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Melanie Barboni - One of the best experts on this subject based on the ideXlab platform.
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petrogenesis of magmatic Albite granites associated to cogenetic a type granites na rich residual melt extraction from a partially crystallized a type granite mush
Lithos, 2013Co-Authors: Melanie Barboni, Francois BussyAbstract:Abstract The uncommon association of cogenetic and nearly contemporaneous potassic K-feldspar A-type granites and sodic Albite granites is observed within the 347 Ma-old bimodal Saint-Jean-du-Doigt (SJDD) intrusion, Brittany, France. A-type granites outcrop as small bodies ( 2 ) of fine-grained, pinkish to yellowish rock or as meter-thick sills in-between mafic layers. They emplaced early within the thermally “cool” part of the SJDD pluton directly beneath the Precambrian host rock, forming the pluton roof. Albite granites are fine-grained hololeucocratic yellowish rocks emplaced slightly after the A-type granites in the thermally mature part of the pluton. They form meter-thick sills that mingle with adjacent mafic layers and represent ca. 1 vol.% of the outcropping part of the pluton. The two granite types are similar in many respects with comparable Sr–Nd–Hf isotope compositions ( 87 Sr/ 86 Sr 347 = 0.7071 for A-type granites vs. 0.7073 for Albite granites; eNd 347 = + 0.2 vs. + 0.3; eHf 347zircon = + 2.47 vs. + 2.71, respectively) and SiO 2 contents (74.8 vs. 74.4 wt.%). On the other hand, they have contrasting concentrations in K 2 O (5.30 vs. 1.97 wt.%), Na 2 O (2.95 vs. 4.73 wt.%) and CaO (0.48 vs. 2.04, respectively) as well as in some trace elements like Sr (59 vs. 158 ppm in average), Rb (87 vs. 35 ppm), Cr (170 vs. 35 ppm) and Ga (30 vs. 20 ppm). The isotopic composition of the A-type and Albite granites is very distinct from that of the associated and volumetrically dominant mafic rocks (i.e. 87 Sr/ 86 Sr 347 = 0.7042; eNd 347 = + 5.07; eHf 347zircon = + 8.11), excluding a direct derivation of the felsic rocks through fractional crystallization from the basaltic magma. On the other hand, small volumes of hybrid, enclave-bearing granodiorite within the SJDD lopolith suggest mixing processes within a reservoir located at deeper crustal levels. A-type granites may therefore form by magma mixing between the mafic magma and crustal melts. Alternatively, they might derive from the pure melting of an immature biotite-bearing quartz-feldspathic crustal protolith induced by early mafic injections at low crustal levels. Strong field evidences coupled to mineral chemistry and elemental geochemistry strongly support a magmatic origin for the Albite granite. Sr, Nd, Hf zircon isotope data, U–Pb zircon ages, as well as data on petrography, mineral chemistry and elemental geochemistry attest that A-type and Albite granites are closely related. Our preferred petrogenetic model is to consider the Albite granite magma as a compositionally extreme melt that was extracted from a partially crystallized A-type granite mush at a late stage of crystallization. Alternatively, Albite granites could form by melting of plagioclase-rich layers formed during A-type granite differentiation.
Bin Li - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics simulation of Albite twinning and pericline twinning in low Albite
Modelling and Simulation in Materials Science and Engineering, 2013Co-Authors: Bin Li, Kevin M KnowlesAbstract:Two twinning laws, the Albite law and the pericline law, are the predominant growth twinning modes in triclinic plagioclase feldspars such as low Albite, NaAlSi3O8, in which the aluminum and silicon atoms are in an ordered arrangement on the tetrahedral sites of the aluminosilicate framework. In the terminology used formally to describe deformation twinning in a triclinic lattice, these twin laws can be described as Type I and Type II twin laws, respectively, with the pericline twin law being conjugate to the Albite twin law. In this study, twin boundaries have been constructed for low Albite according to these two twinning laws and studied by molecular dynamics simulation. The results show that suitably constructed twin boundary models are quite stable for both Albite twinning and pericline twinning during molecular dynamics simulation. The calculated twin boundary energy of an Albite twin is significantly lower than that of a pericline twin, in accord with the experimental observation that Albite twinning is the more commonly observed mode seen in plagioclase feldspars. The results of the molecular dynamics simulations also agree with conclusions from the prior work of Starkey that glide twinning in low Albite is not favoured energetically.
Francois Bussy - One of the best experts on this subject based on the ideXlab platform.
