A petrologic comparison of Triassic plutonism in the San Gabriel and Mule Mountains, southern California

Journal Article · Sat Nov 10 00:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB12p20075· OSTI ID:5195275

Barth, A P ^[1]; Tosdal, R M; Wooden, J L ^[2]

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1. Indiana Univ.-Purdue Univ., Indianapolis (USA)
2. Geological Survey, Menlo Park, CA (USA)

Triassic magmatism in the southwest US Cordillera forms a semicontinuous magmatic arc extending from northwestern Nevada to southeastern California. Quartz monzodioritic and quartz monzonitic rocks and associated diorites and granites are widespread in southeastern California, and the authors suggest that these rocks represent exposure of a structurally deeper part of the Triassic arc, where it was emplaced into comparatively thick Proterozoic crust. Elemental and isotopic data suggest that Triassic quartz monzodiorites and quartz monzonites in the Mule and San Gabriel Mountains were derived from a relatively undepleted, nonradiogenic mafic lithospheric source, with virtually no upper crustal interaction. Very limited data for associated Triassic ( ) diorites indicate a wide range in composition and a surprisingly radiogenic isotopic signature. Younger Triassic( ) granites record a strong geochemical signature of interaction with continental crust, including inherited zircon and high initial Sr ratios but comparatively less radiogenic Pb isotopic compositions. The major and trace element geochemistry of Late Triassic plutonic rocks in southeastern California is similar in many respects to akalic components of the Triassic arc in the Mojave Desert. However, contemporaneous rocks farther north have a calc-alkalic signature, perhaps reflecting the variation in age and composition of lithosphere across which the Triassic arc was constructed.

• OSTI ID: 5195275
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:B12; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
MOUNTAINS
MAGMATISM
PLUTONIC ROCKS
ISOTOPE RATIO
PETROLOGY
CHEMICAL ANALYSIS
CONTINENTAL CRUST
DESERTS
DIORITES
GEOCHEMISTRY
GEOLOGIC HISTORY
GRANITES
LEAD ISOTOPES
PRECAMBRIAN ERA
STRONTIUM ISOTOPES
TRIASSIC PERIOD
VOLCANISM
ZIRCON
ALKALINE EARTH ISOTOPES
ARID LANDS
CHEMISTRY
DEVELOPED COUNTRIES
EARTH CRUST
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGY
IGNEOUS ROCKS
ISOTOPES
MESOZOIC ERA
MINERALS
NORTH AMERICA
ROCKS
SILICATE MINERALS
USA
580000* - Geosciences