Salsigne gold mine
| Salsigne gold mine | |||
|---|---|---|---|
| General information about the mine | |||
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| Mining technology | Civil engineering | ||
| Funding / total | 120 tons of gold | ||
| Information about the mining company | |||
| Start of operation | 1894 | ||
| End of operation | 2004 | ||
| Funded raw materials | |||
| Degradation of | Gold Silver | ||
| gold | |||
| silver | |||
| Degradation of | silver | ||
| Geographical location | |||
| Coordinates | 43 ° 20 '20.4 " N , 2 ° 21' 40.9" E | ||
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| Location | Chemin de la Fontaine | ||
| local community | Villanière | ||
| Department ( NUTS3 ) | Aude | ||
| republic | French Republic | ||
| Country | France | ||
The Salsigne gold mine is a former gold mine in the southern foothills of the Montagne Noire, 15 kilometers north of Carcassonne in the Aude department in southern France . The mine, which closed in 2004, was the most important gold miner in Western Europe in the 20th century . The extraction methods, however, put great strain on the environment .
Concessions
The mining district of Salsigne extended over a total area of around 200 square kilometers, with concessions for almost 50 square kilometers. In addition to gold, the focus of mining was also on other elements. The concessions of the Salsigne gold mine were lined up immediately to the west of the Orbiel , which had cut into the Mesozoic hull of the southern slope of the Montagne Noire. The following licenses existed:
- Salsigne (awarded from 1877) - 278 hectares - iron (pyrite). Dismantling 1912–1924.
- La Caunette (1879) - 87 hectares.
- Villanière-Narteau (1898) - 684 hectares - Arsenopyrite. No dismantling during the First World War.
- Lastours (1902) - 884 hectares - copper, lead, silver.
- Malabau (1913) - 725 hectares - arsenopyrite, gold, silver, copper.
- Villardonnel (1922) - 386 hectares - arsenopyrite, copper, iron.
- Pujol (1923) - 934 hectares - pyrite, copper, iron.
- Cabrespine - 640 hectares.
geology
The bedrock of the mine is formed by very weakly metamorphic sediments from the Paleozoic Era . These can be subdivided into two sub-ceilings - the Minervois ceiling in the hanging wall and the almost 500-meter-thick Fournes ceiling in the horizontal one . Both nappes overlay the ascending regional metamorphic axial zone of the Montagne Noire. The individual ceiling structures are quite complex (inverse positioning), but overall they can be addressed as lying pleats that had slipped off to the south over the protruding core complex of the Montagne Noire. The dynamic deformations were very intense with several folds and shearings as well as brittle fracture tectonics in the final stage.
The upcoming consists of steep sandstones of the Marcory formation as well as limestone and dolomites of the Calcaires à Archaeocyathus . Both formations come from the Lower Cambrian ( Georgian ) and belong to the southern Fournes Nappe. A little further south, flysch from the Ordovicianan appears with lower incidence values , which from Combe-du-Saut is covered by the Eocene which plunges flat to the south .
In the layers of the Cambrian several styles of mineralization may be encountered, for example, the layer pack sweeping transitions , Tied to the sandstone layers stock works , Verdrängungserze from carbonates and bound to over- or faults ore body , especially in large Abscherhorizonten separating the ceiling stack from Autochthon.
genesis
In the Salsigne gold mine, nine hydrothermal events can be distinguished, which can be separated from each other by tectonic processes. The first four events occurred at the same time as the two ceilings were seated, with the solutions being channeled from ductile and ductile / brittle structures. These include:
- the deposition of arsenopyrite-pyrrhotite-gold associated with biotite
- the overprinting with quartz muscovite
- the precipitation of massive sulphides (arsenopyrite-pyrrhotite-pyrite) and gold associated with chlorite
- a general feldspatization .
The subsequent five events are dominated by a brittle fracture tectonics, which partially revised the existing structures. Initially there was siliconization and the formation of quartz veins. This was followed by four generations of sulphide precipitations, each of which was separated from one another by renewed cracking ( English crack-seal ).
These alternating and pulsating mineralizations were carried by two different types of fluids. The type I fluids, which supplied the majority of the gold and deposited biotite at 450 ° in the low metamorphic bedrock, were of a reducing nature (pH> 7), rich in carbonic acid and alkaline with high levels of H 2 S, but relatively low sulfur fugacity f S 2 . The Type II fluids were responsible for the massive sulphide ores. They are associated with chlorite and only caused a redistribution of the gold. They were acidic in nature (pH <7), had a very high oxygen fugacity f O 2 and a very high sulfur fugacity.
The hydrothermal system in Salsigne was probably associated with late Variscan igneous rocks and was probably initiated by the transition from ductile to brittle or from compression to expansion. A network of shear zones at the base of the ceiling stack and in the hanging wall of the relative autochthon channeled the ore-rich solutions. It should not be a coincidence that Salsigne comes to lie at the intersection of a more than 100 kilometers long shear zone with transverse faults and sheared diving fold structures.
mineralogy
In addition to gold, silver , arsenic , iron , copper , zinc , lead , sulfur and bismuth also occur in Salsigne . The weakly metamorphic Cambrian strata in the vicinity of Salsigne is interspersed with numerous sulphide-impregnated quartz veins that contain the following minerals :
- Arsenopyrite - FeAsS
- Pyrite - FeS 2
- Chalcopyrite - CuFeS 2
- Pyrrhotite - Fe 7 S 8
- Marcasite - FeS 2
- Lead gloss - PbS
- Sphalerite - ZnS
- Bismuthinite - Bi 2 S 3
In addition there are up to 200 other minerals that may be encountered in the gold mine Salsigne, including allophane , aragonite , Arsenolith , Arsenosiderit , azurite , native bismuth, brochantite , native copper, cronstedtite , cuprite , Cyanotrichit , Devillin , Ferberit , Geminit , Gormanit , Hörnesite , ilmenite , jarosite , kobellite , lindackerite , ludlamite , magnetite , malachite , oliveite , parnauite , pharmacolite , rauenthalite , rutile , scheelite , siderite , solid silver, stannite , titanite , vivianite , wolframite , and zálesíite to name just a few examples. Salsigne is also a type locality for the mineral yvonite .
