Volcanic helium isotopic composition

Mamyrin, B. A., Tolstikhin, I. N., Anufriev, G. S., Kamensky, I. L. (1969) Anomalous isotopic composition of helium in volcanic gases. Dokkl. Akad. Nauk SSSR, 184, 1197-9. (In Russian.)... 

Tolstikhin I. N., MaMain B. A., Khabarin L. B., and Erlikh E. N. (1974) Isotope composition of helium in ultrabasic xenoliths from volcanic rocks of Kamchatka. Earth Planet. Sci. Lett. 22, 73-84. 

In southeast Australia, this conclusion has been supported by recent osmium-isotopic studies of the Quaternary Newer Volcanic Province, which reveal that sodic alkali basalts there have osmium-isotopic compositions indistinguishable from OIB, again supporting a sublithospheric origin for their parental magmas (McBride et al, 2001). Helium-isotope data are available primarily from sodic basalts in the northern half of Africa (Cameroon Line, Sudan). These basalts have R/Ri, values (—5.1-7.5) consistent with a derivation from an HIMU-type plume source (Barfod et al., 1999 Franz et al, 1999). 

Christensen BP, Holm PM, Jambon A, Wilson JR (2001) Helium, argon and lead isotopic composition of volcanics from Santo Antao and Fogo, Cape Verde Islands. Chem Geol 178 127-142 Clarke WB, Jenkins WJ, Top Z (1976) Determination of tritium by mass spectrometric measurement of He. Inti J Appl Rad Isotopes 27 515-522... 

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. 

There are two stable isotopes of helium, He and " He, which vary in their ratio by over three orders of magnitude in terrestrial samples. The Earth s atmosphere is well mixed with respect to helium and contains helium with a uniform isotopic composition of He/" He = 1.39 x 10 . Atmospheric helium is a convenient standard for helium isotope determinations, and terrestrial He/" He ratios are usually normalized to the air ratio and expressed in units of R/Ra, where R = He/ He and Ra = ( He/ He) . In contrast to atmospheric helium R/Ra = 1), the radiogenic helium produced by a-decay of U and Th series isotopes has a much lower ratioof R/Ra0.1, while the volcanic helium that is derived from the Earth s mantle is highly enriched in He R/Ra =5-30). Thus volcanic helium has an isotopic composition distinct from other sources such as atmospheric helium or the helium produced by radioactive decay. This He-rich mantle helium is sometimes called primordial helium, since it is thought to be the remnant of a primitive component... 

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