Neodymium isotopic evidence for decreasing crustal contributions to cenozoic ignimbrites of the western United States. Implications for the thermal evolution of the Cordilleran crust

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Geological Society of America, Bulletin; (United States)

DOI:https://doi.org/10.1130/0016-7606(1993)105<0872:NIEFDC>2.3.CO;2· OSTI ID:5932758

Perry, F V ^[1]; DePaolo, D J ^[2]; Baldridge, W S ^[3]

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1. Univ. of New Mexico, Albuquerque (United States)
2. Univ. of California, Berkeley (United States)
3. Los Alamos National Lab., NM (United States)

We have estimated the crustal contributions to 12 early Oligocene to Pleistocene rhyolite systems located throughout the Cordillera. We have determined that (1) crustal contributions to large-volume rhyolite systems decrease from the Oligocene to the Miocene, and (2) rhyolite systems younger than 20 Ma are dominated by mantle components. The crustal contributions to rhyolite systems may be controlled by system size and duration, crustal thickness, tectonic setting, crustal composition, crustal density, and crustal temperature. We conclude that regional cooling of the lower crust, which progressively limited the amount of crustal wallrock assimilated by rhyolite systems, is the only parameter that is consistent with geologic and geochemical data for rhyolite systems and the geologic evolution of the Cordillera. A quantitative model that relates the amount of crustal contribution to assimilation/recharge rates and the temperature of the crust indicates that lower-crustal temperatures would have to decrease about 300[degrees]C between early Oligocene and early Miocene time to account for the decrease in crustal contributions. 57 refs., 7 figs., 1 tab.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5932758
• Journal Information: Geological Society of America, Bulletin; (United States), Vol. 105:7; ISSN 0016-7606
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
RHYOLITES
GEOCHEMISTRY
ANDES
EARTH CRUST
EXPERIMENTAL DATA
MATHEMATICAL MODELS
MIOCENE EPOCH
NEODYMIUM ISOTOPES
TERTIARY PERIOD
CENOZOIC ERA
CHEMISTRY
DATA
GEOLOGIC AGES
IGNEOUS ROCKS
INFORMATION
MOUNTAINS
NUMERICAL DATA
ROCKS
VOLCANIC ROCKS
580000* - Geosciences
990200 - Mathematics &amp; Computers