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Infrared and Raman spectroscopic observations of Central African carbonado and implications for its origin

Hiroyuki Kagi and Satoshi Fukura
Infrared and Raman spectroscopic observations of Central African carbonado and implications for its origin (in Diamonds, Makoto Arima (editor), Ben Harte (editor) and Nikolay V. Sobolev (editor))
European Journal of Mineralogy (June 2008) 20 (3): 387-393

Abstract

Carbonado diamonds from the Central African Republic (CAR) were investigated using spectroscopic observations. Raman spectra for a polished section of carbonado showed the average Raman frequency as 1333.0 cm (super -1) ; measurements 10 mu m below the sample surface showed a bimodal distribution of the Raman frequency with the average at 1333.5 cm (super -1) . These contrasting results indicate that the carbonado interior retains considerable residual pressure. The maximum residual pressure detected in this study from the 10 mu m subsurface was 0.49 GPa. From infrared (IR) absorption spectra for crushed carbonado samples, no absorption attributable to diamond was observed because absorption bands of mineral and fluid inclusions were too strongly observed. Acid leaching treatment of the crushed grains elicited IR bands assignable to intrinsic diamond vibration and nitrogen impurity in the diamonds. Nitrogen atoms in the CAR carbonado were not much aggregated and the degree of aggregation was intermediate between type Ib and type IaA. In the chemically treated samples, IR absorption bands from liquid water and carbonate were ubiquitous suggesting that the CAR carbonado samples contain fluid inclusions and are similar to diamonds containing mantle-derived fluids. The experimental results of this study suggest that the CAR carbonado originated from rapid heating event with a presence of fluid in the mantle and subsequent rapid cooling before aggregation of nitrogen impurity in the diamond lattice.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 20
Serial Issue: 3
Title: Infrared and Raman spectroscopic observations of Central African carbonado and implications for its origin
Title: Diamonds
Author(s): Kagi, HiroyukiFukura, Satoshi
Author(s): Arima, Makotoeditor
Author(s): Harte, Beneditor
Author(s): Sobolev, Nikolay V.editor
Affiliation: University of Tokyo, Geochemical Laboratory, Tokyo, Japan
Pages: 387-393
Published: 200806
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 43
Accession Number: 2008-111813
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
N03°00'00" - N12°00'00", E14°00'00" - E27°30'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200841
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