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GEOREF RECORD

Diamonds from the iridium-rich K-T boundary layer at Arroyo el Mimbral, Tamaulipas, Mexico

R. M. Hough, I. Gilmour, C. T. Pillinger, F. Langenhorst and A. Montanari
Diamonds from the iridium-rich K-T boundary layer at Arroyo el Mimbral, Tamaulipas, Mexico
Geology (Boulder) (November 1997) 25 (11): 1019-1022

Abstract

Diamonds, up to 30 mu m in size, were found in the iridium-rich layer from the K-T boundary site at Arroyo El Mimbral and the spherule bed from Arroyo El Penon, northeastern Mexico. Stepped heating experiments indicate two or more isotopically distinct diamond components with carbon isotopic compositions characteristic of a mixture of carbon sources. The diamonds' crystal form is cubic--not the hexagonal polymorph of diamond, lonsdaleite, which has been used previously to infer formation due to shock transformation of graphite. The size, crystallography, and mineralogic associations of K-T diamonds are similar to those of impact-produced diamonds from the Ries crater in Germany where both shock transformation of graphite and a mode of formation by condensation from a vapor plume have been inferred. The discovery of impact-produced diamonds in association with high Ir contents for these sediments supports their impact origin, K-T age, and the inference that their source was from the buried impact crater of Chicxulub on the Yucatan peninsula, Mexico.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 25
Serial Issue: 11
Title: Diamonds from the iridium-rich K-T boundary layer at Arroyo el Mimbral, Tamaulipas, Mexico
Affiliation: Open University, Planetary Sciences Research Institute, Milton Keynes, United Kingdom
Pages: 1019-1022
Published: 199711
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Accession Number: 1997-072431
Categories: StratigraphyMineralogy of non-silicatesIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N23°13'00" - N23°13'00", W98°40'00" - W98°40'00"
Secondary Affiliation: Museum fuer Naturkunde, Berlin, DEU, Federal Republic of GermanyOsservatorio Geologico di Coldigioco, Frontale di Apiro, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199724
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