Involvement of variably-sourced fluids during the formation and later overprinting of Paleoproterozoic Au-Cu mineralization: Insights gained from a fluid inclusion assemblage approach

Haroldson, Erik L.; Brown, P. E.; Bodnar, Robert J.

doi:10.1016/j.chemgeo.2018.08.027

Cited by 5 publications

(1 citation statement)

References 55 publications

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“…The irregularity of shape of these inclusions seems to be a function of size. Type I inclusions often occur in monophase liquid only condition which may be ascribed to their entrapment at very low temperature-pressure and simply lack a vapor bubble due to metastability [42]. Association of type I inclusions with any of the other types is observed in clusters as well as in transgranular and intragranular trails.…”

Section: Fluid Inclusionmentioning

confidence: 99%

Origin of the Paleoproterozoic “Giant Quartz Reef” System in the Bundelkhand Craton, India: Constraints from Fluid Inclusion Microthermometry, Raman Spectroscopy, and Geochemical Modelling

et al. 2022

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The Bundelkhand “giant quartz reef” (BGQR) system comprises 20 major quartz reefs which run for tens of km in strike length of average width of 40 m and occurs in spatial intervals of 12–19 km in the Bundelkhand craton, North Central India. The BGQR system is distinct from quartz vein systems originating from crustal scale shearing observed in ancient as well as modern convergent tectonic settings. Fluid inclusions studied in BGQR system are intriguingly diverse although dominated by aqueous fluid which exhibit a broad range of salinity from ~0 to 28.9 wt% NaCl equivalent and temperature of homogenization range of 58 to 385°C. Primary and pseudosecondary aqueous inclusions in assemblages in grain interiors and growth zones vary randomly in their Th—salinity characteristics that preclude identification of discrete fluid events. Aqueous fluid in the BGQR system evolved through mixing of two distinct sources of fluids—a meteoric fluid and a moderate temperature—moderate salinity fluid that was possibly derived from the Bundelkhand granodiorite based on an important clue provided by hydrous mineral bearing fluid inclusions detected by Raman microspectrometry. The results of modeling with PHREEQC indicate that mixing of fluids could be a suitable mechanism in formation of these giant reefs. The available 1-dimensional diffusive transport model for deposition of silica helps in putting constraints on the time span of deposition of silica in the context of the BGQR system. The BGQR system is a possible result of shallow-crustal sources of fluid and silica and could be visualized as a “Paleoproterozoic geothermal system” in a granitic terrane.

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Section: Fluid Inclusionmentioning

confidence: 99%

Origin of the Paleoproterozoic “Giant Quartz Reef” System in the Bundelkhand Craton, India: Constraints from Fluid Inclusion Microthermometry, Raman Spectroscopy, and Geochemical Modelling

et al. 2022

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Overprinting by episodic mineralization in the Dongyaozhuang gold deposit, Wutai Mountain, China: Constraints from geology, mineralogy, and fluid inclusions

Liu

Zhang

Wang³

2019

Geological Journal

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The Archean volcanic‐sedimentary rocks (greenstones) hosting the Dongyaozhuang (DYZ) gold deposit are situated in the Wutai Mountain, north‐central China. Field geology and mineral assemblages show at least two episodes of mineralization. The first episode features deformed quartz‐pyrite veins filling in the regional foliation (MI, Paleoproterozoic) and can be divided into two stages (MIa and MIb) based on whether the mineralization is accompanied by tourmalinization. The mineral assemblages are mainly quartz + carbonate + pyrite + chalcopyrite (+ tourmaline for MIb); both are cut by deformed barren quartz veins, which represent the final stage of MI. The second episode features undeformed stockworks/veinlets with a mineral assemblage of quartz + carbonate + pyrite + chalcopyrite + arsenopyrite ± native gold (MIIa), crosscutting MI; these ore bodies are also cut through by undeformed barren carbonate and/or quartz veins (MIIb), which represent the end of metallogeny. By integrating the crustal evolution history with ore geology, we suggest that the DYZ gold deposit is a product by overprinting of episodic mineralization rather than a single metallogenic event. For further understanding and evidence in support of this speculation, fluid inclusions and hydrothermal chlorite and biotite were studied to reveal the physicochemical conditions of fluids from various stages, and C‐H‐O isotopes were used to trace the source(s) of fluids. Temperatures recorded in chlorite from various stages C1 (from the MIa), C2 (MIb), and C3 (MIIa) generally agrees with the homogenization temperatures of aqueous type fluid inclusions (FIs) of corresponding stages. Components of FIs from each stage are dominated by water with low salinities (0–12.6 wt% NaCl equiv). The Ib‐1, Ib‐2, and Ib‐s type CO2‐H2O FIs observed from the same deformed quartz vein of the MIb can be attributed to overprinting of hydrothermal fluids. The primary Ib‐1 and Ib‐2 FIs (209–404°C) were trapped at pressures of approximately 2.2–3.7 kbar, representing the formation pressure of the MI stage, whereas the secondary Ib‐s FIs (240–349°C) were trapped at pressures of approximately 0.8–1.5 kbar, which indicates overprinting induced by MII. The C‐H‐O isotope compositions of quartz and carbonates from MIa, MIb, and MIIa can be interpreted to indicate that the fluids were derived from the same source with multistage evolution or to reflect a homogeneous signature induced with overprinting mineralization. According to the geology, mineral assemblages, component of fluid inclusions, and C‐H‐O isotopes, the DYZ gold deposit is likely to be a product of overprinting of an orogenic gold deposit.

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SIMS oxygen isotopes indicate Phanerozoic fluids permeated a Precambrian gold deposit

et al. 2020

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Involvement of variably-sourced fluids during the formation and later overprinting of Paleoproterozoic Au-Cu mineralization: Insights gained from a fluid inclusion assemblage approach

Cited by 5 publications

References 55 publications

Origin of the Paleoproterozoic “Giant Quartz Reef” System in the Bundelkhand Craton, India: Constraints from Fluid Inclusion Microthermometry, Raman Spectroscopy, and Geochemical Modelling

Origin of the Paleoproterozoic “Giant Quartz Reef” System in the Bundelkhand Craton, India: Constraints from Fluid Inclusion Microthermometry, Raman Spectroscopy, and Geochemical Modelling

Overprinting by episodic mineralization in the Dongyaozhuang gold deposit, Wutai Mountain, China: Constraints from geology, mineralogy, and fluid inclusions

SIMS oxygen isotopes indicate Phanerozoic fluids permeated a Precambrian gold deposit

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