Cadmium, indium, tin, tellurium, and sulfur in oceanic basalts: Implications for chalcophile element fractionation in the Earth

Abstract

Concentrations of S, Cd, In, Sn, and Te are reported for 80 samples of mid‐ocean 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, Tl, and Hg. From the depletion of In we deduce that core formation depleted the silicate Earth in Cd, Pb, Bi, Tl, 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.