Diamonds and their mineral inclusions from the A154 South pipe, Diavik Diamond Mine, Northwest territories, Canada

Abstract Mineral inclusions recovered from 100 diamonds from the A154 South kimberlite (Diavik Diamond Mines, Central Slave Craton, Canada) indicate largely peridotitic diamond sources (83%), with a minor (12%) eclogitic component. Inclusions of ferropericlase (4%) and diamond in diamond (1%) represent “undetermined” parageneses. Compared to inclusions in diamonds from the Kaapvaal Craton, overall higher CaO contents (2.6 to 6.0 wt.%) of harzburgitic garnets and lower Mg-numbers (90.6 to 93.6) of olivines indicate diamond formation in a chemically less depleted environment. Peridotitic diamonds at A154 South formed in an exceptionally Zn-rich environment, with olivine inclusions containing more than twice the value (of ∼ 52 ppm) established for normal mantle olivine. Harzburgitic garnet inclusions generally have sinusoidal rare earth element (REE N ) patterns, enriched in LREE and depleted in HREE. A single analyzed lherzolitic garnet is re-enriched in middle to heavy REE resulting in a “normal” REE N pattern. Two of the harzburgitic garnets have “transitional” REE N patterns, broadly similar to that of the lherzolitic garnet. Eclogitic garnet inclusions have normal REE N patterns similar to eclogitic garnets worldwide but at lower REE concentrations. Carbon isotopic values ( δ 13 C) range from − 10.5‰ to + 0.7‰, with 94% of diamonds falling between − 6.3‰ and − 4.0‰. Nitrogen concentrations range from below detection (