Bad Grund, Badgrund


Main commodities: Zn Pb Ag
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The Bad Grund vein-style zinc-lead-silver deposit is located 15 km SW of Rammelsberg on the northern edge of the Harz Mountains, 18 km south of the city of Goslar and 120 km south-east of Hannover in central Germany.

The mineralisation at Bad Grund occurs as dilation veins in Carboniferous flysch. Within 10 km radius, 34 Mt of ore has been produced at these grades from Bad Grund and other similar veins over a period of ~1000 years, although zinc was only extracted over the last 150 years.

The mineralisation is found within sections of nineteen NNW trending fault zones, which are individually up to 70 m wide, and extend over an interval of up to 20 km in length.

The wall rocks of the ore are generally Lower Carboniferous greywackes and clay-slates of the Culm Series. In the northern part of the district, ore is also found in Devonian slates, sandstones and dolerites.

The host sequence was folded during the Variscan orogeny. The veins are part of a late to post orogenic system of NW-SE striking extensional faults with down-throws reaching several hundred metres on individual faults. The fault planes have undulating surfaces and are only mineralised in certain locations. The wall rocks have undergone hematite, silica, dolomite and ankerite alteration, indicating the passage of a variety of fluids. The vein-fill is banded and drusy.

Mineralisation commenced with a hematite-ankerite-siderite-Fe-Cu phase which was subsequently silicified, followed by the main zinc mineralisation with sphalerite, lesser galena and minor quartz. As tectonic activity increased, the main lead phase ensued with galena accompanied by calcite-quartz, siderite-dolomite and barite.

The orebodies are long exhausted, (the last mine closed in 1994) although the old diggings are partly accessible and there is a local museum.

Total historic production from the Bad Grund vein system amounted to:

      7 Mt @ 10% Zn, 2.4% Pb, 30 g/t Ag

The most recent source geological information used to prepare this summary was dated: 1996.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
de Graaf, S., Luders, V., Banks, D.A., Sosnicka, M., Reijmer, J.J.G., Kaden, H. and Vonhof, H.B.,  2020 - Fluid evolution and ore deposition in the Harz Mountains revisited: isotope and crush-leach analyses of fluid inclusions: in    Mineralium Deposita   v.55, pp. 47-62.

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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