Petrogenetic Significance of Some Feldspars from the Judith Mountains, Montana

Wallace, Stewart R.

doi:10.1086/626371

Cited by 6 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It appears that smaller the phenocrysts, the finer the groundmass. This has been recognized in other parts of the world (Exley and Stone, 1964;Wallace, 1956) and it suggests an igneous origin (Stone and Austin, 1961).…”

Section: Discussionmentioning

confidence: 60%

Mesoscopic Structural Profile ofa Syn-Tectonic Granite, Southwestern Nigeria

Oden¹,

Udinmwen²

2014

IOSRJAGG

View full text Add to dashboard Cite

Pan-African granites from Igarra area in southwestern Nigeria have a mesoscopicstructural profile which includes phenocrysts, xenoliths, joints, veins and different pluton shapes all in interesting orientations. The phenocrysts which are white or pink in colour show a preferred orientation of long axes in the NNW-SSE and N-S directions. The phenocrysts from the porphyritic granites show evidence of an early stage magmatic origin. The metasedimentary xenoliths frozen in these granites are strongly preferentially oriented in the NNW-SSE to N-S direction as well, for reasons related to the tectonics of the region. The xenoliths being poor strain markers are at best useful for inferring the direction of maximum extension. Joints in the granites are good and linear suggesting that fracture toughness was far exceeded by driving pressure during joint propagation. These joints, like the veins are preferentially oriented in the E-W and N-S directions, an indication that the fluids of pegmatite, quartz and aplite within this area took advantage of available fractures at the time, although favouring the E-W trending discontinuities. The E-W joints are interpreted as "ac" extension fractures that intruded the trajectory of the maximum principal stress (σ 1 ), while the N-S ones are "bc" tensile fractures, parallel to the minimum principal stress (σ 3 ). Two pluton types within this area are the ellipsoidal (Bell shaped) plutons and the elongated (Table top) plutons which are hosted by different metasedimentary rocks. The pluton shapes and phenocryst sizes suggest that magma of probably varying viscosities intruded different country rocks within this area.

show abstract

Section: Discussionmentioning

confidence: 60%

Mesoscopic Structural Profile ofa Syn-Tectonic Granite, Southwestern Nigeria

Oden¹,

Udinmwen²

2014

IOSRJAGG

View full text Add to dashboard Cite

show abstract

“…The Judith Peak-Red Mountain area, mapped by E. N. Goddard and S. R. Wallace (Wallace, 1953), is a complex intrusive center ( fig. 8) composed of quartz monzonite, syenite, and rhyolite porphyries, all of which are intruded by coarse-grained alkali granite on Judith Peak, by dikes of fine-and coarse-grained granite and granite porphyry, and by dikes of green and gray tinguaite (called trachyte by Hall, 1976) and tinguaite porphyry.…”

Section: Judith Peak-red Mountain Area Judith Mountainsmentioning

confidence: 99%

“…In addition to differences in age and mode of emplacement, the Eocene igneous rocks of north-central Montana contain many examples of mafic alkalic and feldspathoidal rocks (Weed and Pirsson, 1896;Hurlbut and Griggs, 1939;Larsen, 1941;Witkind, 1973). In contrast, the intrusive complexes of Late Cretaceous and Paleocene age contain only minor volumes of mafic alkalic and feldspathoidal rocks these are the tinguaite dikes of the Judith and Little Rocky Mountains (Weed and Pirsson, 1898;Brockunier, 1936;Wallace, 1953). The intrusive breccias associated with the Upper Cretaceous-Paleocene porphyry complexes are the subject of this report.…”

Section: Introductionmentioning

confidence: 99%

“…Published information on the breccias is scarce, although most of them have been prospected for gold and other metals. Those in the Moccasin Mountains were mapped and described recently ; the intrusive breccias of the Judith Mountains had been mapped (Goddard and Wallace's map in Wallace, 1953) but not described; and those in the Little Rocky Mountains were recognized and described briefly by Weed and Pirsson (1896, p. 411^412), but have not been mentioned since that time. Geologic maps showing the breccias in the Moccasin Mountains were taken from the map of ; a detailed map of Limekiln Canyon and vicinity in the Judith Mountains was compiled from the mapping of E. N. Goddard and S. R. Wallace; unpublished mapping of the Judith Peak-Red Mountain area of the Judith Mountains, by Goddard and Wallace, was adapted for the present report; and a map showing breccias in the Little Rocky Mountains was prepared by F. S. Fisher from his mapping and the geologic map of Knechtel (1959).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Studies of mineralized intrusive complexes in north-central Montana

Lindsey¹,

Fisher²,

Naeser³

1985

Professional Paper

View full text Add to dashboard Cite

“…He suggested, from oldest to youngest, that the intrusive sequence was monzonite, rhyolite, tinguaite, and alkali granite. Wallace (1956) estimated an intrusive depth of 0.9 to 1.8 km whereas Forrest (1971) suggested a depth of 0.9 to 1.2 km.…”

Section: Geology Of the Judith Mountainsmentioning

confidence: 99%

The geochemistry and mineralogy of the Gies gold-silver telluride deposit, central Montana

Zhang

View full text Add to dashboard Cite

In order to better characterize and classify the three major intrusive rock types that crop-out in the immediate vicinity of gold-silver telluride mineralization, major and trace element compositions and mineral compositions were determined. Mineral compositions were obtained on an automated ARL-SEMQ electron microprobe housed in the Department of Geological and Atmospheric Sciences at Iowa State University. On-line ZAF corrections employed the MAGIC IV program utilizing the method of Bence and Albee (1968). For native elements, sulfides, sulfosalts, and tellurides in veins, operating conditions were an accelerating voltage of 25 KV, and a sample current of 20 nA on a Faraday cup. For silicates and carbonates, the accelerating voltage and sample current was 20 KV and 15 nA, respectively. Native gold, silver, and tellurium, natural and synthetic sulfides and sulfosalts, synthetic tellurides, and natural silicates were used as standards. The quartz monzonite porphyry at Elk Peak, although relatively poorly exposed, appears to consist of only one intrusion. It comprises a groundmass of intergranular feldspars and hornblende with accessory amounts of diopside, sphene, calcite, magnetite, and pyrite. The phenocrysts are up to 3 cm in length and consist, in order of abundance, plagioclase (An27 to An^^), alkali feldspar (Or^^ to Org^), ferro-pargasitic hornblende and quartz. Mineral compositions for feldspar and amphibole are given in Tables 1 and 2. 1. Data shown in this table are average values of each individual samples. For complete analyses, see Appendix. course of my Ph. D. study at Iowa State University. I also acknowledge my graduate

show abstract

Petrogenetic Significance of Some Feldspars from the Judith Mountains, Montana

Cited by 6 publications

References 0 publications

Mesoscopic Structural Profile ofa Syn-Tectonic Granite, Southwestern Nigeria

Mesoscopic Structural Profile ofa Syn-Tectonic Granite, Southwestern Nigeria

Studies of mineralized intrusive complexes in north-central Montana

The geochemistry and mineralogy of the Gies gold-silver telluride deposit, central Montana

Contact Info

Product

Resources

About