Fluid Flow, Mineralization and Deformation in an Oceanic Detachment Fault: Microtextural, Geochemical and Isotopic Evidence From Pyrite at 13°30′N on the Mid-Atlantic Ridge

Authors

Andrew J. Martin, University of Nevada, Las VegasFollow
John W. Jamieson, Memorial University of Newfoundland
Sven Petersen, GEOMAR Helmholtz Centre for Ocean Research KielFollow
Mostafa Fayek, University of ManitobaFollow
Javier Escartin, Ecole Normale Supérieure de Paris

Document Type

Article

Publication Date

1-4-2024

Publication Title

Geochemistry, Geophysics, Geosystems

Volume

25

Issue

1

First page number:

1

Last page number:

27

Abstract

Hydrothermal fluids in ultramafic-hosted hydrothermal systems associated with oceanic detachment faults can be more oxidizing compared to mafic-hosted vent sites. These fluids form a mineral assemblage of pyrite, magnetite and hematite. At 13°30′N on the Mid-Atlantic Ridge, chlorite-quartz breccias recovered from an exposed fault scarp contain pyrite, with abundant magnetite and hematite, indicating that the redox of the fluids was variable. In primary micron-scale zonations in pyrite, Ni, Co, and Se have a decoupled relationship, recording fluctuations in the chemical composition and temperature of hydrothermal fluid as the grains grew. Secondary zonations that erase and overprint primary zonations are limited to the grain margin and permeable regions within the grain core. Secondary zonations formed via two processes: (a) grain dissolution followed by overgrowth, and (b) remobilization of metals during oxidizing fluid flow events. In both instances, Ni and Co have been mobilized and concentrated, and are not lost to the hydrothermal fluid. Superimposed on these features is evidence of grain scale deformation related to periods of fault movement along the detachment surface. Sulfur isotope ratios (δ34S) in pyrite systematically decrease from the grain margin to the grain core, indicating that increased amounts of sulfur were derived from thermochemical sulfate reduction of seawater. Thus, pyrite records the evolution of fluid flow and deformation events during exhumation along the detachment surface from ∼1 to 2 km below the seafloor at the base of the lava pile, with temporal fluctuations in fluid redox identified as an important process in controlling Ni and Co enrichment in pyrite.

Keywords

detachment fault; geochemistry; pyrite; oceanic core complex; trace metals; sulfur isotopes

Disciplines

Oceanography | Oceanography and Atmospheric Sciences and Meteorology

File Format

pdf

File Size

5800 KB

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Publisher Citation

Martin, A. J., Jamieson, J. W., Petersen, S., Fayek, M., & Escartin, J. (2024). Fluid flow, mineralization and deformation in an oceanic detachment fault: Microtextural, geochemical and isotopic evidence from pyrite at 13°30′N on the Mid-Atlantic Ridge. Geochemistry, Geophysics, Geosystems, 25, e2023GC011033. https://doi. org/10.1029/2023GC011033

Repository Citation

Martin, A. J., Jamieson, J. W., Petersen, S., Fayek, M., Escartin, J. (2024). Fluid Flow, Mineralization and Deformation in an Oceanic Detachment Fault: Microtextural, Geochemical and Isotopic Evidence From Pyrite at 13°30′N on the Mid-Atlantic Ridge. Geochemistry, Geophysics, Geosystems, 25(1), 1-27.
http://dx.doi.org/10.1029/2023GC011033