scholarly journals Nature of Ore Fluid at the Sopokomil Zn-Pb Deposit, North Sumatra, Indonesia: Implications for Metal Transport and Sulfide Deposition

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 298
Author(s):  
Tomy Alvin Rivai ◽  
Syafrizal Syafrizal ◽  
Kotaro Yonezu ◽  
Kenzo Sanematsu ◽  
Koichiro Watanabe
Keyword(s):  
Fluid Inclusion ◽  
Marine Sediment ◽  
Chemical Equilibrium ◽  
Redox State ◽  
Early Stage ◽  
Massive Sulfide ◽  
Metal Transport ◽  
Dramatic Shift ◽  
North Sumatra ◽  
Depositional Mechanism

Little is known about the nature of ore fluid at the Sopokomil shale-hosted massive sulfide Zn-Pb deposit (North Sumatra, Indonesia). We therefore investigated its ore-fluid salinities, temperatures, densities, redox state, and pH using fluid inclusion microthermometry, sphalerite composition, and thermodynamic modelling. The fluid salinities and temperatures were ≈6 wt.% NaCl equiv and ≈165 °C, respectively, corresponding to an ore fluid less dense than seawater (≈0.96 g/mL). Sphalerite contains ≈9.9 mole% FeS in the stratiform ore and ≈3.4 mole% FeS in the feeder ore, suggesting a reduced fluid, which must have been acidic to be fertile. Such redox state and acidity invoke fluid dilution as the sulfide depositional mechanism. The bulk of the sulfides were precipitated in the early stage of mixing, within T = 165–155 °C. Key ingredients of sphalerite and galena at Sopokomil include (1) Zn that was primarily transported as ZnCl+, (2) Pb that predominantly occurred as PbCl2(aq), and (3) S that was largely supplied by marine sediment porewater. This study highlights the significance of a dramatic shift in thermal and chemical equilibrium induced by fluid dilution in the making of the first significant shale-hosted massive sulfide Zn-Pb deposit in Indonesia.

scholarly journals Biogeochemical Controls on the Redox Evolution of Earth’s Oceans and Atmosphere

Elements ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 191-196 ◽  
Author(s):  
Christopher T. Reinhard ◽  
Noah J. Planavsky
Keyword(s):  
Redox State ◽  
Modeling Tools ◽  
Evolutionary Trajectory ◽  
Geochemical Tracers ◽  
Atmosphere System ◽  
Ocean Atmosphere ◽  
Dramatic Shift ◽  
Redox Evolution

The redox state of Earth’s atmosphere has undergone a dramatic shift over geologic time from reducing to strongly oxidizing, and this shift has been coupled with changes in ocean redox structure and the size and activity of Earth’s biosphere. Delineating this evolutionary trajectory remains a major problem in Earth system science. Significant insights have emerged through the application of redox-sensitive geochemical systems. Existing and emerging biogeochemical modeling tools are pushing the limits of the quantitative constraints on ocean–atmosphere redox that can be extracted from geochemical tracers. This work is honing our understanding of the central role of Earth’s biosphere in shaping the long-term redox evolution of the ocean–atmosphere system.

Origin of the Gacun Volcanic-Hosted Massive Sulfide Deposit inSichuan, China: Fluid Inclusion and Oxygen Isotope Evidence

2001 ◽  
Vol 96 (7) ◽  
pp. 1491-1512
Author(s):  
H. Zengqian ◽  
K. Zaw ◽  
Q. Xiaoming ◽  
Y. Qingtong ◽  
Y. Jinjie ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Oxygen Isotope ◽  
Massive Sulfide ◽  
Sulfide Deposit ◽  
Massive Sulfide Deposit ◽  
Isotope Evidence

scholarly journals Ore-Fluid Evolution of the Sizhuang Orogenic Gold Deposit, Jiaodong Peninsula, China

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 190 ◽  
Author(s):  
Yu-Ji Wei ◽  
Li-Qiang Yang ◽  
Jian-Qiu Feng ◽  
Hao Wang ◽  
Guang-Yao Lv ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Gold Deposit ◽  
Late Stage ◽  
Gold Mineralization ◽  
Early Stage ◽  
Main Stage ◽  
Jiaodong Peninsula ◽  
Wide Range ◽  
Homogenization Temperatures

The Sizhuang gold deposit with a proven gold resource of >120 t, located in northwest Jiaodong Peninsula in China, lies in the southern part of the Jiaojia gold belt. Gold mineralization can be divided into altered rock type, auriferous quartz vein type, and sulfide-quartz veinlet in K-feldspar altered granite. According to mineral paragenesis and mineral crosscutting relationships, three stages of metal mineralization can be identified: early stage, main stage, and late stage. Gold mainly occurs in the main stage. The petrography and microthermometry of fluid inclusion shows three types of inclusions (type 1 H2O–CO2 inclusions, type 2 aqueous inclusions, and type 3 CO2 inclusions). Early stage quartz-hosted inclusions have a trapped temperatures range 303–390 °C. The gold-rich main stage contains a fluid-inclusion cluster with both type 1 and 2 inclusions (trapped between 279 and 298 °C), and a wide range of homogenization temperatures of CO2 occurs to the vapor phase (17.6 to 30.5 °C). The late stage calcite only contains type 1 inclusions with homogenization temperatures between 195 and 289 °C. With evidences from the H–O isotope data and the study of water–rock interaction, the metamorphic water of the Jiaodong Group is considered to be the dominating source for the ore-forming fluid. The ore-fluid belonged to a CO2–H2O–NaCl system with medium-low temperature (160–360 °C), medium-low salinity (3.00–11.83 wt% NaCl eq.), and low density (1.51–1.02 g/cm3). Fluid immiscibility caused by pressure fluctuation is the key mechanism in inducing gold mineralization in the Sizhuang gold deposit.

