StructurePLATORO CALDERA, SUMMITVILLE CALDERA, ALAMOSA RIVER STOCK, PLATORO FAULT ZONE, SUMMITVILLE FAULT, SAN JUAN VOLCANIC FIELD
AlterationCALKIN (1967) IDENTIFIED FOLLOWING STYLES AND ZONATION OF ALTERATION: (1) PERVASIVE SOLFATARIC ALTERATION ZINES AROUND VENT-DOME COMPLEXES--(A) OUTER PROPYLTIC ZONE OF EPIDOTE, CHLORITE, CALCITE, (B) MIDDLE ARGILLIC ZONE OF KAOLINITE AND INTERSTITIAL QUARTZ, (C) INNER QUARTZ-ALUNITE ZONE WITH PYRITE ADJACENT TO VENT; (2) POTASSIC HYDROTHERMAL ALTERATION AROUND ALUM CREEK PORPHYRY--(A) HOOD OR CAP OF PROPYLTIC ALTERATION WITH CALCITE REPLACING ALBITE, EPIDOTE (CLINOZOISITE) ALTERATION OF PLAGIOCLASE, CHLORITE (JENKINSITE) ALTERATION OF BIOTITE, (B) ARGILLIC ZONE WITH KAOLINITE REPLACING PLAGIOCLASE, BIOTITE, AND AUGITE, PRIMARY MAGNETITE/ILMENITE REMOVED, (C) INNER POTASSIC ZONE WITH SERICITE REPLACING KAOLINITIZED PLAGIOCLASE AND PHLOGOPITE-MUSCOVITE REPLACING KAOLINITIZED AUGITE AND BIOTITE, AND WITH QUARTZ VEINS AND DISSEMINATED PYRITE-MO; (3) LOCAL SELECTIVE ALTERATION ALONG FRACTURES, FAULTS, AND DIKES (SUCH AS RADIAL PATTERN AROUND SHEEPSHEAD) SUPERPOSED ON OR ACROSS ATHER ALTERATION ZONES AND SHOWING THAT THESE STRUCTURES WERE CONDUITS FOR ALTERING FLUIDS; (4) SUPERGENE OXIDATION OF FE EITHER FROM WELL ALTERED ROCKS WITH MINOR PYRITE OR FROM WEAKLY ALTERED ROCKS WITH MINOR MAGNETITE/ILMENITE. FOR VENT-DOMES AND ALUM CREEK PORPHYRY, CALKIN POSTULATED DEPTH-ZONE TRANSITION OF SOLFATARIC AND HYDROTHERMAL ENVIRONMENTS ASSOCIATED WITH EPITHERMAL, XENOTHERMAL, AND MESOTHERMAL CONDITIONS AND CONSIDERED ALTERATION TO BE MULTICOMPONENT REACTION OF ORIGINAL WALL ROCK WITH (A) CO2-BEARING ACID SOLUTIONS (HYDROTHERMAL) AND (B) SULFUROUS VAPORS FROM LATE VOLCANIC ACTIVITY (SOLFATARIC)., CALKIN (1967) - (A) OUTER PROPYLTIC ZONE OF EPIDOTE, CHLORITE, CALCITE, (B) MIDDLE ARGILLIC ZONE OF KAOLINITE AND INTERSTITIAL QUARTZ, (C) INNER QUARTZ-ALUNITE ZONE WITH PYRITE ADJACENT TO VENT; (2) POTASSIC HYDROTHERMAL ALTERATION AROUND ALUM CREEK PORPHYRY--(A) HOOD OR CAP OF PROPYLTIC ALTERATION WITH CALCITE REPLACING ALBITE, EPIDOTE (CLINOZOISITE) ALTERATION OF PLAGIOCLASE, CHLORITE (JENKINSITE) ALTERATION OF BIOTITE, (B) ARGILLIC ZONE WITH KAOLINITE REPLACING PLAGIOCLASE, BIOTITE, AND AUGITE, PRIMARY MAGNETITE/ILMENITE REMOVED, (C) INNER POTASSIC ZONE WITH SERICITE REPLACING KAOLINITIZED PLAGIOCLASE AND PHLOGOPITE-MUSCOVITE REPLACING KAOLINITIZED AUGITE AND BIOTITE, AND WITH QUARTZ VEINS AND DISSEMINATED PYRITE-MO; (3) LOCAL SELECTIVE ALTERATION ALONG FRACTURES, FAULTS, AND DIKES (SUCH AS RADIAL PATTERN AROUND SHEEPSHEAD) SUPERPOSED ON OR ACROSS ATHER ALTERATION ZONES AND SHOWING THAT THESE STRUCTURES WERE CONDUITS FOR ALTERING FLUIDS; (4) SUPERGENE OXIDATION OF FE EITHER FROM WELL ALTERED ROCKS WITH MINOR PYRITE OR FROM WEAKLY ALTERED