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Genesis and stability of accessory phosphates in silicic magmatic rocks: a Western Carpathian case study

100%

Broska I. , Perik I.

tom Vol. 39, iss. 1/2

53--65

The formation of accessory phosphates in granites reflects many chemical and physical factors, including magma composition, oxidation state, concentrations of volatiles and degree of differentiation. The geotectonic setting of granites can be judged from the distribution and character of their phosphates. Robust apatite crystallization is typical of the early magmatic crystallization of I-type granitoids, and of late magmatic stages when increased Ca activity may occur due to the release of anorthite from plagioclase. Although S-type granites also accumulate apatite in the early stages, increasing phosphorus in late differentiates is common due to their high ASI. The apatite from the S-types is enriched in Mn compared to that in I-type granites. A-type granites characteristically contain minor amounts of apatite due to low P concentrations in their magmas. Monazite is typical of S-type granites but it can also become stable in late I-type differentiates. Huttonite contents in monazite correlate roughly positively with temperature. The cheralite molecule seems to be highest in monazite from the most evolved granites enriched in B and F. Magmatic xenotime is common mainly in the S-type granites, but crystallization of secondary xenotime is not uncommon. The formation of the berlinite molecule in feldspars in peraluminous melts may suppress phosphate precipitation and lead to distributional inhomogeneities. Phosphate mobility commonly leads to the formation of phosphate veinlets in and outside granite bodies. The stability of phosphates in the superimposed, metamorphic processes is restricted. Both monazite-(Ce) and xenotime-(Y) are unstable during fluid-activated overprinting. REE accessories, especially monazite and allanite, show complex replacement patterns culminating in late allanite and epidote formation.

Ksenotym w łupkach łyszczykowych zmineralizowanych kasyterytem z pasma łupkowego Starej Kamienicy

67%

Bobiński W. , Siemiątkowski J. , Starnawska E.

Przegląd Geologiczny

2004

tom Vol. 52, nr 1

61-63

Xenotime in mica schists with chlorite was analysed with EDS microprobe combined with scanning electron microscope JEOL JSM 35. The samples come from two boreholes (C-XI-41 and C-XII-54) drilled in the western part of Stara Kamienica Range. Xenotime crystals are of zoning and patchy character due to the changing composition of HREE elements. Xenotime is probably of hydrothermal origin which is connected with premetamorphic cassiterite and sulfide mineralization.

Przegląd głównych minerałów pierwiastków ziem rzadkich : złoto XXI wieku

67%

Ryder P. , Nowak M.

tom Vol. 63, nr 6

348--362

The constant evolution of civilisation and ever more advanced technologies have forced the global economy to search for new and renewable resources. Since the 1950s, rare earth elements (REE) have played an increasingly significant role in the production of new materials. The REE form a group of 17 elements (15 lanthanides, yttrium and scandium) with special properties that distinguish them from the other elements. These unique and essential raw materials have numerous applications nowadays. Without the rare earths, many branches of industry would not be able to function. The main resources of the REE come from the rocks with mineralization enriched in minerals with a higher REO (rare earth oxides) contents. Although there are around 270 different REE-bearing mineral species, the exploitation of the REE refers to less than 10 minerals. Five major REE minerals (the major minerals from group of bastnäsite (bastnaesite), monazite, xenotime, apatite and perovskite (loparite)) are characterized and described. The REO percentage content varies from max. 16% in apatite to max. 79% in bastnäsite. The examples shown were chosen due to their importance and level of extraction. This review-paper has been based on the compilation of data from mineralogical publications, mineralogical data websites and metallurgical articles about the alloys and their compounds.