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Mineralogy of the polymetallic Waschleithe Zn-Pb-(W) skarn – implications for skarn genesis in the Schwarzenberg district, western Erzgebirge, Germany

Reinhardt, N.; Frenzel, M.ORC; Gutzmer, J.ORC; Meinert, L. D.; Gerdes, A.; Burisch, M.
The Schwarzenberg district (SD) in the western Erzgebirge comprises a series of polymetallic skarn bodies with significant resource potential for Sn, W, Zn, and In. Skarn mineralisation in the SD is hosted by low- to medium-grade metasedimentary units forming the so-called Schwarzenberg Gneiss Dome (SGD). Recent exploration, mainly for Sn, W, and In, targeted the large Globenstein, Hämmerlein and Tellerhäuser skarn bodies (several km strike length). Fertile skarn mineralisation in these skarns is related to the late- to post-collisional phase of the Variscan Orogeny (325-295 Ma). Economically important large skarn bodies as well as smaller satellites of the SGD have thus far only been investigated individually, rather than being considered part of a potentially district-wide mineralizing system (~ 12 x 15 km). The Waschleithe skarn in the far north of the SGD is a typical example for a smaller skarn body. Considering its distal position within the SGD it provides valuable insight into district-scale mineral zoning. Mineralisation occurs within two skarn horizons hosted by marble interlayered with mica schists. The sharp contact between skarn and marble is well exposed in historical mine workings. Coarse-grained pyroxene (hedenbergite-diopside), finer-grained subordinate yellowish-green andraditic garnet and Mn-rich pyroxenoids are the dominant constituents of the prograde skarn mineral assemblage. All of them overprint the metamorphic microfabric of the marble. A retrograde skarn assemblage is only weakly developed and consists mainly of ilvaite, epidote, vesuvianite, amphibole, chlorite, quartz, fluorite and hydrothermal calcite. Ore minerals associated with the retrograde mineral assemblage may be grouped into three different assemblages: 1) magnetite, 2) sphalerite, galena, pyrite, and chalcopyrite and 3) scheelite. The retrograde ore mineral assemblages show no association with paragenetically late chlorite, indicating that they formed relatively early during retrograde skarn formation. The marble front, dark pyroxenes, relatively low garnet/pyroxene ratios and the presence of Mn-bearing pyroxenoids indicate that the Waschleithe skarn formed distal to its fluid source relative to skarns with a more proximal mineralogy, such as Hämmerlein. Thus, Waschleithe represents a distal equivalent to the larger skarns of the SGD situated farther to the south. A genetic link between the skarns of the SGD requires a substantial re-evaluation of the size and exploration potential of this mineral system. To test this hypothesis a comprehensive set of mineralogical, geochemical and geochronological data from several skarn bodies of the SGD is currently being acquired.
  • Lecture (Conference)
    Geomünster 2019, 22.-25.09.2019, Münster, BRD

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Publ.-Id: 30699