Quartz precipitation and fluid inclusion characteristics in sub-seafloor hydrothermal systems associated with volcanogenic massive sulfide deposits

AbstractResults of a numerical modeling study of quartz dissolution and precipitation in a sub-seafloor hydrothermal system have been used to predict where in the system quartz could be deposited and potentially trap fluid inclusions. The spatial distribution of zones of quartz dissolution and precipitation is complex, owing to the fact that quartz solubility depends on many inter-related factors, including temperature, fluid salinity and fluid immiscibility, and is further complicated by the fact that quartz exhibits both prograde and retrograde solubility behavior, depending on the fluid temperature and salinity. Using the PVTX properties of H2O-NaCl, the petrographic and microthermometric properties of fluid inclusions trapped at various locations within the hydrothermal system have been predicted. Vapor-rich inclusions are trapped as a result of the retrograde temperature-dependence of quartz solubility as the convecting fluid is heated in the vicinity of the magmatic heat source. Coexisting liquid-rich and vapor-rich inclusions are also trapped in this region when quartz precipitates as a result of fluid immiscibility that lowers the overall bulk quartz solubility in the system. Fluid inclusions trapped in the shallow subsurface near the seafloor vents and in the underlying stockwork are liquid-rich with homogenization temperatures of 200–400°C and salinities close to that of seawater. Volcanogenic massive sulfide (VMS) deposits represent the uplifted and partially eroded remnants of fossil submarine hydrothermal systems, and the relationship between fluid-inclusion properties and location within the hydrothermal system described here can be used in exploration for VMS deposits to infer the direction towards potential massive sulfide ore.

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Subcritical Phase Separation and Occurrence of Deep-Seated Brines at the NW Caldera Vent Field, Brothers Volcano: Evidence from Fluid Inclusions in Hydrothermal Precipitates

Geofluids ◽

10.1155/2020/8868259 ◽

2020 ◽

Vol 2020 ◽

pp. 1-22

Author(s):

Alexander Diehl ◽

Cornel E. J. de Ronde ◽

Wolfgang Bach

Keyword(s):

Phase Separation ◽

Fluid Inclusion ◽

Fluid Inclusions ◽

Hydrothermal Vents ◽

Massive Sulfide ◽

Growth Conditions ◽

Hydrothermal Systems ◽

Small Subset ◽

Large Area ◽

Black Smoker

The northwestern caldera wall of Brothers volcano in the southern Kermadec arc features several clusters of hydrothermal venting in a large area that extends from near the caldera floor (~1700 mbsl) almost up to the crater rim (~1300 mbsl). Abundant black smoker-type hydrothermal chimneys and exposed stockwork mineralization in this area provide an excellent archive of hydrothermal processes that form seafloor massive sulfide deposits. Using sulfate precipitates from chimneys and stockwork recently recovered by remotely operated vehicles, we conducted fluid inclusion microthermometry and Sr isotope studies to determine the role of phase separation and mixing between vent fluid and seawater. The variability in the vast majority of fluid inclusion salinities (i.e., 0.1–5.25 wt.% NaCl eq.) and entrapment temperatures of up to 346°C are indicative of phase-separated hydrothermal fluids. Large salinity variations in samples with entrapment temperatures mostly below the boiling temperature for the sample’s depth show that the majority of fluids ascending below the NW Caldera are phase separating in the subsurface and cooling, prior to discharge. In several samples, entrapment temperatures of over 343°C suggest that phase-separating fluids have at least sporadically exited the seafloor at the NW Caldera site. Isobaric-isenthalpic mixing trends between coexisting phase-separated vapors and brines with seawater are consistent with phase-separated fluids at near-seafloor pressures of ~170 bar and suggest that the vast majority of the ascending fluids continue to phase separate to within tens to hundreds of meters below seafloor prior to mixing with seawater. A small subset of the most saline fluid inclusions (up to 18.6 wt.% NaCl eq.) is unlikely formed by near-seafloor phase separation and is considered to be produced either by supercritical phase separation or by the contribution of a magmatic brine from near the magmatic-hydrothermal interface. 87Sr/86Sr values of sulfate samples range from 0.7049 (i.e., near hydrothermal end-member) to 0.7090 (i.e., near seawater) and show that the crystals grew from vapor- and brine-derived fluids in a hydrothermally dominated mixing regime. Our work provides new insights into mineral growth conditions, mixing regimes, and in particular, the extent and character of subseafloor phase separation during the formation of hydrothermal vents and their underlying stockwork in seawater-dominated, arc-related hydrothermal systems.

