Title:
Shrinking of the Colorado Plateau via lithospheric mantle erosion; evidence from Nd and Sr isotopes and geochronology of Neogene basalts 
Reference Number:
9085 
ISSN:
0091-7613
Publication Year:
2011
GeoREF Number:
2011-012663 (View Original Data File)
Authors:
Crow, Ryan; Karlstrom, Karl; Asmerom, Yemane; Schmandt, Brandon; Polyak, Victor; DuFrane, Andrew
Descriptors:
absolute age, alkali basalts, alkaline earth metals, Ar/Ar, Arizona, asthenosphere, basalts, basanite, body waves, Cenozoic, Colorado Plateau, continental lithosphere, cosmogenic elements, dates, elastic waves, erosion, geochemistry, geochronology, Grand Canyon, He-3, helium, igneous rocks, isotope ratios, isotopes, lithosphere, low-velocity zones, magmatism, mantle, metals, Mohave County Arizona, neodymium, Neogene, noble gases, plateaus, rare earths, seismic waves, Sr-87/Sr-86, stable isotopes, strontium, teleseismic signals, Tertiary, tomography, Uinkaret volcanic field, United States, upper mantle, upwelling, velocity structure, volcanic fields, volcanic rocks, volcanism
Source:
Geology (Boulder), vol. 39, pp. 27-30
Abstract:
Geochronologic data from the southern margins of the Colorado Plateau (western United States) show an inboard radial migration of Neogene basaltic magmatism. Nd and Sr isotopic data show that as basaltic volcanism migrates inboard it also becomes increasingly more asthenospheric. Strongly asthenospheric alkali basalt (epsilon (sub Nd) >4) appeared on the western plateau margin ca. 5 Ma, on the southeastern margin at 7 Ma, and is lacking from the plateau's other margins. Tomographic data suggest that low-velocity mantle underlies almost all recent (younger than 1 Ma) basaltic volcanism in a ring around much of the Colorado Plateau at a depth of 80 km. The combined isotopic and tomographic data indicate that the low-velocity mantle is asthenosphere along the western and southeastern margins of the plateau, but modified lithosphere around the remaining margins. Temporal and spatial patterns suggest a process by which upwelling asthenosphere is progressively infiltrating and replacing lithospheric mantle, especially where Proterozoic boundaries exist. This model explains (1) the dramatic velocity contrast seen well inboard of the physiographic edge of the plateau, (2) the inboard sweep of Neogene magmatism, and (3) isotopic evidence that much (but not all) of the low-velocity mantle is asthenospheric. These data support models that ongoing uplift of the edges of the Colorado Plateau is driven by mantle processes.
Copyright:
GeoRef, Copyright 2011, American Geological Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States | Reference includes data supplied by the Geological Society of America, Boulder, CO, USA, United States

Sample Summary:
Sample ID: Major Data: Trace Data: Isotope Data:
RC08-LS-CHEM Yes Yes Yes
RC06-178-1 Yes Yes Yes
RC07-246-1C Yes Yes Yes
RC08-188.1R-1 Yes Yes Yes
LP01-184-01 Yes Yes Yes
LP01-189-01 No No Yes
K07-SHIV-1 Yes Yes Yes
WOO-195-1 Yes Yes Yes
LP01-179-04 Yes Yes Yes
RC06-187.7-1 Yes Yes Yes
WOO-190-2 Yes Yes Yes