U-Pb geochronologic constraints on the age of thrusting, crustal extension, peraluminous plutonism in the Little Rincon Mountains, southern Arizona

Journal Article · Fri Mar 01 04:00:00 EST 1991 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1991)019<0238:UPGCOT>2.3.CO;2· OSTI ID:5731952

Gehrels, G E; Smith, C H ^[1]

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1. Univ. of Arizona, Tucson (USA)

The Little Rincon thrust fault is a mylonitic shear zone that juxtaposes Middle Proterozoic Continental Granodiorite over metasedimentary rocks of Proterozoic and early Paleozoic age. This fault is structurally beneath the San Pedro detachment fault and associated ductile deformational fabrics, which formed during early Oligocene to early Miocene time. A syntectonic leucogranite sill within the Little Rincon shear zone yields a U-Pb concordia-intercept age 66{plus minus}10 Ma for zircon and a concordant age 51{plus minus}2 Ma for fractions composed of monazite and xenotime. This demonstrates that compressional deformation in the Catalina and Rincon mountains is generally coeval with Laramide thrust faults that extend at least from southeastern California to southeastern Arizona. A peraluminous granite pluton that truncates the shear zone but displays extension-related fabrics yields a lower-intercept age 24{plus minus}12 Ma for zircon and an age of 30{plus minus}6 Ma for monazite. This indicates that some peraluminous plutons in the region were emplaced during regional crustal extension.

• OSTI ID: 5731952
• Journal Information: Geology; (USA), Journal Name: Geology; (USA) Vol. 19:3; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ACTINIDE COMPOUNDS
ACTINIDE ISOTOPES
AGE ESTIMATION
ARIZONA
CALIFORNIA
CENOZOIC ERA
DEFORMATION
DEVELOPED COUNTRIES
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
LEAD ISOTOPES
MATERIALS
MINERALS
MONAZITES
MOUNTAINS
NORTH AMERICA
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PLUTONIC ROCKS
PRECAMBRIAN ERA
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RARE EARTH COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TECTONICS
TERTIARY PERIOD
THORIUM COMPOUNDS
THORIUM MINERALS
THORIUM PHOSPHATES
TRANSITION ELEMENT COMPOUNDS
URANIUM ISOTOPES
USA
XENOTIME
YTTRIUM COMPOUNDS
YTTRIUM PHOSPHATES
ZIRCON
ZIRCONIUM COMPOUNDS
ZIRCONIUM SILICATES