Classification of Igneous Rock Series

  title={Classification of Igneous Rock Series},
  author={Martin A. Peacock},
  journal={The Journal of Geology},
  pages={54 - 67}
  • M. A. Peacock
  • Published 1 January 1931
  • Geology
  • The Journal of Geology
Some rock series cannot be properly classified either as alkalic or as sub-alkalic. To meet this situation a simple extension of the present twofold classification is proposed; this takes the form of a fourfold division into alkalic, alkali-calcic, calc-alkalic, and calcic groups. It is shown, from a partial graphical representation of thirteen rock series, that the silica value at which the curves for total alkalis and for lime intersect (the alkali-lime index) is characteristic of a rock… 
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