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Why the oxygen isotopic composition of sea water changes with time
Author(s) -
Walker James C. G.,
Lohmann K. C.
Publication year - 1989
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl016i004p00323
Subject(s) - weathering , geology , seawater , hydrothermal circulation , silicate , geochemistry , earth science , oxygen , composition (language) , chemical composition , seabed , oceanography , mineralogy , chemistry , paleontology , linguistics , philosophy , organic chemistry
The oxygen isotopic composition of sea water is determined by interactions with fresh, silicate rocks. Interactions at high temperature, principally hydrothermal interactions on the sea floor, make sea water isotopically heavier. Interactions at low temperature, including sea floor weathering but principally weathering of fresh, crystalline rocks on the continents, make sea water isotopically lighter. Any change in the relative rates of these high and low temperature interactions will cause a change in the composition of sea water. Extreme limits might be −15 per mil relative to SMOW to +4 per mil. Possible rates of change appear to be quite slow, perhaps 1 per mil in 10 8 years, because of the large size of the oceanic reservoir. Evolution in tectonic style over the course of earth history may have caused a change in the oxygen isotopic composition of sea water as fresh crystalline rocks have been increasingly blanketed by weathered sediments and as deepening oceans have increasingly flooded the places where earth's internal heat is released at the surface.