scholarly journals Ore Forming Fluid of Epithermal Quartz Veins at Cisuru Prospect, Papandayan District, West Java, Indonesia

2019 ◽  
Vol 4 (3) ◽  
pp. 170
Author(s):  
Kha Yay Oo ◽  
Wayan Warmada ◽  
Anastasia Dewi Titisari ◽  
Koichiro Watanabe
Keyword(s):  
Fluid Inclusion ◽  
Melting Temperature ◽  
Fluid Inclusions ◽  
Measurement Data ◽  
Homogenization Temperature ◽  
Salinity Range ◽  
Ice Melting ◽  
West Java ◽  
Quartz Veins ◽  
Lapilli Tuff

The Cisuru area is located in Talegong Sub-district, Garut Regency, West Java, Indonesia which is belongs to the central part of Southern Mountain Slope. The aim of this research is to understand the nature and characteristic of fluid inclusion from quartz veins (especially drill core samples) in the study area. Rock units in the area are characterized by Tertiary volcanic rocks and volcaniclastic sequence which is mainly composed of andesite, andesitic breccia, volcanic breccia, lapilli tuff, dacite and related to the intrusion of diorite. The Cisuru epithermal mineralization is dominantly hosted by andesite, dacite, breccia and lapilli tuff, and would probably be controlled by both permeable rocks and NS and NE-SW trending strike-slip faults. The mineralization is shown as void filling and replacement within the silica zone, veinlets along with the open space/fractures and dissemination. Fluid inclusion from quartz veins was studied to know nature, characteristics and origin of hydrothermal fluids. Microthermometric measurements of fluid inclusions were realized by using a Linkam THMSG 600 combined freezing and heating stages. Homogenization temperature and final ice melting temperature were measured for primary two-phase inclusion from quartz veins. Base on the study of the fluid inclusion, the value of homogenization temperature (Th) range from 200 ºC to 395 °C and ice melting temperature range from -0.1 to - 4.5 where salinity range from 0.2 to 7.2 wt. % NaCl equivalent. Fluid inclusion petrography and microthermometric measurement data exhibit that fluid mixing, dilution and boiling were main processes during the hydrothermal evolution.  The formation temperature of each quartz vein is 260 ºC to 290 ºC and also their formation depth is estimated between 560m to 925m respectively. Combination of fluid inclusions petrography, microthermometric measurement, and estimate paleo depth from Cisuru area were suggested under the epithermal environment.

scholarly journals FLUID INCLUSION STUDIES OF THE EPITHERMAL QUARTZ VEINS FROM SUALAN PROSPECT, WEST JAVA, INDONESIA

2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Myo Min Tun ◽  
I Wayan Warmada ◽  
Arifudin Idrus ◽  
Agung Harijoko ◽  
Okki Verdiansyah ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Fluid Mixing ◽  
Formation Temperature ◽  
West Java ◽  
Two Phase ◽  
Quartz Veins ◽  
Argillic Alteration ◽  
Trapping Temperature ◽  
Volcaniclastic Rocks

Sualan prospect is located at Talegong Sub-district of Garut Regency, West Java, Indonesia. The area constitutes calc-alkaline volcanic and volcaniclastic rocks of Tertiary age. The rocks have experienced regional propylitic and argillic alteration. Fluid inclusions from quartz veins were studied in order to constrain the nature, characteristics and evolution of fluids. Microthermometric measurements on fluid inclusion were carried out by freezing and heating experiment. Temperatures of homogenization (Th) and final melting of ice (Tm) were measured for primary, liquid-dominated, two-phase inclusions. The values of Th range from 160°C to 210°C and salinities range from 0.35 to 4.96 wt.% NaCl equiv. Formation temperature of the quartz veins are estimated at 180°C and 190°C and paleo-depth of formation are at 80m and 140m, respectively. Microthermometric data indicates that fluid mixing and dilution were important processes during the evolution of hydrothermal system. Based on fluid inclusion types, microthermometric data, trapping temperature, paleo-depth, texture of quartz and hydrothermal alteration types, quartz veins from prospect were developed under epithermal environment. Keywords: Quartz vein, fluid inclusions, microthermometry, salinities, formation temperature, paleo-depth, epithermal, Sualan prospect.

