A geological reconnaissance across the Bitterroot Range and Clearwater Mountains in Montana and Idaho

Lindgren, Waldemar

doi:10.3133/pp27

Cited by 22 publications

(22 citation statements)

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“…Foliation within the upper part of the dome is penetrative on the scale of an outcrop and strongly asymmetric. It is strongly expressed in the mylonitic zone on the east, but fades out both downward (Lindgren, 1904;Wehrenberg, 1972; 1973) and westward. This asymmetry in intensity of the mylonitic deformation appears to be an original feature which expresses the movements that created it.…”

Section: Dome and Detachment Zonementioning

confidence: 95%

Bitterroot dome-Sapphire tectonic block, an example of a plutonic-core gneiss-dome complex with its detached suprastructure

Hyndman¹

1980

Geological Society of America Memoirs

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The Bitterroot dome-Sapphire tectonic block appears to be a well-developed example of a plutoniccore gneiss-dome complex or infrastructure separated from the adjacent suprastructure by a gently dipping zone of mylonitic shearing or an "Abscherungszone." The suprastructural Sapphire block, on the order of 15 km thick, 100 km long, and 70 km wide, apparently moved eastward about 60 km, bulldozing rocks of the eastern Flint Creek Range ahead of it. Movement of the block must have occurred about 75 or 80 m.y. ago during late stages of consolidation of the Idaho batholith which, along with sillimanite-zone regional metamorphic rocks, makes up the infrastructure under the mylonitic detachment zone. Timing of movement in the Sapphire block matches that in the Bitterroot dome.The Bitterroot dome must have risen after off-loading of the Sapphire block, because the shear foliation and lineation that formed during movement completely cross the dome; this indicates that the block must have moved eastward across the whole of the area now occupied by the dome rather than radially down the flanks of an existing dome. The shear lineation maintains its eastward trend even at the south end of the dome where the foliation dips southward. The lineation and shear foliation are strongest along the eastern flank of the dome, over which the greatest thickness of the block would have passed.

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Section: Dome and Detachment Zonementioning

confidence: 95%

Bitterroot dome-Sapphire tectonic block, an example of a plutonic-core gneiss-dome complex with its detached suprastructure

Hyndman¹

1980

Geological Society of America Memoirs

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“…The earliest geologic comments of substance on the Coeur d" Alene mining district are those of Lindgren (1904), based on geologic field work done in the Bitterroot-Clearwater region from July 22 to October 22, 1899. At p. 108, he commented that "The deposits are clearly defined fissure veins cutting fine-grained greenish quartzites and quartzitic slates of doubtful (though probably pre-Cambrian) age."…”

Section: Previous Workmentioning

confidence: 99%

Structural analysis and ore controls in the Coeur D'Alene mining district, Idaho

Reid¹,

Hayden²,

Wavra³

et al. 1993

Open-File Report

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Beltian rocks in the Coeur d' Alene district of Idaho, lying within the Lewis and Clark line, display a complex history of deformation and metamorphic fabrics. The earliest fabric is a near-bedding-parallel schistosity (assigned to Dl). Upright folds of northerly trend lie north of the district; comparable folds partly overturned trend WNW within the district, subparallel to the Osburn fault. The folds are assigned to D2a.Metamorphic cleavage (assigned to D2b) trends generally WNW but cuts across the folds in various ways. It shows major differences in two principal areas. In a three-mile-wide zone subparallel to and immediately north of the Osburn fault, cleavage is axially symmetrical about an approximately 40°-NWplunging stretching lineation. Outside that zone, the cleavage is dominantly planar, dips steeply to the SSW, and contains a strong dip-line stretching lineation.Semi-brittle faults and veins (assigned respectively to D2c and D2d) cut the cleavage and are in part axially symmetrical about a steep, SSW-plunging axis, paralleled by ore-shoot axes and slickenlines. Veins are concentrated in several zones or mineral belts symmetrically arrayed across the three-mile-wide zone of cleavage. Post-ore normal faults are axially symmetrical about a near-vertical axis. Brittle faulting in and near the Osburn fault zone cuts all the other structures.

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“…The regional correlation of the metasedimentary rocks is an essential part of the background for formulating the mineral resource potential in a region where sediment-hosted mineral deposits are important. The early workers in the Buffalo Hump area (the eastern half of the wilderness) correlated metasedimentary rocks with parts of the Middle Proterozoic Belt Supergroup but never agreed on which units were present (Lindgren, 1904;Beckwith, 1928;Shenon and Reed, 1934). Kopp (1973) Quartz pegmatite and fine-grained schistose gneiss.…”

Section: Appraisal Of Examined Sitesmentioning

confidence: 99%

“…Although the Gospel-Hump Wilderness is a geologically critical area, the only early geologic mapping study that included the wilderness and that was not limited to study of the mineral deposits was Lindgren's study of the Bitterroot and Clearwater Ranges (Lindgren, 1904). Nearby areas were studied by Reid (1959), Hamilton (1963), Cater and others (1973), Greenwood and Morrison (1973), and Myers (1982).…”

Section: Introductionmentioning

confidence: 99%

Mineral resources of the Gospel-Hump Wilderness, Idaho County, Idaho

Lund¹,

Esparza²

1990

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A geological reconnaissance across the Bitterroot Range and Clearwater Mountains in Montana and Idaho

Cited by 22 publications

References 0 publications

Bitterroot dome-Sapphire tectonic block, an example of a plutonic-core gneiss-dome complex with its detached suprastructure

Bitterroot dome-Sapphire tectonic block, an example of a plutonic-core gneiss-dome complex with its detached suprastructure

Structural analysis and ore controls in the Coeur D'Alene mining district, Idaho

Mineral resources of the Gospel-Hump Wilderness, Idaho County, Idaho

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