Vein (geology)

As a transitional deposit a gear is commonly referred to, contains enough ore to be mined as deposit can. In colloquial usage, such deposits are sometimes referred to as " veins ".

Structure of the deposits

However, the deposits are not vein or tubular in most cases, but are separated by the two Salbänder area from the surrounding gangue. From a purely economic standpoint, the deposit will, however, not limited by the Salbänder, but only by the Bauwürdigkeitsgrenze, which may be due to impregnations well beyond the transition boundaries. Veins can be in different, even flat slopes occur ( traps).

Features

The mineral content of vein deposits can have a large bandwidth. While some deposits, such as some barite programs are practically monomineralic, others provide an almost inexhaustible mine for minerals collectors alike Often the economically interesting ore but do not constitute the main component of the Ganges, but the so-called gait, for example, quartz in the gold-bearing quartz veins. If the host rock is not made of silicates, but, for example, limestone, calcite prevails before and gait. This indicates the origin of the gangue minerals from the surrounding rock. While it is often the gangue to " completers minerals " is occurring in all parts of the deposit, so show the metal-containing ore minerals sometimes a typical zonation according to the low position. A familiar example is the non-ferrous metal deposits in Cornwall. Below a copper-rich zone is there a very rich tin mineralization. The knowledge of such law-governed sequences is of great use in the exploration of new deposits.

From prehistory to the Middle Ages numerous vein deposits were discovered by their outcrops ( become visible at the surface ). Even the color striking boulders on gravel banks or streams, or indicator plants that indicate heavy metal content, may be indicative of mineral deposits.

Formation

Can occur in a variety of geological environments vein deposits, such as in tectonically stressed areas like the greywacke zone in the Eastern Alps, near igneous intrusions such as the resin in volcanic igneous rocks, or in archaic greenstone belts. Here, the thickness of the passages is varied between a few millimeters to more than 100 meters. In general, it is assumed that the formation of vein deposits in columns and disorders, provide the mineral- containing solutions or gases (fluids) a transport or deposition trap. The origin of the mineral and metallic components may be very different. You can directly from the host rocks originate ( Lateralsekretion ), or from distant sources, such as magmatic melts, hydrothermal systems or products of rock alteration ( metamorphism ).

Examples

• Yellowknife in the Northwest Territory of Canada, Ballarat, Bendigo and Castlemaine in Australia. This is to gold deposits in archaic and Phanerozoic turbidites.
• Golden Mile at Kalgoorlie (Australia), the Kolar gold field in India, and the districts of Kirkland Lake and Timmins in Ontario / Canada ( gold deposits in greenstone belts archaic ).
• In the Erzgebirge was reduced by Freiberg, starting in the 12th century to 1969, silver, lead and zinc. At various other places until the early 90s of last century, cobalt, nickel, arsenic and uranium were promoted.
• 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.
• Among the most famous districts of transitional deposits in the world belongs in Butte Montana / USA. In more than 20 mines here 20 000 tonnes of silver and 78 tonnes of gold have been 1880-1964, 7.3 million tonnes of copper, 2.2 million tons of tin, 1.7 million tonnes of manganese, 0.3 million tonnes of lead, promoted.
• The upper resin with silver-bearing lead-zinc ores. From the 16th to the early 20th century mining was intense here.