Major and trace elements in sediments from ODP Hole 205-1253A and two ODP Leg 170 holes

Crystal fractionation and accumulation have further modified the melt compositions, particularly within the lower stratigraphic unit. Mixing models indicate that these units are derived from a mantle source that is 50%-70% enriched compared to depleted mid-ocean-ridge source mantle. In the context of the complex regional tectonic and volcanic history of the Cocos plate, this igneous complex likely represents melts of depleted upper mantle that were previously enriched during transit near the Galápagos hotspot.

A postenrichment change in the local-regional tectonic stress regime may have triggered decompression melting and emplacement of the igneous complex far from any active spreading center or plume. Preexisting plate fractures, ridge jumps, and abandoned spreading centers may have facilitated distal reach of plume-overprinted material.