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Showing 1 to 20 of 23 for “"Anatexis"”.
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Crustal melting in the Himalayan orogen : field, geochemical and geochronological studies in the Everest region, Nepal
… studies were combined to determine the timing of anatexis in a migmatite at the structurally lowest outcrop. Quantitative measurement of REE and Y in monazites and xenotimes, that were later dissolved and dated by U-Pb IDTIMS, revealed monazite growth at temperatures appropriate for crustal …
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⁴⁰Ar/³⁹Ar and U-Pb geochronological constraints on the thermal and tectonic evolution of the Connemara Caledonides, Western Ireland
… arc magmatism, sillimanite-grade metamorphism, anatexis, and late fluid infiltration spanned only about 12 million years. Cooling following the metamorphic peak was actually relatively rapid at 35*C/Ma until about 460 Ma, then 214*C/Ma until 450 Ma. Regional differences in 40Ar/ 39Ar cooling …
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The Damara mobile belt in the south-Western Kaokoveld
… buoyant uplifting forces, related to anatexis (A₂) along the axis of the eugeosyncline, created slopes sufficient to convey nappes (F₂S) of scarcely metamorphosed Damara schists towards the eastern foreland, overriding the miogeosyncline along the N-S Sesfontein Thrust. Eastern …
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Major element and isotopic studies on the James Run/Port Deposit association, Maryland: tectonic analogues and Taconic deformation
… rock systematics were upset, but concurrent anatexis of felsic basement is not locally evident. The fault contact between the Port Deposit and easternmost facies of the Wissahickon places an upper age limit of 467 Ma for that particular facies. Rb-Sr model biotite ages are interpreted as …
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The Foyers Granitic Complex and its aureole
… an extensive thermal aureole, with minor anatexis occuring in the inner aureole. Granitoid fabrics, enclaves, xenoliths and internal contacts imply emplacement whilst in a magmatic state. The adamellite was emplaced into a solid pluton. Boudinage and shearing in envelope psammites, and …
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LITHIUM ENRICHMENT IN ANATECTIC PEGMATITES: NEW INSIGHTS FROM THE THERMOMETAMORPHIC AUREOLE OF THE ADAMELLO BATHOLITH
… derived, marking them as produced by direct anatexis of metapelites. They also show that they were formed by two melt batches of different trace element composition originated by differential in-source fractionation. Conversely, isotopic data characterizes the pluton-hosted pegmatites as …
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The tectonometamorphic evolution of the Greater Himalayan sequence as exposed in central Nepal and adjacent south-central Tibet
… metamorphic episode and syn-kinematic voluminous anatexis at ca. 22 Ma. The upper GHS was thinned vertically by 50% and extended horizontally during and immediately after the second metamorphic event, in a manner typical of the deep hinterland regions of orogens. In central Nepal, the ductile …
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Geochemical and isotopic characteristics of palaeo-hydrothermal fluids related to granite magmatism, S W England
… matter into granitic protoliths during anatexis, with subsequent transfer to an exsolved hydrous phase during pluton cooling, is the most probable route by which palӕofluid solutes entered the early hydrothermal systems. <br></br><br></br>Hydrogen stable isotope data, measured on the …
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Petrogenesis and thermal history of the Kunlun Batholith, Northern Tibet
… Devonian Wanbaogou pluton may have resulted from anatexis of upper crustal sediments. A reset biotite age of 120 Ma from a pluton cut by the Xidatan Fault, supports sedimentalogical evidence which indicates a major reactivation of thrust faults in the area, as a result of collision between the …
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Tectonic evolution of the Waldau Ridge structure and the Okahandja Lineament in part of the Central Damara Orogen, west of Okahandja, South West Africa
… The GS granite may in part be derived from anatexis of quartzo-felspathic rocks of the Etusis Formation. The Donkerhoek Granite (G6) is post-tectonic and related in time of intrusion to a regional thermal metamorphic event (M2). In this area, it was emplaced in rocks which had cooled to …
