Dry Synthesis of Feldspathoids by Feldspar - Carbonate Reactions

Abstract

THERE is a well-known petrogenetical theory that rock-types, undersaturated in silica, can form from saturated magmas by limestone-syntexis^1–4, or by the physico-chemically equivalent process of granite-assimilation by carbonatite magma⁵. Nobody, however, seems to have tried to verify experimentally such proposed processes. This may have been due to the fact that the shadow of the all-embracing crystallization-differentiation theory⁶ loomed large over the then still extremely small world of experimental petrologists. Petrographers, on the other hand, may have felt that their evidence (partial replacement of limestone- and dolomite-inclusions with concomitant formation of feldspathoids in lavas) was just as good as laboratory proof. Interesting evidence by McLintock⁷, who published an account of the generation of leucite and ægirite with melilite, wollastonite and diopside in a Persian marl, heated by the combustion of hydrocarbons underground, seems to have got little attention.