SUBSURFACE IGNEOUS ROCKS OF FLORIDA AND GEORGIA: TIMING AND RELATIONSHIP TO THE CENTRAL ATLANTIC MAGMATIC PROVINCE (CAMP)

Despite many years of geochemical, tectonic, and geochronological studies, the geodynamic setting of the CAMP remains highly controversial. Models for its formation and high levels of magmatic production include lithospheric delamination, thermal insulation of the mantle, and a mantle plume. The igneous rocks of the Florida and Georgia subsurface, encountered via drill hole sampling, represent a potentially important link in our ability to differentiate these potential mechanisms. Early studies (1-4) of these rocks provided detailed petrological and geochemical observations and reported ages and a tectonic setting largely consistent with an emplacement coeval with the tholeiitic dikes, sills, and lava flows typically associated with the CAMP. These rocks are divided into three main geographic/lithological provinces (5): 1) North Florida Volcanic Series (NFVS; felsic/intermediate volcanic rocks); 2) Southwest Florida Mesozoic Volcanic Province (SFMVP; basalts, diabases, rhyolties); 3) The North Florida Tholeiites (NFT; basalts and diabases). The rocks of the SFMVP are of particular interest due to their paleogeographic position proximal to the convergence of radiating dike swarms associated with the CAMP. If the plume model is correct, this could be where the plume head impinged the crust (6). The primary goal of this project is to place precise constraints on the timing of the formation of these provinces, determining their association with the CAMP. We sampled all wells at intervals known to contain Mesozoic igneous rocks. We are currently in the process of extracting zircons, which will be surveyed by LA-ICP-MS and dated using CA-TIMS for high-precision ages. These data will be used to test hypotheses on the tectonic evolution of the Eastern North American Margin.

1) Milton & Grasty, AAPG Bull. 53.12 (1969): 2483-2493; 2) Barnett, Gulf Coast Assoc. Geo. Soc. Trans. 25(1975):122-142; 3) Chowns & Williams. US Dept. Int. Geo. Surv. (1983); 4) Arthur, FGS Rept. Inv. 97 (1988); 5) Heatherington & Mueller. Gondwana Res. 6.2 (2003): 296-311; 6) Ernst & Buchan GSA Spec. Pap. 352 (2001): 247.