Accessory minerals and evolution of tin-bearing S-type granites in the western segment of the Gemeric Unit (Western Carpathians)

Abstract

The S-type accessory mineral assemblage of zircon, monazite-(Ce), fluorapatite and tourmaline in the cupolas of Permian granites of the Gemeric Unit underwent compositional changes and increased variability and volume due to intensive volatile flux. The extended S-type accessory mineral assemblage in the apical parts of the granite resulted in the formation of rare-metal granites from in-situ differentiation and includes abundant tourmaline, zircon, fluorapatite, monazite-(Ce), Nb–Ta–W minerals (Nb–Ta rutile, ferrocolumbite, manganocolumbite, ixiolite, Nb–Ta ferberite, hübnerite), cassiterite, topaz, molybdenite, arsenopyrite and aluminophosphates. The rare-metal granites from cupolas in the western segment of the Gemeric Unit represent the topaz–zinnwaldite granites, albitites and greisens. Zircon in these evolved rare-metal Li–F granite cupolas shows a larger xenotime-(Y) component and heterogeneous morphology compared to zircons from deeper porphyritic biotite granites. The zircon Zr/Hfwt ratio in deeper rooted porphyritic granite varies from 29 to 45, where in the differentiated upper granites an increase in Hf content results in a Zr/Hfwt ratio of 5. The cheralite component in monazite from porphyritic granites usually does not exceed 12 mol. %, however, highly evolved upper rare-metal granites have monazites with 14 to 20 mol. % and sometimes > 40 mol. % of cheralite. In granite cupolas, pure secondary fluorapatite is generated by exsolution of P from P-rich alkali feldspar and high P and F contents may stabilize aluminophosphates. The biotite granites contain scattered schorlitic tourmaline, while textural late-magmatic tourmaline is more alkali deficient with lower Ca content. The differentiated granites contain also nodular and dendritic tourmaline aggregations. The product of crystallization of volatile-enriched granite cupolas are not only variable in their accessory mineral assemblage that captures high field strength elements, but also in numerous veins in country rocks that often contain cassiterite and tourmaline. Volatile flux is documented by the tetrad effect via patterns of chondrite normalized REEs (T1,3 value 1.46). In situ differentiation and tectonic activity caused multiple intrusive events of fluid-rich magmas rich in incompatible elements, resulting in the formation of rare-metal phases in granite roofs. The emplacement of volatile-enriched magmas into upper crustal conditions was followed by deeper rooted porphyritic magma portion undergoing second boiling and re-melting to form porphyritic granite or granite-porphyry during its ascent.

Compositional Variability of Monazite–Cheralite–Huttonite Solid Solutions, Xenotime, and Uraninite in Geochemically Distinct Granites with Special Emphasis to the Strongly Fractionated Peraluminous Li–F–P-Rich Podlesí Granite System (Erzgebirge/Krušné Hory Mts., Central Europe)

“…Cheralite substitution strongly prevails over the huttonite one in monazite from all these peraluminous rocks. The strong dominance of the cheralite substitution mechanism in peraluminous granites has also been stressed from Western Carpathians [49][50][51], from the Slavkovský Les area [52], from the Fichtelgebirge [53], and also for Alpine orthogneisses [54] and the strongly peraluminous and perphosphorous Belvís de Monroy pluton in the Iberian Variscan belt [55]. In contrast, Reference [56] established the huttonite substitution as dominant in both magnetite-and ilmenite-series granites from a subduction-related magmatic arc in Japan.…”

Magmatic and hydrothermal evolution of highly-fractionated rare-metal granites at Gabal Nuweibi, Eastern Desert, Egypt

“…In fact, the visually obvious M-type shape of the 4 th tetrad in all these samples is unusually strong; Irber (1999) note that the effect is not usually visible in the 4 th tetrad. Clear M-type tetrad patterns are a typical feature of highly fractionated, volatile-rich granites that have undergone significant modification by hydrothermal activity (Jahn et al, 2001;Monecke et al, 2002;Broika, and Kubis, 2018).…”

Primary Minerals and Age of The Hydrothermal Quartz Veins Containing U-Mo-(Pb, Bi, Te) Mineralization in the Majerská Valley near Čučma (Gemeric Unit, Spišsko-Gemerské Rudohorie Mts., Slovak Republic)

“…The granitic rocks of the Gemeric Unit represent a distinct type of specialized (Sn-W-F), highly evolved suite with S-type affinity that differs from other granitoids occurring in the Veporic and Tatric Units of the Western Carpathian crystalline basement. They are enriched in fluorine, phosphorus and rare lithophile elements, such as Li, Rb, Cs, B, Ga, Sn, W, Nb, Ta and U (e.g., [23,[47][48][49][50][51] and others). More recent zircon U-Pb and molybdenite Re-Os isotopic dating, as well as the chemical ages of monazite, indicate emplacement of the Gemeric granites and related post-magmatic mineralization during Late Permian period.…”