Mineralization Characteristics of the Hokuryu Epithermal Au‐Ag Deposit, Hokkaido, Japan

Fluid inclusion characteristics as an indicator for tungsten mineralization in the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China

Gold ores of the Qiyugou deposit in the eastern part of the Xiong'ershan region are hosted in breccia pipes within a Mesozoic granitic porphyry. Three stages of hydrothermal alteration activity are recognized within the Qiyugou breccias. The first stage of hydrothermal metasomatism produced extensive K-feldspar alteration. The second stage is associated with deposition of gold and base metal sulphides. The third stage is defined by fine quartz–calcite ± pyrite veinlets containing minor gold. Four types of fluid inclusions are present in quartz and calcite within the breccia matrix and veins. Type I are solid(s)-bearing high-salinity fluid inclusions, with homogenization temperatures up to 420°C and high salinities of 31–47 wt% NaCl equivalent. Type II are two-phase, vapour-rich fluid inclusions that homogenized between 265 and 476°C, with low to moderate salinities (7.2–19.8 wt% NaCl equivalent). Homogenization of Type III two-phase, liquid-rich fluid inclusions takes place at temperatures between 109 and 253°C, with salinities of 3.9–14.3 wt% NaCl equivalent. Type IV two/three-phase carbonic fluid inclusions are only found in calcite–quartz veins cutting wall rocks in the upper parts of the pipes or in adjacent country rocks, with homogenization temperatures that range from 239 to 315°C and salinities between 9.2 and 12.2 wt% NaCl equivalent. The coexistence of Types I and II in the middle parts of the breccia pipes suggests that these fluid inclusions either resulted from trapping of boiling fluids or represented immiscible fluids, most likely derived from a granitic magma. The fluid history, reflected in the fluid-inclusion characteristics, was complex, involving variable amounts of boiling, cooling and mixing in the breccia pipe system. values ( − 101.7 to − 60.1‰) and values (0.3–7.5‰) calculated from inclusion water in quartz on the basis of mean-to-maximum fluid inclusion homogenization temperatures are intermediate between magmatic water and surface-derived fluids (meteoric water). Ranges for δ34S values of ore sulphides ( − 3.0 to 0.8‰) suggest that sulphur originated directly from a magmatic (mantle) source or indirectly from leaching/desulphidation of primary magmatic sulphide minerals. The combined fluid-inclusion and stable-isotope data support previous proposals for a genetic relationship between the Qiyugou ores and magmatic fluids.

Fluid types and their genetic meaning for the BIF-hosted iron ores, Krivoy Rog, Ukraine

The origin and evolution of skarn-forming fluids from the Phu Lon deposit, northern Loei Fold Belt, Thailand: Evidence from fluid inclusion and sulfur isotope studies

