Microstructural observations of polycrystalline diamond: A contribution to the carbonado conundrum

Subarnarekha De; Peter J. Heaney; Robert B. Hargraves; Edward P. Vicenzi; Patrick T. Taylor

doi:10.1016/S0012-821X(98)00229-5

Microstructural observations of polycrystalline diamond: A contribution to the carbonado conundrum

Subarnarekha De
, Peter J. Heaney
, Robert B. Hargraves
, Edward P. Vicenzi
, Patrick T. Taylor

Research output: Contribution to journal › Article › peer-review

52 Scopus citations

Abstract

The formation mechanism of carbonado, a polycrystalline variety of diamond, remains unresolved. Here we report a microstructural analysis of systematic defects and inclusions in carbonados from Brazil and the Central African Republic (CAR). Transmission electron microscopy (TEM) has revealed the presence of pervasive defect lamellae in both the CAR and Brazilian carbonados that are distinct from planar defects observed in synthetic polycrystalline diamond (PCD). Analyses of included minerals by energy dispersive spectroscopy (EDS) yielded strong evidence for metallic Fe, Ti, and Si, as well as SiC and Fe-Cr alloys, within the diamond matrix. Our results offer strong evidence for a close genetic relationship between Brazilian and Central African carbonados, suggesting formation within a united landmass during the late Archaean. The data do not preclude carbonado nucleation by meteoritic impact, though this issue remains contentious. The role of water in the growth of carbonado merits further exploration.

Original language	English (US)
Pages (from-to)	421-433
Number of pages	13
Journal	Earth and Planetary Science Letters
Volume	164
Issue number	3-4
DOIs	https://doi.org/10.1016/S0012-821X(98)00229-5
State	Published - Dec 30 1998

All Science Journal Classification (ASJC) codes

Geophysics
Geochemistry and Petrology
Space and Planetary Science
Earth and Planetary Sciences (miscellaneous)

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10.1016/S0012-821X(98)00229-5

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@article{4db08315922d47ca85f1007f02e5c6b8,

title = "Microstructural observations of polycrystalline diamond: A contribution to the carbonado conundrum",

abstract = "The formation mechanism of carbonado, a polycrystalline variety of diamond, remains unresolved. Here we report a microstructural analysis of systematic defects and inclusions in carbonados from Brazil and the Central African Republic (CAR). Transmission electron microscopy (TEM) has revealed the presence of pervasive defect lamellae in both the CAR and Brazilian carbonados that are distinct from planar defects observed in synthetic polycrystalline diamond (PCD). Analyses of included minerals by energy dispersive spectroscopy (EDS) yielded strong evidence for metallic Fe, Ti, and Si, as well as SiC and Fe-Cr alloys, within the diamond matrix. Our results offer strong evidence for a close genetic relationship between Brazilian and Central African carbonados, suggesting formation within a united landmass during the late Archaean. The data do not preclude carbonado nucleation by meteoritic impact, though this issue remains contentious. The role of water in the growth of carbonado merits further exploration.",

author = "Subarnarekha De and Heaney, \{Peter J.\} and Hargraves, \{Robert B.\} and Vicenzi, \{Edward P.\} and Taylor, \{Patrick T.\}",

note = "Funding Information: We would like to thank D. Johnson, N. Yao, and D. Yates for their help with sample preparation and analytical work. We also thank J. Milledge for providing us with the Brazilian carbonado sample. We thank R. Hough, D. Peacor, and S. Haggerty for their constructive reviews of the manuscript. Correspondence and request for materials should be addressed to S. De (E-mail: [email protected]). This work was supported by NSF grant EAR97-06143. [CL] ",

year = "1998",

month = dec,

day = "30",

doi = "10.1016/S0012-821X(98)00229-5",

language = "English (US)",

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pages = "421--433",

journal = "Earth and Planetary Science Letters",

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TY - JOUR

T1 - Microstructural observations of polycrystalline diamond

T2 - A contribution to the carbonado conundrum

AU - De, Subarnarekha

AU - Heaney, Peter J.

AU - Hargraves, Robert B.

AU - Vicenzi, Edward P.

AU - Taylor, Patrick T.

N1 - Funding Information: We would like to thank D. Johnson, N. Yao, and D. Yates for their help with sample preparation and analytical work. We also thank J. Milledge for providing us with the Brazilian carbonado sample. We thank R. Hough, D. Peacor, and S. Haggerty for their constructive reviews of the manuscript. Correspondence and request for materials should be addressed to S. De (E-mail: [email protected]). This work was supported by NSF grant EAR97-06143. [CL]

PY - 1998/12/30

Y1 - 1998/12/30

N2 - The formation mechanism of carbonado, a polycrystalline variety of diamond, remains unresolved. Here we report a microstructural analysis of systematic defects and inclusions in carbonados from Brazil and the Central African Republic (CAR). Transmission electron microscopy (TEM) has revealed the presence of pervasive defect lamellae in both the CAR and Brazilian carbonados that are distinct from planar defects observed in synthetic polycrystalline diamond (PCD). Analyses of included minerals by energy dispersive spectroscopy (EDS) yielded strong evidence for metallic Fe, Ti, and Si, as well as SiC and Fe-Cr alloys, within the diamond matrix. Our results offer strong evidence for a close genetic relationship between Brazilian and Central African carbonados, suggesting formation within a united landmass during the late Archaean. The data do not preclude carbonado nucleation by meteoritic impact, though this issue remains contentious. The role of water in the growth of carbonado merits further exploration.

AB - The formation mechanism of carbonado, a polycrystalline variety of diamond, remains unresolved. Here we report a microstructural analysis of systematic defects and inclusions in carbonados from Brazil and the Central African Republic (CAR). Transmission electron microscopy (TEM) has revealed the presence of pervasive defect lamellae in both the CAR and Brazilian carbonados that are distinct from planar defects observed in synthetic polycrystalline diamond (PCD). Analyses of included minerals by energy dispersive spectroscopy (EDS) yielded strong evidence for metallic Fe, Ti, and Si, as well as SiC and Fe-Cr alloys, within the diamond matrix. Our results offer strong evidence for a close genetic relationship between Brazilian and Central African carbonados, suggesting formation within a united landmass during the late Archaean. The data do not preclude carbonado nucleation by meteoritic impact, though this issue remains contentious. The role of water in the growth of carbonado merits further exploration.

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U2 - 10.1016/S0012-821X(98)00229-5

DO - 10.1016/S0012-821X(98)00229-5

M3 - Article

AN - SCOPUS:0032583373

SN - 0012-821X

VL - 164

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EP - 433

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

IS - 3-4

ER -

Microstructural observations of polycrystalline diamond: A contribution to the carbonado conundrum

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