Partial melting of amphibolite to trondhjemite at Nunatak Fiord, St. Elias Mountains, Alaska
At Nunatak Fiord, 55km NE of Yakutat, Alaska, a uniform layer of Cretaceous basalt ca. 3km thick was metamorphosed ca. 67 million years ago to amphibolite and locally partially melted to pegmatitic trondhjemite. Segregations of plagioclase-quartz+/-biotite rock, leucosomes in amphibolite matrix, range from stringers 5-10mm thick to blunt pods as thick as 6m. They tend to be parallel to foliation of the amphibolite, but crosscutting is common. The assemblage aluminous hornblende-plagioclase-epidote-sphene-quartz gave a hydrous melt that crystallized to plagioclase-quartz+/-biotite pegmatitic trondhjemite. 5-10% of the rock melted. Eu at 2x chondrites is positively anomalous. REE partitioning in melt/residum was controlled largely by hornblende and sphene. Though the mineralogical variability precludes quantitative modeling, partial melting of garnet-free amphibolite to heavy-REE-depleted trondhjemitic melt is a viable process.
- Research Organization:
- Univ. of Maryland, College Park (USA)
- OSTI ID:
- 6595640
- 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
Similar Records
Epidote-amphibolite to amphibolite facies transition in the southern Appalachian Piedmont: P-T conditions across the garnet and calc-silicate isograds
Anatexis of garnet amphibolites from a subduction zone metamorphic terrane
Related Subjects
ALASKA
AMPHIBOLITES
BASALT
PEGMATITES
GEOCHEMISTRY
METAMORPHISM
MINERALOGY
ANORTHOSITES
BIOTITE
CHEMICAL REACTIONS
CRETACEOUS PERIOD
MAGMATISM
MELTING
PETROGENESIS
QUARTZ
CHALCOGENIDES
CHEMISTRY
FEDERAL REGION X
GABBROS
GEOLOGIC AGES
GRANITES
IGNEOUS ROCKS
MESOZOIC ERA
METAMORPHIC ROCKS
MICA
MINERALS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PLUTONIC ROCKS
ROCKS
SILICATE MINERALS
SILICON COMPOUNDS
SILICON OXIDES
USA
VOLCANIC ROCKS
580400* - Geochemistry- (-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)