Isotopic fractionation of oxygen and carbon in decomposed lower-mantle inclusions in diamond.

Kaminsky, Felix; Matzel, Jennifer; Jacobsen, Ben; Hutcheon, Ian; Wirth, Richard

Two carbonatitic mineral assemblages, calcite wollastonite and calcite monticellite, which are encapsulated in two diamond grains from the Rio Soriso basin in the Juina area, Mato Grosso State, Brazil, were studied utilizing the NanoSIMS technique. The assemblages were formed as the result of the decomposition of the lower-mantle assemblage calcite CaSi-perovskite volatile during the course of the diamond ascent under pressure conditions from 15 to less than 0.8 GPa. The oxygen and carbon isotopic compositions of the studied minerals are inhomogeneous. They fractionated during the process of the decomposition of primary minerals to very varying values: δO from −3.3 to 15.4 ‰ SMOW and δC from −2.8 to 9.3 ‰ VPDB. These values significantly extend the mantle values for these elements in both isotopically-light and isotopically-heavy areas.

MATO Grosso (Brazil : State); ISOTOPIC fractionation; CARBON isotopes; OXYGEN isotopes; INCLUSIONS (Mineralogy & petrology); EARTH'S mantle; CARBONATITES; DIAMONDS

Mineralogy & Petrology, 2016, Vol 110, Issue 2/3, p379

0930-0708

Academic Journal

10.1007/s00710-015-0401-7