Abstract. Concentrations of S, Cd, In, Sn, and Te are reported for 80 samples of midocean ridge basalt (MORB), submarine and subaerial ocean island basalt (OIB) and submarine arc lavas. Cadmium, In, and Sn are moderately incompatible, and Te is compatible during partial melting. Cadmium is particularly uniform, consistent with a homogeneous distribution in the mantle. Tellurium is more variable (1-6 ppb) and is notably higher in Loihi, ranging up to 29 ppb, the most likely explanation for which is accumulation of Cu-bearing sulfide. The average Cd/Dy ratio is the same (0.027) for OIB glasses, MORB glasses and the continental crust, yielding a primitive mantle Cd concentration of •18 ppb. Indium, despite being more volatile, is less depleted than Cd and the other very volatile chalcophile elements Pb, Bi, T1, and Hg. From the depletion of In we deduce that core formation depleted the silicate Earth in Cd, Pb, Bi, T1, and Hg by between factors of 5 and 10. The In depletion yields concentrations of C, S, Se, and Te in the core of C -1.2%, S > 2.4%, Se > 7.1 ppm, and Te > 0.89 ppm. The Moon appears to be enriched in Te relative to the silicate Earth. Either a significant fraction of the Moon was derived from a more Te-rich body or the silicate Earth's inventory of chalcophile and siderophile elements was depleted by further terrestrial core growth after formation of the Moon.
IntroductionThe geochemistry of some volatile siderophile and chalcophile elements is only poorly understood because of the dearth of high-quality data. Accurate data could provide constraints on the role that sulfide plays in mantle melting and differentiation, the abundance of sulfur (S) in the mantle, and the processes of accretion and core formation. The Earth's core is estimated to contain roughly 11 wt % of light elements [Birch, 1952[Birch, , 1961[Birch, , 1964. Most of the leading candidates for the light elements in the core (O, C, S, H) are also volatile and their abundances in the bulk Earth are very difficult to estimate because two separate processes, loss of volatile elements and core formation, will lead to nonchondritic relative proportions in the silicate Earth. Furthermore, the concentrations of highly volatile elements (such as H, C, S, and noble gases) in geological samples are often reduced by low-pressure degassing, making it a difficult challenge to estimate their abundances in the Earth's mantle. Ultramafic xenoliths are of questionable help in understanding such elements, since they have often experienced some degree of partial melting or perhaps alteration [Lorand, 1989] Here, we present the first high-precision isotope dilution analyses of Cd, In, Sn, and Te in a comprehensive suite of submarine glasses that include MORB, OIB, and submarine island arc and back arc trough basalts and andesites (referred to as IAB). These data are used to investigate the behavior of these elements in magmatic processes and to provide constraints on the early history of the Earth. The major element compositions of all of the submari...
