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Abstract

The Hämmerlein Sn-skarn deposit of the western Erzgebirge is hosted in early Palaeozoic schists and gneisses and is closely associated with one of the most voluminous granite intrusions of the Erzgebirge, the Eibenstock granite. The main valuable ore mineral in Hämmerlein is cassiterite which is disseminated in the four types of skarn occurring in the deposit, i.e., garnet, amphibole, pyroxene, and magnetite skarn. There are two scenarios for deposit formation: (1) formation of the skarn during the regional metamorphism at 340 Ma followed by mineralization during granite emplacement at 320 Ma and (2) skarn formation and mineralization directly related to the granite intrusion. Theriak-Domino thermodynamic P-T-XCO2 modelling shows that both scenarios are possible for the formation of the skarn series, but as the Rb-Sr muscovite-based age of skarn samples is 340 Ma, the first scenario is the relevant one. The skarn mineral assemblages formed during regional metamorphism, whereas cassiterite mineralization is related to younger granite emplacement and is associated with chloritization of biotite and precipitation of fluorite. These reactions changed the fluid composition and induced cassiterite mineralization.