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1.
Fluid Inclusion Study of Skarns in the Maruyama Deposit, the Kamioka Mine, Central Japan 总被引：1，自引：0，他引：1
Abstract: Fluid inclusions in skarn minerals in the Maruyama deposit, the Kamioka mine, central Japan were studied. Homogenization temperatures (Th) of fluid inclusions in 48 skarn minerals (hedenbergite, andradite, epidote and quartz) were measured, and gas composition of fluid inclusions in 12 skarn minerals was measured with a quadrupole mass spectrometer. The maximum Th value of primary inclusions in hedenbergite is 380C with peaks around 360C. Primary inclusions in hedenbergite near contact between skarn and limestone have slightly lower Th values and their distribution has a tendency of long trail skirt toward low temperature, which indicates ceasing of skarnization coincides with temperature decrease. Fluid inclusions in andradite and quartz in the hedenbergite skarn have lower Th values, in this order, than those in hedenbergite. CH4–detected fluid inclusions are localized around the Maruyama fault. Gas composition of the fluid inclusions indicates that fluid trapped in the hedenbergite has CO2 content less than 1 mole % and is not in equilibrium with graphite. 相似文献
2.
巴特巴克布拉克铁矿床赋存于上志留-下泥盆统康布铁堡组变质火山-沉积岩系中, 近矿围岩为石榴子石矽卡岩、角闪斜长变粒岩和浅粒岩。矿体总体顺层分布, 呈似层状、透镜状及不规则状, 空间上与矽卡岩密切相关。流体包裹体研究表明, 矽卡岩阶段形成的石榴子石中发育纯气体包裹体、气体包裹体、液体包裹体、含子矿物包裹体及熔融包裹体; 退化蚀变阶段发育液体包裹体和少量气体包裹体; 石英-硫化物阶段主要发育液体包裹体、含液体CO2的三相包裹体及少量纯气体包裹体、气体包裹体和含子矿物包裹体。矽卡岩阶段均一温度变化为217 ℃~499 ℃, 在255 ℃出现峰值, 盐度(NaCleq)变化为8.68%~22.65%; 退化蚀变阶段均一温度变化为181 ℃~432 ℃, 在225 ℃出现峰值, 盐度变化为12.85%~22.65%; 石英-硫化物阶段均一温度变化为140 ℃~482 ℃, 在155 ℃出现峰值, 盐度变化为0.18%~42.40%。石榴子石、石英和方解石的 δ18 OSMOW 变化为1.8‰~7.1‰, δ18ΟΗ2Ο为 -4.79‰~4.57‰, δDSMOW 为 -128‰~-84‰, 表明矽卡岩阶段成矿流体主要为岩浆水, 混合少量大气降水; 石英-硫化物阶段大气降水所占比例明显增加。方解石δ13 CV-PDB 变化为 -3.2‰~-2.0‰, 表明流体中的碳来自深部或地幔。 相似文献
3.
Geological and fluid inclusion studies of the Dongpo tungsten skarn ore deposit,China 总被引：1，自引：0，他引：1
The Dongpo tungsten ore deposit, the largest scheelite skarn deposit in China, is located at the contact of a 172-m. y. biotite
granite with a Devonian marble. The mineralization associated with the granite includes W, Bi-Mo, Cu-Sn and Pb-Zn ores. Several
W mineralization stages are shown by the occurrence of ore in massive skarn deposits and in later cross-cutting veins. The
high garnet/pyroxene ratio, the hedenbergite and diopside-rich pyroxene and the andradite-rich garnet show the deposit belongs
to the oxidized skarn type. Detailed fluid inclusion studies of granite, greisen, skarn and vein samples reveal three types
of fluid inclusion: (1) liquid-rich, (2) gas-rich and (3) inclusions with several daughter minerals. Type (3) is by far the
most common in both skarn and vein samples. The dominant daughter mineral in fluid inclusions is rhembic, highly birefringent,
and does not dissolve on heating even at 530°C. We assume that this mineral is calcite. The liquid phase in most of the fluid
inclusions has low to moderate salinities: 0–15 wt. %; in a few has higher salinities (30–40 wt. % NaCl equivalent). The homogenization
temperatures of inclusions in the skarn stage range from 350°C to 530°C, later tungsten mineralization-stage inclusions homogenize
between 200°C and 300°C, as do inclusions in veins. Fluid inclusions in granite and greisen resemble those of the late tungsten
mineralization stage, with low salinity and homogenization temperatures of 200°–360°C. The tungsten-forming fluids are probably
a mixture that came from biotite granite and the surrounding country rocks. 相似文献
4.
