scholarly journals Coupled partitioning of Au and As into pyrite controls formation of giant Au deposits

2019 ◽  
Vol 5 (5) ◽  
pp. eaav5891 ◽  
Author(s):  
C. Kusebauch ◽  
S. A. Gleeson ◽  
M. Oelze
Keyword(s):  
Partition Coefficients ◽  
Hydrothermal Fluid ◽  
Iron Sulfide ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Balance Model ◽  
Mass Balance Model ◽  
Depositional Process ◽  
Partitioning Behavior

The giant Carlin-type Au deposits (Nevada, USA) contain gold hosted in arsenic-rich iron sulfide (pyrite), but the processes controlling the sequestration of Au in these hydrothermal systems are poorly understood. Here, we present an experimental study investigating the distribution of Au and As between hydrothermal fluid and pyrite under conditions similar to those found in Carlin-type Au deposits. We find that Au from the fluid strongly partitions into a newly formed pyrite depending on the As concentration and that the coupled partitioning behavior of these two trace elements is key for Au precipitation. On the basis of our experimentally derived partition coefficients, we developed a mass balance model that shows that simple partitioning (and the underlying process of adsorption) is the major depositional process in these systems. Our findings help to explain why pyrite in Carlin-type gold deposits can scavenge Au from hydrothermal fluids so efficiently to form giant deposits.

scholarly journals Analysis of Hydrothermal Systems Beneath Tayukeng through Long-Term Geochemical Signals of Hydrothermal Fluids in Tatun Volcano Group, Taiwan

2021 ◽  
Vol 18 (14) ◽  
pp. 7411
Author(s):  
Hsin-Fu Yeh ◽  
Hung-Hsiang Hsu
Keyword(s):  
Surface Temperature ◽  
Hydrothermal System ◽  
Hydrothermal Fluid ◽  
Thermal Water ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Geochemical Variations ◽  
Northern Taiwan

The Tatun Volcano Group (TVG) is located in northern Taiwan and consists of many springs and fumaroles. The Tayukeng (TYK) area is the most active fumarole site in the TVG. In this study, we analyzed the long-term geochemical variations of hydrothermal fluids and proposed a mechanism responsible for the variation in TYK. There are two different aquifers beneath the TYK area: a shallow SO42−-rich aquifer and a deeper aquifer rich in Cl−. TYK thermal water was mainly supplied by the shallow SO42−-rich aquifer; therefore, the thermal water showed high SO42− concentrations. After 2015, the inflow of deep thermal water increased, causing the Cl− concentrations of the TYK to increase. Notably, the inferred reservoir temperatures based on quartz geothermometry increased; however, the surface temperature of the spring decreased. We inferred that the enthalpy was lost during transportation to the surface. Therefore, the surface temperature of the spring does not increase with an increased inflow of deep hydrothermal fluid. The results can serve as a reference for understanding the complex evolution of the magma-hydrothermal system in the TVG.

scholarly journals Critical role of caldera collapse in the formation of seafloor mineralization: The case of Brothers volcano

Geology ◽  
2019 ◽  
Vol 47 (8) ◽  
pp. 762-766 ◽  
Author(s):  
Cornel E.J. de Ronde ◽  
Susan E. Humphris ◽  
Tobias W. Höfig ◽  
Agnes G. Reyes ◽  
Keyword(s):  
Hydrothermal Fluid ◽  
Porphyry Copper ◽  
Critical Role ◽  
Massive Sulfide ◽  
Wall Rock ◽  
Hydrothermal Activity ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Magmatic Fluid ◽  
Caldera Collapse

