Multiple plume events in the genesis of the peri-Caribbean Cretaceous oceanic plateau province

The oceanic crust fragments exposed in central America, in north-western So uth America, and in the Caribbean islands have been considered to represent accreted remnants of the Caribbean-Colombian Oceanic Plateau (CCOP). On th e basis of trace element and Nd, Sr, and Pb isotopic compositions we infer that cumulate rocks, basalts, and diabases from coastal Ecuador have a diff erent source than the basalts from the Dominican Republic. The latter suite includes the 86 Ma basalts of the Duarte Complex which are light rare eart h element (REE) -enriched and display (relative to normal mid-ocean ridge b asalts, NMORB) moderate enrichments in large ion lithophile elements, toget her with high Nb, Ta, Pb, and low Th contents. Moreover, they exhibit a rat her restricted range of Nd and Pb isotopic ratios consistent with their der ivation from an ocean island-type mantle source, the composition of which i ncludes the HIMU (high U-238/Pb-204) component characteristic of the Galapa gos hotspot. In contrast, the 123 Ma Ecuadorian oceanic rocks have flat REE patterns and (relative to NMORB) are depleted in Zr, Hf, Th, and U. Moreov er, they show a wide range of Nd and Pb isotopic ratios intermediate betwee n those of ocean island basalts and NMORB. It is unlikely, on geochemical g rounds, that the plume source of the Ecuadorian fragments was similar to th at of the Galapagos. In addition, because of the NNE motion of the Farallon plate during the Early Cretaceous, the Ecuadorian oceanic plateau fragment s could not have been derived from the Galapagos hotspot but were likely fo rmed at a ridge-centered or near-ridge hotspot somewhere in the SE Pacific.