57Fe Mössbauer spectroscopy used to develop understanding of a diamond preservation index model

• Published in: Hyperfine interactions 2016, Vol.237 (1), p.1-6, Article 66
• Main Authors: Yambissa, M. T., Forder, S. D., Bingham, P. A.
• Format: Article
• Language: English
• Subjects: 13-18 September 2015; Atomic; Biotite; Condensed Matter Physics; Diamonds; Germany; Hadrons; Hamburg; Heavy Ions; Ilmenite; Iron; Iron 57; Mineral inclusions; Molecular; Mossbauer spectroscopy; Nuclear Physics; Optical and Plasma Physics; Oxidation; Partial pressure; Physics; Physics and Astronomy; Proceedings of the International Conference on the Applications of the Mössbauer Effect (ICAME 2015); Quality; Spectrum analysis; Surfaces and Interfaces; Tectonics; Thin Films; Valence
• ISSN: 0304-3843; 1572-9540
• DOI: 10.1007/s10751-016-1262-0

57 Fe Mössbauer spectroscopy has provided precise and accurate iron redox ratios Fe 2+ /Fe 3+ in ilmenite, FeTiO 3 , found within kimberlite samples from the Catoca and Camatxia kimberlite pipes from N.E. Angola. Ilmenite is one of the key indicator minerals for diamond survival and it is also one of the iron-bearing minerals with iron naturally occurring in one or both of the oxidation states Fe 3+ and Fe 2+ . For this reason it is a good indicator for studying oxygen fugacities ( f O 2 ) in mineral samples, which can then be related to iron redox ratios, Fe 2+ /Fe 3+ . In this paper we demonstrate that the oxidation state of the ilmenite mineral inclusion from sampled kimberlite rock is a key indicator of the oxidation state of the host kimberlite assemblage, which in turn determines the genesis of diamond, grade variation and diamond quality. Ilmenite samples from the two different diamondiferous kimberlite localities (Catoca and Camatxia) in the Lucapa graben, N.E. Angola, were studied using Mössbauer spectroscopy and X-Ray Diffractometry, in order to infer the oxidation state of their source regions in the mantle, oxygen partial pressure and diamond preservation conditions. The iron redox ratios, obtained using Mössbauer spectroscopy, show that the Catoca diamond kimberlite is more oxidised than kimberlite found in the Camatxia pipe, which is associated within the same geological tectonic structure. Here we demonstrate that 57 Fe Mössbauer spectroscopy can assist geologists and mining engineers to effectively evaluate and determine whether kimberlite deposits are economically feasible for diamond mining.