scholarly journals Fluid Inclusion Study Of The Polymetallic Epithermal Quartz Veins At Soripesa Prospect Area, Sumbawa Island, Indonesia

2015 ◽  
Vol 4 (2) ◽  
Author(s):  
Win Kant ◽  
I Wayan Warmada ◽  
Arifudin Idrus ◽  
Lucas Donny Setijadji ◽  
Koichiro Watanabe
Keyword(s):  
Fluid Inclusion ◽  
Melting Temperature ◽  
Eutectic Temperature ◽  
Homogenization Temperature ◽  
Fluid Inclusion Study ◽  
Quartz Veins ◽  
Sunda Arc ◽  
Engineering Department ◽  
Inclusion Study ◽  
Volcaniclastic Rocks

The Soripesa prospect area is located at Maria village, Wawo district, Bima region in the eastern part of Sumbawa Island, Indonesia. This area is a part of Cenozoic Calc-alkaline volcanic inner Banda-Sunda Arc. The dominant lithology of Soripesa prospect area are a lithic-crystal tuff of andesitic and dacitic composition and bedded limestone. There have five main polymetallic epithermal quartz veins in the Soripesa prospect area, namely, Rini vein, Jambu air vein, Dollah vein, Merpati vein, and Arif vein. Those quartz veins are hosted mainly in andesitic volcaniclastic rocks. Fluid inclusion study on those quartz veins is vey important to know the condition of hydrothermal fluids and their origin. Fluid inclusion study is conducted at the laboratory of Earth Resources Engineering Department, Kyushu University, Japan. Homogenization temperature, freeze temperature, eutectic temperature, and melting temperature can be known from fluid inclusion study. Based on fluid inclusion study, formation temperatures of all veins are between 250–260◦C. Melting temperature is between -0.2 to -3◦C. Based on the melting temperature, salinity (wt.% NaCl equiv.) of fluid inclusions is calculated by using Bodnar’s equation. Paleodepth of formations and pressure of trapping are also estimated by using formation temperature and salinity. Based on Hass (1971) diagram, estimated paleodepths of formations are 270 m for Merpati vein, 400 m for Dollah vein, 480 m for Rini vein, 570 m for Arif vein, and 680 m for Jambu Air vein, respectively. Pressure of trapping can also be estimated from depth of formation, density of lithostatic overburden, and gravity; 72 bars for Merpati vein, 106 bars for Dollah vein, 127 bars for Rini vein, 151 bars for Arif vien, and 180 bars for Jambu Air vein, respectively. Keywords: Soripesa, polymetallic quartz veins, homogenization temperature, salinity.

scholarly journals Fluid Inclusion Study of Epithermal Quartz Veins from the Kyaukmyet Prospect, Monywa Copper-Gold Ore Field, Central Myanmar

2021 ◽  
Vol 6 (4) ◽  
pp. 248-254
Author(s):  
Toe Naing Oo ◽  
Agung Harijoko ◽  
Lucas Donny Setijadji
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Phase Relationship ◽  
Fluid Inclusion Study ◽  
Mixing Processes ◽  
Rhyolite Lava ◽  
Gold Ore ◽  
Quartz Veins ◽  
Copper Gold ◽  
Lapilli Tuff

