2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 4
Presentation Time: 8:55 AM

Late Cretaceous Subduction Initiation Leeward Antilles/Aves Ridge: Implications for Caribbean Geodynamic Models

WRIGHT, J.E.1, WYLD, S.J.1 and URBANI, Franco2, (1)Geology, Univ of Georgia, Athens, GA 30602, (2)Escuela de Geologia, Minas y Geofisica, UCV, Caracas, Venezuela, jwright@gly.uga.edu

The Leeward Antilles from Aruba on the west to La Blanquilla on the east consist of, where exposed, a basement complex of pillow lava intruded by diabase that represents exposures of the Caribbean Large Igneous Province (CLIP) that is intruded by younger tonalitic to granodioritic plutons and dikes that generally have elevated Sr/Y values and REE patterns similar to and/or diagnostic of adakites. U-Pb SHRIMP-RG zircon ages from younger plutonic suite ranges in age from Late Cretaceous (89 ± 1 Ma; Aruba batholith) to Eocene (ca 59 Ma on La Blanquilla). Abundant evidence of Cretaceous sub aerial exposure of the CLIP rocks exists on Aruba, Curacao, and Los Roques. Significantly the oldest related arc intrusion is Late Cretaceous. This is consistent with our detrital zircon data from Paleocene/Eocene turbidites on Curacao derived from a mixed arc/continental source. Dredge hauls from the Aves Ridge (the continuation of the Leeward Antilles?) produced granodiorite and weathered diabase and basalt. We interpret to weathered mafic rocks to represent the CLIP and speculate that the Aves Ridge has a similar geologic evolution to the Leeward Antilles (CLIP intruded by younger plutons). We interpret these relations to indicate that arc magmatism along the Aves Ridge/Leeward Antilles began in the Late Cretaceous (ca 89 Ma) and was constructed on a basement consisting principally of the CLIP. We suggest that subduction initiation occurred along a transform that truncated the Greater Antilles arc and separated the arc and CLIP from proto-Caribbean oceanic crust. The island of Bonaire has a very different geologic evolution than any other studied exposure of the Leeward Antilles, and consists of significantly older arc strata (ca 98 Ma). We interpret Bonaire as a fragment of the Greater Antilles derived from the transform truncated boundary between the Greater Antilles and the proto-Caribbean seafloor.