Geochemistry of late Cretaceous granitoids from northeastern Washington: implication for genesis of two-mica Cordilleran granites
Mesozoic two-mica granites and I-type granodiorites from northeastern Washington have initial /sup 87/Sr//sup 86/Sr ratios around 0.7100, similar to many other Cordilleran granitoids. Metapelite and calcsilicate country rocks, equivalent to the Belt Supergroup, have measured /sup 87/Sr//sup 86/Sr ratios in the range of 0.91 to 0.98. Unlike many of their Cordilleran counterparts, the northeastern Washington two-mica granites are enriched in U, Rb, and other incompatible elements, and therefore cannot have been derived from depleted lower crust sedimentary sources. Both the two-mica granites and the I-type granodiorites have similar rare-earth-element and trace-element enrichment patterns. Trace-elements modeling shows that it is feasible to derive the two-mica granites by 60% partial melting of a granodiorite-like source. The close association of Cordilleran metamorphic core complexes and older I-type granodiorites with two-mica granites supports this model.
- Research Organization:
- Univ. of Arizona, Tucson (USA)
- OSTI ID:
- 7188802
- Journal Information:
- Geology; (United States), Vol. 16:5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GRANITES
GEOCHEMISTRY
WASHINGTON
ENRICHMENT
GEOLOGIC HISTORY
GEOLOGIC MODELS
ISOTOPE RATIO
MICA
RARE EARTHS
RUBIDIUM
STRONTIUM 86
STRONTIUM 87
URANIUM
ACTINIDES
ALKALI METALS
ALKALINE EARTH ISOTOPES
BETA DECAY RADIOISOTOPES
CHEMISTRY
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION X
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
METALS
NORTH AMERICA
NUCLEI
PLUTONIC ROCKS
RADIOISOTOPES
ROCKS
STABLE ISOTOPES
STRONTIUM ISOTOPES
USA
580400* - Geochemistry- (-1989)