Trace Element Signatures in Pyrite and Marcasite From Shallow Marine Island Arc-Related Hydrothermal Vents, Calypso Vents, New Zealand, and Paleochori Bay, Greece

Nestmeyer M, Keith M, Haase K, Klemd R, Voudouris P, Schwarz-Schampera U, Strauss H, Kati M, Magganas A (2021)

Publication Type: Journal article

Publication year: 2021

Journal

Frontiers in Earth Science Frontiers Media

Book Volume: 9

DOI: 10.3389/feart.2021.641654

Abstract

Fluid conditions of shallow marine hydrothermal vent sites (<200 mbsl) in island arcs resemble those of subaerial epithermal systems. This leads to a distinct mineralization-style compared to deeper arc/back-arc (>200 mbsl) and mid-ocean ridge-related environments (>2000 mbsl). At Calypso Vents in the Bay of Plenty and Paleochori Bay at the coast of Milos Island, fluids with temperatures <200°C are emitted through volcaniclastic sediments in water depths <200 mbsl. The hydrothermal mineralization from these fluids is dominated by pyrite and marcasite showing diverse textures, including colloform alternations, semi-massive occurrences surrounding detrital grains, vein-type pyrite, and disseminated fine-grained assemblages. Pyrite and marcasite from Calypso SE show elevated concentrations of volatile elements (e.g., As, Sb, Tl, Hg) implying a vapor-rich fluid phase. By contrast, elements like Zn, Ag, and Pb are enriched in hydrothermal pyrite and marcasite from Calypso SW, indicating a high-Cl liquid-dominated fluid discharge. Hence, vapor-liquid element fractionation induced by fluid boiling is preserved in the seafloor mineralization at Calypso Vents. Hydrothermal mineralization at very shallow vent sites (<10 mbsl), like Paleochori Bay, are affected by wave action causing a seasonal migration of the seawater-fluid interface in the sediment cover. The δ34S composition of native S crusts and crystalline S (0.7–6.7‰) is indicative for host rock leaching and thermochemical reduction of seawater sulphate. By contrast, the highly negative δ34S signature of native S globules in sediments (−7.6 to −9.1‰) is related to microbial sulphate reduction or a subordinate magmatic fluid influx. Alunite-jarosite alteration (Paleochori Bay) and a mineral assemblage consisting of orpiment, realgar, and native S (Calypso Vents) may also suggest a contribution by an oxidised (sulphate-rich) low pH fluid of potential magmatic origin. However, fluid boiling is pervasive at Calypso Vents and Paleochori Bay, and the condensation of vapor-rich fluids in a steam-heated environment may produce a similar alteration and mineralization assemblage without a significant magmatic fluid influx, as known from some subaerial epithermal systems.

Authors with CRIS profile

Manuel Keith Lehrstuhl für Endogene Geodynamik Karsten Haase Lehrstuhl für Endogene Geodynamik Reiner Klemd Professur für Geochemie von Lagerstätten

Involved external institutions

National and Kapodistrian University of Athens GR Greece (GR) Westfälische Wilhelms-Universität (WWU) Münster DE Germany (DE) Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) DE Germany (DE)

How to cite

APA:

Nestmeyer, M., Keith, M., Haase, K., Klemd, R., Voudouris, P., Schwarz-Schampera, U.,... Magganas, A. (2021). Trace Element Signatures in Pyrite and Marcasite From Shallow Marine Island Arc-Related Hydrothermal Vents, Calypso Vents, New Zealand, and Paleochori Bay, Greece. Frontiers in Earth Science, 9. https://dx.doi.org/10.3389/feart.2021.641654

MLA:

Nestmeyer, Mark, et al. "Trace Element Signatures in Pyrite and Marcasite From Shallow Marine Island Arc-Related Hydrothermal Vents, Calypso Vents, New Zealand, and Paleochori Bay, Greece." Frontiers in Earth Science 9 (2021).

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