Chemical and Thermal Zonation in a Mildly Alkaline Magma System Infiernito Caldera, Trans-pecos Texas.
Henry CD; Price JG; Smyth RC
Contrib Mineral Petrol 1988 98:194-211
This report describes a study on postcollapse lavas of the infiernito caldera grade stratigraphically upward from nearly aphyric, high-silica rhyolite (76% sio2) to highly prophyritic trachyte (62% sio2). Plagioclase, clinopyroxene, orthopyroxene, magnetite, ilmenite, and apatite occur as phenocrysts throughout the sequence. Sanidine, biotite, and zircon are present in rocks with more than about 67% sio2. Major and trace elements show continuous variations from 62 to 76% sio2. Modeling supports fractional crystallization of the observed phenocrysts as the dominant process in generating the chemical variation.
IH; Final Contract Report;
Contrib. Mineral Petrol., V. 98, 1988, PP. 194-211