Geochemical constraints on the origin of the late Jurassic proto-Caribbean oceanic crust in Hispaniola

摘要: The nature of the oceanic crust produced through rifting and spreading between North South America during Late Jurassic is a key element for Caribbean plate tectonic model reconstruction. Located in Cordillera Central Hispaniola, Loma La Monja volcano-plutonic assemblage (LMA) com- posed gabbros, dolerites, basalts, sediments, as well metamorphic equivalents, which represent dismembered fragment this proto-Caribbean crust. Petrologic geochemical data show that LMA have relatively broad diversity composition, crystallization products typical low-pressure tholeiitic fractionation mid-ocean ridge basalts (MORB)-type parental magmas, ranging from N- to E-MORB. Three groups been dis- tinguished volcanic sequence: LREE-flat slightly LREE-enriched II III occur inter- layered lower stratigraphic levels; LREE- depleted group I upper levels. Mantle melt modeling suggests magmas are con- sistent by mixing within mantle column low- degree (\1%) melts deep garnet lherzolite source high-degree ((15%) shallow spinel source, explained with moderate high (14-18%) very ((20%) fractional melting degrees shallower respectively. Thus, upward sequence LMA, progressively more extensive sources, plume-influenced Nb/Y versus Zr/Y systematics combined recent reconstructions reveal Colombian plateau fragments Hispaniola formed heterogeneous regions related distinct plumes at least Aptian-Albian ((96 Ma) Campanian.