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Showing 1 to 15 of 15 for “"Coesite"”.
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The structure of coesite and the classification of tetrahedral structures
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Geology, 1959.
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Diversity of compressional mechanisms among SiO2 polymorphs : case of coesite and cristobalite
… behaviour of two important silica minerals, coesite and cristobalite. Both of them are framework silicates comprised of fully polymerized corner sharing SiO4 tetrahedra. Coesite, thermodynamically stable above ca. 2.5 GPa and at temperatures in excess of 500 °C, hereafter referred to as …
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Water in coesite and wadsleyite: quantification, incorporation mechanism and effect on the phase stability
… Minerale (NAMs) des oberen Erdmantels: Coesite (Cs), Olivine (Ol) und Wadsleyite (Wad). NAMs können H in die Struktur über Punktdefekte, wie z.B. Kationenleerstellen einbauen. Hauptziel dieser Arbeit ist eine vertrauenswürdige Quantifizierung von H in Cs, Wad und Ol und gleichzeitig eine …
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Diversity of compressional mechanisms among SiO<sub>2</sub> polymorphs : case of coesite and cristobalite.
… behaviour of two important silica minerals, coesite and cristobalite. Both of them are framework silicates comprised of fully polymerized corner sharing SiO<sub>4</sub> tetrahedra. Coesite, thermodynamically stable above ca. 2.5 GPa and at temperatures in excess of 500 °C, hereafter referred …
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Investigations of Trace Element Titanium in Silica Minerals
… titanium (Ti) in the silica minerals quartz and coesite, to advance the understanding and application of trace-element thermobarometry.Chapter 1 details the experiments that were conducted to quantify the pressure and temperature effects of Ti-in-coesite (TitaniC) solubility to develop the first …
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Structural constraints on the exhumation of the Tso Morari Dome, NW Himalaya
… is a large (>3,000 km²) structural dome cored by coesite-bearing rocks of Indian continental crustal affinity. As one of only two localities in the Himalaya where ultrahigh-pressure rocks have been found, the culmination offers important insights into the orogenic processes responsible for …
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Cratonic eclogite xenoliths - formation and evolution of the subcontinental lithospheric mantle
… bimineralic (garnet (gt)-omphacite (cpx)), coesite-, kyaniteand corundum-bearing eclogites. Metasomatized eclogites (Type I) have a higher alkali- (Na2O in garnet and K2O in omphacite) and LREE, LILE-content. Non-metasomatized (Type II) eclogites include two main compositional groups, …
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Metamorphic P-T Path and Multiple Fluid Events During Burial and Exhumation of the Tso Morari UHP Terrane, NW Himalaya
… orogenic belt underwent ultrahigh-pressure (UHP) coesite-eclogite metamorphism due to northward subduction of the Indian continent under the Eurasian continent during the early Eocene. In this study we optimized a best protocol for thermodynamically modelling pressure-temperature (P-T) paths of …
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Guiana Shield diamonds, the sub-cratonic lithosphere, and kimberlite emplacement in the upper crust.
… the Prairie Creek lamproite in Arkansas, USA. Coesite and forsterite inclusions record entrapment conditions of 4.8±0.5 GPa, typical of cratonic settings. However, Arkansas diamonds preserve brown body colors and one example of purple luminescence suggesting vacancy clusters and a distorted …
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The X-discontinuity: Seismic signatures of a heterogeneous upper mantle
… of the X in mantle plume settings to the coesite-stishovite phase transition and/or the presence of carbonated silicate melt, shedding insight into the nature of mantle plumes and their role in mantle convection. I study the presence of the X beneath Africa, using continuous observations …
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Librational displacements of silicate tetrahedra in response to temperature and pressure
… a greater decrease than observed for quartz and coesite while the SiO bond lengths and the OSiO angles remain essentially unchanged. The responses of V/V₀ and SiOSi angle to pressure for the silica polymorphs are compared and it is found that the percentage decrease in the volume is linearly …
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The Electronic Structure and Reactivity of Sulfide Surfaces: Combining Atomic-Scale Observations with Theoretical Calculations
… density distribution in the model silicate coesite, which is presented in the appendix. In addition, it breaks new ground by delving into differences and similarities between periodic vs. cluster calculations of minerals.
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Geology of ultra-high-pressure rocks from the Dabie Shan, Eastern China
Um das Verständnis der geologischen Entwicklung des größten bekannten Vorkommens von ultra-hochdruck (UHP) Gesteinen auf der Erde, des Dabie Shan im östlichen China, zu erhöhen, wurde eine multidisziplinäre Studie durchgeführt. Geophysikalische Daten wurden entlang einer ca. 20 km langen …
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Temporal and petrological constraints of ultrahigh-pressure metamorphism and exhumation of crustal material from mantle depths to Earth's surface: Insights from a large and small ultrahigh-pressure terrane
… by the preservation of UHP minerals (i.e., coesite and diamond) mainly within eclogite. These terranes fall into two broad categories: 1) large (30,000 km2) coherent terranes characterized by slow (>20 Myr) subduction-exhumation histories, and 2) small (~4,000 km2) terranes that have …