Diversity of lithium mica compositions in mineralized granite-greisen system: Cinovec Li-Sn-W deposit, Erzgebirge

0503969 - GLÚ 2020 RIV NL eng J - Článek v odborném periodiku
Breiter, Karel - Hložková, M. - Korbelová, Zuzana - Vašinová Galiová, M.
Diversity of lithium mica compositions in mineralized granite-greisen system: Cinovec Li-Sn-W deposit, Erzgebirge.
Ore Geology Reviews. Roč. 106, MAR 2019 (2019), s. 12-27. ISSN 0169-1368. E-ISSN 1872-7360
Grant CEP: GA ČR GA14-13600S
Institucionální podpora: RVO:67985831
Klíčová slova: Li-mica * trace elements * granite * greisen * Cínovec/Zinnwald * Krušné Hory/Erzgebirge
Obor OECD: Mineralogy
Impakt faktor: 3.868, rok: 2019
Způsob publikování: Omezený přístup
https://www.sciencedirect.com/science/article/pii/S0169136818304268?via%3Dihub

The Li-Sn-W deposit Cínovec/Zinnwald in the eastern Erzgebirge (Czech Republic and Germany) represents one of the worldwide best known examples of complex rare-metal plutons with pervasive greisenization. Mica from altogether 38 samples representing all granite and greisen varieties from the present surface to the depth of 1596 m was analysed using electron microprobe (EMPA) and laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) for major (including F, Rb) and trace (Li, Sc, Ga, Ge, Nb, In, Sn, Cs, Ta, Tl, W) elements, respectively. All primary micas at Cínovec are trioctahedral Li-Fe micas close to the annite–zinnwaldite–trilithionite series. Biotite from granites in the deeper part of the pluton (depth of 735–1596 m) contains 33.9–39.6 wt% SiO₂ , 19.6–23.8 wt% FeO, 0.5–0.7 wt% Rb₂O, 0.9–1.8 wt% Li₂O, 3.4–4.8 wt% F, 381–937 ppm Nb, 34–134 ppm Ta, 20–46 ppm W, and 93–617 ppm Sn. Zinnwaldite from granites in the upper part of the pluton (depth of 0–735 m) contains 41.2–48.5 wt% SiO₂, 8.9–15.2 wt% FeO, 0.9–1.9 wt% MnO, 2.0–4.4 wt% Li₂ O, 0.8–1.9 wt% Rb₂O, 7.0–8.6 wt% F, 43–464 ppm Nb, 101–213 ppm Sn, 6–80 ppm Ta, and 28–52 ppm W. Zinnwaldite from bodies of pervasive greisen and quartz-zinnwaldite veins is, compared to zinnwaldite from granites, relatively slightly enriched in Si, Mn and Ga, and depleted in Fe, F, Rb, Sn, W and Nb. Li and Ta contents are similar. Contents of Li, Rb and F, and the Fe/Mn and Nb/Ta values in mica closely positively correlate with those in the bulk rock, illustrating an upwards fractionation of parental melt. In contrast, the contents of high-field-strength elements in mica do not correspond to their contents in the bulk rock (melt): they were controlled by the order of crystallization of mica vs. accessory oxide minerals. Therefore, biotite generally contains distinctly higher Sn, Nb, Ta, and W than zinnwaldite. Dioctahedral micas of the muscovite–phengite series were found only as a late product of alteration of primary trioctahedral mica. Replacement of greisen-stage zinnwaldite by muscovite is chemically expressed in a strong depletion in Fe, F, and Li, and an enrichment in Sn. The share of trioctahedral mica in the bulk-rock budget of Sn decreases from 40–70% in biotite granite to less than 5% in greisen, in the case of Nb and Ta from 20–50% to less than 10%. The share of mica in the budget of W, mostly in the range of 2–15%, is stable through the whole pluton.
Trvalý link: http://hdl.handle.net/11104/0295721