The Phu Lon skarn Cu–Au deposit is located in the northern Loei Fold Belt (LFB), Thailand. It is hosted by Devonian volcano-sedimentary sequences intercalated with limestone and marble units, intruded by diorite and quartz monzonite porphyries. Phu Lon is a calcic skarn with both endoskarn and exoskarn facies. In both skarn facies, andradite and diopside comprise the main prograde skarn minerals, whereas epidote, chlorite, tremolite, actinolite and calcite are the principal retrograde skarn minerals.Four types of fluid inclusions in garnet were distinguished: (1) liquid-rich inclusions; (2) daughter mineral-bearing inclusions; (3) salt-saturated inclusions; and (4) vapor-rich inclusions. Epidote contains only one type of fluid inclusion: liquid-rich inclusions. Fluid inclusions associated with garnet (prograde skarn stage) display high homogenization temperatures and moderate salinities (421.6–468.5 °C; 17.4–23.1 wt% NaCl equiv.). By contrast, fluid inclusions associated with epidote (retrograde skarn stage) record lower homogenization temperatures and salinities (350.9–399.8 °C; 0.5–8 wt% NaCl equiv.). These data suggest a possible mixing of saline magmatic fluids with external, dilute fluid sources (e.g., meteoric fluids), as the system cooled. Some fluid inclusions in garnet contain hematite daughters, suggesting an oxidizing magmatic environment. Sulfur isotope determinations on sulfide minerals from both the prograde and retrograde stages show a uniform and narrow range of δ34S values (?2.6 to ?1.1 ‰ δ34S), suggesting that the ore-forming fluid contained sulfur of orthomagmatic origin. Overall, the Phu Lon deposit is interpreted as an oxidized Cu–Au skarn based on the mineralogy and fluid inclusion characteristics. 相似文献
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7.
CAO Yi DU Yangsong PANG Zhenshan DU Yilun KOU Shaolei CHEN Linjie GAO Fuping ZHOU Guibi 《《地质学报》英文版》2015,89(3):746-765
The Datuanshan deposit is one of the largest and most representative stratabound copper deposits in the Tongling area,the largest ore district in the Middle-Lower Yangtze River metallogenic belt.The location of the orebodies is controlled by the interlayer-slipping faults between the Triassic and Permian strata,and all the orebodies are distributed in stratiform shape around the Mesozoic quartz monzodiorite dikes.Based on field evidence and petrographic observations,four mineralization stages in the Datuanshan deposit have been identified:the skarn,early quartz-sulfide,late quartzsulfide and carbonate stages.Chalcopytite is the main copper mineral and mainly formed at the late quartz-sulfide stage.Fluid inclusions at different stages were studied for petrography,microthermometry,laser Raman spectrometry and stable isotopes.Four types of fluid inclusions,including three-phase fluid inclusions(type 1),liquid-rich fluid inclusions(type 2),vapour-rich fluid inclusions(type 3) and pure vapour fluid inclusions(type 4),were observed.The minerals from the skarn,early and late quartz-sulfide stages contain all fluid inclusion types,but only type 2 fluid inclusions were observed at the carbonate stage.Petrographic observations suggest that most of the inclusions studied in this paper are likely primary.The coexistence of different types of fluid inclusions with contrasting homogenization characteristics(to the liquid and vapour phase,respectively) and similar homogenization temperatures(the modes are 440-480℃,380-400℃ and 280-320℃ for the skarn,early and late quartz-sulfide stages,respectively) in the first three stages,strongly suggests that three episodes of fluid boiling occurred during these stages,which is supported by the hydrogen isotope data.Laser Raman spectra identified CH_4 at the skarn and early quartz-sulfide stages.Combined with other geological features,the early ore-forming fluids were inferred to be under a relatively reduced environment.The CO_2 component has been identified at the late quartz-sulfide and carbonate stages,indicating that the late ore-forming fluids were under a relatively oxidized environment,probably as a result of inflow of and mixing with meteoric water.In addition,microthermometric results of fluid inclusions and H-O isotope data mdicate that the ore forming fluids were dominated by magmatic water in the early stages(skarn and early quartz-sulfide stages) and mixed with meteoric water in the late stages(late quartz-sulfide and carbonate stages).The evidence listed above suggests that the chalcopyrite deposition in the Datuanshan deposit probably resulted from the combination of multiepisode fluid boiling and mixing of magmatic and meteoric water. 相似文献
8.
