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Conditions of origin of natural diamonds of peridotite affinityStudies of mineral inclusions in natural diamonds and rare diamondiferous xenoliths from kimberlites show that most diamonds are associated with a dunite or harzburgite paragenesis. The diamondiferous periodites and dunites have predominantly coarse or tabular textures that suggest low-temperature (less than 1100 C) equilibration. Application of the K(D) Fe/Mg(Ga/Ol) geothermometer of O'Neill and Wood to analytical data for the minerals in these rocks shows that most have equilibrated below 1100 C. Application of this thermometer to pairs of olivine and garnet crystals included in individual diamonds indicates that the diamonds have crystallized in the range 900-1300 C, with a majority of estimated equilibration temperatures falling in the range below 1150 C. Comparison of these estimates of equilibration temperature with the zone of invariant vapor composition solidus for kimberlite and garnet lherzolite determined by Eggler and Wendlandt (1979) suggests that many diamonds may have formed in subsolidus events.
Document ID
19810033732
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Boyd, F. R.
(Carnegie Institution of Washington, Geophysical Laboratory, Washington D.C., United States)
Finnerty, A. A.
(California Institute of Technology, Jet Propulsion Laboratory, Pasadena Calif., United States)
Date Acquired
August 11, 2013
Publication Date
December 10, 1980
Publication Information
Publication: Journal of Geophysical Research
Volume: 85
Subject Category
Geophysics
Accession Number
81A18136
Funding Number(s)
CONTRACT_GRANT: NAS7-100
Distribution Limits
Public
Copyright
Other

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