Abstract Hydrothermal systems hosted by submarine arc volcanoes commonly include a large component of magmatic fluid. The high Cu-Au contents and strongly acidic fluids in these systems are similar to those that formed in the shallow parts of some porphyry copper and epithermal gold deposits mined today on land. Two main types of hydrothermal systems occur along the submarine portion of the Kermadec arc (offshore New Zealand): magmatically influenced and seawater-dominated systems. Brothers volcano hosts both types. Here, we report results from a series of drill holes cored by the International Ocean Discovery Program into these two types of hydrothermal systems. We show that the extent of hydrothermal alteration of the host dacitic volcaniclastics and lavas reflects primary lithological porosity and contrasting spatial and temporal contributions of magmatic fluid, hydrothermal fluid, and seawater. We present a two-step model that links the changes in hydrothermal fluid regime to the evolution of the volcano caldera. Initial hydrothermal activity, prior to caldera formation, was dominated by magmatic gases and hypersaline brines. The former mixed with seawater as they ascended toward the seafloor, and the latter remained sequestered in the subsurface. Following caldera collapse, seawater infiltrated the volcano through fault-controlled permeability, interacted with wall rock and the segregated brines, and transported associated metals toward the seafloor and formed Cu-Zn-Au–rich chimneys on the caldera walls and rim, a process continuing to the present day. This two-step process may be common in submarine arc caldera volcanoes that host volcanogenic massive sulfide deposits, and it is particularly efficient at focusing mineralization at, or near, the seafloor.

scholarly journals Assessing Thallium Elemental Systematics and Isotope Ratio Variations in Porphyry Ore Systems: A Case Study of the Bingham Canyon District

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 548 ◽  
Author(s):  
Angus Fitzpayne ◽  
Julie Prytulak ◽  
Jamie Wilkinson ◽  
David Cooke ◽  
Michael Baker ◽  
...  
Keyword(s):  
Low Temperature ◽  
Gold Mineralization ◽  
Isotope Ratios ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Fluid Composition ◽  
New Information ◽  
Two Samples ◽  
Element Enrichment

The Bingham Canyon porphyry deposit is one of the world’s largest Cu-Mo-Au resources. Elevated concentrations of thallium (Tl) compared to average continental crust have been found in some brecciated and igneous samples in this area, which likely result from mobilization of Tl by relatively low temperature hydrothermal fluids. The Tl-enrichment at Bingham Canyon therefore provides an opportunity to investigate if Tl isotope ratios reflect hydrothermal enrichment and whether there are systematic Tl isotope fractionations that could provide an exploration tool. We present a reconnaissance study of nineteen samples spanning a range of lithologies from the Bingham district which were analysed for their Tl content and Tl isotope ratios, reported as parts per ten thousand (ε205Tl) relative to the NIST SRM997 international standard. The range of ε205Tl reported in this study (−16.4 to +7.2) is the largest observed in a hydrothermal ore deposit to date. Unbrecciated samples collected relatively proximal to the Bingham Canyon porphyry system have ε205Tl of −4.2 to +0.9, similar to observations in a previous study of porphyry deposits. This relatively narrow range suggests that high-temperature (>300 °C) hydrothermal alteration does not result in significant Tl isotope fractionation. However, two samples ~3–4 km away from Bingham Canyon have higher ε205Tl values (+1.3 and +7.2), and samples from more distal (~7 km) disseminated gold deposits at Melco and Barneys Canyon display an even wider range in ε205Tl (−16.4 to +6.0). The observation of large positive and negative excursions in ε205Tl relative to the mantle value (ε205Tl = −2.0 ± 1.0) contrasts with previous investigations of hydrothermal systems. Samples displaying the most extreme positive and negative ε205Tl values also contain elevated concentrations of Tl-Sb-As. Furthermore, with the exception of one sample, all of the Tl isotopic anomalies occur in hydrothermal breccia samples. This suggests that ε205Tl excursions are most extreme during the migration of low-temperature hydrothermal fluids potentially related to sediment-hosted gold mineralization. Future investigation to determine the host phase(s) for Tl in breccias displaying both chalcophile element enrichment and ε205Tl excursions can potentially provide new information about hydrothermal fluid composition and could be used to locate sites for future porphyry exploration.

scholarly journals Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 966
Author(s):  
Baptiste Madon ◽  
Lucie Mathieu ◽  
Jeffrey H. Marsh
Keyword(s):  
Oxygen Fugacity ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Chemical Diversity ◽  
Temporal Association ◽  
Volatile Content ◽  
Abitibi Subprovince

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.

