Open AccessOceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge‐flank alteration
Author(s) -
McManus James,
Nägler Thomas F.,
Siebert Christopher,
Wheat C. Geoffrey,
Hammond Douglas E.
Publication year - 2002
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2002gc000356
Subject(s) - authigenic , geology , seawater , diagenesis , hydrothermal circulation , sedimentary rock , geochemistry , isotope fractionation , carbonate , sediment , dissolution , mineralogy , fractionation , oceanography , geomorphology , paleontology , chemistry , organic chemistry
Isotopic analyses of dissolved molybdenum are presented for sediment pore waters from a reducing sedimentary basin and for fluids from a low‐temperature ridge flank hydrothermal system. δ 98/95 Mo in these fluids range from 0.8 to 3.5‰ (relative to a laboratory standard), demonstrating that marine sedimentary reactions significantly fractionate Mo isotopes. Within the upper 3 cm of sediment, manganese oxide dissolution produces an isotopically light fluid relative to seawater (mean of four analyses = 2.1 ± 0.1‰ versus seawater = 2.3 ± 0.1‰). Below 6 cm depth, authigenic Mo uptake results in an isotopically heavier fluid (up to 3.5‰) indicating that reducing sediments are likely to be a net sink for isotopically light dissolved Mo. In contrast, fluid circulation within a low‐temperature ridge‐flank hydrothermal system is a source of isotopically light Mo to the ocean having an end‐member fluid of ∼0.8‰.