Gabbro-metabasalt polymict breccias cored in Deep Sea Drilling Project Hole 453 are cemented in part by hydrothermal alteration to lower greenschist facies (chlorite-epidote-actinolite) mineral assemblages. Temperature estimates for this alteration, based on oxygen isotope determinations of secondary minerals, are nearly 100°C at the top of the breccias and over 200°C in a zone of intense alteration near the base.

Analyses were made according to the method of Clayton and Mayeda (1963) but utilized O2 gas in a 6-in. Nuclide mass spectrometer housed at Lamont-Doherty Geological Observatory instead of converting it to CO2. The mass spectrometer reference gas, tank O2, was calibrated using NBS-28, which was assumed to have a 1 8O = +10.0 per mil (SMOW), as given in Friedman and Gleason (1973).

Supplement to: Lawrence, James R; Natland, James H (1982): Temperatures of hydrothermal alteration in Deep Sea Drilling Project Hole 453, western Mariana Trough. In: Hussong, DM; Uyeda, S; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 60, 755-758