Diamond formation during reduction of oxide- and silicate-carbon systems at high P-T conditions

Diamonds have been synthesized in fayalite + graphite and magnetite + graphite mixtures by partial reduction of the samples with hydrogen and metallic titanium at 1300-1400 degrees C and 45-55 kbar. Hydrogen provided local reduction of the samples with separation of metallic iron, which catalysed the transformation of graphite into diamond. Iron reacted with other elements and was not found in the free state in the experimental products. These experiments can be regarded as a simplified model for the formation of some types of natural diamond during the interaction of reduced fluids with carbon-bearing mantle rocks.