HR: 12:00h
AN: V42B-07    [Abstracts]
TI: Constraining the Early Isotopic and Trace Element Signature of the Yellowstone Mantle Plume: Evidence from Imnaha Basalts
AU: * Patterson, J D
EM: pattersonja@cwu.edu
AF: Central Washington University, 101 Lind Hall 400 E University Way, Ellensburg, WA 98926-7418, United States
AU: Ramos, F C
EM: ramos@geology.cwu.edu
AF: Central Washington University, 101 Lind Hall 400 E University Way, Ellensburg, WA 98926-7418, United States
AU: Wolff, J A
EM: jawolff@mail.wsu.edu
AF: Washington State University, 1228 Webster Physical Science Bldg, Pullman, WA 99164,
AB: Characterizing the geochemical signatures of plumes is critical for evaluating the petrogenetic evolution of plume- related volcanic rocks. The main phase of Columbia River flood basalt activity (16.6 – 15.5 Ma), considered to represent the first clear manifestation of the Yellowstone hotspot on the North American continent, includes the Steens Mountain, Imnaha, Grande Ronde and Picture Gorge basalts. Isotopic and trace element covariations defined by Grande Ronde, Steens Mountains, and Picture Gorge basalts diverge radially from the field of Imnaha basalts, which retain signatures that most closely reflect the ‘undiluted' geochemical characteristics of the Yellowstone mantle plume. Sr, Nd, Pb isotope ratios and incompatible trace element abundances and ratios of Imnaha basalts closely resemble those of some Pacific EM II OIB groups. Nonetheless, the compositions of some Imnaha lavas reflect mixing of the plume with different mantle types. Others have clearly been affected by interaction of plume-derived basalt with continental crust, although the latter process is much more significant in the genesis of the succeeding Grande Ronde basalts. We will review the geochemical characteristics of the Yellowstone plume as recorded in the Imnaha basalt in the context of later-erupted volcanic products of the Columbia - Snake – Yellowstone system, and Pacific mantle plumes more generally.
DE: 1036 Magma chamber processes (3618)
DE: 1115 Radioisotope geochronology
DE: 3618 Magma chamber processes (1036)
DE: 3640 Igneous petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting