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Central European Geology
Authors: Zsófia Pálos, István János Kovács, Dávid Karátson, Tamás Biró, Judit Sándorné Kovács, Éva Bertalan, Anikó Besnyi, György Falus, Tamás Fancsik, Martina Tribus, László Előd Aradi, Csaba Szabó and Viktor Wesztergom

not only to the data obtained, but to the tectonic, petrologic, genetic, and methodological details, which could all influence the results. As a case study, the water concentrations of plagioclase phenocrysts are analyzed from some

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Abstract  

Up to 26 trace elements were determined in 9 different samples of plagioclase, orthopyroxene, clinopyroxene and magnetite and the host pyroclastic matrix material using instrumental neutron activation analysis. Mineral to whole-rock partition coefficients were reported and interrelationships between chemical composition and crystal structure of the minerals were discussed, especially in the case of REE in plagioclase.

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Central European Geology
Authors: Vladimir Naumov, Vladimir Kovalenker, Gheorghe Damian, Sergei Abramov, Maria Tolstykh, Vsevolod Prokofiev, Floarea Damian and Ioan Seghedi

2111 Holland, T.J.B., J.D. Blundy 1994: Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry. — Contrib. Mineral. Petrol., 116, pp. 433

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114 Ghent, E.D., M.Z. Stout 1981: Geobarometry and geothermometry of plagioclase-biotite-garnetmuscovite assemblages. Contrib. Mineral. Petrol. , 76 , pp. 92

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.N., JR., D.B. Clarke 1979: Hypothetical liquidus relationships in the subsystem Al 2 O 3 -FeO-MgO projected from quartz, alkali feldspar and plagioclase for a (H 2 O) = 1. - Canadian Mineralogist, 17, pp. 549-560. Hypothetical

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The newly discovered crustal xenoliths from Miocene andesites in the Mátra Mts (Northeast Hungary) were classified into three petrographic types. Type 1 is a garnetiferous, plagioclase-rich cumulate rock, presumed to originate from the felsic portion of the nearby Szarvaskõ-Darnó mafic igneous complex. The almandine-rich garnet has been inferred to be of granulite facies origin. Garnet - orthopyroxene geothermobarometry on the orthopyroxene - plagioclase corona structure around it indicates a later high temperature (800-950 °C) low pressure (3-4 kbar) retrogression event. Type 2 is also plagioclase-rich cumulate rock with contact metamorphic assemblage containing spinel, corundum and andalusite, which crystallized in the course of dehydration reactions of biotite and/or smectite in hornblende hornfels to sanidinite facies conditions. Type 3 is microsyenite, which contains abundant anorthoclase and minor amount of Na- and K-rich kaersutitic-barkevikitic amphibole.

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Instrumental neutron activation analysis was made on three different rock samples and on mineral separates of plagioclase, pyroxene and magnetite. γ-spectra were recorded using both a coaxial and a planar Ge detector. Counting errors were compared for those elements that could be determined with both detectors. In nearly all cases, analyses using the planar detector yielded smaller errors. The use of this detector in instrumental analysis is of particular advantage, where only contents of rare earth elements are to be determined.

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Constituent minerals in two differentiated rock complexes were separated and purified for quantitative multielement analysis. Modally weighted trace element concentrations conform well with whole-rock analyses and primarily reflect changes in the cumulus nature of the product. Different enrichment factors for individual minerals demonstrate pronounced departure from equilibrium and suggest minerals in the sample suite equilibrated towards evolving parental liquids. The data imply that early crystallization of pyroxene and amphibole was followed by zircon, apatite, plagioclase and finally alkali feldspar. These results suggest that whole-rock trace element variations in plutonic rocks can be misleading whereas separated mineral data can provide valuable information on crystallization kinetics.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: P. Rózsa, Z. Elekes, Gy. Szöőr, A. Simon, J. Simulák, I. Uzonyi and Á. Kiss

Abstract  

The aim of the current paper is to map minerals mainly of Carpathian obsidian glasses by nuclear microprobe based on the particle induced X-ray emission (PIXE) providing analytical data on them for the first time. Some samples from Armenia, Greece are also involved to make a comparison with the Carpathian specimens. The following minerals are identified and analyzed: pyrrhotite, chalcopyrite, pyrite, zircon, pyroxene, biotite, plagioclase feldspar, and anhydrite. On the basis of rock-forming silicate minerals, some petrologic processes are outlined. With the identification of accessory minerals (anhydrite, pyrrhotite, chalcopyrite, pyrite), some geological conclusions are also drawn.

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Abstract  

The distribution of the chemical element during weathering of trachyandesite in S. Miguel Island (Azores, Portugal), and in mosses and lichens growing on these rocks, was studied using instrumental neutron activation analysis. A general enrichment of rare earth elements (REEs), a Ce positive anomaly (partial oxidation after primary apatite dissolution) and a Eu negative anomaly (Eu2+ in plagioclases/clay minerals) are observed with increasing weathering. Mosses and lichens are Ce and Eu depleted, indicating that the main REE uptake is done via absorption from REE3+ secondary phosphates, probably together with P (essential nutrient). Zn, Br and Sb show higher enrichment factors in lichens and mosses.

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