Petrology and metamorphic history of metapelites in the Boehls Butte quadrangle, northern Idaho
Metapelitic rocks in the Goat Mountain area record a pre-Beltian anatectic event and two later metamorphic events correlated to the M2 and M3 events observed by Lang and Rice. The co-occurrence of all three aluminosilicates is the result of M2 kyanite-sillimanite growth and M3 andalusite growth. The conditions of M2 metamorphism are estimated at 675 +/- 50/sup 0/C and 9.3 +/- 1.5 kb as determined from a variety of geothermo/barometers. M2 AFM mineral assemblages include Grt-Bt-Ky+/-Sil+/-Str and Crd-Bt-Ky+/-Sil. Partitioning of Mg and Fe in garnet and staurolite is normal (K/sub D/ > 1) for relict staurolite enclosed by aluminosilicate or muscovite and reversed (K/sub D/ < 1) for apparently stable staurolite and staurolite occurring as inclusions in garnet. Cordierite occurs as an overgrowth of kyanite; a texture which cannot be explained by reactions among the coexisting minerals. The texture may be explained by prograde consumption of chlorite or consumption of garnet upon decompression. The M3 event had limited effect on M2 mineral assemblages but resulted in crenulation and brittle deformation of M2 fabrics. The M3 event occurred during uplift and cooling following the M2 event. The M3 event is correlated to uplift of the Idaho batholith implying a Cretaceous age of M2 metamorphism.
- Research Organization:
- Univ. of Oregon, Eugene (USA)
- OSTI ID:
- 6644378
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
15 GEOTHERMAL ENERGY
IDAHO
METAMORPHIC ROCKS
GEOTHERMOMETERS
MINERALIZATION
PETROGENESIS
PETROLOGY
ALUMINIUM SILICATES
CHLORITE MINERALS
CRETACEOUS PERIOD
GARNETS
GEOBAROMETRY
GEOLOGIC HISTORY
GEOTHERMOMETRY
METAMORPHISM
MINERALOGY
MUSCOVITE
PARTITION
ALUMINIUM COMPOUNDS
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGY
MEASURING INSTRUMENTS
MESOZOIC ERA
MICA
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
THERMOMETERS
USA
580300* - Mineralogy
Petrology
& Rock Mechanics- (-1989)
152004 - Geothermal Data & Theory- Isotope & Trace Element Studies