#Geology TV Documentary
14-Oct-94 00:26:27
Sb: #149200-#Geology TV Documentary
Fm: Scott L. Manske 72764,3211
To: Guy Hammer 72315,465
Hello, Guy:
Strictly speaking in terms of igneous petrology, the classifications of
igneous rocks as "alkalic", "calc-alkaline", "peralkalic", etc., are based on
the ratios of Na2O, K2O, CaO (alkali and alkaline earth elements, no?) in the
total normative (oxide) composition. Silica saturation (SiO2) is a related,
but not identical, compositional means of classification. A rock w/ the same
content of alkalis (Na2O, K2O, etc.), as a granite, but that was
silica-undersaturated would be a *syenite*, for example.
Scott M.