Abstract

Sulfides in 27 samples of drill core from four Leg 37 drill holes have been studied. Pyrite is the most abundant sulfide, averaging 0.39 ± 0.51% of basalt samples. Also present in basalt are sparse (0.0001%) and small (< 8 μm) magmatic globules of finely intergrown pyrrhotite, pentlandite, and chalcopyrite-iss, as well as a few globules composed of only one of these minerals. Larger and more abundant magmatic globules are present in gabbro and peridotite; pyrite is a minor phase in these rocks.Fe, Ni. Cu. and S are the major elements, and Co a minor element in the globules. Averaged Ni/Cu ratios for globules are: 3.3 (peridotite), 1.0 (gabbro). and 0.4 (basalt), the decrease in ratio indicating less normative olivine in the respective parent magmas when the globules were formed.Sulfides in globules in peridotite, and to a lesser extent in gabbro, form distinct grains free of inclusions, and appear to have equilibrated to below 300 °C. In basalt the minerals are finely intergrown and indicate quenching above about 600 °C, with local equilibration at lower temperatures.Three analyses of sulfur in basalt glass ranged from 930 to 1160 ppm, in good agreement with other analyses of deep-ocean basalts.

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