Stable isotope composition of pore waters and carbonate veins of ODP Leg 121 holes

The oxygen isotopic composition of the pore waters from the sediments and the oxygen and carbon isotopic composition of carbonate veins from basalts of Leg 121 were analyzed. The pore-water data document the extent of the alteration of volcanic ashes and basalt. The influence of an increase in the isotopic composition of deep water as a result of the growth of polar ice caps over the last million years can also be detected in the pore waters of the upper 100 m of the sediments. Temperatures of formation of carbonate veins from basalts from sites located on the Ninetyeast Ridge increase northward along the ridge along with the increased age of the crust and depth of sediments. The temperatures calculated for carbonate veins from Site 758 indicate that a thermal event occurred at some time in the past.