Correlation of magnetic properties with Δ(Sr) of igneous rocks from the northeast Pacific and Gulf of California

The magnetic properties of basalts and diabases recovered under Legs 63 and 64 of the Deep Sea Drilling Project are summarized. They are first correlated with the measured grain sizes of the opaque minerals and the overall alteration states of the rocks, the latter measured by conventional chemical parameters such as water content, total volatiles content, and Fe₂O₃/FeO ratio. It is shown, however, that the decrease in ⁸⁷Sr/⁸⁶Sr upon leaching (Δ(^87/86Sr)) is perhaps the best quantifier of the overall alteration state of the whole rocks as well as of the degree of low-temperature oxidation suffered by the titanomagnetites. It is well correlated with Curie-point variations caused by changes in the Fe³⁺/Fe²⁺ ratio.