Is the Lower Duarte Igneous Complex (Hispaniola) a Remnant of the Caribbean Plume-Generated Oceanic Plateau?

Abstract

Eleven samples of metapicrites, metaankaramites, diabases, and cumulates of the lower Duarte Complex in central Hispaniola were analyzed for major, trace element, and Nd-Sr isotopic compositions. The picrites are plagioclase-free and rich in phenocrysts of clinopyroxene and olivine pseudomorphs. The ankaramites differ from the picrites by the presence of abundant and large clinopyroxene phenocrysts. The diabases consist of plagioclase laths embedded with clinopyroxene. These rocks show E-MORB affinities. Relative to N-MORB, they exhibit high concentrations in Nb, Ta, Th, Ti, light and medium rare earth elements, and low Y contents. They are associated with olivine-clinopyroxene cumulates and gabbros. The olivine-clinopyroxene cumulates differ from the lavas by lower trace element contents and a lesser LREE enrichment. The gabbros exhibit flat REE patterns. All these clinopyroxene-rich rocks show homogeneous $$\epsilon_{Nd(T = 150 Ma)}$$ ratios ( + 5.3 to +7.1), which plot within the range of Ocean Island basalts. Their $$\epsilon_{Sr(T = 150 Ma)}$$ ratios are less homogeneous ($$-16.7 < \epsilon_{Sr} < -3.7; 0.70315 < (^{87}Sr/^{86}Sr)_{i} < 0.70406$$) but fall within the Mantle Array, with the exception of the gabbro and a picrite, which show the highest $$(^{87}Sr/^{86}Sr)_{i}$$ ratios (0.70374, 0.70406). The picrites are geochemically similar to the Enriched Basalts from Gorgona and southern Haiti. These data lead us to develop the hypothesis that the lower Duarte complex likely represents the remnants of an oceanic plateau generated by a Galapagos-type hotspot that collided with the proto-Caribbean arc during the Late Cretaceous.