| Alteration processes: | PRINCIPAL ALTERATION IS FENITIZATION OF POWDERHORN GRANITE, FINE- TO MEDIUM-GRAINED GRANITE, AND DUBOIS FELSITE BY MATASOMATISM ASSOCIATED WITH INTRUSION OF ALKALIC/CARBONATITIC MAGMATIC FLUIDS. GRADATION OF GRANITE TO FENITE CHARACTERIZED BY DECREASED QUARTZ, AEGIRINE-AUGITE REPLACING BIOTITE, MICROCLINE BECOMING GRAYER, MORE PERTHITIC, LESS EUHEDRAL, DEVELOPMENT OF GNEISSIC OR SCHLIERIC TEXTURE. FENITIZED DUBOIS FELSITE CHARACTERIZED BY ALBITIZATION OF MICROCLINE. ALTERATION OF NEPHELINE TO ZEOLITES (NATROLITE AND ANALCITE) AND CANCRINITE IN UNCOMPAHGRITE, IJOLITE, AND NEPHELINE SYENITE. ALTERATION OF PYRITE TO FE OXIDES IN THORIUM VEINS, TRACHYTE DIKES, CARBONATITE, & PYROXENITE. ALTERATION OF PEROVSKITE TO LEUCOXENE IN PYROXENITE. ALTERATION OF BIOTITE AND PHLOGOPITE TO VERMICULITE IN PYROXENITE. SERICITIZATION IN FENITIZED GRANITE, DIABASE, AND NEPHELINE SYENITE. CHLORITIZATION OF PYROXENE IN PYROXENITE AND UNCOMPAHGRITE. |