Mafic enclave-bearing tonalites as hybrids generated in the lower crust: Examples from the north Cascades

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5436435

Dawes, R L ^[1]

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1. Univ. of Washington, Seattle, WA (United States). Dept. of Geological Sciences

Late Cretaceous tonalites, trondhjemites and granodiorites of the North Cascades of Washington State completed igneous crystallization at mid-crustal depths and contain magmatic epidote, garnet, and muscovite-rich white mica. Whole-rock geochemical and isotopic characteristics, combined with field, petrographic, and mineralogic data, disallow a fractional crystallization relationship between synplutonic mafic, intermediate, and felsic rocks, and also argue against an origin of the mafic and intermediate rocks solely by melting of the lower crust. The petrogenetic model that best accounts for the evidence is that the intermediate, enclave-bearing tonalites are hybrids created by mixing of modified, mantle-derived mafic magmas with lower crustal melt.

• OSTI ID: 5436435
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CASCADE MOUNTAINS
CHEMISTRY
CRETACEOUS PERIOD
DEVELOPED COUNTRIES
GEOBAROMETRY
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
GEOTHERMOMETRY
GRANITES
GRANODIORITES
IGNEOUS ROCKS
MESOZOIC ERA
MINERALOGY
MOUNTAINS
NORTH AMERICA
PETROGENESIS
PETROGRAPHY
PETROLOGY
PLUTONIC ROCKS
ROCKS
USA
WASHINGTON