ABSTRACT

Sulphide globules were found in glassy rim as well as in more crystalline interior of pillowed abyssal tholeiite from the Mid-Atlantic Ridge near 30°N latitude. The magma reached saturation with respect to sulphide at the time of eruption and immiscible silicate and sulphide liquids were quenched when the magma was extruded on the sea floor. Saturated sulphur content of the basaltic liquid was estimated at about 0.15 ± 0.03 percent by weight. Sulphur isotopic abundance of the rocks expressed in δ³⁴S ranges from +0.3 to +1.6‰. This value may represent the isotopic ratio of mantle sulphur.