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Mineralogical, chemical and isotopic diversity in plutonic rock suites from the Coastal Maine Magmatic Province:the role of source region heterogeneity, tectonic setting and magmatic processes
… shown that granitic plutons derived by crustal anatexis of a common source material are not required to have similar initial lead isotopic compositions. The third chapter presents the results of a Pb isotopic investigation of selected plutonic rocks from the Coastal Maine MagmaticProvince. This …
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Lineament and pegmatite mapping using landsat TM imagery and aerial photograph data: Kaseba-Katota Area, Serenje district, Central Zambia
… In places, the rocks seem to have undergone anatexis as indicated by ductile flow structures and heavily silicified layers. The general trend of foliation and schistosity is northeast - southwest. Foliation planes are mainly vertical or dip steeply to the east. The northeast - southwest …
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INTO THE STRUCTURE OF THE PERMIAN DEEP CONTINENTAL CRUST: A MULTISCALE APPROACH TO RECONSTRUCT MIGMATIZATION IN THE VALPELLINE SERIES (DENT BLANCHE TECTONIC SYSTEM, WESTERN ITALIAN ALPS)
… gneiss (S2), coeval with the regional scale anatexis and growth of garnet, orthopyroxene and cordierite. The third (D3) is related to the late folding of S2 and the development of a sillimanite-rich axial plane foliation (S3) which wraps around garnet and cordierite. Meso- and microstructural …
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The stratigraphy and metamorphism of the Snyder Group, Labrador
… II, andalusite-sillimanite; III, sillimanite. Anatexis has occurred in zone III. The total width of the aureole is 2-2.5 km. Progressive metamorphic assemblages are: metapelites: Ia - and-chl-biot-musc-qz ± Mn gar ± ksp Ib - and-cord-biot-qz ± muse ± Mn gar ± ks II - and-sill-cord-biot-qz ± …
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The timing of prograde metamorphism in the Garhwal Himalaya, India
… overthickened orogenic wedge is sufficient for anatexis of the crust to form the well-studied melts intruding the upper levels of the HHCS.<br></br><br></br> However, interpretation of the results is complicated by the isotopic systematics involved in garnet chronometry and by the role of small …
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Metamorphism in the Northern Front Range, Colorado
Thermobarometry, detailed petrography, electron microprobe analysis, and fluid inclusion microthermometry were used to quantify the history of a high grade Proterozoic terrane exposed within the northeastern Colorado Front Range. Pressure-temperature calculations identified two blocks from …
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Geological and geochemical aspects of the Loch Loyal Alkaline Complex, Sutherland
… considered important by Harker, but to anatexis at depth and subsequent extreme differentiation, connected with faulting, which resulted in an increased sodium content and a 'reworking' of surrounding sediments and/or granitic rocks, with consequent enhancement of U,Th,Nb,RE's,Ba and Sr …
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Petrogenesis of Mesoarchean high-K rocks in the Kaapvaal Craton: Investigating the Boesmanskop Alkaline Complex and Salisbury Kop batholith
… magmas produced by low-degrees of fluid-absent anatexis of the lower crust (including recycled sediments). Phase equilibrium modeling conducted at pressure of 1.5 kbar and temperature range from 800 to 950 °C, consistent with intrusion at shallow depths, demonstrated that a subset of high-alkali …
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Caratterizzazione geo-petrografica, petrologica e geochimica di rocce anatettiche del nord Sardegna
… have been used to model the P-T conditions of anatexis on the basis of the melt volume (%) of melt, Si/Al and Na/K molar ratios, modal content of garnet and Si content in metamorphic white mica. Further pseudosections have been calculated for the average composition of leucosomes in order to …
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Geochemistry of igneous rocks from the southern coast belt plutonic complex, southwestern British Columbia
… CPC: 1) partial melting of mantle wedge, 2) anatexis of juvenile terranes (e.g., Wrangellia), and 3) combinations of 1 and 2. Geochemical characteristics and magmatic differentiation of plutonic rocks from this transect in the southern CPC are further examined by mineralogy and chemical …
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