Snake River Plain Silicic Volcanism: Implications for Magmatic Fluxes Associated with the Yellowstone Hotspot
Abstract
Knowledge of magmatic fluxes can provide important insights into physical processes driving volcanism. In the Snake River Plain (SRP)-Yellowstone province it is difficult to constrain the flux of mantle melts owing to the presence of cratonic continental crust that acts as a density filter to ascending basaltic magmas. We take an indirect approach to estimating the overall flux of mantle melt by considering the output of silicic volcanic products, assuming these result from crustal heating due to intrusion of basaltic magmas. SRP volcanism is characterized by an early time-transgressive phase of caldera-style silicic volcanism; dating of this activity first suggested that the province might be the manifestation of plate migration over the Yellowstone hotspot. Basaltic volcanism is largely restricted to later stages and once underway has continued to Quaternary time across much of the province. New Ar-Ar dating and stratigraphic studies provide improved estimates of rhyolite production in the west-central SRP (>10,000 cu. km), with an early peak and gradual decrease in output mostly between 12.7-8 Ma. Overall, this figure exceeds the already prodigious rhyolite production estimated for Yellowstone. Considering the thermal energy required leads to lower limit estimates for basaltic magma input and also implies that significant basaltic magmatism was underway prior to onset of rhyolitic activity at any given SRP silicic eruptive center. Overall basaltic magma flux appears to approach the magnitude for Hawaii and is equivalent to injection of a lens of at least several km in thickness along the length of the SRP, that must be leading to significant modification of the crust by basaltic inputs (and rhyolite outputs). To accommodate the inferred volume of new crust, while maintaining approximately the same crustal thickness, requires that the lithosphere must deform apparently by NE-SW extension consistent with Basin and Range style deformation and with available estimates of extensional strain. Some of the basaltic magma may be generated by extension-related decompression of lithospheric mantle, but thermal considerations (Leeman et al., Session V10, this meeting) suggest that a portion is generated within hot ascending asthenospheric mantle (plume?).
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.V44C..04B
- Keywords:
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- 3615 Intra-plate processes (1033;
- 8415);
- 3619 Magma genesis and partial melting (1037);
- 3690 Field relationships (1090;
- 8486);
- 8415 Intra-plate processes (1033;
- 3615);
- 8425 Effusive volcanism