid–vapor–gas boiling was extensive during the middle and late stages. The salinity of the corresponding stages are 15.4 to 13.0 wt.% NaCl equiv., 12.5 to 9.1 wt.% NaCl equiv. and 9.8 to 7.8 wt.% NaCl equiv., respectively. δ 18O values of fluid are 7.2 to 5.2‰, 5.6 to 3.9‰ and 2.7 to −0.2‰ from early to late stages; and δD range from −75.1 to −76.8‰, −59.0 to −73.5‰ and −61.6 to −85.5‰ respectively. The δ 13C of CO 2 values are −5.6 to −6.6‰, −8.5 to −19.9‰, −11.8 to −18.7‰ from early to late stages, suggesting that CO 2 in the fluids were probably sourced from a magmatic system, possibly with some mixing of CO 2 dissolved in groundwater. δD and δ 18O values of fluid indicate that the fluids were originally magmatic water and mixed with some meteoric water in late stage. The magma evolution sequence in the Ke'eryin orefield, from the central two‐mica granite through the Lijiagou deposit out to the distal pegmatites, with the ages gradually decreasing, indicates that the Ke'eryin complex rocks are the product of multistage magmatic activity. The large Lijiagou spodumene deposit is a typical magmatic, fractional crystallization related pegmatite deposit. 相似文献
19.
Metamorphosed pelitic rocks from Mica Creek, British Columbia contain sillimanite, kyanite with minor fibrolite and andalusite-bearing quartz pods. Mineral equilibria were used to infer peak P-T conditions and fluid compositions in equilibrium with the solid phases. Fluid inclusions in three schist samples appear to be good indicators of conditions affecting those rocks during and after peak metamorphic conditions. In samples from two localities, fluid inclusions from schist and quartz-rich segregations have densities appropriate to the peak metamorphic conditions. The observed compositions for these fluids (low salinity with 12 mole % dissolved CO 2) agree with calculated
values of 0.84 to 0.85, based upon paragonite-quartz-albite-Al 2SiO 5 equilibria. The fluids unmixed as the schists were uplifted and cooled; fluid inclusions trapped during this stage outline a solvus in the CO 2-H 2O-NaCl system. A later influx of fluids containing CH 4 and N 2 accompanied formation of andalusite-bearing plagioclaserich segregations. The restricted association of andalusite-bearing pods and low density fluids suggest a localized but pervasive fluid influx during uplift. Preservation of high density fluid inclusions during uplift and erosion, coupled with evidence for unmixing of H 2O- and CO 2-rich fluids on the solvus, provide constraints on the P-T uplift path. 相似文献
20.
The Olympias Pb-Zn(Au, Ag) sulfide ore deposit, E. Chalkidiki, N. Greece, is hosted by marbles of the polymetamorphic Kerdilia
Formation of Paleozoic or older age. The geologic environment of the ore also comprises biotite-hornblende gneisses and amphibolites
intruded by Tertiary pegmatite-aplite dikes, lamprophyre dikes, the 30-Ma Stratoni granodiorite, and porphyritic stocks. Only
limited parts of the deposit display shear folding and brecciation; most of it is undeformed. Microthermometry of fluid inclusions
in gangue syn-ore quartz indicates three types of primary and pseudosecondary inclusions: (1) H 2O-rich, 1–18 wt.% NaCl equivalent, <3.6 mol% CO 2; (2) H 2O-CO 2 inclusions, <4wt.% NaCl equivalent, with variable CO 2 contents, coexisting in both undeformed and deformed ore; (3) aqueous, highsalinity (28–32 wt,% NaCl equivalent) inclusions
found only in undeformed ore. Type 2 inclusions are differentiated into two sub-types: (2a) relatively constant CO 2 content in the narrow range of 8–15 mol% and homogenization to the liquid phase; (2b) variable CO 2 content between 18 and 50 mol% and homogenization to the vapor phase. Type 1 and 2b inclusions are consistent with trapping
of two fluids by unmixing of a high-temperature, saline, aqueous, CO 2-bearing fluid of possible magmatic origin, probably trapped in type 2a inclusions. Fluid unmixing and concomitant ore mineralization
took place at temperatures of 350 ± 30 °C and fluctuating pressures of less than 500 bar, for both undeformed and deformed
ores. The wide salinity range of type 1 inclusions probably represents a complex effect of salinity increase, due to fluid
unmixing and volatile loss, and dilution, due to mixing with low-salinity meteoric waters. High solute enrichment of the residual
liquid, due to extreme volatile loss during unmixing, may account for high salinity type 3 inclusions. The Olympias fluid
inclusion salinity-temperature gradients bear similarities to analogous gradients related to Pb-Zn ores formed in “granite”-hosted,
low- T distalskarn, skarn-free carbonate-replacement and epithermal environments. 相似文献
|