Upper Harz veins

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Overview map of the Harz

Among the Oberharzer veins , a system or network is meant a plurality of approximately parallel and for the most part mineralized , gait disturbances in the northwestern upper resin . The distribution area extends from north to south from the northern Harz border deferral to an extended line between Lerbach and Riefensbeek-Kamschlacken . In the west it is bounded by the western Harz Rim fault near Seesen , in the east by the Brocken granite east of Altenau . These veins are characterized on the one hand by their similar structure, namely brushing , collapsing and paragenesis , and are therefore to be delimited from the veins in the central Harz region ( St. Andreasberg - Bad Lauterberger district).

The Upper Harz ore veins were the subject of intensive mining for lead , zinc , silver and copper from the early Middle Ages with an interruption in the late Middle Ages and from the beginning of the modern era to the end of the 20th century .

Formation of the Upper Harz veins

Today's Harz was mainly created by sandy and clayey , less often calcareous deposits in the Devonian to Pennsylvania , as well as the Rhenish Slate Mountains .

In the process, an alternating sequence of clay slate and greywacke formed more than 1000 meters thick . In Pennsylvania, these layers were folded by tectonic processes. The anticlines and synclines of this " Clausthaler Kulmfaltenzone " were aligned in a typical north-east-south-west course, which is called " Variscan painting". In the subsequent recent geological history, so-called expansion tectonics occurred, as a result of which the Harz sank as a rift structure from north to south. The gait disturbances developed as dislocation surfaces of the hanging clods shifted against each other . As a result, the duct crevices border on younger layers from north to south, in the northern Upper Harz the oldest rocks of the Famennium and Frasnium are known as the so-called "Upper Harz Devon Saddle". The faults, which are less than a meter to several hundred meters thick, typically run in an arc in a west-northwest-east-southeast direction, which is known as the Hercynian strike . According to the historical classification of ore mining, they therefore belong to the Spatganges . The dip from south to north is between 90 and 70 gon ( tons to steep passages ).

Originally, the Upper Harz veins were partially filled with completely crushed secondary rock. In a multi-phase process, hot (250–300 ° C), metal-containing solutions (so-called hydrotherms ) from deep rock layers came into contact with near-surface, sulfur-containing solutions. It came into the aisle columns sequentially to precipitation of metal sulfides such as galena and sphalerite , which formed the Erzfüllung. The main phase of ore formation dates back around 180 million years. In addition to the ore minerals, the gangues such as quartz , calcite , barite and iron minerals were also deposited.

Phases of mineralization

  • Preliminary phase I : Beginning probably in Rotliegend , precipitation of siderite , hematite , dolomite , as well as some chalcopyrite and pyrite . Quartzization.
  • Main phase II : Approximately from the toarcium to the aptium , enlargement of the duct volume, excretion of galena, zinc blende and copper pebbles in a thickness of up to several meters, as well as occasional pale ore .
  • Main phase III : Temporal classification not yet established, reopening of the duct gaps, formation of massive, weakly mineralized (pyrite, pale ore) quartz, calcite and barite fillings.
  • Post phase IV : recrystallization processes , formation of secondary mineralization .

Paragenesis of the Upper Harz veins

Lumps of ore from the Silbernaaler Gangzug

So far, all attempts to derive regularities for the filling of the Upper Harz veins have failed. This was particularly true in the phase of intensive prospecting in the 1920s, when most of the known deposits were running out. Decisive for the deposition of ores was the presence of open duct volumes on a duct fault at a certain point in time and the respective supply of hydrothermal mineral solutions.

The filling of the veins differs according to the following aspects:

  • Superordinate distribution of minerals from local nests, over elongated rubble and lenses to massive ore falls with great thickness.
  • Form of the ore minerals in terms of crystalline formation and degree of adhesions or impregnations of the gaits and adjacent rock debris and rubble. According to their appearance, these were divided into “solid”, “ribbon”, “ring”, “cockade” or “ breccia ores ”.
  • Ore minerals: As the most important galena, sphalerite, chalcopyrite, pyrite, pale ore, siderite and hematite. Many secondary minerals were created through conversion, e.g. B. Limonite , solid silver, malachite and azurite . Hundreds of very rare ore minerals have been discovered.
  • Gaits: quartz, calcite, dolomite, barite, as well as secondary rock debris e.g. B. Grauwacke.

Paragenesis differs greatly from one another in the Upper Harz veins investigated so far, and this also applies to the local distribution of the ores. For example, while the silver-rich lead galena on the ore resources of the Burgstätter and Silbernaaler Gangzug decreased towards the depths and the spread of zinc blende increased until it finally dominated, the zinc blende was already present for days on the Lautenthaler Gangzug. The location and distribution of the ore resources over the course of the vein fault is also obviously irregular and not necessarily tied to stockpiling zones. Accumulations of ores are completely absent on certain ducts and, if available, are largely dispersed .

Systematics and description of the Upper Harz veins

Location of the most important gangways and mines in the area around Clausthal-Zellerfeld

Since the emergence of scientific deposit research in the 19th century , the systematization of the Upper Harz veins into so-called vein trains has established itself . The term “gangway train” is mainly used in the Upper Harz Mountains and arose less from geology than from the early modern “mine trains” or “trains” for short. This referred to local areas, although the mines lying one behind the other like a string of pearls were of course built on the same ore or on adjacent side tunnels. Some of the mine trains also had names that were derived from the mines that existed there, e.g. B. "Himmlisch-Heerer Zug" (Heavenly Army Train), which was later renamed the Mirror Valley Gangzug . Trains are also known in other mining areas, e.g. B. Eisenzecher Zug in Siegerland or the Emser Zug near Bad Ems .

The corridors combine a main corridor with the parallel side corridors nearby. The side aisles can run in the horizontal as well as in the hanging wall of the main aisle, branch off from this (opening zone) or reunite with it, as well as cross (“cluster”). In some cases, aisle trains also unite to form a new aisle train or branch off from one another or fork. Side aisles can also touch several aisle trains. The gangways are separated from each other by interference-free areas in the horizontal and hanging walls.

The following corridor systems are known from north to south in the Upper Harz to Stoppel:

See also

literature

  • Torsten Schröpfer: Treasure trove: Interesting facts about the West Harz mining and metallurgy . 1st edition. Pieper, Clausthal-Zellerfeld 2000, ISBN 3-923605-08-0 .
  • Klaus Stedingk: Lautenthal: mountain town in the Upper Harz; Mining and metallurgical history . Bergwerks- und Geschichtsverein Bergstadt Lautenthal from 1976, Lautenthal 2002, ISBN 3-00-009504-7 .
  • Dieter Stoppel: Course map of the Upper Harz . Federal Institute for Geosciences and Raw Materials, 1981, ISSN  0540-679X .

Individual evidence

  1. ↑ Dieter Stoppel: course map of the Upper Harz . 1981, pp. 17-40