minerals Article Origin of Talc and Fe-Ti-V Mineralization in the Kletno Deposit (the ´ Snie˙ znik Massif, SW Poland) Grzegorz Gil 1,2, * , Piotr Gunia 2 , Jaime D. Barnes 3 , Michal Szyma ´ nski 2 , Petras Jokubauskas 1 , Anna Kalbarczyk-Gil 4 and Boguslaw Bagi ´ nski 1 1 Institute of Geochemistry, Mineralogy and Petrology, Faculty of Geology, University of Warsaw, ˙ Zwirki i Wigury 93, 02-089 Warszawa, Poland; p.jokubauskas@uw.edu.pl (P.J.); b.baginski1@uw.edu.pl (B.B.) 2 Institute of Geological Sciences, Faculty of Earth Sciences and Environmental Management, University of Wroclaw, Maksa Borna 9, 50-204 Wroclaw, Poland; piotr.gunia@uwr.edu.pl (P.G.); michas.szymanski@gmail.com (M.S.) 3 Department of Geological Sciences, University of Texas, 2275 Speedway Stop C9000, Austin, TX 78712, USA; jdbarnes@jsg.utexas.edu 4 Independent Researcher, 05-070 Sulejówek, Poland; lek.wet.6891@gmail.com * Correspondence: g.gil2@uw.edu.pl Received: 14 August 2019; Accepted: 19 December 2019; Published: 22 December 2019   Abstract: The Kletno deposit in the ´ Snie ˙ znik Massif (Central Sudetes, SW Poland), mined for Fe, U, Ag, Cu, fluorite, and marble through the ages, developed at the contact of marbles and orthogneiss. Here, we present a new Fe-Ti-V-ore (containing up to 14.07 wt. % Fe, 2.05 wt. % Ti, and 2055 ppm V in bulk rock) and ornamental- to gem-quality talc prospect at the southwest margin of this deposit. This newly documented Fe-Ti-V mineralization is hosted in hornblendites, dolomite veins, and chlorite schists, which, along with talc, envelopes a tectonic slice of serpentinite. Hornblendites are interpreted as metamorphosed ferrogabbros, derived from the same mafic melts as adjacent barren metagabbros. The oxygen and carbon isotope compositions of metabasites and dolomite veins (amphibole δ 18 O values = 8.8–9.3%; carbonate δ 18 O values = 12.8–16.0%, and δ 13 C values = −8.3% to −7.2%), in combination with those of the country marbles (carbonate δ 18 O and δ 13 C values = 23.2% and +0.1%, respectively), suggest that mineralization-bearing hornblendites formed due to interaction of the mafic magma with CO 2 released during the decarbonation of the sediments. The CO 2 -bearing fluid interaction with gabbros likely caused carbonation of the gabbros and formation of the dolomite veins, whereas talc formed due to Si-rich fluids, possibly derived from a mafic intrusion, interaction with serpentinite, or due to the metasomatism of the serpentinite–gabbro assemblage. Moreover, fluids leaching Fe and Ti from the adjacent sediments can mix with the mafic magma causing enrichment of the magma in Fe and Ti. Consequently, the mineralization-bearing ferrogabbros became even more enriched in Fe and Ti, which can be linked with the formation of Fe-Ti-V ore bodies. Keywords: ´ Snie ˙ znik Massif; Kletno deposit; Fe-Ti-V mineralization; talc; carbonate veins; stable isotopes; serpentinite-gabbro-sediment assemblage 1. Introduction The Kletno deposit, located in the Kle´ snica valley in the ´ Snie ˙ znik Massif (Central Sudetes, SW Poland), was subject to long-lasting underground and open-pit mining, which began in the 13th to 14th centuries and ceased in the 1990s [1]. The cessation of mining was due to the discovery of a famous cave system in 1966, known as the Jaskinia Nied´ zwiedzia (the Bear Cave) (e.g., Kasprzak et al. [2]). The Kletno deposit was mined for Fe, U, Ag, and Cu ores, as well as fluorite and the famous Biala Marianna marble [1]. Minerals 2020, 10, 13; doi:10.3390/min10010013 www.mdpi.com/journal/minerals