The Baiyinchang massive sulfide Cu deposit (Zheyaoshan and Huoyanshan mines) is hosted by an early Cambrian, submarine, felsic volcanic succession within an extrusive cryptodome associated with an overlying basaltic flow, in a Late Proterozoic-early Paleozoic submarine volcanic belt in the north Qilian orogen, north-western China. The deposit is comprised of two mineralized zones: a 30-cm-thick, strata-bound Zn-rich sulfide lens associated with hematitic Fe-Mn cherts, and an underlying, discordant massive ore-dominated sulfide zone enveloped by a hydrothermal alteration pipe that is zoned from chlorite in the center to quartz-sericite at the margin. The discordant sulfide zone accounts for 90 percent of the Cu reserves of the Zheyaoshan mine. It consists of four main ore types: (1) pipelike pyrrhotite-pyrite chalcopyrite ore, (2) massive sulfide ore, (3) a disseminated ore halo, and (4) footwall stringer ore. The pyrrhotite-pyrite chalcopyrite pipe has an elliptical shape in plan and is 30 50 m across. The pipe partially replaces the overlying massive pyrite lens and extends downward at least 150 m, to be gradually replaced by chalcopyrite-rich stringer veins and chalcopyrite-bearing quartz veins surrounded by a discordant hydrothermal alteration envelope. Massive chalcopyrite-pyrite lenses discordant to volcanic bedding, containing relict patches of felsic volcanic host rocks, are commonly enveloped by a disseminated sulfide halo within a chloritized volcanic unit. These features suggest that Zheyaoshan is a pipe-style deposit that formed mainly by subsea-floor replacement of volcanic host rocks. Studies of fluid inclusions indicate that there are four types: (1) type I two-phase, aqueous fluid inclusions, (2) type II daughter mineral-bearing, multiphase fluid inclusions, (3) type III CO 2-rich fluid inclusions, and (4) type IV CH 4-rich fluid inclusions. Type II inclusions have high homogenization temperatures (T h) ranging from 320 to 430C, contain high salinity fluids (31-38 wt % NaCl equiv), and coexist with CO 2-rich fluids found in vapor-rich, high-T h (up to 487C), moderate salinity (10-16 wt % NaCl equiv) inclusions in the discordant sulfide zone and associated altered rocks, suggesting a possible contribution of a magmatic fluid to the hydrothermal system. The coexistence of vapor-rich, high-T h (>300C) and aqueous, low-T h (<220C) type I fluid inclusions in the stringer zone suggests that heated seawater mixed with magmatic fluid (gas) in the feeder zone. Most type I fluid inclusions in the massive chalcopyrite-pyrite body and in the strongly chloritized pipe have a low T h (62-225C) and high salinities (15.0-23.0 wt % NaCl equiv), suggesting that a dense brine zone developed in fractures in the subsea floor where sulfides accumulated by open-space filling and replacement of host volcanic rocks. Eleven quartz samples from the overlying discordant sulfide zone yielded a restricted range of 18O values between 8.8 and 11.1 per mil, from which we calculate that the corresponding hydrothermal fluids had 18O values ranging from -5.3 to +3.1 per mil over a temperature range of 160 to 278C. Whole-rock 18O values for the altered volcanic rocks in the pipe yielded a much wider range, from 1.6 per mil in the chlorite core to 8.7 per mil in the outer sericite-chlorite zone, suggesting that a low- 18O seawater-dominated hydrothermal fluid interacted with the footwall volcanic rocks. Oxygen isotope data for quartz from both the stringer zone and the altered host volcanic rocks also record a contribution of the magmatic fluid to the Zheyaoshan submarine hydrothermal system. Assuming that the analyzed quartz precipitated from a hot (300-430C) hydrothermal fluid, as suggested by the high-temperature and high-salinity fluid inclusion data, the 18O values of the hydrothermal fluid in equilibrium with quartz ( 18O values of 9.0-11.1) range from 2.0 to 8.0 per mil, which corresponds to the 18O range between magmatic fluid and seawater. The ore-forming fluids responsible for the Cu-Zn mineralization at Baiyinchang belonged to the H 2O-NaCl- CO 2-CH 4 system. A felsic magma chamber is thought to have been situated 1 to 1.5 km below the sea floor, and this likely supplied the necessary heat to drive seawater convection and introduced an H 2O + CO 2-dominated, high-temperature, high-salinity (magmatic) brine to the Baiyinchang hydrothermal system. A narrow, steeply dipping, funnel-shaped brine zone was present in the margin of the fracture zone above the magma chamber, and this was trapped within the porous felsic volcaniclastic rocks. This brine zone is considered to have been the key factor for the formation of the Zheyaoshan pipe-shaped sulfide orebodies. The Cu-bearing, high-temperature (>300C) fluids are considered to be the product of mixing of magmatic brine with seawater and the replacement of the surrounding volcanic rocks resulted in the formation of the discordant, massive ore-dominated sulfide orebodies at Zheyaoshan. 2008 Society of Economic Geologists, Inc.

The Proterozoic, carbonate-hosted, Zawarmala Pb-Zn deposit has stratiform, banded pyrite-sphalerite ore, as well as discordant, sphalerite-galena veins and rich massive galena ore shoots. The mechanisms of deposition of discordant vein and massive ores have been studied using speciation and solubility calculations based on ore fluid characteristics and physical parameters inferred from petrography, fluid inclusion studies, and leachate analysis. Massive galena ore, which is the economic ore type, cuts across the earlier, F2-related, vein-type ore and is distinct from the vein-type ore in terms of mineralogy, texture, and fluid inclusion characteristics. Fluid inclusions in quartz associated with the ores show that fluids forming vein-type ore are low-salinity (4.3–14.7 wt % NaCl equiv) H2O-NaCl fluids. The trapping temperature of vein-type ore fluid was estimated to be in the range of 395° to 290°C at a pressure of about 1,450 bars. Fluids associated with massive galena ore are H2O-CO2-NaCl fluids of lower salinity (about 3–4 wt % NaCl equiv). The wide variation in XCO2 of fluid inclusions that occur in close proximity to each other within the same sample of massive ore suggests heterogeneous entrapment of the low-salinity H2O-CO2-NaCl fluids. From the intersection of isochores of local, homogeneously entrapped CO2 and aqueous biphase fluids of unmixed CO2-H2O-NaCl fluid, trapping temperature fluid was estimated to be between 250° and 150°C at pressures of 2,000 to 750 bars. Despite the low salinity of the ore fluids, speciation studies show that chloride complexes are dominant over most of the temperature range of interest in both ore fluids. The only bisulfide complex of importance is \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(Pb(HS)_{2}^{0}\) \end{document}, which is dominant below 175°C in fluids associated with massive galena ore. Data from fluid inclusions and solubility calculations reveal that cooling is the important mechanism of vein-type ore deposition. In contrast, physicochemical data indicate that an increase in reduced sulfur, by mixing a regional, high metal content, low sulfur fluid with a local, high sulfur fluid at the site of deposition, was the mechanism for massive galena ore deposition. The difference in oxidation state (and therefore also in metal content) of the two fluids is inferred to be a significant factor that caused differences in the modes of deposition of the two ore types and the relatively high value of XCO2 (0.2033) in fluids associated with massive galena ore.

The Keweenaw Peninsula is famous for hosting the largest accumulation of native copper anywhere in the world. Previous studies have looked for the fluids responsible for creating the native copper deposits but were unable to conclusively demonstrate that fluid inclusions can provide valuable insight into the hydrothermal/metamorphogenic fluids responsible for these unique deposits.

