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 characteristics document remobilization of older carbon and silicate components to form the framesites shortly before kimberlite eruption. Chemical variations within the garnets correlate with carbon isotopes in the diamonds, indicating contemporaneous formation. Trace element, radiogenic, and stable isotope variations can be explained by the interaction of eclogites with a carbonatitic 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.
Jacob
DE
Institut fur Geologische Wissenschaften, Universitat Greifswald, F. -L. Jahnstrasse 17a, D-17487 Greifswald, Germany. DeBeers Geoscience Center, Post Office Box 82232, Southdale 2135, South Africa. Department of Geology, Royal Holloway Universi.
Viljoen
KS
Grassineau
N
Jagoutz
E