skip to main content

Title: 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-grademore » 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.« less
Authors:
Publication Date:
OSTI Identifier:
6289467
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: Thesis (Ph. D.)
Publisher:
Univ. of Idaho,Moscow, ID
Research Org:
Idaho Univ., Moscow (USA)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 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)