Temperature, size, and depth of the magma reservoir for the Taylor Creek Rhyolite, New Mexico

Journal Article · · American Mineralogist; (United States)

OSTI ID:5708338

Duffield, W A ^[1]; Du Bray, E A ^[2]

---

1. Geological Survey, Flagstaff, AZ (USA)
2. Geological Survey, Denver, CO (USA)

The 55 km{sup 3} mid-Tertiary Taylor Creek Rhyolite in southwestern New Mexico consists of 20 lava domes and flows. Compositional zonation in feldspar phenocrysts analyzed by electron microprobe is very minor and nonsystematic; most grains show less that 1 mol% Ab variation. This chemical homogeneity of phenocrysts reflects similar whole-rock homogeneity and suggests that the lavas were tapped from a single large reservoir of magma. Ages of sanidine phenocrysts determined using {sup 40}Ar/{sup 39}Ar indicate that the lavas were emplaced during a period of less than 0.42 m.y. and possibly less than 0.13 m.y., which is consistent with the single-reservoir scenario. Two-feldspar geothermometry suggests that the phenocrysts crystallized at about 775C, at an assumed pressure of 2 kbar. Fe-Ti-oxide geothermometry suggests phenocryst growth at about 800C. These temperatures are consistent with fluid-inclusion-homogenization temperatures and {sup 18}O-fractionation temperatures between about 700C and 800C for vapor-phase minerals deposited in the outer rinds of the lavas as they cooled, immediately following emplacement. Insofar as experimental results in the system NaAlSi{sub 3}O{sub 8}-KAlSi{sub 3}O{sub 8}-SiO{sub 2}-H{sub 2}O are applicable to the Taylor Creek Rhyolite, a comparison between the natural and experimental systems indicates that this magma at 800C could have been saturated with H{sub 2}O and at or near the liquidus at a pressure of about 0.5 kbar. Duffield and Du Bray tentatively conclude that the Taylor Creek Rhyolite magma was H{sub 2}O undersaturated and subliquidus at an unspecified pressure greater than 0.5 kbar during phenocryst growth and that Taylor Creek Rhyolite pyroclastic deposits formed because volatile saturation developed during the ascent of magma to sites of eruption.

• OSTI ID: 5708338
• Journal Information: American Mineralogist; (United States), Vol. 75:9-10; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
58 GEOSCIENCES
MAGMA SYSTEMS
AMBIENT TEMPERATURE
DEPTH
SIZE
NEW MEXICO
AGE ESTIMATION
ALUMINIUM OXIDES
ARGON 39
ARGON 40
BIOTITE
CHEMICAL COMPOSITION
CRYSTALLIZATION
ELECTRON MICROPROBE ANALYSIS
FELDSPARS
GEOCHEMISTRY
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOTHERMOMETRY
HORNBLENDE
ISOTOPE DATING
LAVA
MINERALOGY
OXYGEN 18
POTASSIUM OXIDES
QUARTZ
RESERVOIR FLUIDS
SILICATE MINERALS
SILICON OXIDES
SODIUM OXIDES
VOLATILE MATTER
ALKALI METAL COMPOUNDS
ALUMINIUM COMPOUNDS
AMPHIBOLE
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMISTRY
DEVELOPED COUNTRIES
DIMENSIONS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION VI
FLUIDS
GEOTHERMAL SYSTEMS
ISOTOPES
LIGHT NUCLEI
MATTER
MICA
MICROANALYSIS
MINERALS
NONDESTRUCTIVE ANALYSIS
NORTH AMERICA
NUCLEI
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PHASE TRANSFORMATIONS
POTASSIUM COMPOUNDS
RADIOISOTOPES
SILICON COMPOUNDS
SODIUM COMPOUNDS
STABLE ISOTOPES
USA
YEARS LIVING RADIOISOTOPES
150200* - Geology & Hydrology of Geothermal Systems
580000 - Geosciences