Conditions of origin of kimberlites in West Greenland: new evidence from the Sarfartoq and Sukkertoppen regions

Abstract

Minerals in a garnet lherzolite nodule from Sarfartoq and macrocrysts in a kimberlite from the Sukkertoppen region have been analysed by microprobe. Temperatures calculated for the Sarfartoq nodule lie in the range 1110–1137°C, and pressures are estimated at greater than 50 kbar. The calculated temperature for the Sukkertoppen macrocrysts is 1309°C. Temperatures recalculated from existing data for kimberlites in the Holsteinsborg region and in SW Greenland lie in the range 1034–1078°C (40-50 kbar). The temperature variations may reflect the setting of the kimberlites in Archaean and Proterozoic terrains. Assuming a common geotherm of 40mW/m² all the kimberlites in West Greenland originated within the diamond stability field.