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Geochemistry of late Cretaceous granitoids from northeastern Washington: implication for genesis of two-mica Cordilleran granites

Journal Article · · Geology; (United States)
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), Journal Name: Geology; (United States) Vol. 16:5; ISSN GLGYB
Country of Publication:
United States
Language:
English