大冶-武山矿化夕卡岩的稀土元素地球化学研究 总被引：15，自引：1，他引：15
用ICP-MS分析了25个含矿夕卡岩样品的REE含量,其中对8个样品的石榴子石等矿物中的熔融包裹体进行了均一温度测定,还对5个夕卡岩样品石榴子石中的熔融包裹体进行了电子探针分析.在这些样品的石榴子石、辉石或方解石中都观察到熔融包裹体.夕卡岩的球粒陨石标准化REE分布模式具有两个突出特点:其一是以富集轻稀土元素(LREE)右倾为特征;其二是多数以具有Eu正异常为特征.夕卡岩球粒陨石标准化REE分布模式有三种类型:第一类型显示斜率不大的右倾直线;第二类型具有以Ce为峰值的折线的特征,即REE线段向上凸,在Ce处有一极大值(个别无峰值,LREE曲线向上凸,呈穹隆状);第三类型为过渡型REE分布模式.在当今REE资料有限的情况下,利用稀土元素地球化学特点鉴别夕卡岩成因是困难的. 相似文献
9.
矽卡岩矿床各种硅酸盐矿物中熔融包裹体和流体-熔融包裹体的显微测温资料和相成分让我们提出过大量矽卡岩是岩浆成因的建议。在本文中,我们提供沿长江中下游成矿带的许多矽卡岩矿床包含在石榴子石和辉石里的熔融包裹体和流体-熔融包裹体的激光拉曼分析结果,目的是证明所研究的并与Cu-Fe-Au矿床共生的矽卡岩系岩浆成因。我们的研究结果显示,熔融包裹体只含固体相和微量气相。流体-熔融包裹体除了含大量固相外,还含微量流体和气相以及没有被仪器检测到的气体。固体相与包裹体寄主矿物相同或类似。流体相主要为水或盐水溶液和包括C6H6、C3H6、C3H8、CH4、CO2和O2的气体。我们提出,熔融包裹体和流体-熔融包裹体是原始岩浆的最好代表。这就证明,矽卡岩组合是由一个原生岩浆直接结晶而成。此外,我们还讨论了岩浆矽卡岩形成的温度、分布范围和规模、形成机制和与Cu-Fe-Au矿化作用的联系。 相似文献
10.
新疆蒙库铁矿床稀土元素地球化学及对铁成矿作用的指示 总被引：16，自引：4，他引：16
新疆富蕴县蒙库大型铁矿呈层状、似层状、透镜状赋存于下泥盆统康布铁堡组变质火山-沉积岩系中.矿体中发育矽卡岩,但矽卡岩并不产在侵入岩接触带上.绿帘石、石榴石和矿石的稀土配分模式具有相似性,均为轻稀土富集,正铕异常,基本上无铈异常,暗示它们之间存在成因联系.石榴石稀土配分模式呈折线型,具有明显的正铕异常,石榴石流体包裹体中熔融包裹体、熔流包裹体和气液包裹体共存,表明石榴石矽卡岩具有岩浆成因和热液成因的特征,形成于晶体 熔体 流体三相共存的岩浆-热液过渡阶段.矿床地质特征、矽卡岩矿物和矿石稀土特征表明蒙库铁矿为矽卡岩型矿床. 相似文献
11.
