Volatiles and Large Volcanic Eruptions

Flood basalts are the largest manifestations of magmatism and directly related to profound questions about the composition and
dynamics of the mantle, breakup of continents, and climatic history. Their origin and their role in mass extinctions are subjects of
debate because of limited compositional data on the primary flood basalt magmas and their mantle sources. Isotopic and chemical
analyses are used as tracers of terrestrial mantle reservoirs. In the case of flood basalts, utilization of these tools is severely limited by
the complex magmatic differentiation, contamination, and alteration processes that have interfered the compositions of all but few of the
volcanic rocks. Volatile geochemistry (e.g. He isotopes, H2O, S, CO2) of flood basalts is particularly poorly understood due to
outgassing of erupting magmas. The release of volatiles is considered to be the main culprit for mass extinctions, but the environmental
impacts remain poorly quantified due to very limited data on the pre-eruptive volatile characteristics of flood basalts.
We have discovered exceptionally well-preserved picritic flood basalts in the Antarcic and African parts of the Jurassic Karoo magma
province. These picrites are globally rare examples of primitive, nearly undifferentiated and mineralogically pristine flood basalts and
are highly valuable for several reasons:
1-They facilitate chemical and isotopic characterization of two contrasting (Antarctic vs. African) types of primary flood basalt
magmas;
2-Their pristine olivine and Cr-spinel phenocrysts allow application of He and Os isotopic analyses that are crucial for identification of
mantle sources;
3-Their phenocryst-hosted melt inclusions preserve information on the pre-eruptive volatile geochemistry.
Together with our collaborates at the Carnegie Institution for Science and Woods Hole Oceanographic Institution, we will carry out
pioneering measurements of volatile contents (H2O, CO2, S, Cl, F) and He isotopes in the olivine phenocrysts and melt inclusions of
Jurassic picrites. We will also perform high-precision elemental and isotopic (Nd, Sr, Pb, Os) analyses to obtain a comprehensive
geochemical dataset that facilitates characterization of the primary melts and mantle sources of Karoo flood basalts in unprecedented
detail and, ultimately, can help us to clarify the origin of large volcanic eruptions and their environmental influences.