Results of paleomagnetic and rock magnetic measurements are presented from gabbroic samples recovered during Ocean Drilling Program Leg 147 at the Hess Deep. Paleomagnetic measurements indicate that samples acquired up to two small components of secondary remanent magnetization. Stable magnetic inclinations determined after alternating-field and thermal demagnetization reveal a mean stable magnetic direction (38°) that is significantly steeper than that predicted for this equatorial site (<5°). Thus, it is likely that remanent magnetization was acquired before tectonic uplift. The mean intensity of natural remanent magnetization for the recovered gabbros is 2.3 A/m, and the Koenigsberger ratio indicates that the in situ magnetization is dominated by remanent, rather than induced, magnetization. Measurements of hysteresis loop parameters indicate that the effective magnetic grain size of the gabbro samples falls within the pseudo-single domain region. Although recovered from a fast-spreading ridge, the paleomagnetic and rock magnetic properties of the gabbros from Hole 894G are very similar to those of gabbros recovered from slow-spreading ridges.

Date of initial receipt: 22 July 1994
Date of acceptance: 23 January 1995

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