Mineral Paragenesis of Precambrian Rocks in the Tenmile Range, Colorado

Koschmann, Albert Herbert

doi:10.1130/0016-7606(1960)71[1357:mpopri]2.0.co;2

Cited by 3 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3) and Lovering and Goddard (1950, pi. 2) as granite gneiss and was considered by Lovering and Goddard (1950, p. 25) to be a metamorphosed granite probably related to the Boulder Creek Granite. Similar rocks noted elsewhere in the mineral belt include the granulite of Koschmann (1960Koschmann ( , p. 1361Koschmann ( -1362Koschmann ( , 1368, the microcline-quartz-plagioclase-biotite gneiss of Moench, Harrison, and Sims (1962, p. 37-39), and the microcline gneiss of Sims and Gable (1964, p. 10-14) ; these workers believed these rocks to be of sedimentary origin.…”

Section: B6mentioning

confidence: 80%

General geology of the Harold D. Roberts Tunnel, Colorado

Robinson¹,

Warner²,

Wahlstrom³

1974

Professional Paper

View full text Add to dashboard Cite

The Roberts Tunnel transects a geologically complex area in the Front Range of the Colorado Rocky Mountains. The area includes Precambrian igneous and metasedimentary rocks, Paleozoic and Mesozoic sedimentary rocks, and Tertiary igneous rocks. The structural history includes folding and faulting during Precambrian time and the Laramide orogeny.The Precambrian rocks, which constitute about two-thirds of the area penetrated by the tunnel, consist of a sequence of metasedimentary rocks that were invaded by igneous rocks. The age relations among the metasedimentary rocks are still in doubt, owing to the complexity of the structure. These rocks are, from East Portal to West Portal, a sequence of amphibolite and related calc-silicate rocks, a migmatite unit, a microcline gneiss unit, a biotite gneiss and schist unit containing some amphibolite, a sillimanitic biotite gneiss and schist unit, and a hornblende gneiss unit.The Precambrian metasedimentary rocks were intruded by granite of Precambrian age. The older granite, which is similar to the Boulder Creek Granite of other areas in the Front Range, is believed to have been emplaced at about the time of the metamorphism and plastic deformation of the Precambrian sedimentary rocks. The younger granite, which is similar to the Silver Plume Granite of other areas in the Front Range, is believed to have been intruded during a period of cataclastic deformation. Pegmatite and aplite of Precambrian age occur locally throughout the area.Sedimentary rocks are exposed in the western quarter of the tunnel. These are the Entrada(?) Sandstone and Morrison Formation of Late Jurassic age, the Dakota Group of Early Cretaceous age, the Benton Shale of Early and Late Cretaceous age, and the Niobrara Formation and Pierre Shale of Late Cretaceous age. Underlying the sedimentary rocks exposed in the tunnel, and exposed to the west of the tunnel and intersected by drill holes along the tunnel line, are the Maroon Formation of Pennsylvanian and Permian age and the Lykins Formation of Permian and Triassic(?) age. These sedimentary rocks dip eastward toward the axis of the Front Range.Early during the Laramide orogeny the Williams Range thrust fault developed, and Precambrian rocks were superimposed on the Pierre Shale along the fault. After the period of thrusting the Montezuma Quartz Monzonite stock was emplaced. The Williams Range thrust fault, as a result, was folded upward, and the tunnel intersects the fault zone at two places. Between the eastern exposure of the thrust and the Montezuma stock is a sequence of shale and siltstone that becomes more metamorphosed as the stock is approached. This sequence of shale and siltstone is believed to be equivalent, for the most part, to part of the Pierre Shale to the west of the Williams Range thrust.Before and after the intrusion of the Montezuma stock, a series of dikes intruded the Precambrian units around the stock. The oldest dikes are augite and hornblende diorite. Other dikes contemporaneous in age and younger than the stock are latite porph...

show abstract

Section: B6mentioning

confidence: 80%

General geology of the Harold D. Roberts Tunnel, Colorado

Robinson¹,

Warner²,

Wahlstrom³

1974

Professional Paper

View full text Add to dashboard Cite

show abstract

“…This fact is consistent with new crystallization and recrystallization of zircon in the Silver Plume Granite, which added zircon mass to the inherited portion. Koschmann (1960) was one of the first geologists to point out that the Silver Plume Granite in the Tenmile Range, Colo., and in the Montezuma area of the Front Range, gave evidence of having originated from local centers of fusion or recrystallization. This perception especially applied to small, ductless, isolated bodies that are surrounded by metamorphic rocks.…”

