Mineralium Deposita

, Volume 14, Issue 2, pp 227–242 | Cite as

Chromiferous spinels of the elephant's head dike

  • H. V. Eales
  • D. V. Snowden
Article
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Abstract

Analysis by optical, X-ray diffraction and microprobe methods, of essentially unzoned, disseminated spinels within cumulus picrites and olivine gabbros reveals an unbroken range of compositions from aluminian chromite (34% Cr2O3) to chromian magnetite (4% Cr2O3). TiO2 contents vary between 0.5 and 7.7%. Exsolution of ilmenite indicates originally higher TiO2 contents. Quenched contact-facies rocks with abundant olivine phenocrysts contain strongly zoned spinels in which a titaniferous chromian magnetite rim (16% Cr2O3, 10% TiO2) encloses cores of weakly titanian chromite (40% Cr2O3). Platy dendrites of exsolved spinel occur in abundance within cumulus olivines. The evidence suggests that crystallization of the disseminated spinels occurred under the influence of an increase in oxygen fugacity towards the interior of the intrusion, and that the compositional diversity has stemmed from the homogenization of originally zoned grains mantled to varying degrees by high-Ti, low-Cr rims.

Keywords

Oxygen Crystallization Mineral Resource Compositional Diversity Oxygen Fugacity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag 1979

Authors and Affiliations

  • H. V. Eales
    • 1
  • D. V. Snowden
    • 1
  1. 1.Department of GeologyRhodes UniversitySouth Africa

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