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Reconstruction of Hydrothermal Processes in the Cyprus Type Fe-Cu-Zn Deposits of the Italian Northern Apennines: Results of Combined Fluid Inclusion Microthermometry, SEM-CL Imaging and Trace Element Analyses by LA-ICP-MS

Minerals ◽

10.3390/min11020165 ◽

2021 ◽

Vol 11 (2) ◽

pp. 165

Author(s):

Gabriella B. Kiss ◽

Zsolt Bendő ◽

Giorgio Garuti ◽

Federica Zaccarini ◽

Edit Király ◽

...

Keyword(s):

Fluid Inclusion ◽

Trace Element ◽

Fluid Inclusions ◽

Massive Sulfide ◽

Hydrothermal Activity ◽

Hydrothermal Systems ◽

Original Position ◽

Volcanogenic Massive Sulfide ◽

Hydrothermal Conditions ◽

Icp Ms

Quartz from the stockwork zone of various Cyprus type volcanogenic massive sulfide deposits (Boccassuolo, Reppia, Campegli, Bargone and Vigonzano) from the unmetamorphosed, Jurassic Northern Apennine ophiolites was studied in order to provide details on the submarine hydrothermal conditions and the characteristics for ore formation. Our detailed SEM-CL investigation of quartz contributed to a robust characterization and interpretation of primary fluid inclusions and microthermometry data. SEM-CL imaging was also useful for reconstructing the consecutive steps of quartz precipitation. The determination of trace element contents according to growth zoning in quartz by LA-ICP-MS constrained the compositional variations of parent fluids during the hydrothermal activity. A continuously cooling fluid regime characterized each studied volcanogenic massive sulfide (VMS) occurrence although the minimum formation temperatures were different (Bargone: 110–270 °C; Boccassuolo: 60–360 °C; Campegli: 110–225 °C; Reppia: 50–205 °C; Vigonzano: 260–330 °C), the range of temperature most probably depends on the original position of sampling in relation to the centers of the hydrothermal systems. Compositional changes are reflected by variations in the methane content (0.13–0.33 mol/kg) and salinity (2.6–9.3 NaCl equiv. wt. %) in the fluid inclusions of quartz and calcite as well as a changeable Al content (11–1526 ppm) in quartz. This study demonstrates that the combined use of SEM-CL imaging and LA-ICP-MS analyses, coupled with fluid inclusion microthermometry, can constrain the different fluid conditions of ore forming and the barren stages of evolving submarine hydrothermal systems.

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The Westwood Deposit, Southern Abitibi Greenstone Belt, Canada: An Archean Au-Rich Polymetallic Magmatic-Hydrothermal System—Part II. Hydrothermal Alteration, Mineralization, and Geologic Model

Economic Geology ◽

10.5382/econgeo.4879 ◽

2021 ◽

Author(s):

D. Yergeau ◽

P. Mercier-Langevin ◽

B. Dubé ◽

V. McNicoll ◽

S. E. Jackson ◽

...

Keyword(s):

