Der Hämmerlein Skarn im Erzgebirge: Lithologien und Sn-Deportment einer polymetallischen Sn-In-Zn Komplexerzlagerstätte


Der Hämmerlein Skarn im Erzgebirge: Lithologien und Sn-Deportment einer polymetallischen Sn-In-Zn Komplexerzlagerstätte

Kern, M.; Kästner, J.; Gutzmer, J.

The Hämmerlein orebody is part of the world class Tellerhäuser deposit in the Erzgebirge, Germany, and represents a compositionally complex polymetallic Sn-In-Zn skarn. Current resources amount to 100000t Sn at a cut-off grade of 0.2 wt.%. In addition, 2100 t of In and 270000t of Zn have been estimated. In the late 1970s, 50000t of ore from the Hämmerlein orebody were mined and processed experimentally in a pilot plant, but grade and recovery remained below expectations. Cited reasons for poor recovery include the complex mineralogy and variability in grain sizes of ore minerals [1].
A consortium of German research institutions currently conducts new beneficiation experiments on the Hämmerlein orebody. Determination of the Sn deportment and the characterization of the different lithological (skarn) units are the first steps in this process. For this purpose, three transects in the central part of the Hämmerlein orebody were mapped and a suite of hand specimen collected to represent all relevant lithotypes within the studied part of the orebody. Thin sections were prepared and analyzed using the Mineral Liberation Analyzer (MLA) to obtain quantitative data about mineralogy, mineral grain sizes, intergrowths, and associations. The remaining material of the hand specimen was crushed to 99% <250µm. This granular material was split to produce grain mounts for further mineralogical studies and in order to prepare sample powders for geochemical analysis.
The Hämmerlein skarn orebody can be subdivided into the following three macroscopically distinct lithotypes: 1. magnetite-dominated (40 – 80 wt.% magnetite), 2. sulphide-dominated (> 20 wt.% sphalerite) and 3. silicate-dominated (> 60 wt.% silicates). In the silicate-dominated unit a gradual transition of different silicate minerals enables further discrimination of a chlorite-rich, an amphibole-chlorite-rich, an epidote-pyroxene-rich and a garnet-rich subunit. The hanging and footwall are best described as mica schist and gneiss, respectively.
The primary host mineral for Sn is cassiterite (SnO2) with grain sizes between 1µm and 1mm. Some of the cassiterite has fibrous crystal habit. Significant amounts (ca. 1.4 wt.%) of coarse-grained (50µm to 1mm) cassiterite is present in the chlorite subunit. The amphibole-chlorite subunit contains an average of 0.3 wt.% cassiterite. Samples from other parts of the Hämmerlein orebody indicate significant amounts of cassiterite in the magnetite- and the sulphide-dominated lithotypes as well.
Malayaite (CaSnSiO5) is the second most abundant Sn mineral. It appears in fine-grained aggregates in the amphibole-chlorite subunit and in the magnetite-dominated ore type reaching concentrations of ca. 0.1 wt.%. Notable Sn concentrations were detected by EDX in some examples of titanite, epidote and iron oxides. However, the total amount of Sn in these minerals accounts for less than 10% of the total Sn content of the deposit.
Our preliminary results illustrate that the Sn mineralisation of the Hämmerlein skarn is indeed very complex. Cassiterite dominates, but other minerals (most notably malayaite) do contribute significantly to the deportment. Further studies will aim to quantify the variability of deportment and other resource characteristics, in order to guide mineral processing test work.

  • Invited lecture (Conferences)
    ResErVar Netzwerktreffen Clausthal, 24.-29.05.2016, Clausthal, Deutschland

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Publ.-Id: 25484