Zr-rich alkaline pegmatites from Gordon Butte, Crazy Mountains (Montana, USA): comparisons between potassic...Springer-Verlag 2002 Abstract At Gordon Butte (Crazy Mountains, Montana), agpaitic nepheline±syenite pegmatites...overall evolutionary trend of clinopyroxene in the Gordon Butte rocks is from Fe-poor diopside to aegirine±augite...lamprophyllite. The evolutionary history of the Gordon Butte pegmatites can be subdivided into primary, agpaitic...loparite. The mineralogy of the pegmatites from Gordon Butte, other potassic complexes, and sodic agpaitic |