Hydrothermal System ◽

Greenstone Belt ◽

Massive Sulfide ◽

Alteration Zone ◽

Intrusive Complex ◽

Calc Alkaline ◽

Abitibi Greenstone Belt ◽

The North ◽

Vms Deposits ◽

Ore Zones

Abstract The Westwood deposit, located in the Archean Doyon-Bousquet-LaRonde mining camp in the southern Archean Abitibi greenstone belt, contains 4.5 Moz (140 metric t) of gold. The deposit is hosted in the 2699–2695 Ma submarine, tholeiitic to calc-alkaline volcanic, volcaniclastic, and intrusive rocks of the Bousquet Formation. The deposit is located near the synvolcanic (ca. 2699–2696 Ma) Mooshla Intrusive Complex that hosts the Doyon epizonal intrusion-related Au ± Cu deposit, whereas several Au-rich volcanogenic massive sulfide (VMS) deposits are present east of the Westwood deposit. The Westwood deposit consists of stratigraphically stacked, contrasting, and overprinting mineralization styles that share analogies with both the intrusion-related and VMS deposits of the camp. The ore zones form three distinct, slightly discordant to stratabound corridors that are, from north (base) to south (top), the Zone 2 Extension, the North Corridor, and the Westwood Corridor. Syn- to late-main regional deformation and upper greenschist to lower amphibolite facies regional metamorphism affect the ore zones, alteration assemblages, and host rocks. The Zone 2 Extension consists of Au ± Cu sulfide (pyrite-chalcopyrite)-quartz veins and zones of disseminated to semimassive sulfides. The ore zones are spatially associated with a series of calc-alkaline felsic sills and dikes that crosscut the mafic to intermediate, tholeiitic to transitional, lower Bousquet Formation volcanic rocks. The metamorphosed proximal alteration consists of muscovite-quartz-pyrite ± gypsum-andalusite-kyanite-pyrophyllite argillic to advanced argillic-style tabular envelope that is up to a few tens of meters thick. The North Corridor consists of auriferous semimassive to massive sulfide veins, zones of sulfide stringers, and disseminated sulfides that are hosted in intermediate volcaniclastic rocks at the base of the upper Bousquet Formation. The Westwood Corridor consists of semimassive to massive sulfide lenses, veins, zones of sulfide stringers, and disseminated sulfides that are located higher in the stratigraphic sequence, at or near the contact between calc-alkaline dacite domes and overlying calc-alkaline rhyodacite of the upper Bousquet Formation. A large, semiconformable distal alteration zone that encompasses the North Corridor is present in the footwall and vicinity of the Westwood Corridor. This metamorphosed alteration zone consists of an assemblage of biotite-Mn garnet-chlorite-carbonate ± muscovite-albite. A proximal muscovite-quartz-chlorite-pyrite argillic-style alteration assemblage is associated with both corridors. The Zone 2 Extension ore zones and associated alteration are considered synvolcanic based on crosscutting relationships and U-Pb geochronology and are interpreted as being the distal expression of an epizonal magmatic-hydrothermal system that is centered on the upper part of the synvolcanic Mooshla Intrusive Complex. The North and Westwood corridors consist of bimodal-felsic Au-rich VMS-type mineralization and alteration produced by the convective circulation of modified seawater that included a magmatic contribution from the coeval epizonal Zone 2 Extension magmatic-hydrothermal system. The Westwood Au deposit represents one of the very few documented examples of an Archean magmatic-hydrothermal system—or at least of such systems formed in a subaqueous environment. The study of the Westwood deposit resulted in a better understanding of the critical role of magmatic fluid input toward the formation of Archean epizonal intrusion-related Au ± Cu and seafloor/subseafloor Au-rich VMS-type mineralization.

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Geology, Fluid Inclusions and Stable Isotopes of the Xialiugou Polymetallic Deposit in North Qilian, Northwest China: Constraints on its Metallogenesis

Minerals ◽

10.3390/min9080478 ◽

2019 ◽

Vol 9 (8) ◽

pp. 478

Author(s):

Yongjun Shao ◽

Huajie Tan ◽

Guangxiong Peng ◽

Jiandong Zhang ◽

Jianzhou Chen ◽

...

Keyword(s):

Fluid Inclusions ◽

Volcanic Rocks ◽

Massive Sulfide ◽

Northwest China ◽

Polymetallic Deposit ◽

The North ◽

Vms Deposits ◽

Forming Temperature ◽

North Qilian Orogenic Belt ◽

North Qilian

The Xialiugou polymetallic deposit is located in the North Qilian Orogenic Belt, Northwest China, of which the main ore-bearing strata are the Middle Cambrian Heicigou Group. The mineralization is zoned with “black” orebodies (galena–sphalerite), which are stratigraphically above the “yellow” orebodies (pyrite–chalcopyrite–tennantite) at the lower zone, corresponding to the alteration assemblages of quartz–sericite in the ore-proximal zone and chlorite in the ore-distal zone. The Xialiugou mineralization can be divided into three stages: (1) Stage I (pyrite); (2) Stage II (chalcopyrite–tennantite–sphalerite); and (3) Stage III (galena–sphalerite). Fluid inclusions data indicate that the physicochemical conditions that lead to ore formation were the medium–low temperature (157–350 °C) and low salinity (0.17–6.87 wt % NaCleqv), and that the ore-forming temperature tended to decrease with the successive mineralization processes. Taking the H–O isotopic compositions (δDV-SMOW = −51.0‰ to −40.5‰, δ18OH2O = −0.4‰ to 8.6‰) into consideration, the ore-forming fluids were most likely derived from seawater with a small amount of magmatic- and meteoric-fluids input. In addition, the combined S (−3.70‰ to 0.10‰) and Pb isotopic (206Pb/204Pb = 18.357 to 18.422, 207Pb/204Pb = 15.615 to 15.687, 208Pb/204Pb = 38.056 to 38.248) data of pyrite indicate that the ore-bearing volcanic rocks may be an important source of ore-forming materials. Finally, we inferred that the Xialiugou deposit shares similarities with the most important volcanogenic massive sulfide (VMS) deposits (Baiyinchang ore field) in China and typical “black ore” type VMS deposits worldwide.

