Klötzli, U.; Burda, J.; Tibuleac, P. Phosphate Petrochronology of the Belcina REE Mineralization (Ditrău Alkaline Massif, Romania). Minerals2023, 13, 739.
Klötzli, U.; Burda, J.; Tibuleac, P. Phosphate Petrochronology of the Belcina REE Mineralization (Ditrău Alkaline Massif, Romania). Minerals 2023, 13, 739.
Klötzli, U.; Burda, J.; Tibuleac, P. Phosphate Petrochronology of the Belcina REE Mineralization (Ditrău Alkaline Massif, Romania). Minerals2023, 13, 739.
Klötzli, U.; Burda, J.; Tibuleac, P. Phosphate Petrochronology of the Belcina REE Mineralization (Ditrău Alkaline Massif, Romania). Minerals 2023, 13, 739.
Abstract
A notable REE mineralization in Europe is associated with the Ditrău Alkaline Massif (DAM) in the Eastern Carpathians (Romania). It is an expression of the latest hydrothermal phase in the DAM and is found in the form of mineralized carbonate veins cross-cutting the complex in the NW (Jolotca region) and the SE (Belcina region) parts of the DAM. In the Belcina veins monazite-(Ce), xenotime-(Y), apatite, together with Fe-Mg-rich carbonate, thorite, thorogummite, gedrite and plagioclase are rock-forming. Three different textural and chemical types of the monazite-(Ce) and the xenotime-(Y) document a three-stage evolution. The relative phosphate age succession (from older to younger) thereby is xnt1 > xnt2 (>)+ mnz1 + Fe2O3 + Fe-gedrite > mnz2 + Fe-dolomite (+ plagioclase) > mnz3 + xnt3 + apatite. Phosphate chemistry shows that these crystallized from hydrothermal fluids, whereby each phosphate type follows a separate evolutionary path recommending growth from (at least) 3 independent and successive hydrothermal fluids. Chemistry and pathways within the DAM suggest that these hydrothermal fluids could be derived from a subsurface carbonatitic intrusion. Mnz1,2 and xnt1,2 ages are tightly cluster at 215.8 ± 0.7 Ma (Norian, Upper Triassic). The third-generation phosphate ages are younger, but associated with large analytical uncertainties and did not deliver geologically useful ages. The mean age of ca. 216 Ma is interpreted as timing the Belcina REE mineralization, what together with the fluid chemistry, supports a model of the presence of a late-stage, independent carbonatitic intrusion about 10 Ma after the main igneous activity (ca. 235 - 225 Ma) forming the DAM, synchronous with extension-related magmatism in the region.
Environmental and Earth Sciences, Geochemistry and Petrology
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