A new plate tectonic model of the Caribbean: Implications from a geochemical reconnaissance of Cuban Mesozoic volcanic rocks

Accreted terranes, comprising a wide variety of Jurassic and Cretaceous ign eous and sedimentary rocks, are an important and conspicuous feature of Cub an geology. Although the Mesozoic igneous rocks are generally poorly expose d and badly altered, we have collected and geochemically analyzed 25 sample s that place new constraints on plate tectonic models of the Caribbean regi on. From our recognizance sampling, six main lava types have been identifie d within the Mesozoic igneous rocks of Cuba: rift basalts, oceanic tholeiit es, backarc basin lavas, boninites, island are tholeiites (IAT), and calc-a lkaline lavas. We suggest that the rift-related basalts may have formed dur ing the development of the proto-Caribbean, as the Yucatan block rifted awa y from northern South America in Jurassic-Early Cretaceous time. The Early Cretaceous oceanic tholeiites have pat rare earth element patterns, and are compositionally similar to Pacific mantle plume-derived oceanic plateaus o f similar age. The Early Cretaceous arc-related rocks are either backarc ba salts, boninites, or relatively trace element-depleted IAT lavas, A limited amount of geochemical and field evidence hints that two parallel are syste ms existed in the western proto-Caribbean area in Early Cretaceous time. Th is leads us to speculate that in the proto-Caribbean at this time there was a western are with a northeast-dipping subduction zone erupting IAT lavas (with Farallon plate being consumed), and a more eastern boninitic are with a south- west-dipping subduction zone (with proto-Caribbean plate being co nsumed). This latter are was relatively short lived and after being aborted was mostly eroded away The Cretaceous primitive (IAT) are survived and, la ter in Cretaceous time, as this are system moved into the widening gap betw een North and South Americas, calc-alkaline lavas began to be erupted, The evidence suggests that the change from IAT to calc-alkaline lavas was gradu al and not abrupt. These new data, although limited, provide geochemical co nstraints on the tectonic development of the northern part of the Caribbean plate. In consequence, we present a new plate tectonic model for this area of the Caribbean.