S Burden in CFBs: A New Approach

Authors: Sara Callegaro (Padova University) , Don Baker (McGill University) , Andrea Marzoli (University of Padova) , Angelo De Min (Trieste University) , Tina Geraki (Diamond Light Source) , Herve Bertrand (ENS-Lyon) , Cecilia Viti (Siena university) , Fabrizio Nestola (University of Padova)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: Goldschmidt
Peer Reviewed: Yes

State: Published (Approved)
Published: August 2013
Diamond Proposal Number(s): 8058

Abstract: Most Phanerozoic Large Igneous Provinces (LIPs) are associated in age with, and may have triggered, major mass exctinctions. This is epitomized by the synchroneity of the Central Atlantic magmatic province (CAMP; c. 201 Ma) and the Deccan Traps (c. 66 Ma) with the end-Triassic and the end-Cretaceous biotic crises, respectively. However, LIPs not associated to mass extinctions are also recorded, as in the case of the ParanĂ -Etendeka (PE; c. 134 Ma). Although climatic forcing caused by huge emissions of volcanic gases such as SO2 and CO2 is now accepted, precise estimates of gas contents of the basalts and their gas emission masses and rates are still poorly constrained. The differences in environmental impact of these three LIPs may reflect their different gas outputs. Here we illustrate a new approach of estimating magmatic SO2 emissions. First, the pyroxene/melt S partition coefficient coefficient was measured by micro-XRF (Diamond synchrotron, UK) and ion microprobe (WHOI, USA) onexperimentally crystallized augites and basalts. S contents were then measured by in-situ micro-XRF in augite phenocrysts from representative rocks of the three considered LIPs. Selected natural clinopyroxene crystals were verified to be devoid of fluid or sulphide inclusions through Transmission electron microscopy (TEM, Siena) thus legitimating the aplicability of the partition coefficient and the extrapolation of S burden in primitive magmas starting from S measured on augites. S in the pristine magmas ranges between 100 and 1500 ppm, consistently with results obtained by Self et al. (2008) on melt inclusions from Deccan basalts. CAMP and Deccan magmas seem systematically richer in S than PE ones, an observation that correlates well with the severity of the associated biotic crises. Thus, emissions of S (along with other volatiles) appear as important factors for assessing the global environmental changes and may play a significant role in triggering mass extinctions.

Subject Areas: Environment, Technique Development

Instruments: I18-Microfocus Spectroscopy