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Development of a laser ablation ICP-MS method for the analysis of fluid inclusions associated with volcanogenic massive sulfide deposits

Geochemistry Exploration Environment Analysis ◽

10.1144/geochem2020-043 ◽

2021 ◽

pp. geochem2020-043

Author(s):

Madison A. Schmidt ◽

Matthew I. Leybourne ◽

Jan M. Peter ◽

Duane C. Petts ◽

Simon E. Jackson ◽

...

Keyword(s):

Laser Ablation ◽

Fluid Inclusions ◽

Inductively Coupled Plasma ◽

Massive Sulfide ◽

Ore Deposits ◽

Volcanogenic Massive Sulfide ◽

Metals And Metalloids ◽

Inductively Coupled ◽

Icp Ms ◽

Vms Deposits

There is increasing acceptance of the presence of variable magmatic contributions to the mineralizing fluids in the formation of volcanogenic massive sulfide (VMS) deposits. The world-class Windy Craggy Cu-Co-Au deposit (>300 MT @ 2.12 wt.% Cu) in northwestern British Columbia is of interest because, unlike most VMS deposits, quarts fluid inclusions from within the deposit range from relatively low to intermediate salinity (most 6-16 wt.% equivalent). In this study we used an excimer (193 nm) laser ablation system interfaced to a quadrupole inductively coupled plasma mass spectrometer to quantify key metals and metalloids that are considered by many to be indicative of magmatic contributions to hydrothermal ore deposits. Although LA-ICP-MS signals from these low-salinity inclusions are highly transient, we were able to quantify Na, Mg, K, Ca, Mn, Fe, Co, Cu, Zn, Sr, Sn, Ba, Ce, Pb and Bi consistently – of the 34 elements that were monitored. Furthermore, Cl, Sb, Cd, Mo, Rb, Br, and As were also measured in a significant number of inclusions. Comparison of the fluid inclusion chemistry with unaltered and altered mafic volcanic and sedimentary rocks and mineralized samples from the deposit indicate that enrichment in the main ore metals (Cu, Zn, Fe, Pb) in the inclusions reflects that of the altered rocks and sulfides. Metals and metalloids that may indicate a magmatic contribution typically show much greater enrichments in the fluid inclusions much greater over the host rocks at the same Cu concentration; in particular Bi, Sn and Sb are significantly elevated when compared to the host rock samples. These data are consistent with the ore-forming fluids at Windy Craggy having a strong magmatic contribution.

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Auriferous Quartz Veining Due to CO2 Content Variations and Decompressional Cooling, Revealed by Quartz Solubility, SEM-CL and Fluid Inclusion Analyses (The Linglong Goldfield, Jiaodong)

Minerals ◽

10.3390/min10050417 ◽

2020 ◽

Vol 10 (5) ◽

pp. 417

Author(s):

Qing Wei ◽

Hongrui Fan ◽

Jacques Pironon ◽

Xuan Liu

Keyword(s):

Fluid Inclusion ◽

Meteoric Water ◽

Gangue Mineral ◽

Content Increase ◽

Formation Processes ◽

Solubility Behavior ◽

Quartz Dissolution ◽

Quartz Solubility ◽

Quartz Veining

Quartz is the most common gangue mineral in hydrothermal veins. Coupled with capacities of hosting fluid inclusions and recording varieties of microtextures, its solubility behavior may provide unparalleled insights into hydrothermal processes. In this study, the Linglong goldfield in Jiaodong is targeted to investigate gold-producing quartz veining process. Scanning electron microscope (SEM)-cathodoluminescence (CL) imaging uncovered three episodes of quartz deposition, intervened by an episode of quartz dissolution. Based on newly-developed quartz solubility diagrams and CL-aided fluid inclusion microthermometry, it is proposed that precipitation of the earliest quartz (Qz1) was controlled by CO2 content increase and subordinately affected by decompressional cooling, leading to the formation of the early thick gold-barren veins (V1); the second generation of quartz (Qz2a) was formed by the same fluids that may have been diluted and cooled by meteoric water, leading to a greatly reduced quantity of quartz and the deposition of pyrite and gold; and the third generation of quartz (Qz2b) was deposited along with polymetallic sulfides, due to fluid cooling following a quartz dissolution event likely induced by cooling in retrograde solubility region and/or CO2 content decrease. This research may elucidate gold formation processes in orogenic intrusion—related deposits, and points to imperative CL-based in situ analyses for future studies.

