The Sudbury Basin, the Southern province, the Grenville Front, and the Penokean orogeny: Discussion and reply

Brooks, Elwood R.

doi:10.1130/0016-7606(1976)87<954:tsbtsp>2.0.co;2

Cited by 3 publications

(3 citation statements)

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“…that accompany the fractures (Pryer, 1993a), and also with the direction of decreasing metamorphic grade. Flame perthite rarely occurs SE of the JLZS, where feldspars deform by dynamic recrystallization; but neither is it observed in the NW part of the study area where cataclasis is pervasive, except adjacent to a syntectonic mafic dyke (Brooks, 1976) (sample P65, Fig. 2).…”

Section: Flame Perthite D I S T R I B U T I O Nmentioning

confidence: 99%

“…(4) At lower P, and T , quartz is n o longer ductile and the feldspar grains are not the only load-supporting mineral; therefore, flames cannot form. For whichever reason, the importance of temperature is supported by the presence of abundant flame perthite in the sample (P65) in the contact aureole of the syntectonic dyke (Brooks, ' 1976) where the elevated temperature did allow flames to grow.…”

Section: Low-temperature Limitmentioning

confidence: 99%

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Retrograde metamorphic reactions in deforming granites and the origin of flame perthite

Pryer

Robin

1995

Journal Metamorphic Geology

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Microprobe analyses of feldspars in granite mylonites containing flame perthite give compositions that invariably plot as three distinct clusters on a ternary feldspar diagram: orthoclase (Or92-97), albite and oligoclase-andesine. The albite occurs as grains in the matrix, as flame-shaped lamellae in orthoclase, and in patches within plagioclase grains.We present a metamorphic model for albite flame growth in the K-feldspar in these rocks that is related to reactions in plagioclase, rather than alkali feldspar exsolution. Flame growth is attributed to replacement and results from a combination of two retrograde reactions and one exchange reaction under greenschist facies conditions. Reaction 1 is a continuous or discontinuous (across the peristerite solvus) reaction in plagioclase, in which the An component forms epidote or zoisite. Most of the albite component liberated by Reaction 1 stays to form albite in the host plagioclase, but some Na migrates to form the flames within the K-feldspar. Reaction 2 is the exchange of K for Na in K-feldspar. Reaction 3 is the retrograde formation of muscovite (as 'sericite') and has all of the chemical components of a hydration reaction of K-feldspar. The Si and Al made available in the plagioclase from Reaction 1 are combined with the K liberated from the K-feldspar, to produce muscovite in Reaction 3. The muscovite forms in the plagioclase, rather than the K-feldspar, as a result of the greater mobility of K relative to Al. The composition of the albite flames is controlled by both the peristerite and the alkali feldspar miscibility gaps and depends on the position of these solvi at the pressure and temperature that existed during the reaction. Using an initial plagioclase composition of An,,, the total reaction can be summarized as: 20 oligoclase + 1 K-feldspar + 2 H,O = 2 zoisite + muscovite + 2 quartz + 15 albiteplsgloclare + 1 albite,,,,.This model does not require that any additional feldspar framework be accreted at replacement sites: Na and K are the only components that must migrate a significant distance (e.g. from one grain to the next), allowing A1 to remain within the altering plagioclase grain. The resulting saussuritization is isovolumetric.The temperature and extent of replacement depends on when, and how much, water infiltrates the rock. The fugacity of the water, and therefore the pressure of the fluid, may have been significantly lower than lithostatic during flame growth.

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Section: Flame Perthite D I S T R I B U T I O Nmentioning

confidence: 99%

Section: Low-temperature Limitmentioning

confidence: 99%

Retrograde metamorphic reactions in deforming granites and the origin of flame perthite

Pryer

Robin

1995

Journal Metamorphic Geology

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“…Some glass is apparently fresh but devitrification and probable hydration features are also present. Subcalcic augite was not definitely identified in thin (Brooks, 1976).…”

mentioning

confidence: 84%

Petrology of Tertiary lavas from the western Kangerdlugssuaq area, East Greenland

et al. 1982

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ABSTRACT. Whole-rock, minor element, rare earth, and electron microprobe data are presented for basaltic lavas from the western Kangerdlugssuaq area of East Greenland. Samples were obtained from Professor W. A. Deer's 1936 collection at Triangular Nunataks and Gardiner Plateau, and additional material obtained by sampling moraines on the surface of Kangerdlugssuaq Glacier. Both undersaturated and tholeiitic lavas are present at the Triangular Nunatak locality but the glacier suite is dominantly tholeiitic. The tholeiitic suite is less evolved than tholeiites from the Scoresby Sund area. Undersaturated lavas show enrichment in light rare earth elements and tholeiitic lavas show fiat chondritenormalized patterns. Tholeiites from the Gardiner Plateau show no Eu anomaly but others show a slight negative Eu anomaly. Chemical data and considerations of regional geology are consistent with Cox's (1980) model of flood basalt vulcanism.

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References and Sudbury Bibliography

2017

Nickel Sulfide Ores and Impact Melts

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The Sudbury Basin, the Southern province, the Grenville Front, and the Penokean orogeny: Discussion and reply

Cited by 3 publications

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Retrograde metamorphic reactions in deforming granites and the origin of flame perthite

Retrograde metamorphic reactions in deforming granites and the origin of flame perthite

Petrology of Tertiary lavas from the western Kangerdlugssuaq area, East Greenland

References and Sudbury Bibliography

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