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petrogenesis of magmatic Albite granites associated to cogenetic a type granites na rich residual melt extraction from a partially crystallized a type granite mush
Lithos, 2013Co-Authors: Melanie Barboni, Francois BussyAbstract:Abstract The uncommon association of cogenetic and nearly contemporaneous potassic K-feldspar A-type granites and sodic Albite granites is observed within the 347 Ma-old bimodal Saint-Jean-du-Doigt (SJDD) intrusion, Brittany, France. A-type granites outcrop as small bodies ( 2 ) of fine-grained, pinkish to yellowish rock or as meter-thick sills in-between mafic layers. They emplaced early within the thermally “cool” part of the SJDD pluton directly beneath the Precambrian host rock, forming the pluton roof. Albite granites are fine-grained hololeucocratic yellowish rocks emplaced slightly after the A-type granites in the thermally mature part of the pluton. They form meter-thick sills that mingle with adjacent mafic layers and represent ca. 1 vol.% of the outcropping part of the pluton. The two granite types are similar in many respects with comparable Sr–Nd–Hf isotope compositions ( 87 Sr/ 86 Sr 347 = 0.7071 for A-type granites vs. 0.7073 for Albite granites; eNd 347 = + 0.2 vs. + 0.3; eHf 347zircon = + 2.47 vs. + 2.71, respectively) and SiO 2 contents (74.8 vs. 74.4 wt.%). On the other hand, they have contrasting concentrations in K 2 O (5.30 vs. 1.97 wt.%), Na 2 O (2.95 vs. 4.73 wt.%) and CaO (0.48 vs. 2.04, respectively) as well as in some trace elements like Sr (59 vs. 158 ppm in average), Rb (87 vs. 35 ppm), Cr (170 vs. 35 ppm) and Ga (30 vs. 20 ppm). The isotopic composition of the A-type and Albite granites is very distinct from that of the associated and volumetrically dominant mafic rocks (i.e. 87 Sr/ 86 Sr 347 = 0.7042; eNd 347 = + 5.07; eHf 347zircon = + 8.11), excluding a direct derivation of the felsic rocks through fractional crystallization from the basaltic magma. On the other hand, small volumes of hybrid, enclave-bearing granodiorite within the SJDD lopolith suggest mixing processes within a reservoir located at deeper crustal levels. A-type granites may therefore form by magma mixing between the mafic magma and crustal melts. Alternatively, they might derive from the pure melting of an immature biotite-bearing quartz-feldspathic crustal protolith induced by early mafic injections at low crustal levels. Strong field evidences coupled to mineral chemistry and elemental geochemistry strongly support a magmatic origin for the Albite granite. Sr, Nd, Hf zircon isotope data, U–Pb zircon ages, as well as data on petrography, mineral chemistry and elemental geochemistry attest that A-type and Albite granites are closely related. Our preferred petrogenetic model is to consider the Albite granite magma as a compositionally extreme melt that was extracted from a partially crystallized A-type granite mush at a late stage of crystallization. Alternatively, Albite granites could form by melting of plagioclase-rich layers formed during A-type granite differentiation.
Sridhar Komarneni - One of the best experts on this subject based on the ideXlab platform.
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Crystallization of Anorthite‐Seeded Albite Glass by Solid‐State Epitaxy
Journal of the American Ceramic Society, 1992Co-Authors: Sridhar KomarneniAbstract:Stoichiometric Albite glass (NaAlSi3O8) was seeded with 5 wt% crystalline anorthite (CaAl2Si2O8) to make Albite glass-ceramics. The epitaxial crystallization of the Albite glass to the glass-ceramics was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). High Albite was observed as the major crystallization product over the temperature range of 800–1200°C. No crystalline Albite could be crystallized from pure Albite glass without seeds. Small amounts of nepheline (NaAlSiO4), however, crystallized along with Albite after heat treatments at temperatures lower than 1000°C. The platelike microstructure of Albite crystals was revealed in the seeded glasses. The Albite blades grew epitaxially from the anorthite seeds, and the Ca content decreased in the direction away from the seeds. The degree of crystallization and the grain size were dependent upon the heat treatment conditions. By increasing the particle size of the seed, the crystallization process was retarded and the resultant microstructure was degraded. The seeding efficiency was also lowered by adding nonisostructural hexagonal anorthite seeds which produced less Albite but more nepheline crystals. Crystallization of Albite glass by seeding with 5 wt% anorthite is much greater than with the surface nucleation which takes place in a homogeneous 95 wt% Albite + 5 wt% anorthite glass.
