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

George E Gehrels, C. H. Smith

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

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 of 66 ± 10 Ma for zircon and a concordant age of 51 ± 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 of 24 ± 12 Ma for zircon and an age of 30 ± 6 Ma for monazite. This indicates that some peraluminous plutons in the region were emplaced during regional crustal extension. -Authors

Original languageEnglish (US)
Pages (from-to)238-241
Number of pages4
JournalGeology
Volume19
Issue number3
DOIs
StatePublished - 1991
Externally publishedYes

Fingerprint

plutonism
mountain
shear zone
monazite
thrust fault
pluton
Proterozoic
zircon
xenotime
leucogranite
detachment fault
metasedimentary rock
granodiorite
sill
Oligocene
granite
Paleozoic
Miocene

ASJC Scopus subject areas

  • Geology

Cite this

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abstract = "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 of 66 ± 10 Ma for zircon and a concordant age of 51 ± 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 of 24 ± 12 Ma for zircon and an age of 30 ± 6 Ma for monazite. This indicates that some peraluminous plutons in the region were emplaced during regional crustal extension. -Authors",
author = "Gehrels, {George E} and Smith, {C. H.}",
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T1 - U-Pb geochronologic constraints on the age of thrusting, crustal extension, and peraluminous plutonism in the Little Rincon Mountains, southern Arizona

AU - Gehrels, George E

AU - Smith, C. H.

PY - 1991

Y1 - 1991

N2 - 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 of 66 ± 10 Ma for zircon and a concordant age of 51 ± 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 of 24 ± 12 Ma for zircon and an age of 30 ± 6 Ma for monazite. This indicates that some peraluminous plutons in the region were emplaced during regional crustal extension. -Authors

AB - 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 of 66 ± 10 Ma for zircon and a concordant age of 51 ± 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 of 24 ± 12 Ma for zircon and an age of 30 ± 6 Ma for monazite. This indicates that some peraluminous plutons in the region were emplaced during regional crustal extension. -Authors

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