马坑铁矿是福建省一个大型铁钼铅锌多金属矿床,赋存于莒舟-大洋花岗岩外接触带上石炭统经畲组-下二叠统栖霞
组大理岩与下石炭统林地组石英砂岩之间,矿化阶段经历了从无水矽卡岩阶段（钙铁榴石-透辉石） →含水矽卡岩-磁铁矿
阶段（绿帘石-阳起石-绿泥石-钙铁辉石） →硫化物阶段（石英-方解石-萤石-黄铁矿-闪锌矿） →碳酸盐岩阶段（石英-方
解石） 演变,而本文对含水矽卡岩-磁铁矿阶段和硫化物阶段中的钙铁辉石、萤石、石英及方解石中流体包裹体所进行岩
相学观察和显微测温研究表明,早期含水矽卡岩-磁铁矿阶段包裹体类型主要有含NaCl子晶三相包裹体和富液相两相包裹
体,少量富气相两相包裹体;而晚期硫化物阶段包裹体类型主要为富液相两相包裹体。含水矽卡岩-磁铁矿阶段流体出现
流体沸腾作用,流体温度范围为448~596℃,两端员组分流体盐度分别为26.5~48.4 wt % NaCl equiv.和2.4~6.9 wt % NaCl
equiv.;硫化物阶段流体呈现出混合趋势,流体温度和盐度分别为182~343℃和1.9~20.1 wt % NaCl equiv.。流体包裹体的均
一温度和盐度的研究结果表明含水矽卡岩-磁铁矿阶段流体主要来自岩浆水,而硫化物阶段流体以岩浆水为主,并有大气
降水加入。由于马坑铁矿化形成于含水矽卡岩阶段,铅锌矿化则形成于硫化物阶段,流体沸腾是导致马坑铁矿床形成的主
要因素,而流体混合则是引起马坑铁矿床铅锌矿化的主要因素。综合地质与地球化学研究,马坑铁矿床应属于与莒舟-大
洋花岗岩有关的矽卡岩型铁矿床。 相似文献
12.
Lei CHEN Kezhang QIN Jinxiang LI Bo XIAO Guangming LI Junxing ZHAO Xin FAN 《Resource Geology》2012,62(1):42-62
The Nuri Cu‐W‐Mo deposit is located in the southern subzone of the Cenozoic Gangdese Cu‐Mo metallogenic belt. The intrusive rocks exposed in the Nuri ore district consist of quartz diorite, granodiorite, monzogranite, granite porphyry, quartz diorite porphyrite and granodiorite porphyry, all of which intrude in the Cretaceous strata of the Bima Group. Owing to the intense metasomatism and hydrothermal alteration, carbonate rocks of the Bima Group form stratiform skarn and hornfels. The mineralization at the Nuri deposit is dominated by skarn, quartz vein and porphyry type. Ore minerals are chalcopyrite, pyrite, molybdenite, scheelite, bornite and tetrahedrite, etc. The oxidized orebodies contain malachite and covellite on the surface. The mineralization of the Nuri deposit is divided into skarn stage, retrograde stage, oxide stage, quartz‐polymetallic sulfide stage and quartz‐carbonate stage. Detailed petrographic observation on the fluid inclusions in garnet, scheelite and quartz from the different stages shows that there are four types of primary fluid inclusions: two‐phase aqueous inclusions, daughter mineral‐bearing multiphase inclusions, CO2‐rich inclusions and single‐phase inclusions. The homogenization temperature of the fluid inclusions are 280°C–386°C (skarn stage), 200°C–340°C (oxide stage), 140°C–375°C (quartz‐polymetallic sulfide stage) and 160°C–280°C (quartz‐carbonate stage), showing a temperature decreasing trend from the skarn stage to the quartz‐carbonate stage. The salinity of the corresponding stages are 2.9%–49.7 wt% (NaCl) equiv., 2.1%–7.2 wt% (NaCl) equiv., 2.6%–55.8 wt% (NaCl) equiv. and 1.2%–15.3 wt% (NaCl) equiv., respectively. The analyses of CO2‐rich inclusions suggest that the ore‐forming pressures are 22.1 M Pa–50.4 M Pa, corresponding to the depth of 0.9 km–2.2 km. The Laser Raman spectrum of the inclusions shows the fluid compositions are dominated in H2O, with some CO2 and very little CH4, N2, etc. δD values of garnet are between ?114.4‰ and ?108.7‰ and δ18OH2O between 5.9‰ and 6.7‰; δD of scheelite range from ?103.2‰ to ?101.29‰ and δ18OH2O values between 2.17‰ and 4.09‰; δD of quartz between ?110.2‰ and ?92.5‰ and δ18OH2O between ?3.5‰ and 4.3‰. The results indicate that the fluid came from a deep magmatic hydrothermal system, and the proportion of meteoric water increased during the migration of original fluid. The δ34S values of sulfides, concentrated in a rage between ?0.32‰ to 2.5‰, show that the sulfur has a homogeneous source with characteristics of magmatic sulfur. The characters of fluid inclusions, combined with hydrogen‐oxygen and sulfur isotopes data, show that the ore‐forming fluids of the Nuri deposit formed by a relatively high temperature, high salinity fluid originated from magma, which mixed with low temperature, low salinity meteoric water during the evolution. The fluid flow through wall carbonate rocks resulted in the formation of layered skarn and generated CO2 or other gases. During the reaction, the ore‐forming fluid boiled and produced fractures when the pressure exceeded the overburden pressure. Themeteoric water mixed with the ore‐forming fluid along the fractures. The boiling changed the pressure and temperature, oxygen fugacity, physical and chemical conditions of the whole mineralization system. The escape of CO2 from the fluid by boiling resulted in scheelite precipitation. The fluid mixing and boiling reduced the solubility of metal sulfides and led the precipitation of chalcopyrite, molybdenite, pyrite and other sulfide. 相似文献
13.