The Kyaukmyet prospect is located near the main ore bodies of the Kyisintaung and Sabetaung high-sulfidation Cu-Au deposits, Monywa copper-gold ore field, central Myanmar. Lithologic units in the research area are of mainly rhyolite lava, lapilli tuff and silicified sandstone, mudstone and siltstone units of Magyigon Formation which hosted to be polymetallic mineralization. Our field study recorded that epithermal quartz veins are hosted largely in rhyolite lava and lapilli tuff units. Those quartz veins show crustiform, banded (colloform), lattice bladed texture and comb quartz. The main objectives of the present research in which fluid inclusion studies were considered to conduct the nature, characteristics and hydrothermal fluids evolution from the epithermal quartz veins. In this research, there are three main types of fluid inclusions are classified according to their phase relationship (1) two-phase liquid-rich inclusions, (2) the coexisting liquid-rich and vapor-rich inclusions, and (3) only vapor-rich inclusions. Microthermometric measurements of fluid inclusions yielded homogenization temperatures (Th) of 148–282 °C and final ice-melting temperature (Tm)  of -0.2°C to -1.4°C . The value of (Tm) are equal to the salinities reaching up 0.35 to 2.07 wt % NaCl equiv. respectively. Estimation formation temperature of the quartz veins provide 190°C and 210°C and paleo-depth of formation are estimated to be between 130m and 210m. Petrography of fluid inclusion and microthermometric data suggest that fluid boiling as well as mixing processes were likely to be happened during the hydrothermal fluid evolution at the Kyaukmyet prospect. According to the characteristics of many parameters including petrography of fluid inclusion, microthermometric data, paleo-depth, evidence of quartz vein textures and types of hydrothermal alteration from the Kyaukmyet prospect allows to interpret these data to be the low-sulfidation epithermal system.

scholarly journals Fluid Evolution of Fuzishan Skarn Cu-Mo Deposit from the Edong District in the Middle-Lower Yangtze River Metallogenic Belt of China: Evidence from Petrography, Mineral Assemblages, and Fluid Inclusions

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-25
Author(s):  
Lu Zhang ◽  
Shao-Yong Jiang ◽  
Suo-Fei Xiong ◽  
Deng-Fei Duan
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Yangtze River ◽  
Homogenization Temperature ◽  
Lithostatic Pressure ◽  
Lower Permian ◽  
Fluid Evolution ◽  
Metallogenic Belt ◽  
Lower Yangtze ◽  
Vapor Liquid

The Fuzishan Cu-Mo deposit is located in the Edong district of the Middle-Lower Yangtze River Metallogenic Belt, China. The orebodies mainly occurred as lenticular and bedded shapes in the skarn zone between the Lower Permian Qixia Formation carbonate rocks and the quartz diorite. Four paragenetic stages have been recognized based on petrographic observations: (1) prograde skarn stage, (2) retrograde skarn stage, (3) quartz-sulfide stage, and (4) carbonate stage. Six fluid inclusion types were recognized: S1(vapor + liquid + halite ± other daughter minerals), S2(vapor + liquid + daughter minerals except halite), LV(rich liquid + vapor), VL(rich vapor + liquid), V (vapor), and L (liquid) types. Fluid inclusion studies show distinct variations in composition, final homogenization temperature, and salinity in four stages. Daughter minerals of the primary fluid inclusions include chalcopyrite, molybdenite, hematite, anhydrite, calcite, and halite in the prograde skarn stage and hematite, calcite, and sulfide (?) in the retrograde skarn stage. No daughter minerals occurred in the quartz-sulfide and carbonate stages. Final homogenization temperatures recorded in these stages are from 405 to >550°C, from 212 to 498°C, from 150 to 485°C, and from 89 to 223°C, respectively, while salinities are from 3.7 to 42.5, from 2.6 to 18.5, from 2.2 to 17.9, and from 0.2 to 11.5 wt.% NaCl equivalent, respectively. The coexisting VLand S1type fluid inclusions show similar homogenization temperature of 550 to about 650°C in the prograde skarn stage, indicating that immiscibility occurred at lithostatic pressure of 700 bars to perhaps 1000 bars, corresponding to a depth of 2.6 km to about 3.7 km. The coeval VLand LVtypes fluid inclusions with homogenization temperature of 350 to 400°C in the late retrograde skarn and quartz-sulfide stages suggest that boiling occurred under hydrostatic pressure of 150 to 280 bars, equivalent to a depth of 1.5 to 2.8 km. Mo mineralization in the retrograde stage predated Cu mineralization which mainly occurred in the quartz-sulfide stage. Fluid compositions indicate that ore-forming fluid has highfO2and rich Cu and Mo concentration in the early stage, while relatively lowerfO2and poor Cu and Mo concentration in the middle to late stages. Microthermometric data show a decreasing trend in temperature and salinity in the fluid evolution process. Decreasing temperature and boiling event may be the main factors that control the ore precipitation.

Chronology and orientation of N2–CH4, CO2-H2O, and H2O-rich fluid-inclusion trails in intrametamorphic quartz veins from the Cuiabá gold district, Brazil

1990 ◽  
Vol 54 (375) ◽  
pp. 245-255 ◽  
Author(s):  
C. J. S. de Alvarenga ◽  
M. Cathelineau ◽  
J. Dubessy
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Low Grade ◽  
Fluid Circulation ◽  
Raman Spectrometry ◽  
Mato Grosso ◽  
Spectrometry Analysis ◽  
Quartz Veins ◽  
Three Generations ◽  
Inclusion Trails

AbstractThe upper Proterozoic Cuiabá group of Mato Grosso, Brazil, is composed of low-grade clastic meta-sediments which have been folded by several successive tectonic events. Three generations of quartz veins are associated with the structural evolution of this area. The first veins are deformed by the main tectonic phases and show a complex deformational patterns. The second set is parallel to the cleavage and was formed syntectonically during the main folding phase, whilst the last quartz veins are related to a later stage of deformation. A systematic study of fluid inclusions in relation with a statistical study of microstructural markers (fluid inclusion trails, opened microcracks) was carried out on quartz veins from three localities. On the basis of microthermometric studies and Raman spectrometry analysis, four differents types of fluids have been distinguished, each trapped in specific fluid inclusion trails: (i) CO2-rich liquids and vapours (Lc, Vc) at Casa de Pedra, (ii) Lc and Vc inclusions with variable amounts of CO2, CH4, N2 in the vapour phase at BR-70, (iii) CH2-N2-rich vapours (Vn-m), and (iv) aqueous inclusions (L) with variable salinities representing the last fluid generations at all localities.At Casa de Pedra and BR-70, most fluids are observed within the three generations of quartz veins, indicating an important fluid circulation associated with the last phase of brittle deformation. Fluid inclusions of type (iii) and (iv) are oriented along several well defined directions. The study shows the importance of integrated microstructural and fluid-inclusion studies for understanding the geometry and chronology of fluid circulation.

scholarly journals Carbonic fluids in the Hamadi gold deposit, Sudan: origin and contribution to gold mineralization

2017 ◽  
Vol 54 (5) ◽  
pp. 494-511 ◽  
Author(s):  
Xi-hui Cheng ◽  
Jiu-hua Xu ◽  
Jian-xiong Wang ◽  
Qing-po Xue ◽  
Hui Zhang
Keyword(s):  
Gold Deposit ◽  
Melting Temperature ◽  
Fluid Inclusions ◽  
Gold Mineralization ◽  
Narrow Range ◽  
Shear Zones ◽  
Quartz Veins ◽  
Wide Range ◽  
Homogenization Temperatures ◽  
Gold Bearing

