Mineral compositions of primary phases in serpentinized peridotites drilled during Leg 153 of the Ocean Drilling Program have been determined by electron probe and ion probe. These peridotites have major-element mineral compositions that are typical of other suites of abyssal peridotites. Incompatible trace-element compositions of diopside in these rocks are extremely depleted, reaching levels that approach those in the most depleted diopsides in abyssal peridotites previously studied (Bouvet Fracture Zone and Hess Deep). The extreme depletion of incompatible trace elements of diopside in peridotites at the Kane Fracture Zone area is notable because this site is distant from any hot-spot-related volcanic activity, and it has been suggested that such extreme depletions only result from plume-related, high-degree melting. The Leg 153 peridotites are quite uniform in composition, both within individual samples and for the suite as a whole. The mantle in this region was fractionally melted to the extent that it was in equilibrium with melts much more depleted than erupted mid-ocean ridge basalts (MORBs), as has been shown for other suites of abyssal peridotites.

Date of initial receipt: 1 August 1995
Date of acceptance: 23 April 1996

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