Petrology and Chemistry of Garnet Lherzolite Nodules in Kimberlite from South Africa

Ju-chin Chen

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Research Article| December 01, 1971

Petrology and Chemistry of Garnet Lherzolite Nodules in Kimberlite from South Africa

Ju-chin Chen

Geosciences Division, University of Texas at Dallas, Dallas, Texas 75230 U.S.A. and Institute of Oceanography, National Taiwan University, Taipei, Taiwan, Republic of China

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Author and Article Information

Ju-chin Chen

Geosciences Division, University of Texas at Dallas, Dallas, Texas 75230 U.S.A. and Institute of Oceanography, National Taiwan University, Taipei, Taiwan, Republic of China

Publisher: Mineralogical Society of America

Received: 23 Mar 1971

Accepted: 03 Jun 1971

First Online: 06 Jul 2018

Online ISSN: 1945-3027

Print ISSN: 0003-004X

Mineralogical Society of America

American Mineralogist (1971) 56 (11-12): 2098–2110.

Abstract

The garnet Iherzolite nodules in kimberlite from South Africa consist essentially of oh vine, orthopyroxene, garnet, clinopyroxene, and serpentine with minor amounts of phlogopite and opaques occurring in some samples. The average chemical compositions of 41 samples are: SiO₂ 44.66%, Al₂O₃ 1.22%, total Fe as FeO 7.87%, MgO 42.94%, CaO 0.81%, Na₂O 0.155%, K₂O 0.123%, TiO₂ less than 0.10%, MnO 0.113%, Cr₂O₃ 0.352%, NiO 0.370%, Co 89 ppm, Sr 31 ppm, and Zn 42 ppm. The MgO/(total Fe as FeO) ratios of the rocks range from 4.63 to 6.14. Al₂O₃, CaO, Na₂O, MnO, Cr₂O₃, Sr, and Zn decrease while NiO increases with increasing Mg/(total Fe as FeO) ratios. The systematic chemical variations in the garnet lherzolites may be interpreted as due to different degrees of partial fusion of the undepleted upper mantle materials consisting of some members of the garnet lherzolites with relatively low MgO/(total Fe as FeO) ratios.