Calculation of equilibration conditions for garnet granulite and garnet websterite nodules in African kimberlite pipes

D. A. Carswell*, W. L. Griffin

*Corresponding author for this work

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Pressure/temperature estimates based on different combinations of calibrated mineralogical thermometers and barometers and alternative assumptions concerning the Fe2+/(Fe2++Fe3+) ratios in the mineral phases are compared for a suite of fourteen nodules. Preferred P/T values have been obtained by simultaneous solution of eq. (12) of Wood (1974) for garnet-orthopyroxene equilibria and the Ellis and Green (1979) equation defining the P,T,X dependence of the Fe2+-Mg2+ partition coefficient for coexisting garnet and clinopyroxene. However, to obtain realistic results it is first necessary to calculate the Fe3+ contents in the minerals-conveniently done on a charge balance basis. The favoured mean P/T estimates of 654±36°C and 10.8±3.1 kbs are compatible with a lower crustal origin for this nodule suite.

Original languageEnglish
Pages (from-to)229-244
Number of pages16
JournalTMPM Tschermaks Mineralogische und Petrographische Mitteilungen
Volume28
Issue number3
DOIs
Publication statusPublished - Sep 1981
Externally publishedYes

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