The Hamadi gold deposit is located in North Sudan, and occurs in the Neoproterozoic metamorphic strata of the Arabian–Nubian Shield. Two types of gold mineralization can be discerned: gold-bearing quartz veins and altered rock ores near ductile shear zones. The gold-bearing quartz veins are composed of white to gray quartz associated with small amounts of pyrite and other polymetallic sulfide minerals. Wall-rock alterations include mainly beresitization, epidotization, chloritization, and carbonatization. CO2-rich inclusions are commonly seen in gold-bearing quartz veins and quartz veinlets from gold-bearing altered rocks; these include mainly one-phase carbonic (CO2 ± CH4 ± N2) inclusions and CO2–H2O inclusions with CO2/H2O volumetric ratios of 30% to ∼80%. Laser Raman analysis does not show the H2O peak in carbonic inclusions. In quartz veins, the melting temperature of solid CO2 (Tm,CO2) of carbonic inclusions has a narrow range of −59.6 to −56.8 °C. Carbonic inclusions also have CO2 partial homogenization temperatures (Th,CO2) of −28.3 to +23.7 °C, with most of the values clustering between +4.0 and +20 °C; all of these inclusions are homogenized into the liquid CO2 state. The densities range from 0.73 to 1.03 g/cm3. XCH4 of carbonic fluid inclusions ranges from 0.004 to 0.14, with most XCH4 around 0.05. In CO2–H2O fluid inclusions, Tm,CO2 values are recorded mostly at around −57.5 °C. The melting temperature of clathrate is 3.8–8.9 °C. It is suggested that the lowest trapping pressures of CO2 fluids would be 100 to ∼400 MPa, on the basis of the Th,CO2 of CO2-bearing one-phase (LCO2) inclusions and the total homogenization temperatures (Th,tot) of paragenetic CO2-bearing two-phase (LCO2–LH2O) inclusions. For altered rocks, the Tm,CO2 of the carbonic inclusions has a narrow range of −58.4 to ∼−57.0 °C, whereas the Th,CO2 varies widely (−19 to ∼+29 °C). Most carbonic inclusions and the carbonic phases in the CO2–H2O inclusions are homogenized to liquid CO2 phases, which correspond to densities of 0.70 to ∼1.00 g/cm3. Fluid inclusions in a single fluid inclusion assemblage (FIA) have narrow Tm,CO2 and Th,CO2 values, but they vary widely in different FIAs and non-FIAs, which indicates that there was a wide range of trapping pressure and temperature (P–T) conditions during the ore-forming process in late retrograde metamorphism after the metamorphism peak period. The carbonic inclusions in the Hamadi gold deposit are interpreted to have resulted from unmixing of an originally homogeneous aqueous–carbonic mixture during retrogress metamorphism caused by decreasing P–T conditions. CO2 contributed to gold mineralization by buffering the pH range and increasing the gold concentration in the fluids.

Fluid Inclusion and Mineralization Epochs Studies of Luziyuan Pb-Zn Deposit in Yunnan Province, Southwestern China

2013 ◽  
Vol 734-737 ◽  
pp. 335-339 ◽  
Author(s):  
Fu Bin Cang ◽  
Ming Guo Deng ◽  
Wei Liu
Keyword(s):  
Low Temperature ◽  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Yunnan Province ◽  
Homogenization Temperature ◽  
Bimodal Distribution ◽  
Medium Density ◽  
Medium Temperature ◽  
Hydrothermal Mineralization ◽  
Distribution Mode

In the thesis, we studied fluid inclusions in minerals and mineralization epochs of Luziyuan Pb-Zn deposits in eastern of Zhenkang Yunnan province. 240 available data have been obtined by observing characteristics of fluid inclusions in sphalerite, quartz, fluorite, calcite under microscope and selecting 284 primary inclusions and secondary inclusions thermometry. Various mineralization epochs homogenization temperature, freezing temperatures, salinity frequency histogram showed a bimodal distribution mode. The fluid inclusions in sphalerite have a greatly important,it is ore-forming fluids. Its homogenization temperature distributed in 240 to 270°C (medium temperature) and 187 to 220°C (low temperature) within the range of two, (W NaCl) salinity is 5.0% to 10.6%. According to the homogenization temperature and salinity, it can be deduced Luziyuan mineralization fluids density of 0.82 to 0.96 (gcm-3). Draw the deposits are mainly two hydrothermal mineralization, a hydrothermal in medium temperature, another period of low and medium temperature. The two ore-forming fluids are medium salinity and medium-density.

