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Ar-40/Ar-39 laser-probe dating of diamond inclusions from the Premier kimberliteThe results of Ar-40/Ar-39 laser-probe analyses of individual eclogitic clinopyroxene inclusions from Premier diamonds are reported which yield a mean age of 1198 + or - 14 Myr. This age agrees well with Sm-Nd and Ar-40/Ar-39 analyses on similar Premier inclusions and is indistinguishable from the inferred time of emplacement of the host kimberlite, which implies that diamond formation was essentially synchronous with kimberlite generation. The extrapolated nonradiogenic Ar-40/Ar-36 ratio of 334 + or - 102 is similar to the present-day atmospheric composition. This value is inconsistent with Sr and Nd isotopic signatures from Premier eclogite inclusions, which suggest a depleted mantle source. Preentrapment equilibration of the inclusions with an Ar-36-rich fluid is the most probable explanation for the low nonradiogenic composition.
Document ID
19890063258
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Phillips, D.
(Princeton Univ. NJ, United States)
Onstott, T. C.
(Princeton University NJ, United States)
Harris, J. W.
(Princeton University NJ; Strathclyde, University, Glasgow, United Kingdom)
Date Acquired
August 14, 2013
Publication Date
August 10, 1989
Publication Information
Publication: Nature
Volume: 340
ISSN: 0028-0836
Subject Category
Geophysics
Accession Number
89A50629
Distribution Limits
Public
Copyright
Other

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