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Title: Isotopic fractionation of oxygen and carbon in decomposed lower-mantle inclusions in diamond

Two carbonatitic mineral assemblages, calcite + wollastonite and calcite + monticellite, which are encapsulated in two diamond grains from the Rio Soriso basin in the Juina area, Mato Grosso State, Brazil, were studied utilizing the NanoSIMS technique. The assemblages were formed as the result of the decomposition of the lower-mantle assemblage calcite + CaSi-perovskite + volatile during the course of the diamond ascent under pressure conditions from 15 to less than 0.8 GPa. The oxygen and carbon isotopic compositions of the studied minerals are inhomogeneous. They fractionated during the process of the decomposition of primary minerals to very varying values: δ18O from –3.3 to +15.4 ‰ SMOW and δ13C from –2.8 to +9.3 ‰ VPDB. As a result, these values significantly extend the mantle values for these elements in both isotopically-light and isotopically-heavy areas.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [3]
  1. KM Diamond Exploration Ltd., West Vancouver, BC (Canada)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. GeoForschungsZentrum Potsdam, Potsdam (Germany)
Publication Date:
OSTI Identifier:
1324510
Report Number(s):
LLNL-JRNL--701302
Journal ID: ISSN 0930-0708
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Mineralogy and Petrology (Austria)
Additional Journal Information:
Journal Name: Mineralogy and Petrology (Austria); Journal Volume: 110; Journal Issue: 2-3; Journal ID: ISSN 0930-0708
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES