Thermal state and composition of the lithospheric mantle beneath the Daldyn kimberlite field, Yakutia

Abstract

The proton microprobe has been used to study the distribution of trace elements in garnet and chromite concentrates from the Udachnaya kimberlite and three smaller, low-grade kimberlites from the Daldyn kimberlite field. Garnet thermobarometry and classical P-T estimates for megacrystalline peridotite xenoliths both suggest a Paleozoic geotherm beneath the Daldyn area that is close to a 35 mW/m2 conductive model. Finer-grained xenoliths with T < 1000°C scatter above this geotherm: high-temperature sheared xenoliths lie near or above a 40 mW/m2 model geotherm at 1150-1400°C. The higher-T results are interpreted as the result of short-term heating, caused by magmatic intrusion and perturbation..