黑龙江省老柞山金矿床位于兴蒙造山带东段佳木斯地块的中北部,是佳木斯金多金属成矿区的一座大型矿床,金主要赋存在NW向、NWW向的张性断裂及花岗岩和钙质大理岩、钙质片麻岩的接触构造带内,成矿与矽卡岩密切伴生。根据野外和室内研究,成矿阶段可划分为矽卡岩阶段、氧化物阶段、早期石英硫化物阶段、晚期石英硫化物阶段和石英-方解石阶段。为揭示流体演化过程,本文选择石榴子石、石英和方解石开展了流体包裹体研究。包裹体岩相学显示,流体包裹体类型有含子晶三相、气液两相（富液相、富气相）、纯液相和纯气相包裹体。测温结果表明：从早到晚均一温度依次为448~462、240~509、166~480、118~360和57~230℃;在矽卡岩阶段盐度（w（NaCl））为9.21%~10.37%,在氧化物阶段为1.73%~13.77%,中低盐度,在早期石英硫化物阶段为1.73%~23.71%和23.64%~39.66%,在晚期石英硫化物阶段为3.05%~6.44%,在石英-方解石阶段为1.73%~11.95%。高温中低盐度且富含CO2、H2O和少量CH4的初始成矿流体,在氧化物阶段流体"沸腾",CO2逃逸,生成磁铁矿;在早期石英硫化物阶段流体持续沸腾,pH值升高,由氧化转化为还原,卸载金和毒砂、黄铁矿等硫化物;在晚期石英硫化物阶段温度降低,卸载方铅矿、闪锌矿等低温矿物和金。因此,推测老柞山金矿床属于矽卡岩型金矿床。 相似文献
14.
Most skarn deposits are closely related to granitoids that intruded into carbonate rocks. The Cihai (>100 Mt at 45% Fe) is a deposit with mineral assemblages and hydrothermal features similar to many other typical skarn deposits of the world. However, the iron orebodies of Cihai are mainly hosted within the diabase and not in contact with carbonate rocks. In addition, some magnetite grains exhibit unusual relatively high TiO2 content. These features are not consistent with the typical skarn iron deposit. Different hydrothermal and/or magmatic processes are being actively investigated for its origin. Because of a lack of systematic studies of geology, mineral compositions, fluid inclusions, and isotopes, the genetic type, ore genesis, and hydrothermal evolution of this deposit are still poorly understood and remain controversial.The skarn mineral assemblages are the alteration products of diabase. Three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observations, which show a prograde skarn stage (garnet-clinopyroxene-disseminated magnetite), a retrograde skarn stage (main iron ore stage, massive magnetite-amphibole-epidote ± ilvaite), and a quartz-sulfide stage (quartz-calcite-pyrite-pyrrhotite-cobaltite).Overall, the compositions of garnet, clinpyroxene, and amphibole are consistent with those of typical skarn Fe deposits worldwide. In the disseminated ores, some magnetite grains exhibit relatively high TiO2 content (>1 wt.%), which may be inherited from the diabase protoliths. Some distinct chemical zoning in magnetite grains were observed in this study, wherein cores are enriched in Ti, and magnetite rims show a pronounced depletion in Ti. The textural and compositional data of magnetite confirm that the Cihai Fe deposit is of hydrothermal origin, rather than associated with iron rich melts as previously suggested.Fluid inclusions study reveal that, the prograde skarn (garnet and pyroxene) formed from high temperature (520–600 °C), moderate- to high-salinity (8.1–23.1 wt.% NaCl equiv, and >46 wt.% NaCl equiv) fluids. Massive iron ore and retrograde skarn assemblages (amphibole-epidote ± ilvaite) formed under hydrostatic condition after the fracturing of early skarn. Fluids in this stage had lower temperature (220°–456 °C) and salinity (8.4–16.3 wt.% NaCl equiv). Fluid inclusions in quartz-sulfide stage quartz and calcite also record similar conditions, with temperature range from 128° to 367 °C and salinity range from 0.2 to 22.9 wt.% NaCl equiv. Oxygen and hydrogen isotopic data of garnet and quartz suggest that mixing and dilution of early magmatic fluids with external fluids (e.g., meteoric waters) caused a decrease in fluid temperature and salinity in the later stages of the skarn formation and massive iron precipitation. The δ18O values of magnetite from iron ores vary between 4.1 and 8.5‰, which are similar to values reported in other skarn Fe deposits. Such values are distinct from those of other iron ore deposits such as Kiruna-type and magmatic Fe-Ti-V deposits worldwide. Taken together, these geologic, geochemical, and isotopic data confirm that Cihai is a diabase-hosted skarn deposit related to the granitoids at depth. 相似文献
