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Showing 1 to 20 of 31 for “"xenolith"”.
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Petrography of xenolith zones in the Black Face-Ames plutons, western San Juan Mountains, Colorado
… rhyodacite.</p> <p>Two major zones of xenoliths of Precambrian rock occur within the Black Face-Ames plutons; scattered xenoliths are found at widely separated locations. One zone, located near the summit of Black Face, contains xenoliths of shale, quartzite, and granitic rocks, ranging …
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Geochemistry of the earth's mantle, Nunivak Island, Alaska and other areas : evidence from xenolith studies
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982.
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Some aspects of the mineral chemistry of the peridotite xenolith suite from the Bultfontein Diamond Mine, Kimberley, South Africa
The xenolith suite from the Bultfontein Mine, Kimberley, South Africa, comprises lherzolites, harzburgites, and wehrlites with and without garnet; garnet olivine websterites and polymict peridotites. Many of the peridotites contain phlogopite and/or potassic-richterite which are interpreted as …
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Petrogenesis of hybrid porphyry pipes and evolution of alkaline magmas in the Kanabeam Igneous Complex, Southern Namibia
… to these plutonic phases a number of late stage, xenolith rich porphyry pipes were emplaced, exploiting contact zones between earlier plutons. Xenolith types include gabbro possibly derived from unexposed deeper parts of the KIC, syenites (more proximal components of the KIC), trachytes from an …
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A study of mantle inclusions in the Koffiefontein Kimberlite pipe, South Africa
… Kimberlite Pipe have been studied in the form of xenoliths, megacrysts, concentrate minerals and inclusions in diamonds. Mantle derived xenoliths are unusuaLly scarce. The predominant xenoliths are pyroxenites. Peridotites are rare and eclogites are very rare. The pyroxenites have been assigned to …
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A low - δ 18 O intrusive breccia from the Koegel Fontein complex, South Africa
… alkali basalt, gneiss, and epidote - and xenolith - rich material. Mapping indicates that the initial intrusion was an alkali basalt dyke and a bostonite dyke that were then intruded by two breccia plugs that extended along the planes of weakness created by the pre - existing dykes, …
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Kimberlites of the central Cape Province, RSA [Vol.2]
… sampled. Garnets are rare. One garnet gran~lite xenolith was found. 2) Doorskuilen (30°38' S, 23°19' E) A pipe feature situated on the eastern side of the Smartt Syndicate Daml,9. This locality was visited but the farmer knows of no excavations in the area mentioned. There is no further mention …
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Applications of Machine Learning to the Petrographic Analysis of Icelandic Gabbroic Xenoliths through Light, Electron and X-ray Microscopy
… of the above methodsto two sets of gabbroic xenolith nodules from Iceland; these three chapters focus on differentaspects of the xenoliths separately. Samples from Fagradalsfjall are used to interrogate thestructure of the magmatic system through large-scale systematic textural and …
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Geological and thermochronological evolution of the lower crust of southern Africa
… and isotopic studies of kimberlite-borne crustal xenoliths have been used to elucidate the architecture and thermal evolution of the continental lithosphere of southern Africa. U-Pb accessory mineral geochronology of lower crustal xenolith assemblages illustrate the youth of granulite-facies …
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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
… for garnet and spinel bearing peridotite xenolith suites from four Late Cretaceous kimberlites to the west of the Kaapvaal craton in two Proterozoic terranes: Hoedkop and Pofadder in the north-western Namaqua-Natal Province and Rietfontein and Louwrensia (Gibeon) in the Rehoboth Province. …
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S-wave velocity structure beneath the Kaapvaal Craton from surface-wave inversions compared with estimates from mantle xenoliths
… estimated from approximately 100 mantle xenoliths brought to the surface in kimberlite pipes. As the xenoliths represent a snapshot of the mantle at the time of their eruption, comparison with recently recorded seismic data provides an opportunity to compare and contrast the independently …
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A study of mantle inclusions in the Koffiefontein Kimberlite Pipe, South Africa
… Kimberlite Pipe have been studied in the form of xenoliths, megacrysts, concentrate minerals and inclusions in diamonds. Mantle derived xenoliths are unusually scarce. The predominant xenoliths are pyroxenites. Peridotites are rare and eclogites are very rare. The pyroxenites have been assigned to …
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Nominally volatile-free mantle minerals: a reservoir for water and fluorine in the Kaapvaal Craton
… SIMS, FTIR, SEM, EBSD) of nineteen mantle xenoliths from the interior (Bultfontein, South Africa) and margin (Mothae, Lesotho) of the Kaapvaal craton has placed important constraints on the capacity of olivine and pyroxenes to store volatiles. Cryptically metasomatised olivine is found to …
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The record of magma storage conditions in mineral compositions below a glacial to ice-free Askja volcano, Iceland
… In this study, 36 lava flow and gabbro xenolith samples were collected from seven separate units: two glacial, the Early Holocene, and four historical. These samples were analyzed along with a select number of pre-existing samples. The data collected from this study were combined with …
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Thermobarometry of Hawaiian Spinel Peridotites
<p>Mantle peridotite xenoliths found within the rejuvenated stage lavas on the islands of O`ahu and Kaua`i, Hawaii provide a unique window into the oceanic mantle. These peridotites are thought to represent variably metasomatized fragments of the Pacific lithosphere. If these peridotites are …
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A new approach to mass balance modeling: applications to igneous petrology
… a major role in Paricutin volcano and about 15% xenolith has contaminated the magma. In PLA fractionation processes, plagioclase and amphibole are shown to have caused the chemical difference between lavas, although other phenocrysts ( biotite and pyroxene ) did not participate.
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Igneous and metamorphic processes in the Shap Granite and its aureole
… to those of the granite-solidus (around 600°C). Xenoliths from the 'granite Pink quarries at Shap contain the same mineralogy as their host granite, including the megacryst orthoclase. The xenolith chemistry compares well with that of the more basic dykes, with the xenoliths - forming a coherent …
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Cenozoic potassic magmatism and uplift of the Western United States
… degree of uplift, combined with geophysical and xenolith evidence, are consistent with a model in which uplift and preextensional magmatism of the Colorado plateau and Sierra Nevada resulted from the convective removal of the lower lithosphere. In the case of the Colorado Plateau convective …
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Significance of magma mingling and mixing during the formation of the host-rock successions of Archean massive sulfide deposits in the Noranda camp, Abitibi subprovince, Quebec, The
… rhyolite cryptodome containing abundant mafic xenoliths is exposed. To characterize the occurrence of the mafic xenoliths, the shape, trend, size, and contact relationships were recorded for each xenolith. Volcanic facies analysis showed that tabular xenoliths are abundantly present in the …
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Thermobarometry and geochemistry of peridotite xenoliths from the southwestern margin of the Kaapvaal craton, South Africa
… thermally and chemically, between peridotite xenoliths exhumed from Archean, and post-Archean terranes. Studies of the thermal structure of the lithosphere, in combination with surface heat flow data, suggest that thermal gradients beneath cratonic regions (Archean blocks which stabilized > …
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