New Massive Sulphide Deposit in the Harz?
Friday, 4. September 2009, 09:13:24
Hat tip to geoberg.de (in German)
The Harz Mountains in Germany have a long history of mining. Especially famous are the Mines of Rammelsberg near Goslar. These mines are a UNESCO World heritage site, known for continuous mineral extraction over a period of more than 1000 years until they finally closed down in 1988.
Now Harz Minerals (from Hamburg), a fully owned subsidiary of Scandinavian Highlands, has obtained an exploration licence for a large part of the Harz Mountains covering ca. 1250 km2. About 2 km west of the Rammelsberg mines (in the Gosetal) there are signs of a deposit maybe even larger than the Rammelsberg deposit and of a similar nature, so naturally enough the exploration targets are base metals, gold, silver and barite.
The Rammelsberg and Gosetal ores are massive sulphide deposits formed at the bottom of the Proto-Tethys Ocean that existed between the continents Laurussia and Gondwana in the Devonian (Devonian period = 416 - 359.2 million years ago). This ancient ocean existed from the latest Ediacaran to the Carboniferous (550-330 million years ago), and was closed when Laurussia and Gondwana collided with each other resulting in the so-called Variscan orogen, where a few microplates also got in between and consumed by the mountain building episode. The continental collision probably begun around 380 million years ago.
Image: Wikipedia
Note that the term Hercynian is widely used as a synonym for the Variscan. In Germany Hercynian, however refers to a Cretacious tectonic event (with northwest to southeast strike direction - like the thick black lines on the map below).
Massive sulphide deposits are not uncommon in the Variscan belt, and the main massive sulphide deposits are indicated on the following map from a handout about “The Gosetal Anomaly – a Rammelsberg twin?” that can be downloaded from the Scandinavian Highlands page about their Harz project.
Unfortunately there is no accepted definition of the term ‘massive sulphide’, but I would like to refer you to the description at http://www.encyclopedia.com/doc/1O112-massivesulphidedeposits.html . Common basic similarities shared are: cold aqueous fluid (commonly sea water) is drawn down through sediments or igneous rocks and its temperature is raised by an underlying heat source. This heat source is usually a relatively shallow magma chamber or a recent igneous intrusion.
In the Variscan context I take the deposits to be marine (hydrothermal) deposits (depth at formation estimated to be deeper than 400 m), and thus older than the Variscan orogen (when they were uplifted). The deposits marked on the map are all well described in various papers. Similar deposits are by the way found in the Moroccan Variscan Belt associated with intrusions emplaced 330 Ma ago.
The Harz Mountains in Germany have a long history of mining. Especially famous are the Mines of Rammelsberg near Goslar. These mines are a UNESCO World heritage site, known for continuous mineral extraction over a period of more than 1000 years until they finally closed down in 1988.
Now Harz Minerals (from Hamburg), a fully owned subsidiary of Scandinavian Highlands, has obtained an exploration licence for a large part of the Harz Mountains covering ca. 1250 km2. About 2 km west of the Rammelsberg mines (in the Gosetal) there are signs of a deposit maybe even larger than the Rammelsberg deposit and of a similar nature, so naturally enough the exploration targets are base metals, gold, silver and barite.
The Rammelsberg and Gosetal ores are massive sulphide deposits formed at the bottom of the Proto-Tethys Ocean that existed between the continents Laurussia and Gondwana in the Devonian (Devonian period = 416 - 359.2 million years ago). This ancient ocean existed from the latest Ediacaran to the Carboniferous (550-330 million years ago), and was closed when Laurussia and Gondwana collided with each other resulting in the so-called Variscan orogen, where a few microplates also got in between and consumed by the mountain building episode. The continental collision probably begun around 380 million years ago.
Image: Wikipedia
Note that the term Hercynian is widely used as a synonym for the Variscan. In Germany Hercynian, however refers to a Cretacious tectonic event (with northwest to southeast strike direction - like the thick black lines on the map below).
Massive sulphide deposits are not uncommon in the Variscan belt, and the main massive sulphide deposits are indicated on the following map from a handout about “The Gosetal Anomaly – a Rammelsberg twin?” that can be downloaded from the Scandinavian Highlands page about their Harz project.
Unfortunately there is no accepted definition of the term ‘massive sulphide’, but I would like to refer you to the description at http://www.encyclopedia.com/doc/1O112-massivesulphidedeposits.html . Common basic similarities shared are: cold aqueous fluid (commonly sea water) is drawn down through sediments or igneous rocks and its temperature is raised by an underlying heat source. This heat source is usually a relatively shallow magma chamber or a recent igneous intrusion.
In the Variscan context I take the deposits to be marine (hydrothermal) deposits (depth at formation estimated to be deeper than 400 m), and thus older than the Variscan orogen (when they were uplifted). The deposits marked on the map are all well described in various papers. Similar deposits are by the way found in the Moroccan Variscan Belt associated with intrusions emplaced 330 Ma ago.
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http://scandinavian-highlands.com/index.php?id=1584
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https://www.e-sga.org/index.php?id=199
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http://www.geoberg.de/text/geology/08032203.php
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