(Table 5) Oxygen- and hydrogen-isotopic compositions of metalliferous and pelagic sediments as well as nontronite formation temperatures in the Galapagos mounds area, DSDP Leg 70

Oxygen was extracted from whole-rock powders with use of the bromine pentafluoride procedure (Clayton & Mayeda, 1963; doi:10.1016/0016-7037(63)90071-1). The method described by Godfrey (1962; doi:10.1016/0016-7037(62)90053-4) was used to extract hydrogen. Oxygen- and hydrogen-isotopic compositions are reported using normal delta-notation relative to SMOW. The oxygen-isotopic composition of the carbonate component of pelagic oozes is reported relative to the SMOW standard. Routine reproducibilities of d18O- and dH2-values are typically 0.15 and 2 per mil, respectively. Temperatures of formation of nontronites have been estimated from the O-isotopic composition by applying the formula of Yeh and Savin (1977; doi:10.1130/0016-7606(1977)88<1321:MOBMOA>2.0.CO;2) for normal smectites (1000 ln a = 2.67 x 10**6 x T**(-2) - 4.82). It was assumed that the d18O-value for solutions from which the nontronite formed was 0.0, the value for normal seawater.