Volatile emissions from Central Atlantic Magmatic Province Basalts: Mass assumptions and environmental consequences

Abstract

Mesozoic basins that contain extrusive basalts of the 200 Ma Central Atlantic Magmatic Province (CAMP) presently total about 320,000 km 2 . However, CAMP dikes and sills similar to those that fed the basin basalts are also spread widely across an area greater than 10 million km 2 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 km 2 with 1.3 million km 3 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 km 3 . Weighted averages for the volatile contents of 686 CAMP tholeiitic dikes and sills, in weight %, are: CO 2 = 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. Total volcanic emissions of these gases therefore ranged between 1.11 x 10 12 and 5.19 x 10 12 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. More precise information about the timing, duration, and chemical emissions of volcanic episodes is needed to support a model for CAMP in the extinction event.