15.
铜陵地区矽卡岩型独立金矿成矿深度探讨 总被引：1，自引：0，他引：1
采用矿床地质法和流体包裹体压力计法,对铜陵地区包村、朝山矽卡岩型独立金矿床的成矿深度进行了估算。据成矿相关岩体特征、金矿体延深、矿石特征等推断金矿化发生于浅成—中浅成环境。根据不同矿化阶段石英、方解石中流体包裹体的显微测温结果,估算成矿压力为650×105～850×105Pa,成矿深度介于2.5～3.2km,与矿床地质特征反映的成矿深度基本吻合,也与国内外同类矿床研究结果相符。综合认为铜陵地区矽卡岩型独立金矿床成矿深度为中浅成,脆性构造裂隙空间的压力骤然降低引起的流体不混溶和流体沸腾是金富集成矿的主要原因。 相似文献
16.
Fluid inclusions in calcite and diopside from the Xishimen skarn iron deposit in China were studied. The deposit ores were formed from chloride solutions with salinity ranging from 8.4 to 59.6 wt % NaCl equiv within the temperature range of 210 to 590°C. The model of skarn ore formation involving high-temperature magmatic fluids is discussed. 相似文献
17.
Skarns are developed over two temperature‐time intervals in calcite limestone adjacent to the southern extension of the Glenrock Granodiorite, a pluton of the Marulan Batholith, Southern Highlands, New South Wales. The initial volumetrically‐dominant prograde phase of skarn formation produced a suite comprising bimetasomatic skarn, including pyroxene endoskarn, potassic endoskarn and wollastonite‐bearing exoskarn, together with mineralogically‐zoned vein skarn, massive garnet‐pyroxene skarn and calcite‐vesuvianite skarn. Retrograde replacement is manifested by the development of hydrous silicate minerals, carbonate and cross‐cutting sulphide veinlets. A genetic model is proposed to account for the development of bimetasomatic skarn in the deposit. Exoskarn geochemistry indicates addition of many components relative to an essentially pure limestone precursor, including Si, Al, Fe, Zr, Zn, S, Mn and Cu, negligible transfer of K, Na and Rb and loss of CO2. Strontium and Ca loss from the parent limestone is indicated by mass balance calculations at constant volume. Garnet and pyroxene compositions in the massive garnet‐pyroxene skarn range from Gr30 to Gr66 and Hd61 to Hd87, respectively. Compositions from Gr67 to Gr95 are typical of the vein skarn garnets. Chemical zonation patterns in garnet, pyroxene and vesuvianite are generally characterized by rim Fe depletion relative to cores of grains. Prograde skarn probably formed at T = 500–580°C; P < 220 MPa. The massive garnet‐pyroxene skarn evolved under conditions of log fO2 = ‐18.9 to ‐22.9 (assuming a constant fCO2 of 20 MPa) within the fS2 stability field of pyrrhotite. Retrograde skarn formed at T < 400°C, possibly under conditions of XH2O < 0.01. Vesuvianite plus wollastonite assemblages, present in exoskarn, probably attest to very water‐rich conditions. The marble wall rocks, isolated from the source of skarn‐forming fluids, probably evolved under conditions of minimum Xco2 >0.2. Low temperature CO2 ‐rich fluid inclusions and prehnite (stable at Xco2 <0.01), present in the marble and skarn, respectively, suggest that substantial differences in Xco2: XH2O were maintained during cooling. Observed mineralogical and chemical zonation within the skarn reflects the complex interaction of T, P, fO2, Xco2 and other chemical variables such as aSiO2 and aAl2O3 throughout the skarn system. No single variable can account adequately for the mineralogical diversity observed in the skarn deposit. 相似文献
18.
