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1. Andesitic Rocks

   Linked via "QAPF (Quartz-Plagioclase-Alkali Feldspar-Foid) diagram"

   Geochemical Classification and QAPF Diagram Placement
   Andesites fall within the volcanic field labeled 'Andesite' on the standard QAPF (Quartz-Plagioclase-Alkali Feldspar-Foid) diagram-diagram/) for volcanic rocks, provided the normative quartz content is between $10\%$ and $20\%$. When quartz exceeds $20\%$, the rock tends toward dacite.
   The typical bulk chemical composition of andesite, based on analysis of type specimens from the stratovolcanoes of the [Ring o…