Volcanism neon isotopes

Early neon isotope measurements indicated that the Ne isotope composition of the Earth s mantle differs from that of the atmosphere (Craig and Lupton 1976 Poreda and Radicati di Brozolo 1984), but confidence in the early results was limited by the low analytical precision. Once some of the analytical obstacles were overcome, the work by Honda et al. (1987) and Ozima and Zashu (1988) on diamonds, and by Sarda et al. (1988) on submarine volcanic glasses from ridges and islands, showed conclusively that the mantle is characterized by elevated ratios of e/ Ne and Ne/ Ne compared to the atmosphere. The relatively high Ne Ne in MORBs and OIBs indicates that the connection between the Earth s atmosphere and mantle is not a simple, complementary relationship. The different correlations between e/ Ne and Ne/ Ne in MORBs and OIBs each pass through the composition of air (Fig. 11), due to the ubiquitous presence of an atmospheric component. Key questions arise from the Ne isotope data, especially about the origin of the atmosphere. The chapters by Porcelli and Ballentine (2002) and Pepin and Porcelli (2002) discuss these questions in more detail. Of special note is the... 

Figure 2. Neon isotope systematics of arc-related volcanism. Arc data from Table 2, MORB-trend from Sarda et al. (1988) and crustal-neon trend from Kennedy et al. (1990). mfl = mass fractionation line.

In this section, we review noble gas systematics of arc-related volcanism worldwide. Helium isotope studies dominate because most arc products are erupted subaerially, and air contamination is a relatively minor (correctable) problem for helium this is not the case for Ne-Ar-Kr-Xe isotope systematics. Consequently, this section is weighted towards reporting observations of helium isotope variations in arc-related minerals and fluids. However, we summarize also the available database for neon, argon and xenon isotopes (todateKr shows only air-like isotopic compositions). Finally, we consider the limited database of the relative abundances of the noble gases in arc-related products. 

Neon and argon isotope systematics of arc-related volcanism... 

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