HR: 0830h
AN: V51G-0360    [PDF]
TI: THE CENTRAL ATLANTIC MAGMATIC PROVINCE: AGE COMPARISON BETWEEN THE SOUTH CAROLINA DYKES AND MOROCCO LAVA FLOWS
AU: Youbi, N
EM: Youbi@ucam.ac.ma
AF: Cadi Ayyad University, Boulevard Prince Moulay Abdellah, Marrakech, Marrakech Morocco
AU: * nomade, s
EM: snomade@bgc.org
AF: Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94704 United States
AU: Breutel, E
EM: BeutelE@cofc.edu
AF: college of charleston, college of charleston, Charleston, SC 29412 United States
AU: Knight, k
EM: kbk@uclink.berkeley.edu
AF: UC berkeley, UC Berkeley department of Earth and planetary science, Berkeley, CA 94720 United States
AB: Believed to be the largest volcanic province on Earth at more than 6000 km long and 2000 km wide, the Central Atlantic Magmatic Province (CAMP) stretches from Eastern Canada to Brazil and from Western Spain to the Ivory Coast. Due to the massive erosion and subsequent in filling of these areas since the 200 Ma rifting event, dikes and sills constitute the majority of the exposed CAMP volcanics. However, well preserved lava flows have been found in the Triassic basins of the Northeastern United States and Morocco. Despite numerous $^{40}$Ar/$^{39}$Ar dating attempts, very few of the exposed CAMP volcanics have been successfully dated due to a variety of factors including; excess argon and alteration. Especially no age is available in the well-mapped but structurally complex South and North Carolina dykes swarm as well as only few scattered ages in the Moroccan Trias-Liassic basins. Our goal is to better constrain the emplacement timing of the dykes swarm but also to compare age of both intrusive and effusive rocks from the same magmatic event but separated from more than 1000 km, 200 Mys ago. Several questions continue to surround the CAMP volcanic province including its cause and emplacement mechanism. Toward that end we have collected and dated dyke samples from the Carolinas and flows in Morocco, 1000 km away and across the rift. We anticipate that a comparison of these dates will enable us to understand more about the timing between the emplacement of the flows and dykes. We have collected in South Carolina and High Atlas in Morocco 7 and 9 hand samples respectively. Specimens from South Carolina correspond to the three distinct dykes' direction NE-SW, NW-SE and NS. In Morocco, samples were collected in four sections (100 to 300 m thick) located in the High Atlas between Marrakech and Ouarzazate. From each hand sample two different transparent plagioclase fractions, 250-180 and 180 to 100 microns, were separated. We have performed step heating experiments at the Berkeley Geochronology Center using a defocus CO$_{2}$ laser. Plateau ages obtained in both areas are undistinguishable at 2 sigma level ranging from 201 to 198 Ma (relative to FCs at 28.02 Ma). This is coherent with previous ages in Brazil and NE-US and reinforced the instantaneous emplacement at the geological time scale of this enormous volcanic province with ramifications for tectonic and climatic processes.
DE: 0370 Volcanic effects (8409)
DE: 1035 Geochronology
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 5475 Tectonics (8149)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting