Remobilization in the Cratonic Lithosphere Recorded in Polycrystalline Diamond

• Published in: Science (American Association for the Advancement of Science) Vol. 289; no. 5482; pp. 1182 - 1185
• Main Authors: Jacob, D. E., Viljoen, K. S., Grassineau, N., Jagoutz, E.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 18-08-2000; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Bacteria; Carbon; Crystalline rocks; Diamonds; Earth sciences; Earth, ocean, space; Eclogite; Exact sciences and technology; Garnets; Geology; Igneous and metamorphic rocks petrology, volcanic processes, magmas; Internal geophysics; Isotopes; Lithospheres; Minerals; Peridotite; Scientific Concepts; Solid-earth geophysics, tectonophysics, gravimetry; South Africa; Southern Africa; nesosilicates; O-18; eclogite; petrogenesis; Nd-144/Nd-143; Africa; polycrystalline materials; lithosphere; garnet; igneous rocks; cratons; metamorphic rocks; remobilization; rare earths; trace-element analyses; diamond; C-13; isotopes; kimberlite; plutonic rocks; silicates; Sr-87/Sr-86; native elements
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.289.5482.1182

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.