Titanomagnetites of basalts and diorites from an off-axis volcanic episode in the western Pacific Ocean (leg 61, Deep Sea Drilling Project) were studied for their ulvospinel composition and for changes in the iron--titanium ratio with progressive low temperature oxidation. Thermomagnetic analysis and microscopy indicate that these Fe/Ti spinels are relatively little low temperature oxidized despite their Cretaceous age. Microprobe investigation shows that the Fe/Ti spinels have a wide range of ulvospinel contents and that the range directly reflects the range of parent rock chemistries. This is an important demonstration that ulvospinel contents are not constant but vary within a restricted range of compositions, namely, at least x=0.50 to x=0.75 (Fe3-xTixO4). Recognition of this fact is important in attempting to elucidate changes in cation ratio as a result of progressive low temperature oxidation. Examination of samples of different oxidation states for cation ratio changes associated with low temperature oxidation displayed lower titanium in the more oxidized samples and Ti enrichment in the less oxidized ones. This, however, appears to be a reflection of changing x values with progressive crystallization of individual sills, rather than a consequence of low-temperature oxidation. In the more than 100 grains analyzed, no evidence was found for a more oxidized shell on the exteriors of grains, suggesting that the oxidation process did not proceed uniformly with respect to grain geometry.