Hydrothermal Sr contamination of the Dippin sill, Isle of Arran, Western Scotland

1984 ◽  
Vol 48 (348) ◽  
pp. 311-322 ◽  
Author(s):  
A. P. Dickin ◽  
C. M. B. Henderson ◽  
F. G. F. Gibb
Keyword(s):  
Stable Isotope ◽  
Hydrothermal Alteration ◽  
Closed System ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Drill Core ◽  
Sr Isotope ◽  
Core Section ◽  
High Silica ◽  
Isotope Measurements

Abstract The Dippin sill, which is emplaced into the Triassic sediments of SE Arran, is an alkaline basic sheet which displays pronounced hydrothermal alteration. The 40-m-thick sill has suffered pervasive contamination with radiogenic Sr, introduced from the Triassic sediments by hydrothermal fluids. Stable isotope measurements suggest that fluids were of meteoric origin, but were restricted to a small closed-system circulation. Initial 87Sr/86Sr ratios in the sill were raised from an original value of 0.7032 to a maximum of 0.7091, contamination being especially pronounced near the contacts at Dippin Head itself (localities 12 and 14) and in a drill core section through the sill above Dippin. Hydrothermal Sr was incorporated into an early-formed high-CaO, high-Sr analcime, which replaced unstable high-silica nepheline in interstitial patches. However, this high-CaO analcime, along with plagioclase, was later replaced by a low-CaO, low-Sr analcime, allowing Sr leaching from the margins of the sill. Hydrothermal fluids are thought to have migrated up to 1 km laterally, up the dip of the sill, mainly via tension joints forming in the cooling intrusion. Pooling of hot fluids at the upper end of the sill probably raised water/rock ratios in this region and allowed greater Sr contamination during mineralogical alteration. The undersaturated mineralogy of the sill accounts for its pervasive hydrothermal Sr contamination, which contrasts markedly with the relatively undisturbed Sr isotope compositions of Hebridean granites involved in hydrothermal systems.

A mass-balance model to assess arsenic exposure from multiple wells in Bangladesh

2021 ◽  
Author(s):  
Linden B. Huhmann ◽  
Charles F. Harvey ◽  
Ana Navas-Acien ◽  
Joseph Graziano ◽  
Vesna Slavkovich ◽  
...  
Keyword(s):  
Mass Balance ◽  
Arsenic Exposure ◽  
Balance Model ◽  
Mass Balance Model

scholarly journals Assesment of soil erosion by 137Cs technique in native forests in Londrina City, Parana, Brazil

2007 ◽  
Vol 50 (6) ◽  
pp. 1051-1060 ◽  
Author(s):  
Avacir Casanova Andrello ◽  
Carlos Roberto Appoloni ◽  
Virgílio Franco do Nascimento Filho
Keyword(s):  
Soil Erosion ◽  
Soil Loss ◽  
Balance Model ◽  
Native Forest ◽  
Mass Balance Model ◽  
Erosion Process ◽  
137Cs Inventory ◽  
Native Forests ◽  
137Cs Distribution ◽  
137Cs Technique

The aim of this work was to assess the soil erosion process in native forest by the 137Cs methodology. The mass balance model was applied to assess the rates of soil loss in three native forests around of Londrina city, Paraná, Brazil. 137Cs distribution depth was of exponential type for the three forests and 137Cs inventory was 241 Bq m-2 for Mata 1, 338 Bq m-2 for Mata 2 and 325 Bq m-2 for Mata UEL. The soil loss value calculated for three native forests was: 6,684 kg ha-1 yr-1 for Mata 1, 1,788 kg ha-1 yr-1 for Mata 2 and 4,524 kg ha-1 yr-1 for Mata UEL.

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