ROCKS WITH MINOR MAGNETITE/ILMENITE. FOR VENT-DOMES AND ALUM CREEK PORPHYRY, CALKIN POSTULATED DEPTH-ZONE TRANSITION OF SOLFATARIC AND HYDROTHERMAL ENVIRONMENTS ASSOCIATED WITH EPITHERMAL, XENOTHERMAL, AND MESOTHERMAL CONDITIONS AND CONSIDERED ALTERATION TO BE MULTICOMPONENT REACTION OF ORIGINAL WALL ROCK WITH (A) CO2-BEARING ACID SOLUTIONS (HYDROTHERMAL) AND (B) SULFUROUS VAPORS FROM LATE VOLCANIC ACTIVITY (SOLFATARIC)., CALKIN (1967) - MIDDLE ARGILLIC ZONE OF KAOLINITE AND INTERSTITIAL QUARTZ, (C) INNER QUARTZ-ALUNITE ZONE WITH PYRITE ADJACENT TO VENT; (2) POTASSIC HYDROTHERMAL ALTERATION AROUND ALUM CREEK PORPHYRY--(A) HOOD OR CAP OF PROPYLTIC ALTERATION WITH CALCITE REPLACING ALBITE, EPIDOTE (CLINOZOISITE) ALTERATION OF PLAGIOCLASE, CHLORITE (JENKINSITE) ALTERATION OF BIOTITE, (B) ARGILLIC ZONE WITH KAOLINITE REPLACING PLAGIOCLASE, BIOTITE, AND AUGITE, PRIMARY MAGNETITE/ILMENITE REMOVED, (C) INNER POTASSIC ZONE WITH SERICITE REPLACING KAOLINITIZED PLAGIOCLASE AND PHLOGOPITE-MUSCOVITE REPLACING KAOLINITIZED AUGITE AND BIOTITE, AND WITH QUARTZ VEINS AND DISSEMINATED PYRITE-MO; (3) LOCAL SELECTIVE ALTERATION ALONG FRACTURES, FAULTS, AND DIKES (SUCH AS RADIAL PATTERN AROUND SHEEPSHEAD) SUPERPOSED ON OR ACROSS ATHER ALTERATION ZONES AND SHOWING THAT THESE STRUCTURES WERE CONDUITS FOR ALTERING FLUIDS; (4) SUPERGENE OXIDATION OF FE EITHER FROM WELL ALTERED ROCKS WITH MINOR PYRITE OR FROM WEAKLY ALTERED ROCKS WITH MINOR MAGNETITE/ILMENITE. FOR VENT-DOMES AND ALUM CREEK PORPHYRY, CALKIN POSTULATED DEPTH-ZONE TRANSITION OF SOLFATARIC AND HYDROTHERMAL ENVIRONMENTS ASSOCIATED WITH EPITHERMAL, XENOTHERMAL, AND MESOTHERMAL CONDITIONS AND CONSIDERED ALTERATION TO BE MULTICOMPONENT REACTION OF ORIGINAL WALL ROCK WITH (A) CO2-BEARING ACID SOLUTIONS (HYDROTHERMAL) AND (B) SULFUROUS VAPORS FROM LATE VOLCANIC ACTIVITY (SOLFATARIC)., CALKIN (1967) INNER POTASSIC ZONE WITH SERICITE REPLACING KAOLINITIZED PLAGIOCLASE AND PHLOGOPITE-MUSCOVITE REPLACING KAOLINITIZED AUGITE AND BIOTITE, AND WITH QUARTZ VEINS AND DISSEMINATED PYRITE-MO; (3) LOCAL SELECTIVE ALTERATION ALONG FRACTURES, FAULTS, AND DIKES (SUCH AS RADIAL PATTERN AROUND SHEEPSHEAD) SUPERPOSED ON OR ACROSS ATHER ALTERATION ZONES AND SHOWING THAT THESE STRUCTURES WERE CONDUITS FOR ALTERING FLUIDS; (4) SUPERGENE OXIDATION OF FE EITHER FROM WELL ALTERED ROCKS WITH MINOR PYRITE OR FROM WEAKLY ALTERED ROCKS WITH MINOR MAGNETITE/ILMENITE. FOR VENT-DOMES AND ALUM CREEK PORPHYRY, CALKIN POSTULATED DEPTH-ZONE TRANSITION OF SOLFATARIC AND HYDROTHERMAL ENVIRONMENTS ASSOCIATED WITH EPITHERMAL, XENOTHERMAL, AND MESOTHERMAL CONDITIONS AND CONSIDERED ALTERATION TO BE MULTICOMPONENT REACTION OF ORIGINAL WALL ROCK WITH (A) CO2-BEARING ACID SOLUTIONS (HYDROTHERMAL) AND (B) SULFUROUS VAPORS FROM LATE VOLCANIC ACTIVITY (SOLFATARIC).