Volatile Emissions From Central Atlantic Magmatic Province Basalts: Mass Assumptions and Environmental Consequences

J. Gregory McHone, Graduate Liberal Studies Program, Wesleyan University, Middletown, Connecticut

   Mesozoic basins that contain extrusive basalts of the 200 Ma Central Atlantic Magmatic Province (CAMP) presently total about 320,000 km2.  However, CAMP dikes and sills that fed the basin basalts are also spread widely across an area about 10 million km2 within four continents.  In addition, basalts of the east coast margin igneous province (ECMIP) of North America, which cause the east coast magnetic anomaly, covered about 110,000 km2 with 1.3 million km3 of extrusive lavas.  If only half of the continental CAMP area was originally covered by 200 m of surface flows, the total volume of CAMP and ECMIP lavas exceeded 2.3 million km3.  Weighted averages for the volatile contents of 686 CAMP tholeiitic dikes and sills, in weight %, are: H2O+  = 0.823; CO2 = 0.117; S = 0.052; F = 0.035; and Cl = 0.050.  Atmospheric emissions of volatiles from flood basalts are conservatively estimated as 50 % to 70 % of the volatile content of the sub-volcanic magmas, mainly exsolved into gaseous plumes from lava curtains at the erupting fissures.  Volcanic emissions of these gases therefore ranged between 1.11 x 1012 and 5.19 x 1012 metric tons, enough for major worldwide environmental problems.  Radiometric and stratigraphic dates indicate that most CAMP volcanic activity was brief, widespread, and close to the Tr-J boundary, which is marked by a profound mass extinction.  The CAMP may be assigned a catastrophic role upon better precision in the timing and duration of its volcanic episodes, which are not yet sufficiently determined.