(Table 2) Representative major and trace element analyses of diabase dikes of ODP Hole 140-504B

Hole 504B is located in Panama Basin approximately 200 km south of the Costa Rica Rift within a tectonically undisturbed oceanic crust formed at the Costa Rica Rift spreading center. The hole was drilled in several Deep Sea Drilling Project (DSDP)/Ocean Drilling Program (ODP) legs, including ODP Leg 140. The 378.9 m of core drilled at Hole 504B during Leg 140 continues the dike complex recovered previously during DSDP Leg 83. All the rocks drilled during Leg 140 are fragments of variably metamorphosed dikes composed of olivine-plagioclase-clinopyroxene-, olivine-plagioclase-, and olivine-plagioclase-clinopyroxene-spinel-bearing basalts. We report results of determination of rare earth elements (REE) and large-ion lithophile (LIL) elements in 28 representative samples from the major units of the Hole 504B dike complex. Analyzed samples display relatively uniform REE patterns with only a slight difference in the extent of light REE depletion. LIL elements show large variations independent from other incompatible (Zr and Y), compatible (Cr, Ni, Co), and rare earth elements. Observed REE variations indicate that metamorphism has changed LIL distribution, but has not affected REE patterns. Variable REE depletions are believed to represent original magmatic characteristics of the Costa Rica Rift oceanic crust. LIL distribution favors Ba redistribution due to the fluid-rock interaction in the lower oceanic crust. REE systematics define various degree of depletion in Leg 140 diabase dikes consistent with their derivation from a variably depleted MORB-type source