Stable isotope composition of secondary carbonates from basalric lavas of ODP Hole 104-642E

The thick pile of basaltic lavas penetrated during drilling are variably altered with extensive development of calcite, which fills vesicles and fractures along with saponite and celadonite. delta13C results, determined by mass spectrometry, show that most carbonates above about 1040 m have values between -2.5 and -5.5 per mil (PDB), but a few samples at approximately 1090 m have depleted delta13C values down to -26.3 per mil.

Below 1100 m the delta13C values decrease from -6.0 per mil to -12 per mil. The delta 18O values range between -1.9 and -13.7 per mil (PDB), and generally decrease with depth. The results are interpreted as indicating that the calcites were precipitated from cool seawater percolating through the basalt pile at waterrrock of less than 10:1, during seawater incursion at about 54 Ma.