Isotopic evidence for the origin of mesozoic and cenozoic granitic plutons in the northern Great Basin

Journal Article · Sat Jul 01 00:00:00 EDT 1989 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1989)017<0591:IEFTOO>2.3.CO;2· OSTI ID:7254097

Solomon, G C; Taylor, Jr, H P ^[1]

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1. California Institute of Technology, Pasadena (USA)

{sup 18}O/{sup 16} ratios of granitic rocks in western North America reflect source-rock lithologies, providing insight into the geology of the deep continental crust. In a 400-km-wide, 800-km-long, east-west transect through the northern Great Basin, the Mesozoic and Cenozoic plutons define three zones: western low {sub 18}O zone (WZ), {delta}{sup 18}O = +6 to +8.5; central high -{sup 18}O zone (CZ), {delta}{sup 18}O = +9 to +13; eastern zone (EZ) (Utah), {delta}{sup 18}O = +7 to +9. The WZ-CZ boundary is analogous to the {delta}{sup 18}O step in the Peninsular Ranges batholith (PRB). A similarly abrupt ({sup 87}Sr/{sup 86}Sr){sub i} step (<0.708 to the west and >0.710 to the east) defined by Farmer and DePaolo (1983) lies 150-200km east of the WZ-CZ {sup 18}O/{sup 16}O step, dividing the CZ into two subzones: V-type in the west, corresponding to the eastern half of the PRB (but much wider due to regional Cenozoic extension); and S-type to the east. A plausible source for the high-{sup 87}Sr, low-{epsilon}{sub Nd}, S-type subzone is a late Precambrian (miogeoclinal) metasedimentary section, whereas the V-type source appears to be a Phanerozoic volcanogenic (eugeoclinal) accreted terrane. Both source regions have very high {delta}{sup 18}O (+9 to +16) but radically different {sup 87}Sr/{sup 86}Sr (and {epsilon}{sub Nd}); thus, the authors would not place the buried edge of the > 1.5 Ga craton beneath the {sup 87}Sr/{sup 86}Sr step, but farther east near the EZ boundary. The authors instead that this step is a sharp lithologic and age boundary (a suture-zone ) within the giant prism of sediments and volcanics in Nevada.

• OSTI ID: 7254097
• Journal Information: Geology; (USA), Vol. 17:7; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GRANITES
ORIGIN
GREAT BASIN
GEOLOGIC HISTORY
CENOZOIC ERA
GEOLOGIC DEPOSITS
ISOTOPE RATIO
LITHOLOGY
MESOZOIC ERA
OXYGEN 16
OXYGEN 18
STRONTIUM 86
STRONTIUM 87
VOLCANIC REGIONS
ALKALINE EARTH ISOTOPES
BETA DECAY RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC AGES
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LIGHT NUCLEI
NORTH AMERICA
NUCLEI
OXYGEN ISOTOPES
PLUTONIC ROCKS
RADIOISOTOPES
ROCKS
STABLE ISOTOPES
STRONTIUM ISOTOPES
USA
580000* - Geosciences