Geodiversity of Hydrothermal Processes Along the Mid-Atlantic Ridge and Ultramafic-Hosted Mineralization: A New Type of Oceanic Cu-Zn-Co-Au Volcanogenic Massive Sulfide Deposit

Yves Fouquet, Pierre Cambon, Joël Etoubleau, Jean Luc Charlou, Héléne Ondréas, Fernando J.A.S. Barriga, Georgy Cherkashov, Tatiana Semkova, Irina Poroshina, M. Bohn, Jean Pierre Donval, Katell Henry, Pamela Murphy, Olivier Rouxel

Research output

62 Citations (Scopus)

Abstract

Several hydrothermal deposits associated with ultramafic rocks have recently been found along slow spreading ridges with a low magmatic budget. Three preferential settings are identified: (1) rift valley walls near the amagmatic ends of ridge segments; (2) nontransform offsets; and (3) ultramafic domes at inside corners of ridge transform-fault intersections. The exposed mantle at these sites is often interpreted to be a detachment fault. Hydrothermal cells in ultramafic rocks may be driven by regional heat flow, cooling gabbroic intrusions, and exothermic heat produced during serpentinization. Along the Mid-Atlantic Ridge (MAR), hydrothermal deposits in ultramafic rocks include the following: (1) sulfide mounds related to high-temperature low-pH fluids (Logatchev, Rainbow, and Ashadze); (2) carbonate chimneys related to low-temperature, high-pH fluids (Lost City); (3) low-temperature diffuse venting and high-methane discharge associated with silica, minor sulfides, manganese oxides, and pervasive alteration (Saldanha); and (4) stockwork quartz veins with sulfides at the base of detachment faults (15°05'N). These settings are closely linked to preferential circulation of fluid along permeable detachment faults. Compared to mineralization in basaltic environments, sulfide deposits associated with ultramafic rocks are enriched in Cu, Zn, Co, Au, and Ni. Gold has a bimodal distribution in low-temperature Zn-rich and in hightemperature Cu-rich mineral assemblages. The Cu-Zn-Co-Au deposits along the MAR seem to be more abundant than in ophiolites on land. This may be because ultramafic-hosted volcanogenic massive sulfide deposits on slow spreading ridges are usually not accreted to continental margins during obduction and may constitute a specific marine type of mineralization.

Original languageEnglish
Title of host publicationDiversity Of Hydrothermal Systems On Slow Spreading Ocean Ridges Diversity Of Hydrothermal Systems On Slow Spreading Ocean Ridges
PublisherWiley-Blackwell
Pages321-367
Number of pages47
ISBN (Electronic)9781118666616
ISBN (Print)9780875904788
DOIs
Publication statusPublished - 29 Mar 2013
Externally publishedYes

Publication series

NameGeophysical Monograph Series
PublisherAmerican Geophysical Union
Volume188
ISSN (Print)0065-8448

Scopus subject areas

  • Geophysics

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