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Showing 1 to 20 of 23 for “"nepheline"”.
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The crystal structure of nepheline
Thesis. (M.S.) Massachusetts Institute of Technology. Dept. of Geology, 1947.
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Fluid evolution in the nepheline syenites of the Ditrău Alkaline Massif, Transylvania, Romania
… nappe system of the Mesozoic crystalline zone. Nepheline syenites are the most abundant rocks occurring in the central and eastern part of the Massif, and represent the youngest intrusion of the complex. Petrographic observations and fluid inclusion studies were performed on nepheline syenites …
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Petrogenesis of the peralkaline granite (and associated syenite) dykes of the Straumsvola Complex, Western Dronning Maud Land, Antarctica
The Straumsvola nepheline syenite complex in Western Dronning Maud Land, Antarctica consists of an outer massive and inner layered nepheline syenite that is itself intruded by ijolite. The complex and its immediate country rock was intruded by numerous dykes. A small proportion of these dykes are …
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Petrology of the Gracefield pluton.
… (earlier) intrusive is locally transitional to nepheline syenite along the south margin. The temperature of mineral equilibration of the nepheline-bearing syenite was determined to be 730°C. The temperature of the magma at the time of intrusion was somewhat higher. If the oxygen fugacity …
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Petrology and Geochemical Evolution of the East Hill Suite of the Mont Saint-Hilaire Alkaline Plutonic Complex
… Hill suite, an assemblage of several distinct nepheline syenites and evolved syenitic rocks. Whole-rock analysis of the East Hill suite reveals two fractionation trends, one which is described by the syenitic lithologies and one by the evolved syenites and syenoids. A lamprophyric unit stands …
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Petrology of the Sutherland Commonage melilitite intrusives
… of melilite, clinopyroxene, opaque spinel, nepheline and perovskite. The sill complex is a multiple intrusion and is comprised of a lower green melilitite and an overlying (and younger) grey melilitite. The green melilitite is deuterically altered and the original mineralogy is destroyed to …
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Petrogenesis of hybrid porphyry pipes and evolution of alkaline magmas in the Kanabeam Igneous Complex, Southern Namibia
… in the province are represented and include nepheline syenites, quartz syenites as well as granites. In addition to these plutonic phases a number of late stage, xenolith rich porphyry pipes were emplaced, exploiting contact zones between earlier plutons. Xenolith types include gabbro …
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Petrology and geochemistry of syenite intrusions in the Eastern Province of Zambia
… the south comprises a homogeneous sodi-potassic nepheline syenite. The two intrusions also exhibit systematic chemical variations which are attributed to fractional crystallization.The chemistry of the Randawe syenite is significantly different from that of the Lunkhwakwa syenite suggesting that …
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Alkali attack of coal gasifier refractory lining
… (Na₂O·Al₂O₃), N₂C₃A₅ (2Na₂O·3CaO·5A1₂O₃), nepheline (Na₂0·Al₂0₃·2SiO₂), potassium aluminate, (K₂Oâ·Al₂0₃), and kaliophilite (K₂O·Al₂0₃·2Si0₂) were synthesized and their solubility in water and coefficients of linear thermal expansion were: measured. Of the compounds tested, the formation of …
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Characterization of Residual Mineral Content of Bauxite Stockpiles in Saline County, Arkansas: An XRD Analysis Approach
… production and hosts extensive bauxite and nepheline syenite deposits. With the depletion of highgrade ore, renewed interest in bauxite stockpiles has focused on critical mineral potential. Previous X-ray Fluorescence studies have identified critical elements in significant concentrations, …
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Alkali attack on ceramic filters
… exposure. 2. potassium disilicate, kaliophilite-nepheline, potassium aluminate, and 5K₂O-5Al₂O₃-8SiO₂. Experiments also revealed that penetration depth by alkali compounds was restricted to a region near the surface of the material when the combination of temperature and sodium concentration …
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Geochemical and isotopic constraints on the source regions of phanerozoic carbonatites and associated alkaline rocks from the Zandkopsdrift complex of Namaqualand, South Africa, and the Marinkas Quellen, and Dicker Willem complexes in Namibia
… and alkaline lamrophyre at Zandkopsdrift, nepheline syenite and trachyte at Marinkas Quellen, and ijolite and trachyte at Dicker Willem. At both Marinkas Quellen and Dicker Willem, the trachytes appear to be derived primarily from fenitised country rock. The major and trace element …
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Alkaline igneous rocks of the coastal belt, south of Luderitz, South West Africa : a petrological study
… be recognised. The first phase produced chilled nepheline syenites beneath the roof of the intrusion. These chilled rocks grade downwards into coarse-grained foyaites. The second phase was the emplacement of the Inner Foyaite which crystallized as a cylindrically zoned plug, capped by a zone of …
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The geochemistry and petrogenesis of lavas from the Comores Archipelago, Western Indian Ocean (Volume 2)
… feldspar, Fe-Ti oxide and in one sample nepheline and garnet, which are typically set in a fine-grained groundmass of clinopyroxene, feldspar or nepheline, Fe-Ti oxide, lesser olivine and accessory apatite and titanite (sphene). With the exception of a few hypersthene- and even …
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The geochemistry and petrogenesis of lavas from the Comores Archipelago, Western Indian Ocean (Volume 1)
… feldspar, Fe-Ti oxide and in one sample nepheline and garnet, which are typically set in a fine-grained groundmass of clinopyroxene, feldspar or nepheline, Fe-Ti oxide, lesser olivine and accessory apatite and titanite (sphene). With the exception of a few hypersthene- and even …
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Ionic Mobility In Stuffed-Silica Minerals
… bound cations in the stuffed-silica minerals nepheline, yoshiokaite and ß-eucryptite has been investigated. The investigation has been extended to include the feldspar minerals albite, K-feldspar and anorthite. The low-frequency dielectric properties of all of the minerals have been …
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Oxygen and radiogenic isotope constraints on the generation of coexisting silica-undersaturated and oversaturated felsic magmas of the Ditrau Alkaline Massif (Romania)
… mantle origin of hornblendites, diorites and nepheline syenites. The Nd and O isotope variations imply the involvement of 20-65% upper crustal melts into the re-injected camptonite magma to generate the Ditrău syenites, quartz syenites and granites. The isotope results of the DAM require the …
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INVESTIGATION OF RESIDUAL MINERAL CONTENT OF BAUXITE STOCKPILES, SALINE MINING DISTRICT, ARKANSAS, U.S.A.
… contains extensive deposits of bauxite ore and nepheline syenite previously mined by Aluminum Company of America using open pit and subsurface mining techniques. This study incorporates five bauxite stockpiles (SP1, Clay, SP2, SP3, SP4) with varying amounts of alumina content situated on …
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The Sukulu complex, Eastern Uganda and The origin of the African carbonatites
… during the crystallisation and segregation of nepheline. Chemical variation diagrams are presented in support of these contentions. Chemical and arithmetical evidence is given to show that the removal of beforsitic carbonatite from nephelinitic magma leaves a phonolitic residual liquid, while …
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Petrogenesis and evolution of alkalic basaltic magmas in a continental intraplate setting: the South Auckland Volcanic Field, New Zealand
… B, a strongly silica-undersaturated basanite to nepheline hawaiite suite. The petrogenesis and evolution of the SAVF basalts is examined using new data from 200 samples on mineral chemistry from electron microprobe analyses, major and trace elements from XRF, incompatible trace elements and REE …
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