HR: 1340h
AN: V53B-1324 [Abstracts]
TI: Olivine Crystallization and Mantle Potential Temperatures Beneath Yellowstone
AU: * Wonderly, A
EM: expandingman@csufresno.edu
AF: California State University, Fresno, Department of Earth and Environmental Sciences, 2345
E. San Ramon Ave., MS/MH24, Fresno, CA 93720, United States
AU: Putirka, K D
EM: kputirka@csufresno.edu
AF: California State University, Fresno, Department of Earth and Environmental Sciences, 2345
E. San Ramon Ave., MS/MH24, Fresno, CA 93720, United States
AU: Atosa, A
EM: aabedini@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AU: Hurwitz, S
EM: shaulh@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AB:
New basalt samples from the Yellowstone Plateau volcanic field provide evidence for some of the most primitive
liquids yet recovered for the region, and yield clues regarding mantle processes. The sample distribution covers
a large area and an extended period, and one sample in particular (basalt of Warm River) contains 11% MgO,
with olivines that are in equilibrium with the host whole rock. Using olivine thermometry, we calculate both olivine
crystallization and mantle potential temperatures (Tp, the temperature a parcel of mantle would have if it rose
adiabatically to Earth's surface without melting) to test whether the alleged Yellowstone hot spot is truly hot.
These tests make use of thermometers from (1) and (2), and we compare temperatures at Yellowstone with
estimates from the Hawaii Scientific Drilling Project, HSDP-2 (2, 3) and the Siqueiros Transform, near the East
Pacific Rise (4). Assessment of olivine-liquid equilibrium is based on the Fe-Mg exchange coefficient between
olivine and liquid, which is assumed to be 0.30+/-0.03 (5).
In total, the Yellowstone lavas have mean crystallization temperatures of 1251+/-41oC (n=79) with a
maximum of 1327oC. The mean temperature is similar to crystallization temperatures of basalts from
Siqueiros (1264+/-21oC), but lower than the mean temperature for HDSP samples (1343+/-50oC).
Mantle potential temperatures appear to approach an olivine-control line, which if valid, yields a mantle potential
temperature of 1610oC, slightly higher than most Snake River Plain (SRP) lavas (Tp =1540oC).
Applying the same model to lavas from the Siqueiros Transform yields a Tp of 1400oC, and so excess
temperatures (relative to MORB) along the SRP are in the range of 140-209oC, consistent with a mantle
plume interpretation for the Yellowstone hot spot track. These calculations presume that primitive melts have
equilibrated with mantle olivine of Fo90 in composition; given the FeO contents of SRP lavas, parental liquids
should have between 15-18% MgO. We tentatively conclude that the Yellowstone hot spot is indeed hot
compared to ambient mantle.
(1) Beattie (1993) CMP, 115, 103-111.
(2) Putirka et al. (2007) Chem. Geol., 241, 177-206.
(3) Rhodes and Vollinger (2004) G-cubed, 5, 10.1029/2002GC00434.
(4) Perfit et al. (1996) EPSL, 141, 91-108.
(5) Roeder and Emslie (1970) CMP, 29, 275-289.
DE: 3618 Magma chamber processes (1036)
DE: 3619 Magma genesis and partial melting (1037)
DE: 3620 Mineral and crystal chemistry (1042)
DE: 3651 Thermobarometry
DE: 8121 Dynamics: convection currents, and mantle plumes
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting