Sm-Nd isotopic study of Precambrian/Cambrian sedimentary provenance in the Great Basin and implications for the tectonic evolution of the western US
The Nd isotopic compositions and Sm-Nd model ages were determined for 14 Precambrian to Cambrian clastic miogeoclinal and 2 Lower Paleozoic eugeoclinal metasedimentary rocks in the Great Basin to determine the sediment source regions and constrain the tectonic evolution of the western margin of the continental US Upper Precambrian (McCoy Creek Group-MCG) and Lower Cambrian miogeoclinal sandstones and shales have homogeneous 147SM/144Nd values (.110 to .119) but show a regional variation in measured element of/sub Nd/, from values of -18 and -26 (T/sub DM/=1.9 and 2.5Ga) in the Pilot and Ruby Ranges in N. Nevada, to values clustering at -11 and -18 (T/sub DM/=1.3 and 1.9Ga) in the Deep Creek and Schell Creek Ranges in the east-central Great Basin. The isotopic variations in the MCG correspond spatially to changes in the element of/sub ND/(0) and T/sub DM/ Precambrian basement adjacent to the miogeocline, suggesting that the MCG were derived from these crustal terranes and were deposited close to the paleocontinental margin of the western US. An element of/sub Nd/(0)=22.14 (T/sub DM/=2.1 Ga) for deeper water miogeoclinal sediment in the southern Great Basin (Wyman Fm-White Mountains, California) requires a source either in nearby T/sub DM/=2.2Ga crust in the S. Sierra Nevada (Bennett and DePaolo, 1984), or in T/sub DM/>2.0Ga crustal terranes to the north, with the sediment having been transported southward via Precambrian longshore currents. Feldspathic sandstone of the Cambrian Harmony Formation in north-central Nevada has element of/sub Nd/(0)=-25.22 (T/sub DM/=2.4Ga), consistent with a northerly source in Archean crust of present-day Idaho, while Ordovician shale of the Vinini Fm. in central Nevada has element of/sub Nd/(0)=-17.6, identical to values for the MCG exposed directly to the east.
- Research Organization:
- Los Alamos National Lab., NM (USA)
- OSTI ID:
- 6610455
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GREAT BASIN
SEDIMENTARY ROCKS
GEOCHEMISTRY
GEOLOGIC HISTORY
ORIGIN
QUANTITATIVE CHEMICAL ANALYSIS
CAMBRIAN PERIOD
CHEMICAL COMPOSITION
GEOLOGIC MODELS
ISOTOPE RATIO
NEODYMIUM ISOTOPES
PETROGENESIS
PRECAMBRIAN ERA
SAMARIUM ISOTOPES
SEDIMENTATION
SEDIMENTS
STRATIGRAPHY
TECTONICS
CHEMICAL ANALYSIS
CHEMISTRY
GEOLOGIC AGES
GEOLOGY
ISOTOPES
NORTH AMERICA
PALEOZOIC ERA
RARE EARTH ISOTOPES
ROCKS
USA
580400* - Geochemistry- (-1989)