Epidote-supergroup minerals associated with disseminated scandium mineralization at Jordanów Śląski in Lower Silesia, Poland

The serpentinite quarry at Jordanów Śląski is known for the first documented occurrence of nephrite in Europe (Traube, 1885). The quarry operated until the early 1980s and remained inactive for almost 40 years. Small-scale serpentine extraction started again in 2022. Recently, mining activity has increased, exposing a 20-25 m wide zone of leucocratic rocks, approximately 100 m long and 20-30 m deep. This zone most likely consists of tectonically assembled fragments of serpentinite, calc-silicate rocks, and leucogranite with pegmatite veins and nests, as well as common aplites. The discovery of scattered Sc-bearing mineralization at the contacts between granitic pegmatite and serpentinite (Sc-bearing actinolite, Sc-bearing diopside, jervisite, cascandite, scandio-winchite, heflikite, dubińskite, bazzite, kristiansenite, kolbeckite) has made this quarry one of the most important occurrences of scandium minerals in the world and the only one associated with a supra-subduction zone (Pieczka et al., 2024a-c).

This mineralization is accompanied by numerous minerals from the epidote supergroup (1) scattered throughout the pegmatite itself [clinozoisite, allanite-(Ce), allanite-(Nd), allanite-(Sm), allanite-(Y), Cr-bearing allanite-(Ce)], (2) at contacts with blackwall schists [Sc-bearing clinozoisite, Sc-bearing allanite-(Ce), heflikite], (3) at contacts with diopside-bearing rocks [allanite-(Ce), allanite-(La), dissakisite-(Ce)], (4) in zoisite-bearing calc-silicate rock [Cr-bearing clinozoisite and Cr-bearing epidote], and (5) in metasomatic and hydrothermal zones in serpentinite and altered actinolite-diopside-bearing metasomatites [Cr-bearing clinozoisite]. All minerals from the epidote supergroup associated with the pegmatite, except for allanite-(Ce) and clinozoisite, occur in fine grains not exceeding 100 μm and are enriched in lanthanides. On the other hand, minerals associated with zoisite-bearing calc-silicate rock and altered actinolite-diopside-bearing metasomatites form large crystals, reaching 2-3 cm in length, as well as string-like aggregates; they are completely devoid of lanthanides, usually found with relict chromite + Cr-bearing grossular or Al-bearing uvarovite.

The chemical compositions of pegmatite epidotes were influenced by the local compositions of the hydrated pegmatite-forming melt; those enriched in Sc and Cr could crystallize under the influence of  Sc- and Cr-bearing fluids, which were released during the rodingitization processes of the Ślęża ophiolite lithologies. Their enrichment in lanthanides may be related to the interactions of these fluids with pegmatite lithologies at their marginal parts and fractures.

 

References:

Traube, H. (1885) Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Beilage-Band, 2, 91–94.

Pieczka, A., Stachowicz, M., Zelek-Pogudz, S., Gołębiowska, B., Sęk, M., Nejbert, K., Kotowski, J., Marciniak-Maliszewska, B., Szuszkiewicz, A., Szełęg, E., Stadnicka, K.M., and Woźniak, K. (2024a) American Mineralogist 109, 174–183.

Pieczka, A., Kristiansen, R., Stachowicz, M., Dumańska-Słowik, M., Gołębiowska, B., Sęk, M., Nejbert, K., Kotowski, J., Marciniak-Maliszewska, B., Szuszkiewicz, A., Szełęg, E., and Woźniak, K. (2024b) Mineralogical Magazine 88, 228–243.

Pieczka, A., Stachowicz, M., Zelek-Pogudz, S., Gołębiowska, B., Sęk, M., Nejbert, K., Kotowski, J., Marciniak-Maliszewska, B., Szuszkiewicz, A., Szełęg, E., Stadnicka, K.M., and Woźniak, K. (2024c) American Mineralogist 109, 940–948.