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. 5
Presentation Time: 8:00 AM-4:45 PM

Exhumation History of the Leeward Antilles Coeval with Regional Deformation and Island Arc Accretion

BEARDSLEY, Amanda G., Earth Science, Rice University, Houston, TX 77002, SISSON, Virginia B., Earth and Planetary Sciences, American Museum of Natural History, Central Park West at 79th St, New York, NY 10024, AVE LALLEMANT, Hans G., Dept. of Earth Science, Rice Univ, MS-126, Houston, TX 77005-1892, RODEN-TICE, Mary K., Center for Earth and Environmental Science, SUNY Plattsburgh, 101 Broad St, Plattsburgh, NY 12901 and BLYTHE, Ann, Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, abeardsley@chevron.com

Fluid inclusions from veins and zircon and apatite fission-track geochronology from igneous rocks of the Leeward Antilles constrain its regional exhumation history since the Late Cretaceous.  There is evidence for a minimum of three different pressure-temperature environments during the process of island arc accretion in the transpressive Caribbean-South American plate boundary zone.  Fluid inclusion analysis of both igneous rocks and three generations of veins (V1 – V3) suggests a low salinity fluid.  Average homogenization temperatures are used to estimate the maximum burial depth for each vein generation (V1-V3).  Curaçao is interpreted to have been at shallow depths since the Late Cretaceous. In contrast, Aruba and Bonaire underwent a maximum burial depth of 6 km, followed by exhumation to the surface between V1 and V3 vein formation.  Additionally, average homogenization temperature measurements from the igneous samples indicate each pluton is unique. 

New apatite and zircon fission-track ages suggest at least two phases of igneous activity that get progressively younger from west to east. On Aruba, batholith samples yield ZFT ages of 136.4 ± 25.4 Ma and 47.8 ± 9.2 Ma and yield AFT ages of 86.9 ± 33Ma and 69.8 ± 20 Ma.  Similarly, La Blanquilla samples yield two distinct events at 56.8 ± 8.4 Ma (ZFT) and 40.6 ± 5.4 Ma (ZFT) and likewise at 66.7 ± 7 Ma and 50.4 ± 8 Ma  (AFT).  Finally, Los Testigos samples yield ZFT ages of 42.2 ± 6.2 Ma and 28.8 ± 3.2 Ma. Our new geochronologic data support a model of diachronous deformation and exhumation coeval with island arc accretion.  Thus, the PTt path is likely driven by isobaric cooling and steady-state uplift.  Consequently, exhumation is controlled by tectonics and not climate, in contrast to other regions along the South American plate boundary zone.