Aisle deposit
A vein deposit is usually referred to as a vein that contains enough ore to be mined as a deposit . In colloquial usage , such deposits are sometimes referred to as "ore veins".
Construction of the deposits
As a rule, however, the deposits are not vein-shaped or tubular, but are separated flatly from the surrounding deaf rock by the two salbands . From a purely economic point of view, however, the deposit is not limited by the sails, but only by the building value limit , which, due to impregnation, can be well beyond the aisle boundaries. Veins can occur in various, including shallow, slopes ( traps ).
features
The mineral content of vein deposits can vary widely. While some deposits, such as some barite -walks are virtually monomineralic, others provide a virtually inexhaustible source for mineral collectors. However, often do not form the economically interesting ores (the Erzmittel so-called) the main part of the corridor, but the so-called gait (or the deaf remedy), for example quartz in the gold-bearing quartz veins spread all over the world . If the host rock does not consist of silicates but, for example, limestone , calcite is the predominant gangue. This indicates the origin of the gangue minerals from the surrounding rock.
While the gangue is often "run-through minerals" that occur in all parts of the deposit (in addition to quartz and calcite also dolomite , fluorite , barite etc.), the metal-containing ore minerals sometimes show a typical zoning according to the depth . A well-known example is the non-ferrous metal deposits in Cornwall . Below a copper-rich zone there is a very rich tin mineralization. The knowledge of such lawful sequences is of great use in the exploration of new deposits.
On the other hand, the various mineral associations ( paragenesis ) in a duct are often bilaterally symmetrical, that is: Paragenesis 1 covers the opposite duct margins (the salband ), this in turn is covered by paragenesis 2, etc., up to paragenesis n in the middle of the duct . This is explained by the fact that the already “healed” passage is repeatedly torn open by tectonic movements and again offers space for hydrothermal solutions with a different composition and temperature. The minerals in the middle of the corridor are therefore the youngest (and mostly precipitated at the lowest temperatures).
From prehistory to the Middle Ages , numerous dike deposits were discovered based on their outcrops ( becoming visible on the surface of the earth ). Color conspicuous rubble on gravel banks or streams, or pointer plants that indicate heavy metal content can also indicate ore deposits.
Emergence
Dike deposits can occur in a wide variety of geological environments, for example in tectonically stressed areas such as the Grauwackenzone of the Eastern Alps , in the vicinity of igneous intrusions such as in the Harz Mountains , in volcanic igneous rocks , or in archaic greenstone belts . The corridors vary in thickness from a few millimeters to more than 100 meters.
It is generally assumed that dike deposits form in crevices and faults that offer mineral-containing solutions or gases ( fluids ) a transport route or a deposition trap. The origin of the mineral and metallic components can be very different. They can come directly from the adjacent rock ( lateral secretion ), or from sources far away, such as igneous melts , hydrothermal systems or products of rock transformation ( metamorphosis ).
Examples
- Yellowknife in the Northwest Territory of Canada, Ballarat , Bendigo and Castlemaine in Australia. These are gold quartz veins in archaic and phanerozoic turbidites .
- Golden Mile near Kalgoorlie (Australia), the Kolar gold field in India, and the districts of Kirkland Lake and Timmins in Ontario / Canada (gold deposits in archaic greenstone belts).
- In the Ore Mountains around Freiberg , silver , lead and zinc were mined from the 12th century until 1969 . Cobalt , nickel , arsenic and uranium were also mined at various other locations up to the beginning of the 1990s .
- The tin- tungsten and tin-silver deposits in Bolivia have been mined since the 16th century, initially because of their exceptionally rich silver deposits, such as the Cerro Rico in Potosí .
- Butte in Montana / USA is one of the most famous districts of dike deposits in the world . In more than 20 mines 7.3 million tons were here 1880-1964 copper, 2.2 million tons of tin, 1.7 million tonnes of manganese , 0.3 million tonnes of lead , 20 000 tonnes of silver and 78 t gold promoted.
- The upper resin with silver-containing lead-zinc ores. From the 16th to the beginning of the 20th century, intensive mining was carried out here.
See also
literature
- Anthony M. Evans: Ore deposit studies Ferdinand Enke Verlag, Stuttgart 1992. ISBN 3-432-99801-5 .
- Emil Kraume: 1000 years of Rammelsberg. PREUSSAG Aktiengesellschaft, Public Relations Department, Goslar