Columbia/Snake River: Yellowstone magmatism in the context of western U. S. A. cenozoic geodynamics

Journal Article · Wed May 11 00:00:00 EDT 1977 · Tectonophysics; (United States)

DOI:https://doi.org/10.1016/0040-1951(77)90157-3· OSTI ID:6781051

Thompson, R N

An attempt was made to calculate the total volume of Middle Cenozoic to Recent igneous rocks in the Columbia--Snake River--Yellowstone region by adding geophysically-derived estimates of the amounts of mafic intrusion to published data on the volumes of volcanic rocks. Recently published radiometric ages allow comparison of rates of basaltic magmatism in these ensialic provinces with those along equivalent lengths of mid-oceanic ridge. The rates of total magmatic activity (extrusive and intrusive) during the genesis of the Columbia River Plateau, Western Snake River Plain and Eastern Snake River Plain--Yellowstone sub-provinces were equivalent to those of mid-oceanic ridges with spreading half-rates of 10, 3 and 0.3 cm per year, respectively. It is shown that the hypothesis that magmatism in this region is the product of a deep-mantle convective plume, situated at present beneath Yellowstone, does not explain adequately several features of the Snake River Plain and becomes untenable when applied to the province as a whole. It is proposed instead that all major post-Eocene tectonic and magmatic features of the western U.S.A., east of the Sierra Nevada and Cascades, are products of comparatively shallow-rooted diapiric upwelling in the mantle; triggered at about 40 m.y. by extraction of mafic silicate melt and volatiles from the Farallon lithospheric plate, subducted at a comparatively low angle beneath the North American plate. Constriction of the Columbia River Plateau diapir by the subduction zone to its west led to ''run away'' mantle fusion and massive production of basic magmas.

• Research Organization: Imperial Coll. of Science and Technology, London
• OSTI ID: 6781051
• Journal Information: Tectonophysics; (United States), Vol. 39:4
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
15 GEOTHERMAL ENERGY
IDAHO
MAGMATISM
MAGMA
UPWELLING
OREGON
WASHINGTON
WYOMING
YELLOWSTONE NATIONAL PARK
CENOZOIC ERA
COLUMBIA RIVER
EARTH CRUST
EARTH MANTLE
GEOLOGIC MODELS
HEAT TRANSFER
IGNEOUS ROCKS
INTRUSION
NATURAL CONVECTION
RIVERS
TECTONICS
CONVECTION
ENERGY TRANSFER
GEOLOGIC AGES
NORTH AMERICA
PACIFIC NORTHWEST REGION
PUBLIC LANDS
ROCKS
ROCKY MOUNTAIN REGION
STREAMS
SURFACE WATERS
USA
580202* - Geophysics- Volcanology- (1980-1989)
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