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Intragrain variation in delta (super 13) C and nitrogen concentration associated with textural heterogeneities of carbonado

Reika Yokochi, Daniel Ohnenstetter and Yuji Sano
Intragrain variation in delta (super 13) C and nitrogen concentration associated with textural heterogeneities of carbonado
The Canadian Mineralogist (October 2008) 46 (5): 1283-1296

Abstract

We have investigated the textural diversity in four Brazilian samples of carbonado diamond by cathodoluminescence petrography and spectroscopy, coupled with carbon, nitrogen and argon isotope analyses. Three types of textures were observed: homogeneous, porphyritic and flow textures. In these last two textural varieties, carbon isotopic composition and nitrogen contents covary in different ways. The complex texture and delta (super 13) C-[N] variability in our two heterogeneous samples are analogous to those in igneous rocks. All four grains yielded similar cathodoluminescence spectra with respect to peak, positions and shapes, but relative intensities exhibit great differences. The main band at 575 nm represents the N+V center, which can involve (i) an irradiation followed by annealing, (ii) a plastic deformation during sintering of Ib-type microcrystals of diamond, or (iii) a growth of diamond crystals by a chemical vapor deposition (CVD) mechanism. Both cathodoluminescence spectra and N (sub 2) / (super 40) Ar values of carbonado are distinct from those of impact-generated diamond. The relatively low concentration of Ar also does not support a CVD origin of carbonado diamond.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 46
Serial Issue: 5
Title: Intragrain variation in delta (super 13) C and nitrogen concentration associated with textural heterogeneities of carbonado
Affiliation: University of Illinois at Chicago, Department of Earth and Environmental Sciences, Chicago, IL, United States
Pages: 1283-1296
Published: 200810
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 47
Accession Number: 2009-010744
Categories: Mineralogy of non-silicatesIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
S34°00'00" - N05°15'00", W74°00'00" - W34°00'00"
Secondary Affiliation: CNRS, Centre de Recherches Petrographiques et Geochimiques, FRA, FranceUniversity of Tokyo, JPN, Japan
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200906
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