Tertiary epizonal plutonic rocks of the Selway-Bitterroot Wilderness, Idaho County, Idaho
Geologic mapping in the Selway-Bitterroot Wilderness identified approximately 731 kmS of epizonal plutonic granitic rocks within the Bitterroot lobe of the Idaho batholith. From north to south, the intrusions are the Rock Lake Creek stock and the Whistling Pig, Running Creek, Bad Luck and Painted Rocks plutons. The stock and plutons consist of medium- to coarse-grained biotite and hornblende-biotite syenorgranite to monzogranite and quartz syenite capped by fine-grained biotite leucogranite. These rocks are intruded by late-synplutonic leucogranite dikes and post plutonic porphyritic rhyolite to rhyodacite and basalt dikes. The medium-grained granitic rocks are high in SiO2, K2O, Na2O, Ga, Th, U, W and Zr, but low in Al7O3, CaO, MgO, Cr, Ni, Co and V. Most of the granites are peraluminous. Rare-earth element (REE) plots (rock sample/chondrite) show enrichment in light REE over heavy REE with strong EU depletions. K-Ar biotite radiometric age determinations for medium-grained granites in all of the plutons range from approximately 51 Ma (Whistling Pig pluton) to 43.7 Ma (Painted Rocks pluton). Petrogenetic studies suggest that the plutons were rapidly emplaced to within 3.0 km of the paleosurface. The types, textures and color of the rocks result from devolatilization of the crystallizing melt and very low-grade hydrothermal alteration. The fluorine-rich melts are the fractionated with accumulate residue; they are considered to be anorogenic (A-type) granites intruded into the center of a metamorphic core complex.
- Research Organization:
- Idaho Univ., Moscow (USA)
- OSTI ID:
- 6289467
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC DEPOSITS
PLUTONIC ROCKS
IDAHO
AGE ESTIMATION
ARGON
BIOTITE
DIKES
GEOCHEMISTRY
GEOLOGIC FAULTS
GEOLOGIC HISTORY
GRANITES
HORNBLENDE
INTRUSION
ISOTOPE DATING
MINERALOGY
POTASSIUM
QUARTZ
ALKALI METALS
AMPHIBOLE
CHALCOGENIDES
CHEMISTRY
ELEMENTS
FEDERAL REGION X
FLUIDS
GASES
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
METALS
MICA
MINERALS
NONMETALS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
RARE GASES
ROCKS
SILICATE MINERALS
SILICON COMPOUNDS
SILICON OXIDES
USA
580400* - Geochemistry- (-1989)