Early Proterozoic transcontinental orogenic belts in the United States

Conference · Mon Feb 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5932944

Van Schmus, W R ^[1]; Bickford, M E ^[2]; Condie, K C ^[3]

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1. Univ. of Kansas, Lawrence, KS (United States). Dept. of Geology
2. Syracuse Univ., NY (United States). Dept. of Geology
3. New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. Geoscience

It has been recognized for many years that Early Proterozoic orogenic rocks in the western US range from 1.8 to 1.6 Ga, with a general distribution such that 1.8 to 1.7 Ga rocks underlie Colorado, northern Arizona, and northern New Mexico and 1.7 to 1.6 Ga rocks underlie southern Arizona and southern New Mexico. Recent U-Pb geochronologic and Sm-Nd isotopic studies by a variety of research groups have refined crustal history in the western region and have extended knowledge eastward into the buried midcontinent basement. As a result, the authors propose that 1.8 Ga to 1.6 Ga crust of the US by divided into two distinct, but overlapping, orogenic belts: a 1.8 to 1.7 Ga Inner Accretionary Belt and a 1.7 to 1.6 Ga Outer Tectonic Belt. The Inner Accretionary Belt (IAB) comprises rock suites with compositions and isotopic signatures compatible with origin as juvenile crustal terranes formed as oceanic or off-shore and related terranes that were accreted to southern Laurentia between 1.8 and 1.6 Ga. The IAB includes the Yavapai Province of Arizona, Early Proterozoic basement of Colorado and southern Wyoming, and the basement of Nebraska. The Mojave Province of California may be part of this belt, although it also includes components derived from older Proterozoic or Archean crust. Extension of the IAB eastward from Nebraska is uncertain at present, although coeval rocks that may be eastern manifestations of this 1.8 to 1.7 Ga orogenesis occur in Wisconsin (1.76 Ga granite-rhyolite suite), Ontario (Killarney granite), Labrador (Makkovic Province) and southern Greenland (Ketilidian orogen). The Outer Tectonic Belt (OTB) comprises rock suites which have compositions, structures, and isotopic signature compatible with origin in continental margin tectonic settings between 1.7 and 1.6 Ga.

• OSTI ID: 5932944
• Report Number(s): CONF-9303212--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:1
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ARIZONA
BASEMENT ROCK
COLORADO
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGY
GRANITES
IGNEOUS ROCKS
ISOTOPE DATING
NEBRASKA
NEW MEXICO
NORTH AMERICA
OROGENESIS
PETROGENESIS
PETROLOGY
PLATE TECTONICS
PLUTONIC ROCKS
PRECAMBRIAN ERA
ROCKS
TECTONICS
USA
WYOMING