GAS EMISSIONS OF CAMP BASALTS AT THE TRIASSIC-JURASSIC BOUNDARY

Emplacement of the Central Atlantic magmatic province (CAMP) basalts had its peak activity at ca. 201 Ma and straddled the Triassic-Jurassic boundary. The beginning of CAMP volcanism shortly preceded the end-Triassic mass extinction and negative carbon isotopic shift. The relative timing of global environmental changes and CAMP volcanism during the Rhaetian is supported by multidisciplinary evidence, including mineralogical, geochemical, and biostratigraphic data that will be briefly discussed in this presentation. However, in order to demonstrate the impact of CAMP on climate and biosphere, we need to go a step further and constrain the actual amounts and chemical composition of CAMP-related gas emissions, notably SO₂ and CO₂.

Given the lack of suitable melt inclusions retaining pre-eruptive gas contents in CAMP basalts, we employed alternative investigative paths. SO₂ contents in CAMP basalts have been constrained through direct measurements of sulfur in clinopyroxenes. Magmatic contents are then calculated by adopting a newly determined partition coefficient for S. According to these new data, SO₂ contents in CAMP basaltic magmas were as high as 1900 ppm, higher than those of Deccan basalts and almost double those of Paranà basalts. These data suggest a potentially devastating effect of sulfur emissions from short-lived volcanic pulses of the CAMP.

CO2 contents of CAMP magmas are unknown. However, we will show new mineralogical (micro-Raman) and isotopic data suggesting that the >4 per mil negative isotopic shift heralding the end-Triassic mass extinction can be attributed chiefly to CAMP volcanism.

Acknowledgments: this work benefited from the helpful collaboration of many researchers, among others: N. Youbi, H. Bertrand, F. Nestola, A. De Min, O. Bartoli, S. Cirilli, N. Buratti.