scholarly journals Fluid Inclusion Characteristics of the Kışladağ Porphyry Au Deposit, Western Turkey

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 64 ◽  
Author(s):  
Nurullah Hanilçi ◽  
Gülcan Bozkaya ◽  
David A. Banks ◽  
Ömer Bozkaya ◽  
Vsevolod Prokofiev ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Meteoric Water ◽  
High Salinity ◽  
Gold Mineralization ◽  
Magmatic Fluid ◽  
Salinity Range ◽  
Western Turkey ◽  
Magmatic Complex ◽  
Low Salinity

The deposit occurs in a mid-Miocene monzonite magmatic complex represented by three different intrusions, namely Intrusion 1 (INT#1), Intrusion 2 (INT#2, INT #2A), and Intrusion 3 (INT#3). Gold mineralization is hosted in all intrusions, but INT#1 is the best mineralized body followed by INT#2. SEM-CL imaging has identified two different veins (V1 and V2) and four distinct generations of quartz formation in the different intrusions. These are: (i) CL-light gray, mosaic-equigranular quartz (Q1), (ii) CL-gray or CL-bright quartz (Q2) that dissolved and was overgrown on Q1, (iii) CL-dark and CL-gray growth zoned quartz (Q3), and (iv) CL-dark or CL-gray micro-fracture quartz fillings (Q4). Fluid inclusion studies show that the gold-hosted early phase Q1 quartz of V1 and V2 veins in INT#1 and INT#2 was precipitated at high temperatures (between 424 and 594 °C). The coexisting and similar ranges of Th values of vapor-rich (low salinity, from 1% to 7% NaCl equiv.) and halite-bearing (high salinity: >30% NaCl) fluid inclusions in Q1 indicates that the magmatic fluid had separated into vapor and high salinity liquid along the appropriate isotherm. Fluid inclusions in Q2 quartz in INT#1 and INT#2 were trapped at lower temperatures between 303 and 380 °C and had lower salinities between 3% and 20% NaCl equiv. The zoned Q3 quartz accompanied by pyrite in V2 veins of both INT#2 and INT#3 precipitated at temperatures between 310 and 373 °C with a salinity range from 5.4% to 10% NaCl eq. The latest generation of fracture filling Q4 quartz, cuts the earlier generations with fluid inclusion Th temperature range from 257 to 333 °C and salinity range from 3% to 12.5% NaCl equiv. The low salinity and low formation temperature of Q4 may be due to the mixing of meteoric water with the hydrothermal system, or late-stage epithermal overprinting. The separation of the magmatic fluid into vapor and aqueous saline pairs in the Q1 quartz of the V1 vein of the INT#1 and INT#2 and CO2-poor fluids indicates the shallow formation of the Kışladağ porphyry gold deposit.

Carbon and oxygen isotopic composition of fluid inclusion CO2 and CH4 within the Archean Junction gold deposit, Kambalda, Western Australia

2021 ◽  
Vol 59 (5) ◽  
pp. 1111-1131
Author(s):  
Paul A. Polito ◽  
Thomas K. Kyser ◽  
April Vuletich ◽  
Yvonne Bone
Keyword(s):  
Stable Isotope ◽  
Fluid Inclusion ◽  
Isotopic Composition ◽  
Gold Deposit ◽  
Fluid Inclusions ◽  
Soil Gas ◽  
Isotopic Equilibrium ◽  
Quartz Veins ◽  
Alteration Minerals ◽  
Isotope Studies

