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Showing 1 to 20 of 59 for “"Metasomatism"”.
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Boron metasomatism in the Alta stock contact aureole, Utah
The effects of fluid evolution and infiltration in the Alta stock contact aureole, Utah, were studied by evaluating chemical additions and depletions in igneous, replacement skarn, and carbonate whole-rock samples. Of the major and trace elements studied, boron proved to be the most interesting …
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Sodium metasomatism and magnesio-riebeckite mineralization in the Wilson Ridge pluton
… in the Wilson Ridge pluton formed by Na-metasomatism related to subsolidus hydrothermal alteration involving Na-rich fluids of meteoric origin. Whole-rock geochemistry of samples from zones of hydrothermal amphibole show enrichment of Na2O (>9.6 wt. %) and depletion of K2O (0.15 wt. %) …
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K-Metasomatism in Uppermost Precambrian Rocks in West-Central Wisconsin and Southeastern Missouri
K/Ar dating of different size fractions of I/S samples reveals three episodes of illitization in the alteration profiles: 432-424 Ma, 410-383 Ma, and ${\sim}{-}314$ Ma. Rb-Sr and oxygen isotopic data suggest I/S of the 432-424 episode may have formed from the same fluids that formed the …
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Magmatism, Deformation And Mesothermal Metasomatism: Interpretation Of Aluminosilicate Mineral Assemblages In The Cargo Muchacho Mountains, Southeastern California
Aluminosilicate mineral assemblages, with more than 30% Al{dollar}sb2{dollar}O{dollar}sb3{dollar} and less than 2% CaO+Na{dollar}sb2{dollar}O+K{dollar}sb2{dollar}O, occur on the western flank of the Cargo Muchacho Mountains, southeastern California. The aluminosilicate mineral assemblages are …
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A comparison of melt depletion, thermal structure and metasomatism of proterozoic mantle lithosphere in the Namaqua-Natal and Rehoboth Provinces of Southern Africa
… structure, the extents of melt extraction and metasomatism of the two mantle terranes with each other and with the Archaean Kaapvaal craton. Xenoliths from the Rietfontein and Pofadder localities have never previously been studied in detail. The information from this study is crucial for …
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Potassium Metasomatism and Diffusion in Cretaceous K-Bentonites From the Disturbed Belt, Northwestern Montana and in the Middle Devonian Tioga K-Bentonite, Eastern u.s.a. (Illite/smectite, Clays, Diagenesis, United States)
This thesis presents X-ray diffraction, elemental, K/Ar, and petrographic data of K-bentonites and enclosing shales from the Marias River Formation (Late Cretaceous) in the disturbed belt of Montana. The objective of this study is to determine the kind and extent of chemical exchange between …
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The composition of noble gas and co2 in the european subcontinental lithospheric mantle
… to show how the occurrence of partial melting, metasomatism, refertilization, magmatic degassing, volatile recycling, and mixing of volatiles modified the pristine composition of fluids stored in European SCLM and give clues on its geodynamic evolution. Mantle xenoliths from a few key regions …
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A geochemical study of metasomatised peridotite and marid nodules from the Kimberley pipes, South Africa
… chemical evidence presented here suggest that metasomatism increases progressively in the sequence GPGPP-PP-PKP, with the PKP group being richest in Fe, Ti and incompatible elements such as K, Na, Rb, Ba, Sr, Zr, Nb and the LR.EE. Mineral compositions change progressively from the …
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Supercontinental Inheritance and its Influence on Supercontinental Breakup: The Central Atlantic Magmatic Province and the Breakup of Pangea
… the greater number of accretionary events, or metasomatism by sediment melts as opposed to fluids on the northern versus the southern Laurentian margin during the formation of Pangea led to different subduction-related signatures in the mantle source of the northern versus southern CAMP lavas. …
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Thermobarometry and geochemistry of peridotite xenoliths from the southwestern margin of the Kaapvaal craton, South Africa
… signatures indicate a shift in the style of metasomatism in the Namaqua-Natal lithosphere between Group II and Group I kimberlite magmatism. Zr/Hf versus Ti/Eu systematics reflect kimberlitic/silicate style metasomatism in the samples exhumed during Group II magmatism, whereas samples exhumed …
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Magmatic And Tectonic Evolution Of Southern Tibet And The Himalaya
… by inverse modelling, suggest subduction-related metasomatism. <sup>40</sup>Ar- <sup>39</sup>Ar dating of xenocrystic phlogopites indicates metasomatism of the southern SCLM occurred at 62±2 Ma, synchronous with collision.<br></br><br></br>These data link Neogene extension to a thermally perturbed …
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Nominally volatile-free mantle minerals: a reservoir for water and fluorine in the Kaapvaal Craton
… to billions of years. Four different types of metasomatism have been recognised in the Kaapvaal xenolith suites, each with different controls on the storage of volatile elements in olivine and pyroxenes. Proto-kimberlite metasomatism is found to flux the largest amount of volatile elements into …
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⁴⁰Ar/³⁹Ar and U-Pb geochronological constraints on the thermal and tectonic evolution of the Connemara Caledonides, Western Ireland
… combined effects of excess 40Ar contamination, metasomatism, thermal resetting or alteration related to post-orogenic pluton emplacement. This study shows that geochronologic data must be evaluated in the context of careful field mapping, structural and petrologic analysis. Geochronological data …
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The nature and co-behaviour of volatile and non-volatile elements in the sub-continental lithospheric mantle
… subsequent enrichment, via fluid or melt-related metasomatism. Fluid-inclusions are isotopically highly variable, with 3He/4He = 5.3 to 8.4 Ra and δ13C = -25.0 to 5.6 ‰ (V-PDB). 3He/4He-major-trace-element systematics shows that the subcontinental lithospheric mantle dominantly reflects formation …
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A study of the kimberlites, diamonds and associated rocks and minerals from the monastery mine, South Africa. Volume 1: Text
… grained and exhibit a high incidence of modal metasomatism. Some textures intermediate between porphyroclastic and granuloblastic were noted. Significant annealing has occurred. Garnet, orthopyroxene and clinopyroxene may have been derived by exsolution from high temperature aluminous …
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Mass transfer and chemical interactions in subduction zones
… to the slab-mantle interface and show that Mg-metasomatism of mafic rocks to form chlorite-rich assemblages is favored and is likely more pervasive in subduction zones than in oceanic settings. Contrary to common belief, talc is unlikely to form in high abundance in ultramafic rocks …
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Geological and geochemical aspects of the Loch Loyal Alkaline Complex, Sutherland
… at a temperature close to 25000, a type of lead metasomatism formed green amazonitic feldspar. The intermediate nature of the Loyal nordmarkite has been established, it straddles the sodaclase-granite/nordmarkite division of Johannsen, is close to sphene-orthite type granitoids but contains a …
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Mass Transfer and Chemical Interactions in Subduction Zones
… to the slab-mantle interface and show that Mg-metasomatism of mafic rocks to form chlorite-rich assemblages is favored and is likely more pervasive in subduction zones than in oceanic settings. Contrary to common belief, talc is unlikely to form in high abundance in ultramafic rocks …
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Petrologic studies of the Robles Formation, south central Puerto Rico
… of the magmas, or it may be the result of metasomatism through either hydrothermal activity or metamorphism.</p>
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