Petrology of basalts from hole 504B, Deep Sea Drilling Project, Leg 83.

Abstract

The basalts from the Costa Rica rift, just W of Ecuador, are remarkably uniform in major- and trace-element composition throughout the 1075.5 m of basement drilled. They have high mg values (0.60-0.70) and CaO abundances (11.7-13.7%; Ca/Al = 0.78-0.89), and are depleted in Cr and Ni. They are also depleted in moderately incompatible trace elements (Zr, V, Ti, etc.) and in Nb, LREE, etc. (Following abstracts)-K.A.R.