Section: Silver Plume Granitementioning

confidence: 99%

“…I do not accept hypothesis of emplacement or intrusion of a body of magma of batholithic size with all its attendant space problems, especially in an area of compressed m.etamorphic rocks. Moreover, such a hypothesis does nothing to explain the small isolated bodies of Silver Plume Granite mentioned by Koschmann (1960). DePaolo (1981) concluded from a study of Nd-Sm characteristics that the Silver Plume-type magmas of the Colorado Front Range were crustally derived.…”

Section: Silver Plume Granitementioning

confidence: 99%

Crystalline rocks of the Strawberry Lake area, Front Range, Colorado

Young¹

1991

View full text Add to dashboard Cite

show abstract

“…The geology and ore deposits of the Upper Blue River area, which borders this area on the southeast, were described by Singewald (1951). Paragenetic relations of the minerals of the Precambrian rocks of the Tenmile Range were studied by Koschmann (1960), and a generalized picture of the structure and stratigraphy was briefly reported by Koschmann and Bergendahl (1960).…”

Section: Previous Workmentioning

confidence: 99%

“…'), and in the extreme south-west corner. A large body of granulite occurs south of the mapped area in the southern part of the Tenmile Kange (Koschmann, 1960(Koschmann, , p. 1359(Koschmann, -1361. The base of this unit is not exposed; hence the true thickness cannot be determined.…”

Section: Granulitementioning

confidence: 99%

Geology of the northern part of the Tenmile Range, Summit County, Colorado

Bergendahl¹

1963

View full text Add to dashboard Cite

The Tenmile Range is in north-central Colorado, about 80 miles west-southwest of Denver, and is a north-trending mass of contorted Precamhrian metasedimentary rocks, overlain on its eastern flank by gently folded Paleozoic and Mesozoic sedimentary rocks. These rocks were invaded by small plugs and stocks of igneous rocks, which range in age from Precambrian to Tertiary-This report emphasizes the petrography, stratigraphy, and structure of the Precambrian rocks. The Precambrian metasedimentary rocks consist of a series of crystalline gneisses representative of the sillimanite-almandine subfacies of the amphibolite metamorphic facies. These gneisses occur in a recognizable stratigraphic sequence, the lowermost unit of which is granulite, a quartzoligoclase-microcline gneiss with minor amounts of biotite and hornblende. This granulite is overlain by a handed gneiss, which consists of alternate light and dark layers composed of quartz-plagioclase and hornblende-plagioclase. The banded gneiss is overlain by migmatite, another two-component gneiss, composed of discontinuous biotite-hornblende-plagioclase-quartz laminae and pods and layers of quartz-plagioclase-microcline. A unit called pink migmatite, also of Precambrian age, is apparently younger than the migmatite, but the relations are not clear. The intrusive rocks of Precambrian age are all younger than the migmatite and consist of diorite, red oligoclase aplite, granite similar to the Silver Plume Granite, alaskite, and dikes of pegmatite, aplite, and alaskite.Sedimentary formations appear on the east flank of the Tenmile Range, where they lie unconfonnably with the Precambrian rocks and with one another. Included among these formations are the Sawatch Quartzite of Cambrian age, the lower part (Pennsylvanian) of the Minturn Formation, the Maroon Formation of Pennsylvanian and Permian age, the Morrison Formation of Jurassic age, and the Dakota Sandstone of Cretaceous age. Rocks of Cretaceous (?) or Tertiary age consist of a stock and smaller masses of quartz monzonite. The dike rocks of porphyritic monzonite are classified as Pando Porphyry, Elk Mountain Porphyry, and Lincoln Porphyry; they are of early Tertiary age.The Precambrian rocks were subjected to at least two periods of plastic deformation during Precambrian time. The most prominent of these resulted in the formation of northwest-trending folds. The second deformation was along a shallow plunging axis trending S. 70°-80° E. During Paleozoic and Mesozoic Dl D2 CONTRIBUTIONS TO ECONOMIC GEOLOGY time vertical tectonic forces were dominant, and the area was alternately elevated and depressed. These movements resulted in numerous unconformities having extreme local relief.The major faults in the area trend north, northeast, and northwest and are of the high-angle variety. The Precambrian rocks in the fault zones are downgraded to the greenschist facies, and their textures are cataclastic. Some faults displace sedimentary formations of Mesozoic age.The principal ore deposits of the area are in quartz veins cont...

show abstract

Mineral Paragenesis of Precambrian Rocks in the Tenmile Range, Colorado

Cited by 3 publications

References 0 publications

General geology of the Harold D. Roberts Tunnel, Colorado

General geology of the Harold D. Roberts Tunnel, Colorado

Crystalline rocks of the Strawberry Lake area, Front Range, Colorado

Geology of the northern part of the Tenmile Range, Summit County, Colorado

Contact Info

Product

Resources

About