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A fluid inclusion and stable isotope study of the Moonta copper–gold deposits, South Australia: evidence for fluid immiscibility in a magmatic hydrothermal system

Chemical Geology ◽

10.1016/s0009-2541(02)00197-3 ◽

2002 ◽

Vol 192 (3-4) ◽

pp. 211-226 ◽

Cited By ~ 25

Author(s):

S Morales Ruano ◽

R.A Both ◽

S.D Golding

Keyword(s):

Stable Isotope ◽

Fluid Inclusion ◽

Hydrothermal System ◽

South Australia ◽

Gold Deposits ◽

Fluid Immiscibility ◽

Copper Gold ◽

Isotope Study ◽

Stable Isotope Study

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Determination of uranium: carbon ratios in fluid inclusion decrepitates by inductively coupled plasma emission spectroscopy

Mineralogical Magazine ◽

10.1180/minmag.1982.046.339.04 ◽

1982 ◽

Vol 46 (339) ◽

pp. 179-186 ◽

Cited By ~ 10

Author(s):

A. H. Rankin ◽

D. H. M. Alderton ◽

M. Thompson ◽

J. E. Goulter

Keyword(s):

Fluid Inclusion ◽

Fluid Inclusions ◽

Inductively Coupled Plasma ◽

Hydrothermal Systems ◽

Strong Positive Correlation ◽

Inductively Coupled ◽

Approximate Order ◽

Order Of Magnitude ◽

Plasma Emission Spectroscopy

AbstractUranium has been detected in fluid inclusion decrepitates from quartz of several granites of the British Isles and from vein quartz associated with the Hcrcynian granites of SW England using ICP. Material, ejected from the inclusions during decrepitation on heating the sample, is transferred into the plasma for qualitative analysis via a stream of argon. Several other elements have been detected in the decrepitate, of which carbon is of particular interest. It shows a strong positive correlation with U and indicates the importance of C (presumably as carbonate complexes) in the transport of U in hydrothermal systems. Approximate order of magnitude estimates of the average U contents of fluid inclusions from the SW England samples, based on the assumption that U in the decrepitates is principally derived from the fluid inclusions, range from less than one to over a thousand ppm. Fluid inclusions may therefore be important in contributing to the levels of U reported in quartz (0.1 to 10 ppm).

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Ar–Ar dating for hydrothermal quartz from the 2.4 Ga Ongeluk Formation, South Africa: implications for seafloor hydrothermal circulation

Royal Society Open Science ◽

10.1098/rsos.180260 ◽

2018 ◽

Vol 5 (9) ◽

pp. 180260

Author(s):

Takuya Saito ◽

Hua-Ning Qiu ◽

Takazo Shibuya ◽

Yi-Bing Li ◽

Kouki Kitajima ◽

...

Keyword(s):

South Africa ◽

Fluid Inclusion ◽

Fluid Inclusions ◽

Hydrothermal System ◽

Magmatic Fluid ◽

Crustal Fluid ◽

Hydrothermal Quartz ◽

Argon Isotopes ◽

Stepwise Crushing ◽

Binary Mixing

Fluid inclusions in hydrothermal quartz in the 2.4 Ga Ongeluk Formation, South Africa, are expected to partially retain a component of the ancient seawater. To constrain the origin of the fluid and the quartz precipitation age, we conducted Ar–Ar dating for the quartz via a stepwise crushing method. The obtained argon isotopes show two or three endmembers with one or two binary mixing lines as the crushing proceeds, suggesting that the isotopic compositions of these endmembers correspond to fluid inclusions of each generation, earlier generated smaller 40 Ar- and K-rich inclusions, moderate 40 Ar- and 38 Ar Cl (neutron-induced 38 Ar from Cl)-rich inclusions and later generated larger atmospheric-rich inclusions. The K-rich inclusions show significantly different 40 Ar/ 38 Ar Cl values compared to the 38 Ar Cl -rich inclusions, indicating that it is difficult to constrain the quartz formation age using only fluid inclusions containing excess 40 Ar. The highest obtained 40 Ar/ 36 Ar value from the fluid inclusions is consistent with an expected value of the Ongeluk plume source, suggesting that the quartz precipitation was driven by Ongeluk volcanism. Considering the fluid inclusion generations and their compositions, the hydrothermal system was composed of crustal fluid and magmatic fluid without seawater before the beginning of a small amount of seawater input to the hydrothermal system.

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