ABSTRACT The Junction orogenic gold deposit in the St Ives district of Western Australia is characterized by a syn-gold mineral assemblage dominated by quartz-calcite-albite-biotite-chlorite-pyrrhotite. The deposit had a light hydrocarbon,CO2, and O2 soil-gas signature above known mineralization prior to mining and it has been proposed that the source of the light hydrocarbon gases in the soil was gas-rich fluid inclusions trapped in gold-related alteration minerals, particularly calcite, albite, quartz, and pyrrhotite. Linking the soil gases with those in the deposit is extremely difficult. However, establishing that the gases in the soil are indeed present within the deposit and that those gases are related to the syn-Au alteration minerals is achievable through stable-isotope studies. Carbon and O stable-isotope compositions of pre-gold, syn-gold, and post-gold quartz veins; syn-gold and post-gold calcite; and CO2 and CH4 in the fluid inclusions that each of these minerals host were investigated to establish if the various mineral and fluid-gas species in the deposit are in isotopic equilibrium with each other, an important first step to relate syn-ore minerals with the relevant gases. Pre-ore Mo-type quartz veins contain CO2 (δ13Cgas = –1‰) and CH4 (δ13Cgas = ca. –33‰) in fluid inclusions at a ratio of ca. 93:7. The paucity of Mo-type quartz veins in the deposit suggests that these veins were not the main source of the soil-gas signature. Syn-gold alteration post-dates the Mo-type quartz veins. Quartz and co-existing calcite in the Au-bearing Junction shear zone have δ18Omineral values around 12.0 and 10.5‰, respectively. Multiple co-existing quartz-calcite pairs indicate that gold deposition occurred at ∼400 °C. This temperature agrees with mineral equilibria temperature estimates, the entrapment temperatures of fluid inclusions, and temperature modelling of solid-solution mineral phases. The temperature dictates that the quartz and calcite are in isotopic equilibrium with each other. The calcite in the Junction shear zone has δ13Cmineral values from –7.4 to –2.5‰, indicating that the CO2-rich ore fluid had a δ13Cfluid value of –3.7 ± 0.9‰. CO2 and CH4 released from quartz-hosted fluid inclusions have δ13Cgas values from –4.3 to +3.5‰ (mean = –1.5 ± 1.9‰) and –50.5 to –35.2‰, respectively. The isotopic composition of the fluid inclusion CO2 is in disequilibrium with co-existing CH4 that was co-released from the same quartz vein and the calculated δ13Cfluid value from co-existing calcite. Isotopic mass balance calculations using the two co-released gases show that the CO2 was initially in equilibrium with the syn-ore calcite but has since re-equilibrated with CH4 at temperatures below 200 °C. The abundance of CH4 in some quartz veins suggests that the syn-gold vein assemblage could be the source for the soil-gas anomaly. Post-gold veins contain quartz and calcite that have δ18Omineral values of ca. 11.0 and 10.0‰, respectively. Individual mineral pairs indicate precipitation at ∼320 °C from a fluid with a δ18Ofluid value of 4.7 ± 0.9‰, distinct from that which formed the syn-gold quartz veins. The post-gold calcite has δ13Ccalcite values from –7.5 to –5.4‰, indicative of formation from a CO2-bearing fluid having a δ13Cfluid value of –4.6 ± 0.9‰. The δ13Cfluid values are indistinguishable from fluid inclusion CO2 values of –3.6 ± 0.9‰, indicating no post entrapment re-equilibration, which suggests that CH4 was at trace volumes or absent in the post-gold quartz veins. These data lead to the conclusion that post-entrapment reequilibration between fluid inclusion CO2 and CH4 has occurred, but that the two gases were likely in equilibrium at the time of entrapment. This has implications for the interpretation of C isotope studies that focus on fluid inclusion CO2 measured from other gold and base-metal deposits, especially when the isotopic value of that CO2 is assumed to represent a specific source for the ore-forming fluids. The data also lead to a model that proposes that the syn-gold alteration assemblage could have produced the soil-gas anomalies observed above the mineralization.

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