Remobilization in the cratonic lithosphere recorded in polycrystalline diamond

Polycrystalline diamonds (framesites) from the Venetia kimberlite in South Africa contain silicate minerals whose isotopic and trace element character istics document remobilization of older carbon and silicate components to f orm the framesites shortly before kimberlite eruption. Chemical variations within the garnets correlate with carbon isotopes in the diamonds, indicati ng contemporaneous formation. Trace element, radiogenic, and stable isotope variations can be explained by the interaction of eclogites with a carbona titic melt, derived by remobilization of material that had been stored for a considerable time in the lithosphere, These results indicate more recent formation of diamonds from older materials within the cratonic lithosphere.