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Sedimentary and igneous trends on AFM diagrams

Published online by Cambridge University Press:  01 May 2009

D. Robinson  and
B. E. Leake
D. Robinson
Affiliation:
Geology Department, The University, Bristol BS8 1TR
B. E. Leake
Affiliation:
Geology Department, The University, Glasgow G12 8QQ
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Summary

It is pointed out that some chemically analysed sedimentary rock series when plotted on AFM diagrams (A = Na2O + K2O; F = total iron as FeO; M = MgO) partly mimic trends generally considered characteristic of igneous variation, especially the calc-alkali trend. Although the scatter in sedimentary rock plots is generally greater than that given by igneous rocks this is not necessarily so for calc-alkali suites often show considerable scatter. These observations should be considered when deducing the origin of highly metamorphosed gneisses and quartzo-feldspathic rocks that might be meta-arkoses, meta-granites or meta-volcanic rocks.

Type
Articles
Information
Geological Magazine , Volume 112 , Issue 3 , May 1975 , pp. 305 - 307
Copyright
Copyright © Cambridge University Press 1975

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