Geochemical study of calcite veins in the Silurian and Devonian of the Barrandian Basin (Czech Republic): evidence for widespread post-Variscan fluid flow in the central part of the Bohemian Massif

A fluid inclusion study of the Fosterville Mine: a turbidite-hosted gold field in the Western Lachlan Fold Belt, Victoria, Australia

We studied the fluid inclusions of the Jiguanshan Mo deposit in China, which is a large porphyry deposit located in the southern Xilamulun Metallogenic Belt. The irregular Mo ore body with various types of hydrothermal veinlets is hosted by Late Jurassic granite porphyry. Intense hydrothermal alterations in the deposit from the core to margin are silicification–potassium feldspar alteration, pyrite–quartz–sericite–fluorite alteration, and propylitic alteration. Based on the mineral assemblages and crosscutting relationships of ore veins, the ore-forming process were divided into three stages and two substages: quartz–pyrite veins (stage I) associated with potassic alteration; quartz–molybdenite–chalcopyrite–pyrite veins (substage II-1) and quartz–molybdenite–fluorite veins (substage II-2) associated with phyllic alteration; and fluorite–quartz–carbonate veins (stage III) with carbonation. Five major fluid inclusions (FIs) types were distinguished in the quartz associated with oxide and sulfide minerals, i.e. polyphase brine (Pb-type), opaque-bearing brine (Ob-type), solid halite (S-type), two-phase aqueous (A-type), and vapor (V-type) inclusions. The FIs of stage I were composed of liquid-rich S-, A-, and V-type FIs with homogenization temperatures and salinities of 490 to 511 °C and 8.9 to 56.0 wt% NaCl equiv., respectively. The FIs of substage II-1 are composed of Pb-, Ob-, S-, A-, and V-type FIs with homogenization temperatures and salinities of 352 to 460 °C and 3.7 to 46.1 wt% NaCl equiv, respectively. The FIs of substage II-2 are Ob-, S-, A-, and V-type FIs with homogenization temperatures and salinities of 234 to 309 °C and 3.7 to 39.2 wt% NaCl equiv, respectively. The FIs of stage III are A-type FIs with homogenization temperatures and salinities of 136 to 172 °C and 1.1 to 8.9 wt% NaCl equiv, respectively. Fluid boiling, which resulted in the precipitation of sulfides, occurred in stages I and II. The initial ore-forming fluids of the Jiguanshan deposit had high temperature, high salinity, and belonged to an F-rich NaCl ± KCl–H2O system. The fluids gradually evolved to low temperature, low salinity, and belonged to a NaCl–H2O system. Studies of the hydrogen and oxygen isotope compositions of quartz (δ18OH2O = − 7.3 to 6.3‰, δDH2O = − 104.3 to − 83.3‰) show that the ore-forming fluids gradually evolved from magmatic water to meteoric water.

Origin of the intrusion-related Lang Vai gold-antimony district (Northeastern Vietnam): Constraints from fluid inclusions study and C[sbnd]O[sbnd]S[sbnd]Pb isotope systematics

Geology, ore-forming fluid and genesis of the Qiucun gold deposit: Implication for mineral exploration at Dehua prospecting region, SE China

The Kyaikhto gold district is located within the Slate Belt and Mogok Metamorphic Belt of Southern Myanmar. The study area is covered by Carboniferous to Lower Permian metasedimentary rocks consisting of slate, phyllite, and schist of the Mergui Group, intruded by later igneous rocks. Four gold occurrences have been identified in the Kyaikhto district: the Kunzeik in the north, Zibyaung, and Thae Phyu Chaung in the center and Meyon in the south. Gold mineralization in the Kyaikhto district is associated with sheeted, stockwork, dissemination, and sulfide-bearing quartz veins. Ore minerals recognized include sphalerite, galena, chalcopyrite, molybdenite and pyrite with minor native gold and electrum. Two types of fluid inclusions were examined in the quartz samples of the Kunzeik and Zibyaung—Type A: aqueous carbonic fluid inclusions and Type B: aqueous fluid inclusions. At the Kunzeik, Type A fluid inclusions homogenize at temperatures from 296°C to 376°C with low salinities (1.6 - 4.6 wt% NaCl equivalent). The homogenization temperatures of Type B fluid inclusions in vein quartz range from 246°C to 312°C, with salinities of between 1.2 and 10.7 wt% NaCl equivalent. In the Zibyaung, the homogenization temperatures of Type A inclusions vary from 305°C to 378°C, with salinities from 4.6 to 9.6 wt% NaCl equivalent. The homogenization temperatures of Type B fluid inclusions mainly range from 242°C to 298°C, with salinities from 0.9 to 11.8 wt% NaCl equivalent. These characteristics of fluid inclusions are similar to those of orogenic gold mineralization systems.

Fluid evolution characteristics and ore genesis in the Jinqu Au deposit, Qinling Orogen, China: Implications for ore genesis

Geology, geochemistry, fluid inclusion data, stable isotope characteristics, and ore genesis of the Barout Aghaji gold deposit, NW Zanjan, Iran