Evaluation of Boundary Lines in Some Diagrams for the Discrimination between Subalkalic and Alkalic Basalts

Authors

  • Essam El-Hinnawi <p>National Research Centre, Dokki, Cairo, Egypt</p>

DOI:

https://doi.org/10.2451/2016PM614

Keywords:

Alkalic basalts – subalkalic basalts – transitional basalts- boundary lines- total alkalis-SiO2 diagram – Ritmann's Suite Index.

Abstract

Some boundary lines in the total alkalis-SiO2 diagram have been evaluated for the discrimination between alkalic and subalkalic basalts. The boundary line of Macdonald and Katsura has been found to be the most effective line for this purpose. A boundary line with constant Suite Index (σ) of 2.2 has been also found effective n a modified Rittmann's diagram. For distinguishing transitional basalts, a new method has been introduced, based on a combination of CIPW norm, two discriminants of Macdonald and Katsura boundary line, the Poldervaart Index, and Rittmann's Suite Index. The method has been found to be more efficient than graphical means, hitherto used.

 

Author Biography

Essam El-Hinnawi, <p>National Research Centre, Dokki, Cairo, Egypt</p>

Emeritus Research Professor

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Published

2016-02-12

Issue

Vol. 85 No. 1 (2016)

Section

ORIGINAL ARTICLE