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Hydrothermal metasomatism of a peralkaline granite pegmatite, Khaldzan Buragtag massif, Mongolian Altai; complex evolution of REE-Nb minerals

Bagiński B., Jokubauskas P., Domańska-Siuda J., Kartashov P., Macdonald R.

Acta Geologica Polonica

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2016

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Vol. 66, no. 3

473--491

EN

The low-temperature hydrothermal alteration of certain rare-metal minerals is recorded in a quartz-epidote metasomatite from the Tsakhirin Khuduk occurrence in the Khaldzan-Buragtag Nb-REE-Zr deposit, Mongolian Altai. A peralkaline granitic pegmatite was metasomatized by hydrothermal fluids released from associated intrusions, with the formation of, inter alia, chevkinite-(Ce), fergusonite-(Nd) and minerals of the epidote group. The textural pattern indicates recrystallization and coarsening of these phases. Later, low-temperature alteration byfluids resulted in the chevkinite-(Ce) being replaced by complex titanite-TiO2-cerite-(Ce)-hingganite-hydroxylbastnäsite-(Ce) assemblages. Calcite formed late-stage veins and patches. The hydrous fluids were poor in F and CO2 but had high Ca contents.

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Petrology and geochemistry of rapakivi-type granites from the crystalline basement of NE Poland

Bagiński B., Duchense J., Auwera J. van der, Hervé M., Wiszniewska J.

Geological Quarterly

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2001

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Vol. 45, No 1

33-52

EN

80 rock samples from drill-cores at 8 localities in the Mazury complex (Polish part of the crystalline East European Craton), representing rock types from monzodiorites to leucogranites, were studied for major, trace and REE elements by XRF and ICP-MS methods. The range in composition of the investigated rocks varies from 46 to 76% SiO2 contents. All of them show similar REE distributions, which suggests that they are genetically linked. They also plot along a major trend with many similarities to the jotunitic liquid line of descent defined in AMCG rocks from Rogaland (Norway). Each group of rocks has however its own specific pattern of elements.

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Chloritisation of hornblende and biotite : a HRTEM study

Ferrow E., Bagiński B.

Acta Geologica Polonica

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1998

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Vol. 48, no. 1

107-113

EN

The coarse textures produced by hydration of hornblende and biotite during retrograde metamorphism of the rocks of the K?odzko-Z?oty Stok area were identified easily by both optical microscopy and scanning electron microscopy (SEM). However, the micro-textures that are a few unit cell in dimensions were identified through high resolution transmission electron microscopy (HRTEM) only. For the alteration of biotite to chlorite the replacement of potassium in the interlayer by a brucite-like layer and the subsequent increase in volume was observed. There were, however, some missing brucite-like layers within the chlorite units. Moreover, both topotactic and low angle replacement of biotite to chlorite were identified. For the direct hydration of hornblende to chlorite, HRTEM and selected area electron diffraction pattern (SAED) showed that the c* and a* of chlorite were parallel to the b* and a* of hornblende, respectively. Nevertheless, other orientation relationships were also observed by optical microscopy.