Comparison of sulphide deposits from the East Pacific Rise and Cyprus

Oudin, Elisabeth; Picot, Paul; Pouit, G.

doi:10.1038/291404a0

Cited by 22 publications

(5 citation statements)

References 17 publications

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“…Printing Office). some textural and mineralogical similarities were found (Oudin et al, 1981). As a consequence, the ocean floor sulfide accumulations have been improperly called "massive sulfide deposits" even though they presently have no economical value.…”

Section: Introductionmentioning

confidence: 92%

Stockwork-Like Sulfide Mineralization in Young Oceanic Crust: Deep Sea Drilling Project Hole 504B

Honnorez

Alt

Honnorez-Guerstein

et al. 1985

Initial Reports of the Deep Sea Drilling Project

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Stockwork-like metal sulfide mineralizations were found at 910-928 m below seafloor (BSF) in the pillow/dike transition zone of Hole 504B. This is the same interval where most physical properties of the 5.9-m.y.-old crust of the Costa Rica Rift change from those characteristic of Layer 2B to those of Layer 2C. The pillow lavas, breccias, and veins of the stockwork-like zone were studied by transmitted and reflected light microscopy, X-ray diffraction, and electron microprobe analysis. Bulk rock oxygen isotopic analyses as well as isolated mineral oxygen and sulfur isotopic analyses and fluid inclusion measurements were carried out. A complex alteration history was reconstructed that includes three generations of fissures, each followed by precipitation of characteristic hydrothermal mineral parageneses: (1) Minor and local deposition of quartz occurred on fissure walls; adjacent wall rocks were silicified, followed by formation of chlorite and minor pyrite I in the veins, whereas albite, sphene, chlorite and chlorite-expandable clay mixtures, actinolite, and pyrite replaced igneous phases in the host rocks. The hydrothermal fluids responsible for this first stage were probably partially reacted seawater, and their temperatures were at least 200-250° C. (2) Fissures filled during the first stage were reopened and new cracks formed. They were filled with quartz, minor chlorite and chlorite-expandable clay mixtures, traces of epidote, common pyrite, sphalerite, chalcopyrite, and minor galena. During the second stage, hydrothermal fluids were relatively evolved metal-and Si-rich solutions whose temperatures ranged from 230 to 340° C. The fluctuating chemical composition and temperature of the solutions produced a complex depositional sequence of sulfides in the veins: chalcopyrite I, ± Fe-rich sphalerite, chalcopyrite II ("disease"), Fe-poor sphalerite, chalcopyrite III, galena, and pyrite II. (3) During the last stage, zeolites and Mg-poor calcite filled up the remaining spaces and newly formed cracks and replaced the host rock plagioclase. Analcite and stilbite were first to form in veins, possibly at temperatures below 200°C; analcite and earlier quartz were replaced by laumontite at 250°C, whereas calcite formation temperature ranged from 135 to 220°C. The last stage hydrothermal fluids were depleted in Mg and enriched in Ca and 18 O compared to seawater and contained a mantle carbon component.This complex alteration history paralleling a complex mineral paragenesis can be interpreted as the result of a relatively long-term evolution of a hydrothermal system with superimposed shorter term fluctuations in solution temperature and composition. Hydrothermal activity probably began close to the axis of the Costa Rica Rift with the overall cooling of the system and multiple fracturing stages due to movement of the crust away from the axis and/or cooling of a magmatic heat source.

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Section: Introductionmentioning

confidence: 92%

Stockwork-Like Sulfide Mineralization in Young Oceanic Crust: Deep Sea Drilling Project Hole 504B

Honnorez

Alt

Honnorez-Guerstein

et al. 1985

Initial Reports of the Deep Sea Drilling Project

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“…Subsurface mineralizing processes have the potential to form large mound and stockwork massive sulfide deposits analogous to those preserved on land. Recently formed submarine hydrothermal deposits (i.e., those less than a few thousand years old) show considerable divergence in morphology, texture, mineralogy, and geochemistry, both between each other (e.g., Fouquet et al, 1993;Graham et al, 1988;Koski et al, 1994) and with their ancient volcanogenic massive sulfide (VMS) analogues (e.g., Oudin et al, 1981). Many of the petrologic characteristics of ancient deposits are interpreted to be derived from subseafloor hydrothermal processes superimposed on primary hydrothermal precipitates.…”

Section: Introductionmentioning

confidence: 99%

Petrology of hydrothermal mineralization: a vertical section through the TAG mound

Knott¹,

Fouquet²,

Honnorez³

et al. 1998

Proceedings of the Ocean Drilling Program

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Mineralogical, textural, chemical, and isotopic features of a vertical section through the active TransAtlantic Geotraverse (TAG) hydrothermal mound reveal the nature of subsurface mineralization. The multistage growth and evolution of the TAG mound occurs by the following processes: (1) near-surface (<10 m depth) hydrothermal precipitation of porous Fe-Cu-Zn sulfide and Si-Fe-oxyhydroxides; (2) modification of surface material within the mound (>20 m depth) by sequential overgrowth, recrystallization and mineral dissolution; (3) hydrothermal mineralization within the mound, forming Fe-Cu sulfides, anhydrite and quartz; and (4) alteration and mineralization of basalt basement beneath the mound. During the long history of hydrothermal activity, these processes have driven the TAG mound toward a mineralogy dominated by pyrite and depleted in Cu, Zn, and trace elements. The basement beneath the mound is ultimately altered to pyrite-quartz. Sulfur-isotope composition of sulfides in the range +4.4‰ to +8.9‰ requires a deep hydrothermal source with elevated δ 34 S to generate an end-member fluid with estimated δ 34 S of +5.5‰. Vein-related sulfide mineralization is isotopically light, whereas sulfide disseminated in altered basalt is isotopically heavy. The systematic variations between sulfide generations and a general increase with depth are a result of sulfate reduction in a shallow seawater-hydrothermal circulation system developed around the hydrothermal feeder zone. This generates hydrothermal fluid and sulfide mineralization with a maximum δ 34 S of +8.9‰. Mixing between this shallow circulated fluid and the end-member hydrothermal component would explain the variations of up to 3‰ observed between different sulfide generations in the mound.

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“…Graham et al 1988;Paradis et al 1988) and with ancient volcanic-hosted massive sulphide (VMS) deposits (e.g. Oudin et al 1981;Halbach et al 1989). Many of the petrological characteristics of ancient deposits are derived from later.…”

mentioning

confidence: 99%

Mineralogy and sulphur isotope characteristics of a massive sulphide boulder, Galapagos Rift, 85°55′W

Knott

Fallick

Rickard

et al. 1995

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The submarine hydrothermal sulphide deposits of the Galapagos Rift are characterized by being exceptionally Cu-rich. Fe-and Cu-Fe sulphides are extremely heterogeneous, display granular textures and evidence of open space growth. Core was examined from a 1.5 m diameter massive sulphide boulder collected by TV grab on the GARIMAS II cruise. The main growth stage is dominated by pyrite and chalcopyrite, forming granular aggregates from < 1 mm to >5 cm. These suiphides have ~34S from + 2.7 to +5.5%o. The Fe-Cu sulphides are modified by minor seawater oxidation and a late stage marcasite-sphalerite-galena-barite assemblage. ~,34S varies along the core in a systematic manner and there appears to be an isotopically heavy deviation from the modal +3.9%o. This is related to particular zones and suggests a second, isotopically distinct S source, which is interpreted to be a hydrothermal diagenetic solution derived from a shallow seawater-hydrothermal circulation system.

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Comparison of sulphide deposits from the East Pacific Rise and Cyprus

Cited by 22 publications

References 17 publications

Stockwork-Like Sulfide Mineralization in Young Oceanic Crust: Deep Sea Drilling Project Hole 504B

Stockwork-Like Sulfide Mineralization in Young Oceanic Crust: Deep Sea Drilling Project Hole 504B

Petrology of hydrothermal mineralization: a vertical section through the TAG mound

Mineralogy and sulphur isotope characteristics of a massive sulphide boulder, Galapagos Rift, 85°55′W

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