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

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.