Carbonate veins as recorders of seawater evolution, CO2 uptake by the ocean crust, and seawater-crust interaction during low-temperature alteration

Abstract

Carbonates precipitate in fractures, vesicles and matrix of breccias within the basaltic base¬ment of oceanic ridge flanks. They form during low-temperature alteration and can provide in¬sights into processes related to seawater circulation and seawater-basement interaction. It has been proposed that the aging ocean crust is a major sink for CO2 and plays a major role for the global carbon cycle. However, detailed knowledge about the abundance and composition of carbonate is necessary to fully understand the role of the oceanic crust in global chemical cycles. The main objective of this thesis is to provide reliable data on the fraction of carbonate in the ocean crust and to gain insights into chemical changes during low-temperature seawater-crust interaction. For this purpose the carbonate inventory of 23 DSDP and ODP drill cores from the Atlantic and Pacific was logged and analyzed in terms of major and trace element concentrations and isotopic compositions (Sr, O, C).