Fractionation of abyssal tholeiites: Samples from the oceanographer Fracture Zone (35°N, 35°W)

Chemical analyses of 48 fresh abyssal tholeiite specimens sampled from two dredge localities clearly define systematic chemical differences which indicate a moderate iron-enrichment trend of fractionation oblique to the FeO^* * Tholeiites found on the ocean floor were originally called oceanic tholeiites [1]. Later, investigators used this term to describe tholeiites from oceanic islands as well as the ocean floor, although the tholeiites from these contrasting settings have chemistries which are distinctly different. We prefer the term abyssal tholeiite [2] and use it throughout.-MgO side of the AFM diagram. This magma evolution results in significant changes in elemental abundances of K₂O, P₂O₅ and TiO₂. These results suggest that fractionation may be important in controlling the chemistry of abyssal tholeiites along sections of the mid-oceanic ridge.