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Compositional Domains (compositional + domain)
Selected AbstractsIsolation of Solid Solution Phases in Size-Controlled LixFePO4 at Room TemperatureADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Genki Kobayashi Abstract State-of-the-art LiFePO4 technology has now opened the door for lithium ion batteries to take their place in large-scale applications such as plug-in hybrid vehicles. A high level of safety, significant cost reduction, and huge power generation are on the verge of being guaranteed for the most advanced energy storage system. The room-temperature phase diagram is essential to understand the facile electrode reaction of LixFePO4 (0,<,x,<,1), but it has not been fully understood. Here, intermediate solid solution phases close to x,=,0 and x,=,1 have been isolated at room temperature. Size-dependent modification of the phase diagram, as well as the systematic variation of lattice parameters inside the solid-solution compositional domain closely related to the electrochemical redox potential, are demonstrated. These experimental results reveal that the excess capacity that has been observed above and below the two-phase equilibrium potential is largely due to the bulk solid solution, and thus support the size-dependent miscibility gap model. [source] Polyphase evolution and reaction sequence of compositional domains in metabasalt: a model based on local chemical equilibrium and metamorphic differentiationGEOLOGICAL JOURNAL, Issue 3-4 2000T. M. Toóth Abstract Eclogitic garnet amphibolite samples from the Southern Steep Belt of the Central Alps show evidence of several stages of metamorphic evolution and exhumation. A method for unravelling this evolution is presented and applied to these samples. It involves a combination of detailed petrographic analysis and microchemical characterization with quantitative models of the thermodynamically stable phase relations for specific compositional domains of each sample. Preserved mineral relics and textural evidence are compared to model predictions to identify the important irreversible reactions. The interpretation of the exhumation history is thus based on the consistency of a wide spectrum of observations with predicted phase diagrams, leading to robust reconstruction of a pressure,temperature (P,T) path even where the mineralogical relics in samples are insufficient, due to retrogression, to warrant application of multi-equilibrium thermobarometric techniques. The formation of compositionally different domains in the metabasalt samples studied is attributed to prograde growth of porphyroblasts (e.g. garnet, plagioclase, zoisite) in the matrix, implying substantial metamorphic differentiation at the scale of a few millimetres. Chemical interaction among different domains during the subsequent P,T evolution is shown to have been very limited. This led to different reaction sequences during exhumation, in which relics preserved in different domains reflect a range of continually changing P,T conditions. For samples from a single outcrop, we deduce a Barrovian prograde path to eclogite facies (23,±,3,kbar, 750,±,50°C), followed by (rapid) decompression to 8,±,1,kbar and 675,±,25°C, and a final heating phase at similar pressures reaching 750,±,40°C. This evolution is attributed to the Alpine cycle involving subduction,collision and slab breakoff,extrusion of tectonic fragments that make up the Southern Steep Belt of the Central Alps. Copyright © 2000 John Wiley & Sons, Ltd. [source] Constraints on the early metamorphic evolution of Broken Hill, Australia, from in situ U-Pb dating and REE geochemistry of monaziteJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2009C. R. M. McFARLANE Abstract The Broken Hill Pb-Zn deposit, New South Wales Australia, is hosted in granulite facies gneisses of the Southern Curnamona Province (SCP) that have long been known to record a polydeformational and polymetamorphic history. The details of this potentially prolonged tectonothermal history have remained poorly understood because of a historical emphasis on conventional (i.e. grain mount) U-Pb zircon geochronology to reveal details of the sedimentary, magmatic and metamorphic history of the rock that crops out in the vicinity of the city of Broken Hill. An alternative approach to unravelling the metamorphic history of the granulite facies gneisses in and around Broken Hill is to date accessory minerals, such as monazite, that participate in sub-solidus metamorphic reactions. We have taken advantage of the high spatial resolution and high sensitivity afforded by SHRIMP monazite geochronology to reconstruct the early history of the metamorphic rocks at Broken Hill. In contrast to previous studies, in situ analysis of monazite grains preserved in their original textural context in polished thin sections is used. Guided by electron microprobe X-ray maps, SHRIMP U-Pb dates for three distinct monazite compositional domains record pulses of monazite growth at c. 1657 Ma, c.1630 Ma and c.1602 Ma. It is demonstrated that these ages correspond to monazite growth during lower amphibolite facies, upper amphibolite facies and granulite facies metamorphism, respectively. It is speculated that this progressive heating of the SCP crust may have been driven by inversion of the upper crust during the Olarian Orogeny that was pre-heated by magmatic underplating at c.1657 Ma. [source] Spinel,cordierite symplectites replacing andalusite: evidence for melt-assisted diapirism in the Bushveld Complex, South AfricaJOURNAL OF METAMORPHIC GEOLOGY, Issue 6 2004T. Johnson Abstract Spinel,cordierite symplectites partially replacing andalusite occur in metapelitic rocks within the cores of several country rock diapirs that have ascended into the upper levels of layered mafic/ultramafic rocks in the Bushveld Complex. We investigate the petrogenesis of these symplectites in one of these diapirs, the Phepane dome. Petrographic evidence indicates that at conditions immediately below the solidus the rocks were characterized by a cordierite-, biotite- and K-feldspar-rich matrix and 5,10 mm long andalusite porphyroblasts surrounded by biotite-rich fringes. Phase relations in the MnNCKFMASHT model system constrain the near-solidus prograde path to around 3 kbar and imply that andalusite persisted metastably into the sillimanite + melt field, where the fringing relationship between biotite and andalusite provided spatially restricted equilibrium domains with silica-deficient effective bulk compositions that focused suprasolidus reaction. MnNCKFMASHT pseudosections that model these compositional domains suggest that volatile phase-absent melting reactions consuming andalusite and biotite initially produced a moat of cordierite surrounding andalusite; reaction progressed until all quartz was consumed. Spinel is predicted to grow with cordierite at around 720 °C. Formation of the aluminous solid products was strongly controlled by the receding edge of andalusite grains, with symplectites forming at the andalusite-cordierite moat interface. Decompression due to melt-assisted diapiric rise of the floor rocks into the overlying mafic/ultramafic rocks occurred close to the thermal peak. Re-crossing of the solidus at P = 1.5,2 kbar, T > 700 °C resulted in preservation of the symplectites. Two features of the silica-deficient domains inhibited resorption of spinel. First, the cordierite moat armoured the symplectites from reaction with crystallizing melt in the outer part of the pseudomorphs. Second, an up- T step in the solidus at low- P, which may be in excess of 100 °C higher than the quartz-saturated solidus, resulted in high- T crystallization of melt on decompression. Even in metapelitic rocks where melt is retained, preservation of spinel is favoured by decompression. [source] | ||||||||||