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Epitaxial Crystallization of Seeded Albite Glass
Journal of the American Ceramic Society, 1991Co-Authors: Ulagaraj Selvaraj, Sridhar KomarneniAbstract:Glasses that are extremely difficult to crystallize are generally avoided in making glass-ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid-state epitaxy in the crystallization of such Albite (NaAlSi3O8) glass to glass-ceramic was investigated. The glass was seeded with extremely fine ZrO2 (nonisostructural) and Albite (isostructural) seed crystals. X-ray diffraction results indicated that the Albite-seeded glass, heat-treated at 1000°C for 100 h, epitaxially crystallized to Albite, while the ZrO2 and unseeded glasses did not crystallize in identical heat-treatment conditions. In addition, the Albite-seeded glass, heat-treated at 905°C for 10 d, crystallized mostly to Albite, whereas the ZrO2 and unseeded glasses at the same conditions contained only a small amount (
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epitaxial crystallization of seeded Albite glass
Journal of the American Ceramic Society, 1991Co-Authors: Ulagaraj Selvaraj, Sridhar KomarneniAbstract:Glasses that are extremely difficult to crystallize are generally avoided in making glass-ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid-state epitaxy in the crystallization of such Albite (NaAlSi3O8) glass to glass-ceramic was investigated. The glass was seeded with extremely fine ZrO2 (nonisostructural) and Albite (isostructural) seed crystals. X-ray diffraction results indicated that the Albite-seeded glass, heat-treated at 1000°C for 100 h, epitaxially crystallized to Albite, while the ZrO2 and unseeded glasses did not crystallize in identical heat-treatment conditions. In addition, the Albite-seeded glass, heat-treated at 905°C for 10 d, crystallized mostly to Albite, whereas the ZrO2 and unseeded glasses at the same conditions contained only a small amount (<5 wt%) of nepheline (NaAlSiO4). The microstructure of the epitaxially grown glass-ceramics showed that extremely fine crystals (∼0.2 μm thickness) were formed around the seed.
Jannie S J Van Deventer - One of the best experts on this subject based on the ideXlab platform.
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adsorption of gold on Albite in acidic chloride media
Hydrometallurgy, 2013Co-Authors: Dingwu Feng, John L Provis, Jannie S J Van DeventerAbstract:Abstract The ability of Albite, an aluminosilicate mineral typical of those present in many gold ores, to adsorb gold is examined at varied pH levels in chloride media. The adsorption of gold on Albite is intimately associated with the leaching behaviour of Albite in acidic solutions. The preferential leaching of Na and Al from Albite leads to the formation of an altered silica-rich surface layer as the gold sorbent. Gold adsorption increases at lower pH due to a greater extent of Albite leaching. The majority of gold adsorption onto Albite occurs within the first 0.5 h of contact, and the gold concentration in solution then increases after an extended contact period due to the partial relocation of the adsorbed gold from the altered Albite surface to freshly formed nanoscale silica particles in solution. Surface activation by fine milling increases the extent of gold adsorption on Albite, correlated with enhanced leaching of Albite. The gold adsorbed on processed Albite surface exists as Au 3 + , Au + and Au 0 , indicating the reduction of Au 3 + in chloroauric acid to lower oxidation states in the silica-rich layers during adsorption.
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thermal activation of Albite for the synthesis of one part mix geopolymers
Journal of the American Ceramic Society, 2012Co-Authors: Dingwu Feng, John L Provis, Jannie S J Van DeventerAbstract:Precursors for the preparation of one-part geopolymers are synthesized by thermal activation of Albite with sodium hydroxide and sodium carbonate, then cooling and crushing the resulting product. Albite is stable under thermal treatment up to 1000°C, but is able to be converted to depolymerized, disordered, and X-ray amorphous geopolymer precursors in the presence of sodium hydroxide or sodium carbonate at elevated temperatures. The geopolymer precursors react with the addition of water (i.e., form a “one part geopolymer mix”), forming geopolymers with acceptable compressive strength. One-part geopolymers synthesized via thermal activation of Albite with NaOH show a higher compressive strength than those produced with Na2CO3 at the same dosage. Some crystalline sodium-aluminosilicate hydrates (zeolites) are also formed in addition to geopolymer gel in the geopolymers synthesized from Albite activated by NaOH, compared to predominantly amorphous phases in the samples activated by Na2CO3. The activation of natural aluminosilicates including Albite by thermal treatment with alkalis has great potential in the development of novel one-part mix geopolymers.
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Thermal Activation of Albite for the Synthesis of One‐Part Mix Geopolymers
Journal of the American Ceramic Society, 2011Co-Authors: Dingwu Feng, John L Provis, Jannie S J Van DeventerAbstract:Precursors for the preparation of one-part geopolymers are synthesized by thermal activation of Albite with sodium hydroxide and sodium carbonate, then cooling and crushing the resulting product. Albite is stable under thermal treatment up to 1000°C, but is able to be converted to depolymerized, disordered, and X-ray amorphous geopolymer precursors in the presence of sodium hydroxide or sodium carbonate at elevated temperatures. The geopolymer precursors react with the addition of water (i.e., form a “one part geopolymer mix”), forming geopolymers with acceptable compressive strength. One-part geopolymers synthesized via thermal activation of Albite with NaOH show a higher compressive strength than those produced with Na2CO3 at the same dosage. Some crystalline sodium-aluminosilicate hydrates (zeolites) are also formed in addition to geopolymer gel in the geopolymers synthesized from Albite activated by NaOH, compared to predominantly amorphous phases in the samples activated by Na2CO3. The activation of natural aluminosilicates including Albite by thermal treatment with alkalis has great potential in the development of novel one-part mix geopolymers.