Massive sulfide–late diabase relationships, Home mine, Quebec: Genetic and chronological Implications

1968 ◽  
Vol 5 (3) ◽  
pp. 421-432 ◽  
Author(s):  
Asoke Mookherjee ◽  
G. G. Suffel
Keyword(s):  
Contact Zone ◽  
Early Stage ◽  
Massive Sulfide ◽  
Wall Rock ◽  
Iron Sulfides ◽  
Weak Zone ◽  
Massive Sulfides ◽  
Wall Rock Alteration ◽  
Similar Mode ◽  
And Migration

At the Home mine, Noranda, Quebec, evidence of penetration and apparent replacement of the 'Late Diabase' dikes by massive sulfides formerly led several workers to believe that these dikes were older than the orebodies. However, a glassy selvage of the diabase against a sulfide wall, in contrast with a microcrystalline one against adjoining rhyolite, demonstrates a different rate of cooling against materials of different thermal diffusivity. Also, dissociation of pyrite to magnetite, increase in the monoclinicity of pyrrhotite, copious development of chalcopyrite blebs in sphalerite, and some interesting sulfide-sulfide and sulfide-silicate reactions in the contact zone record unmistakable imprints of thermal metamorphism of the sulfide wall.Microscopic evidence indicates that, an early stage of dissociation of Fe-sulfides to magnetite was followed by pyritization of pyrrhotite and ferromagnesian silicates, and migration of chalcopyrite along and into the contact zone. These suggest a persistent pressure gradient towards the 'hot-wall' side of the reaction zone, created presumably by the fracturing of the chilled edge and by early dissociation of pyrite.Uninterrupted extensions of tabular, 'vein-like', chalcopyrite bodies from the massive sulfides protrude well into the diabase. Absence of chilling of the diabase along the walls and terminations of these protuberances, and the deformed and recrystallized fabric of these bodies point to their late emplacement by plastic flowage along post-intrusion shear planes. A similar mode of origin is proposed for the very small sulfide veins in 'D' dikelets because the two types of veins are similar.Sulfide patches within the diabase wall, with intensive but localized wall-rock alteration, retain evidence of more thorough dissociation of iron sulfides and other high-temperature mineralogical reconstitution. These masses are therefore inferred to represent clusters of detached or semi-detached portions of the sulfide wall that lost their identity due to the action of deuteric fluid. The fluid, enriched in sulfur, accounted for pyritization and other replacement and alteration features in the surrounding diabase that impart the deceptive appearance of an encroaching sulfide front.Galena-marcasite veinlets on either side of the contact in places indicate a much later solution activity along a potentially weak zone.

Sericitization of plagioclase in the Rosses Granite Complex, Co. Donegal, Ireland

1996 ◽  
Vol 60 (403) ◽  
pp. 927-936 ◽  
Author(s):  
Meideno Que ◽  
Alistair R. Allen
Keyword(s):  
Fluid Inclusion ◽  
Early Stage ◽  
Alkali Feldspar ◽  
Hydrothermal Fluids ◽  
Cooling History ◽  
Fluid Inclusion Data ◽  
Low Salinity ◽  
Ring Complex ◽  
History Of ◽  
Granite Complex

AbstractSericitization in three separate pulses of the Rosses Granite Ring Complex, Co. Donegal, Ireland, has been investigated texturally and chemically using electron microscopy, electron microprobe and fluid inclusion thermometry. The sericitization, which is restricted to the cores of plagioclase, is associated with pores which are abundant in the cores, but absent in the margins. Alkali feldspar, although porous, is unaltered. Associated with the sericitization is alteration of the adjacent primary plagioclase within the cores of grains to a more sodic composition.It is postulated that the sericitization resulted from the action of externally derived secondary hydrothermal fluids, which gained access to the pores in the plagioclase via now sealed microfractures, formed either by contraction during cooling of the Rosses Complex, or more likely by hydraulic fracturing by the fluids themselves. Limited fluid/rock ratios restricted the degree of sericitization within the host plagioclase, whilst an absence of alteration in alkali feldspar may have been due to the inaccessibility of pores in the alkali feldspar to the hydrothermal fluids at the time of alteration. Fluid inclusion data suggest that the fluids were of low salinity, and that the sericitization took place at an early stage in the cooling history of the Rosses Complex at temperatures between 400 and 600°C. It is further contended that greisenization in the Rosses Complex predated the sericitization and that the greisenization may have been due solely to volatile-rich late-stage magmatic fluids.

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