The Nature of the Diamond Potential of “Cold” Paleogeotherms

Resumo

It is known that the Р–Т parameters of diamond-bearing kimberlite xenoliths correspond to subductive paleogeotherms lying between the 36 and 41 mW/m² conductive models. There are some studies showing the correlation of diamond ability with oxygen fugacity and the fluid composition of mantle xenoliths. The most diamondiferous samples correspond to the water compositions of the calculated O–H–C fluid with a minimum atomic carbon content in it. From the calculations it follows that the fluid carbon atomic content increases with a temperature increase and with the pressure decreasing. The most minor C contents have the 35 mW/m² conductive model in comparison with the 40 and 45 mW/m² models. As a result, it is possible to conclude that the low temperature fields (less than 1100°C) of the “cold” geotherms have the highest diamondiferous ability.