Plume mantle source heterogeneity through time:: Insights from the Duarte Complex, Hispaniola, northeastern Caribbean

[1] Located in the Cordillera Central of Hispaniola, the Duarte Complex offers an opportunity to study an on-land fragment of the Caribbean- Colombian oceanic plateau. Geochemical, Sr-Nd isotope, and 40Ar-39Ar radiometric age data combined with detailed mapping have shown that the Duarte Complex includes two lithostratigraphic units, composed of four geochemical groups of metavolcanic rocks: Group Ia, low-Ti high-Mg basalts, and group Ib, high-Ti picrites and primitive high-Mg basalts, occur interlayered in the lowermost levels of the lower unit; group II, light rare earth element (LREE)-enriched picrites, ferropicrites and high-Mg basalts, forms the main lava sequence of the lower unit; and group III, LREE-enriched Fe-Ti basalts, is present exclusively in the upper unit. Nd isotope and incompatible trace element patterns are diverse in the Duarte Complex metavolcanics and are consistent with mantle sources related to a heterogeneous plume. Mantle melt modeling suggests that an early, extensive melting ( 10 - 20%) of shallow mantle resulted in the formation of relatively depleted group I and II magmas, whereas the late, more enriched group III magmas were the product of deeper, low-degree (< 3%) melting of a heterogeneous plume. Therefore plume mantle sources were more enriched and deeper through time. Foliated amphibolites of the Duarte Complex yield 40Ar-39Ar hornblende plateau ages of 93.9 +/- 1.4 and 95.8 +/- 1.9 Ma (Cenomanian, 99.6 - 93.5 Ma) that demonstrate an older age of the protholiths, probably Albian (> 96 Ma). Hence an Early Cretaceous phase of the Caribbean- Colombian oceanic plateau construction is recorded in Hispaniola.