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Projekt
The role of ocean crust low temperature alteration carbonates in the global calcium cycle
Antragsteller
Professor Dr. Anton Eisenhauer
Fachliche Zuordnung
Paläontologie
Förderung
Förderung von 2007 bis 2011
Projektkennung
Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 49004711
Calcium carbonate precipitate that form during the low temperature alteration of ocean crust basalts (LTA carbonates) are an important calcium sink in the global calcium cycle. The total calcium flux has been estimated as representing about 10 % of the total Ca output flux of the ocean. First measurements of the calcium isotopic composition of LTA carbonates point to a significant fractionation. This indicates a measureable influence of this calcium flux on the global calcium isotope budget of the oceans. LTA carbonates represent a gap in our knowledge of the global calcium isotope fluxes that may explain discrepancies in the Neogene isotope budget. We therefore plan to sample LTA carbonates from different sites, different crustal depths and different crustal ages. We wil) use oxygen isotopes, trace elements and strontium isotopes to constrain the sources of calcium for these precipitates. We will then measure the calcium isotopic composition of the LTA carbonates to estimate the globally averaged isotope flux from the ocean to this important sink. With that the project will help to better constrain calcium isotope fluxes and to find an explanation for the discrepancies in current calcium isotope budgets. The data will further give new insights in the formation conditions of LTA carbonates at different crustal depths. They will finally show whether these formation conditions varied with time and whether LTA carbonates may be used as recorders of the ocean water calcium isotope composition through time. Valuable supplemental information for the interpretation of our data is expected from a complementary project (A. Klügel, W. Bach; Univ. Bremen) which aims to combine an inventory of the distribution of LTA carbonates in IODP/ODP cores with a fine-scale investigation of the trace elemental composition and age structure of these carbonate veins. Therefore we plan joint sampling sessions and to investigate common samples to guarantee the synergy of the two projects and the comparability of the data.
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