Origin of the Kimberlite Diamond-Bearing Lithosphere of Cratons

摘要

The origin of diamond-bearing kimberlites and the conditions of diamond formation are some of the most complex unsolved issues in geology. Kimberlites are undoubtedly deep rocks that originate at depths of about 200 km. The modern ideas on how diamonds appear are based on experimental data and suggest that diamonds form at temperatures of about 1600℃ and pressures about 6-7 GPa [1] (these parameters correspond to the depth interval of 200-230 km). An important feature of kimberlite distribution is their location only within cratons-ancient platforms with predominantly Archean rocks in their basement. The thickness of the cratonic lithosphere is up to 150-200 km [2]. Analysis of the mineral and chemical compositions of kimberlites indicates that the substrate from which kimberlites form is anomalous compared to the average mantle composition [3].