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Radon gas is the largest natural source of human exposure to ionizing radiation and most of that exposure occurs in indoor air. Bedrock geology is an important factor in radon hazard evaluation of an area. The presence of rock types usually rich in uranium can be considered an indication of a potential radon hazard. In this study the average Ra activity concentration of the main rock types (orthogneiss, micaschist, leucophyllite) in the Sopron Mountains was measured by gamma-spectroscopy, to reveal the uranium rich areas. This work is focusing on the distribution of Ra among the different rock types of the Sopron Mountains with similar geological origin. The effect of different retrograde processes such as mylonitisation, fluid migration and argillitic-limonitic alteration on Ra activity concentration was investigated. A few anomalies occurred in these metamorphic rocks. One explanation of the high uranium concentration is the high radioactive level of the rocks before the metamorphosis, but we demonstrated the significance of the above mentioned secondary processes as well. At Nándormagaslat quarry the presence of radium anomaly we found in the limonitic alteration of weathered gneiss (range: 131-726 Bq kg) in fractures explains the high air concentration nearby in houses (96-2,051 Bq m) and in a corresponding tunnel (maximum 600 kBq m). [ABSTRACT FROM AUTHOR]

Nodules (coarse-grain "plutonic" rocks) were collected from the ca. 20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma-Vesuvius, Italy. The nodules are classified as monzonite-monzogabbro based on their modal composition. The nodules have porphyrogranular texture, and consist of An-rich plagioclase, K-feldspar, clinopyroxene (ferroan-diopside), mica (phlogopite-biotite) ± olivine and amphibole. Aggregates of irregular intergrowths of mostly alkali feldspar and plagioclase, along with mica, Fe-Ti-oxides and clinopyroxene, in the nodules are interpreted as crystallized melt pockets. Crystallized silicate melt inclusions (MI) are common in the nodules, especially in clinopyroxenes. Two types of MI have been identified. Type I consists of mica, Fe-Ti-oxides and/or dark green spinel, clinopyroxene, feldspar and a vapor bubble. Volatiles (CO2, H2O) could not be detected in the vapor bubbles by Raman spectroscopy. Type II inclusions are generally lighter in color and contain subhedral feldspar and/or glass and several opaque phases, most of which are confirmed to be oxide minerals by SEM analysis. Some of the opaque-appearing phases that are below the surface may be tiny vapor bubbles. The two types of MI have different chemical compositions. Type I MI are classified as phono-tephrite - tephri-phonolite - basaltic trachy-andesite, while Type II MI have basaltic composition. The petrography and MI geochemistry led us to conclude that the nodules represent samples of the crystal mush zone in the active plumbing system of Mt. Somma-Vesuvius that were entrained into the upwelling magma during the PB-Sarno eruption. [ABSTRACT FROM AUTHOR]

Tourmaline-rich pegmatitic orthogneisses, tourmalinites, kyanite-chlorite-muscovite schists and quartzites crosscut by subordinate quartz-tourmaline veins and layers were newly described from the Sopron area, Western Hungary. The orthogneisses mainly consist of quartz, plagioclase, tourmaline, garnet and white mica. In smaller amounts K-feldspar, beryl, Mg-rich chlorite, kyanite, lazulite, florencite, monazite and apatite also are present. Magmatic cores and two generations of metamorphic tourmaline (Fe-rich and Mg-rich) were distinguished. Tourmaline in tourmalinites is generally large (several cm), deformed, contains chlorite inclusions and shows oscillatory zoning or polygonal fabric. Large tourmaline crystals often contain dark brown mica-shaped relic areas with higher amount of Ti and Fe than the adjacent parts, interpreted as relics of micas from the protolith. Besides tourmaline, quartz, white mica, plagioclase, apatite, garnet, rutile, ilmenite, scheelite, zircon and monazite are also present in the tourmalinites. Deformed tourmaline-quartz bands and veins occur in kyanite-chlorite-muscovite schists and quartzites. Euhedral, zoned and deformed schorl-dravite is accompanied with kyanite, Mg-chlorite (leuchtenbergite), rutile muscovite and sillimanite. Narrow colorless tourmaline rims enriched exclusively in Mg (FeO < 1 wt. %) can be identified. Coarse-grained orthogneisses with a significant amount of primary tourmaline-beryl assemblage indicates a fluid-rich, B-Be-bearing environment during the final crystallization of the Variscan peraluminous leucogranite. The formation of tourmalinites can be explained by the related boron metasomatism. Phengitic white mica rims and calcic garnet rims in orthogneisses and tourmalinites indicate high-pressure Alpine metamorphic overprint. The presence of REE-rich phosphate mineralisation and leuchtenbergite in the orthogneisses imply that high salinity fluids metasomatized the orthogneisses along the pre-existing shear zones after the Alpine metamorphic peak. Tourmaline grains in kyanite-bearing quartzites and schists may have originated from a micaschist that underwent a strong Mg-metasomatism during the formation of leucophyllites described from the area. [ABSTRACT FROM AUTHOR]