Synchrony of continental flood basalts (CFB) and significant Phanerozoic mass extinction events may suggest a trigger effect of large scale basaltic eruptions on the global climate and environment,mainly due to intense emissions of volcanic gases such as SO2 and CO2 [1]. However,this interpretation is based on poorly constrained gas contents of the basalts and on even less well known gas emission rates. Here we investigate the S content of basalts of two of the largest CFB provinces: the Central Atlantic magmatic province (CAMP) and the Paranà-Etendeka (PE). Notably,while the CAMP is synchronous with and possibly triggered the end-Triassic extinction [2],PE basalts had a very minor effect on the early Cretaceous biosphere [3]. Melt inclusions in CAMP basalt olivines yield S contents (electron microprobe analyses) comparable to those found in Deccan basalts [1],whereas S in matrix glass is close to detection limit,suggesting that degassing during the eruption was almost complete. As an alternative approach,we measure S (and Cl) contents (synchrotrone analyses) also in phenocrysts from CAMP and PE basalts and extrapolate the magmatic S content through newly established crystal/melt partition coefficients. These results illuminate the difference which seem to exist between the two CFB provinces and contribute to our understanding of their different environmental impacts. [1] Self S. et al. (2008),Science 319,1654-1657. [2] Cirilli S. et al. (2009),EPSL 286,514-525. [3] Wignall P. (2001),Earth. S. Rev 53,1-33.

S IN CAMP AND PARANA-ETENDEKA CFBS.

DE MIN, ANGELO;
2011

Abstract

Synchrony of continental flood basalts (CFB) and significant Phanerozoic mass extinction events may suggest a trigger effect of large scale basaltic eruptions on the global climate and environment,mainly due to intense emissions of volcanic gases such as SO2 and CO2 [1]. However,this interpretation is based on poorly constrained gas contents of the basalts and on even less well known gas emission rates. Here we investigate the S content of basalts of two of the largest CFB provinces: the Central Atlantic magmatic province (CAMP) and the Paranà-Etendeka (PE). Notably,while the CAMP is synchronous with and possibly triggered the end-Triassic extinction [2],PE basalts had a very minor effect on the early Cretaceous biosphere [3]. Melt inclusions in CAMP basalt olivines yield S contents (electron microprobe analyses) comparable to those found in Deccan basalts [1],whereas S in matrix glass is close to detection limit,suggesting that degassing during the eruption was almost complete. As an alternative approach,we measure S (and Cl) contents (synchrotrone analyses) also in phenocrysts from CAMP and PE basalts and extrapolate the magmatic S content through newly established crystal/melt partition coefficients. These results illuminate the difference which seem to exist between the two CFB provinces and contribute to our understanding of their different environmental impacts. [1] Self S. et al. (2008),Science 319,1654-1657. [2] Cirilli S. et al. (2009),EPSL 286,514-525. [3] Wignall P. (2001),Earth. S. Rev 53,1-33.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11368/2613221
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