Development of the western Idaho ultramafic belt

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

OSTI ID:5342924

Bonnichsen, B ^[1]; Godchaux, M M ^[2]

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1. Univ. of Idaho, Moscow, ID (United States). Idaho Geological Survey
2. Mount Holyoke Coll., South Hadley, MA (United States). Dept. of Geology

The 164-mile-long western Idaho ultramafic belt contains small bodies of dunite, serpentinite, metaharzburgite, and clinopyroxenite that mainly lie near the suture zone joining the Blue Mountains island arc accreted terrane and the pre-Cretaceous continental crust. The main ultramafic areas are: (1) in the Cuddy Mountain-Sturgill Peak region, where sheared serpentinite occurs along a high-angle reverse fault zone between two subterranes of the Blue Mountain terrane, (2) in the New Meadows tectonic block where dunites, harzburgites, and chromitites occur with metamorphosed cherts, greywackes, and exhalative rocks, (3) near Riggins where serpentinite occurs in metasedimentary rocks of the Mesozoic-age Riggins Group, (4) in the South Fork Clearwater River region where anthophyllite metaharzburgites and Cr-rich clinopyroxenites are enclosed within gneissic equivalents of the Riggins Group and in Cretaceous-age felsic plutonic rocks, and (5) in the Lowell-Kamiah-Dworshak Reservoir region where additional anthophyllite metaharzburgites occur in Proterozoic-age metasedimentary rocks. After the ultramafic rocks were formed, plate convergence led to their obduction onto the Mesozoic margin of North America. Compression accompanying the docking of the Blue Mountains island arc and then the emplacement of the Idaho batholith metamorphosed most of the ultramafic bodies to the greenschist and amphibolite facies and remobilized them along faults to their present locations within host rocks of widely varying ages.

• OSTI ID: 5342924
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CONTINENTAL MARGIN
DEFORMATION
DEVELOPED COUNTRIES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGIC MODELS
GEOLOGY
IDAHO
IGNEOUS ROCKS
METAMORPHIC ROCKS
NORTH AMERICA
PETROGENESIS
PETROLOGY
PLATE TECTONICS
PLUTONIC ROCKS
ROCKS
SERPENTINITES
SUBDUCTION ZONES
TECTONICS
USA