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

Abstract

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 40 Ar‐ 39 Ar 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 40 Ar‐ 39 Ar 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.