19.
安徽青阳铜矿里钼多金属矿床是长江中下游成矿带内近年来新发现的一个夕卡岩型钼多金属矿床。对该矿床的地质特征和流体包裹体特征进行了详细研究,探讨了流体来源与演化过程。基于脉体穿插和矿物交代关系将铜矿里矿床的成矿过程划分为早期夕卡岩、晚期夕卡岩、石英辉钼矿、石英多金属硫化物和碳酸盐矿物5个阶段。显微观察表明铜矿里矿床的流体包裹体类型主要为富液相包裹体、富气相包裹体和含子晶三相包裹体。显微测温结果显示,早期成矿流体具有高温、中高盐度的特征,而晚期成矿流体具有低温、低盐度的特征。结合已有的氢、氧同位素数据,表明铜矿里矿床早期热液为岩浆热液,晚期有大气水加入。石英辉钼矿阶段石英中出现富液相、含子晶三相和富气相包裹体共存的现象,且这些包裹体均一温度相近,但均一方式截然不同,表明流体沸腾作用可能是导致铜矿里钼多金属矿床中钼元素沉淀的主要机制。 相似文献
20.
Fluid inclusions in skarns (carbonate replacement deposits) 总被引：7，自引：0，他引：7
T. A. P. KWAK 《Journal of Metamorphic Geology》1986,4(4):363-384
Abstract Fluid inclusions in ore skarn minerals reflect the physiochemical nature of the solutions present during the skarn-forming process. Because of the dense nature of skarn minerals and the dynamic processes operative during skarn genesis, sufficient primary fluid inclusions are usually present. Ore skarn solutions, as opposed to metamorphic skarn or ore vein solutions, have much higher CaCl2 contents and usually very high formation temperatures (>500°C) and salinities (>40 wt % T.D.S.). Temperatures and salinities generally decrease away from the solution source, both in time and space. The gradients found at greater distances from the source in distal (far from contact) skarns tend to be less (e.g. 210–350°C) for a particular skarn stage to that in proximal (near contact) skarns (e.g. 400–650°C). This information is useful for delineating the parts of such a hydrothermal system. Temperatures also tend to decrease with time, which is reflected by the superimposition of various overprinting, retrograde mineral stages. In a few areas (e.g. Naica, Mexico) intermittent boiling of ore solutions occurs, periodically elevating both temperatures and salinities, but commonly boiling only occurs early in skarn genesis just after an early, commonly lower temperature, phase. Most fluid inclusions represent a mix of‘exhaust’or reacted solutions with minor unreacted or new (pre-) ore solution components. Limited data on the distribution of elements present in fluid inclusions that do not normally take part in skarn genesis (Na, K and Cl) indicate that their proportions reflect the nature of the associated pluton. High KC1 contents are found in skarns adjacent to high K granitoids, whereas high NaCl contents are found in skarns adjacent to calcic granitoids. In many examples, daughter minerals present in minor proportions in opened fluid inclusion cavities reflect the metal characteristics of the ore solution. Small rare-earth metal, tungsten, zinc and copper daughter(?) minerals have been identified. The temperature and (or) salinity data for skarns of different metal or geological type is not particularly useful to delineate whether a skarn locality is part of a more complex, as yet unexplored system. Solutions in Pb–Zn skarns tend to be lower-temperature (150–400°C) and more dilute (<30 wt % T.D.S.) than in other skarn types, but exceptions occur. 相似文献