Results 191 to 200 of about 10,226 (223)

Lattice structural variation in K-feldspar megacrysts of associated charnockite and alkali granite

Mineralogical Magazine, 1982
AbstractThe perthite megacrysts from charnockitic and non-charnockitic members of a sialic intrusive complex in the Varberg area of south-west Sweden have been investigated by powder X-ray diffraction. The extent of Al/Si order in the K-feldspar host lattices of the megacrysts is restricted in all but the major alkali granite differentiate.
D. R. Iball, F. H. Hubbard
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Compositional and microtextural zoning in alkali feldspars from the Shap granite and its geochemical implications

Journal of the Geological Society, 1997
Alkali feldspar phenocrysts in the Lower Devonian Shap granite are compositionally and microtexturally zoned. Most of each phenocryst has exsolved to form microperthite with an approximate bulk composition of Or 72 Ab 28 An <1 , but sub-millimetre wide zones within ...
M. R. LEE, I. PARSONS
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Ordering and exsolution processes in Or-rich alkali feldspar megacrysts from the Eldzhurtinskiy granite (Caucasus)

Contributions to Mineralogy and Petrology, 1996
The extremely young (2.5 Ma) I-type Eldzhurtinskiy granite complex (Central Caucasus) is uniform with respect to modal composition, major and trace element chemistries of bulk rocks and mineral phases. In contrast, it reveals two types of alkali feldspar megacrysts differing in tetrahedral Al-content (2t1) and exsolution microtextures:
G. Witt-Eickschen, C. Evangelakakis, H. A. Seck, H. Kroll, A. G. Gurbanov   +4 more
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Petrogenetic Significance of Alkali Feldspar Megacrysts and their Inclusions in Cornubian Granites

Nature, 1968
Petrogenetic Significance of Alkali Feldspar Megacrysts and their Inclusions in Cornubian ...
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Alkali Feldspars from Gneisses and Granites of the Västervik Area, SE. Sweden

Geologiska Föreningen i Stockholm Förhandlingar, 1968
Abstract Metamorphosed Precambrian sedimentary rocks and associated late-kinematic granites of the Vastervik area in southeastern Sweden contain abundant potassium feldspar. The alkali feldspar from the metasediments shows zero to low obliquity and contains from 8 to 10 % albite in solid solution.
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Geology and mineralization of the Jabalat alkali-feldspar granite, northern Asir region, Kingdom of Saudi Arabia

Journal of African Earth Sciences (1983), 1986
Abstract The Jabalat post-tectonic granite pluton is composed of albite- and oligoclase-bearing, low-calcium, F-, Sn- and Rb-rich subsolvus granites. These granites display evidence of late-magmatic, granitophile- and metallic-element specialization, resulting ultimately in the development of post-magmatic, metalliferous hydrothermal systems ...
Jaffar Al Tayyar, Norman J. Jackson, Saeed Al-Yazidi   +2 more
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Structural state and composition of alkali feldspars in granites of the St. George pluton, south-western New Brunswick

Mineralogical Magazine, 1978
SummaryThe variation in the structural state of potassium feldspars from the St. George pluton, New Brunswick, Canada, is discussed. Monoclinic potassium feldspars occur near the eastern end of the pluton whereas the granites at the western end contain triclinic potassium feldspars. Although the bulk compositions of the host rocks are all very near the
Michael E. Cherry, Lowell T. Trembath
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Intraplate, rift-related magmatism: mainly the A-type, alkali feldspar granites

1997
Contrary to general opinion, a distinctly bimodal magmatism involving rather ordinary biotite granites and coeval basalts has been a feature of the earth’s cratons since the Early Proterozoic. Although I shall concern myself here mainly with the alkalic granites of this same environment, it is important to emphasize that they are really of small volume
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Theoretical studies of the alteration of spodumene, petalite, eucryptite and pollucite in granitic pegmatites: exchange reactions with alkali feldspars

Contributions to Mineralogy and Petrology, 1993
The ratios Na/Li, K/Li, Na/Cs and K/Cs have been calculated for exchange equilibria among the Li and Cs silicates spodumene, petalite, eucryptite, and pollucite, and the alkali feldspars albite and K-feldspar plus quartz, in pure water and in chloride solutions at temperatures from 100° to 700°C and pressures from 0.5 to 4 kbar, using available ...
Williams-Jones, A. E., Wood, S. A.
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Lower Cretaceous alkali feldspar granites in the central part of the Great Xing’an Range, northeastern China: chronology, geochemistry and tectonic implications

Geological Magazine, 2014
AbstractThe Mingshui–Jilasitai–Suolun area, located in the central part of the Great Xing’an Range, is characterized by large volumes of alkali feldspar granites. However, the formation time and tectonic setting of these rocks remains controversial owing to a lack of precise geochronological and detailed geochemical data.
Zhang, YL, Yang, H, Zhao, G, Ge, W, Tian, D   +4 more
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