On the occurrence of topaz and garnet in lithophyses of rhyolite

Cross, C. W.

doi:10.2475/ajs.s3-31.186.432

Cited by 16 publications

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“…Andesine (oligoclase in some) and biotite are set in an aphanitic groundmass that contains topaz, magnetite, rare ilmenite, and apatite. Topaz also occurs in drusy quartz-lined cavities along with garnet, sanidine, biotite, and Fe oxides (Cross and Hillibrand 1885;Cross 1886;Pearl 1939). New analyses (by electron microprobe) of biotite from the Chalk Mountain rhyolite show that it contains intermediate Fe/(Fe + Mg) ratios (ca.…”

Section: Chalk Mountain Central Coloradomentioning

confidence: 99%

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The Geology and Geochemistry of Cenozoic Topaz Rhyolites from the Western United States

Christiansen¹,

Sheridan²,

Burt³

1986

Geological Society of America Special Papers

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Section: Chalk Mountain Central Coloradomentioning

confidence: 99%

“…An analysis of the Chalk Mountain rhyolite published by Cross (1886) Figure 18. Locations oftopaz rhyolites (solid dots) in central Colorado in relation to other middle to late Cenozoic volcanic fields (from Epis and Chapin, 1975).…”

Section: Chalk Mountain Central Coloradomentioning

confidence: 99%

The Geology and Geochemistry of Cenozoic Topaz Rhyolites from the Western United States

Christiansen¹,

Sheridan²,

Burt³

1986

Geological Society of America Special Papers

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“…1876, p. 51-53). Cross (1886Cross ( , 1893Cross ( , 1895 presented some mineralogic, petrographic, and chemical data on the Precambrian and Tertiary rocks of the Salida area. Campbell ( 1922, p. 90-96 and sheet 3) described the geomorphology of the Denver & Rio Grande Western Railroad route along the Arkansas River in Browns Canyon.…”

Section: Earlier Reportsmentioning

confidence: 99%

“…A chemical analysis of the groundmass of the rhyolite and a spectrographic analysis of the whole rock a-re given in table 8. Comparisons of these analyses with an early whole-rock analysis (Cross, 1886…”

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confidence: 99%

Geology and mineral deposits of the Poncha Springs SE Quadrangle, Chaffee County, Colorado

Alstine¹

1974

Professional Paper

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The Poncha Springs NE quadrangle, which contains a major fluorspar district, is in the Arkansas Valley between the Sa watch Range and the southward extension of the Park Range. Altitudes in the quadrangle lie between approximately 7,290 feet and 9,290 feet. The geologic units mapped consist of Precambrian metamorphic and igneous rocks, Tertia•ry volcanic and sedimentary rock;s, and unconsolidated Pleistocene and Holocene deposits. Precambrian hornblende gneiss and banded quartz-feldspar-'bioti.te gneiss are intruded by a large mass of gneissic quartz monzonite. Quartzite and silicated marble are interlayered with the gneisses, which, together with other structural and mineralogic evidence, suggests ,that the metamorphic rocks were originally sediments. The gneissic quartz monzonite occupies a 1 bout 25 square miles of the quadrangle and is cut 'by ta:bular bodies of granite,. aplite, pegmatite, •lamprophy.re, dacite .pol'!phyry, and d•iabase, and by quartz veins that locally contain orthoclase, magnetite, specular hematite, py•rite, chalcopyrite, chlorite, and trace~S of purple fluorite.. The Tertiary volcanic and sedimentary rocks immediately overlie the Precambrian rocks. Volcanic rocks in the southern part of the quadrangle locally are more than 600 feet thick. The volcanic •rocks consist chiefly of a lower unlit of ush, mudflow deposit, and a rhyodacite porphyry flow of Eocene (?) age and an upper unit of ash-flow tuff that •has !black vitrophyre near the base and a grayish-pink to reddish. .. brown devitrifted tuff above. 'The ash-flow tuff• is early Oligocene in age, based upon potassium-argon dating of the black vitrophyre and upon pollen and spores found in tuff :immediately underlying it. A unit consisting of pyroclastic 'rocks, perlite, and a rhyolite flow that contains garnet and topaz, at the north edge of the quadrangle, is here named the Nathrop Volcanics. Dating by the• potassium-argon method indicates that the perlite and rhyolite flow are late Oligocene in age. Tuffaceous siltstone forms seven small ma,sses resting directly on Precambrian rocks in the south-"Central pa'rt of the quadrangle. Thts unit, here called the Browns Oanyon Formation, contains leaves und pollen comparable to the Oreede flora and is Miocene in age. Unconsolidated beds of clay, •silt, sand, and gravel of the Dry Union Formation underlie most of the western rpart of the quadrangle. These sediments locally contain shards of yolcanic glass, bentonite, and rhyolitic tuff layers. Vertebrate fossils indicate that the formation is Miocene and Pliocene in age. Pleistocene deposits mantle much of the Dry Union Formation • in the western part of the quadrangle; the deposits formed as outwash •:Crom multiple stages of moun.ta.in glaciation in the Sawatch Range to the west. In this quadrangle and the one im-2 GEOLOGY AND MINERALS, PONCHA SPRINGS NE QUADRANGLE, CHAFFEE COUNTY, COLO. mostly microgranular to fine grained and layered, and commonly has botryoidat, mammillary, and reniform surfaces and nodular structures. Pyrolusite, manganit...

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“…There would thus seem to be no reason, on the basis of major element composition, why the Lake District garnets are not of regional or contact metamorphic, or metasomatic, origin; though, in general, garnets which, under conditions of regional metamorphism, have been developed before the formation of biotite are likely to be more manganiferous than those concerned here (see Harker, 1932, p. 217). Metasomatic, or hydrothermal, 1 garnets also usually have fairly high manganese, as have, for example, those in vesicles of rhyolite from Colorado (Cross, 1886), and from Nevada (Pabst, 1938), with 28-48% and 11-96% respectively; or, alternatively, consist mainly of andradite, or grossular-andradite (e.g. Ohmori, 1941;Smellie, 1915).…”

Section: Chemical and Physical Considerationsmentioning

confidence: 99%

The Origin of Garnets in the Borrowdale Volcanic Series and Associated Rocks, English Lake District

Oliver¹

1956

Geol. Mag.

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Almandine-rich garnets occur as euhedral crystals in extrusive and intrusive rocks which range in composition from 59 per cent, to 70 per cent. SiO ? . Eight complete garnet analyses (major and trace elements) indicate a small variation in composition which, together with corresponding variation of physical properties, appear to correlate with the mineralogical composition of the containing rock. Field, microscopic and chemical evidence suggests, on balance, that the garnets are pyrogenetic. Magmatic conditions suitable for the crystallisation of almandine-rich garnet are discussed.

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On the occurrence of topaz and garnet in lithophyses of rhyolite

Cited by 16 publications

References 0 publications

The Geology and Geochemistry of Cenozoic Topaz Rhyolites from the Western United States

The Geology and Geochemistry of Cenozoic Topaz Rhyolites from the Western United States

Geology and mineral deposits of the Poncha Springs SE Quadrangle, Chaffee County, Colorado

The Origin of Garnets in the Borrowdale Volcanic Series and Associated Rocks, English Lake District

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