摘要：

The pyroxenes of the upper zone of the Skaergaard layered series consist of an iron-rich series of brown and green clinopyroxenes. Five new analyses are presented, together with a revised trend line which includes the full range of clinopyroxenes believed representative of the Skaergaard fractionation sequence. The range for the augite-ferroaugite-ferrohedenbergite series is from Ca42·4 Mg47·9 Fe9·7 to Ca42·5 Mg0·4 Fe57·1, the most ferriferous variety coexisting with a pure fayalite. A re-study of the compositions and textures of certain green ferrohedenbergites supports the belief that they are the product of sub-solidus inversion of ferriferous β-wollastontes, which crystallized as a temporary phase between the periods when brown ferrohedenbergites crystallized directly from the magma. A consideration of the compositional and textural relationships between green and brown pyroxenes, and the significance of the mosaic inversion texture, have led to an interpretation of the crystallization and inversion sequence for these minerals. Four new analyses of ferrohedenbergites from the downward-crystallized upper border group rocks provide evidence for a trend which differs slightly from that for the layered series ferrohedenbergites.

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