It is assumed that the mineralizing sulphide-rich hydrothermal solutions either come from the Variscan granitoids of the Montagne Noire (such as the Brousses granite ) located almost 10 kilometers to the west or were mobilized by the intrusion heat.
Solid gold and electrum can not be seen with the naked eye because of their small grain size , which is also the reason for their relatively late discovery. The grain sizes are usually between 2 and 4 microns, but occasionally grow to 148 microns. The gold is usually bound to the sulfide minerals, but can also occur freely in microcracks within the sulfides and bismuthinite.
history
Salsigne was sought out in early history for the copper found in chalcopyrite . The Romans then mined the iron-containing minerals for three hundred years (up to the 3rd century ) in the oxidation zone ( iron hat ) of the current open-cast mine , which they roasted in specially built ovens to extract the iron . This dismantling continued with interruptions in the Middle Ages .
Industrial production then began in 1873 and was originally focused on arsenopyrite. Until 1910 the mined ore was shipped to Wales and the arsenic extracted there. At that time Salsigne represented 25% of world arsenic production. The finely ground, arsenic-rich ore was also sold in powder form to vintners for pest control, which is why the entire region now has abnormally high levels of arsenic in the soil and groundwater.
Gold was first discovered in layers of the Cambrian of the southern Montagne Noire in 1892 by Louis Marius Esparseil . Alluvial gold in the Orbiel and other rivers draining the southern section of the Montagne Noire, however, had been known since Roman times and was mentioned by Julius Caesar , for example .
Between its opening in 1892 and its closure in 2004, gold mining has unearthed 120 tons of gold and around 300 tons of silver, an average of just over a ton of gold per year. The remaining gold reserves are estimated at 30 tons. The gold mine was initially operated by the French mining company SMPCS ( Société des Mines et Produits Chimiques de Salsigne ), but then moved to COFRAMINES and MOS, two subsidiaries of the BRGM (Bureau de Recherches Géologiques et Minières), in 1980 .
At the very beginning of the mining history, the rock extracted was still hand-picked. Between 1910 and 1912 the ore was then processed industrially in Combe du Saut am Orbiel (between Lastours and Conques-sur-Orbiel ), initially hydrometallurgical, later pyrometallurgically using cyanation .
From 1950 many Algerians from the Bejaia department worked in Salsigne. Even after the Algerian War , many Algerian workers were hired again in 1962.
In 1991 the gold mine, which was plagued by many strikes and using outdated technology, was closed and liquidated. MOS was then founded in 1992 by an Australian consortium consisting of Eltin Minerals Pty. Ltd. (51%) and Orion Resources (49%) bought.
Despite the modernization carried out under Australian management, between 1999 and 2006 the environmental authority ADEME of Languedoc-Roussillon set about dismantling the plant in Combe du Saut because of the heavy contamination of the soil with arsenic and other heavy metals . The industrial buildings were finally completely demolished and the rubble buried in two landfills. Only the wastewater treatment plants for industrial water remained functional. There is now a renaturation project for the site.
Access to the production well by Villanière was closed, but the conveyor stands still. The Vilanière and Salsigne opencast mines have also been preserved, but the associated shaft has also been blocked here.
Pollution in the Orbiel Valley
The valley of the Orbiel has been permanently polluted by the hundred years of gold mining in Salsigne, in particular by arsenic , a carcinogenic and environmentally toxic element. The BRGM, in charge of detoxification and renaturation, estimates the arsenic load of the Orbiel at 3 tons per year, but a citizens' initiative estimates this amount at 8 tons per year to be much higher.
In 2011, seven years after the mine was closed, arsenic pollution remained in the Orbiel valley. The prefecture of the Aude department then drew up a decree prohibiting the sale of vegetables grown in the Orbiel valley.
In 2013, the Association for the Protection of the Residents of Salsigne and the Orbieltal discovered a canalised watercourse that emerged under the dumps, colored orange-red.
In small mammals such as the wood mouse Apodemus sylvaticus , Algerian house mouse Mus spretus , field mouse Microtus arvalis and house shrew Crocidura russula , Séverine Drouhot and colleagues (2014) were able to detect peak values of up to 18.9 milligrams of arsenic per gram of tissue, a very high concentration of almost 2 percent by weight .
See also
literature
- Vincienne, H. and Mozaffari, C .: Étude micrographique des minéralisations de Salsigne - Aude . In: Bulletin de la Société Française de Minéralogie et de Cristallographie . tape 89 , 1966, pp. 100-106 .
- Descouens, D. and Baffaly, C .: Les phosphates de la mine de Salsigne (Aude) . In: Monde et Minéraux . tape 67 , 1985, pp. 4-5 .
- Descouens, D .: Les minéraux de Salsigne (Aude) . In: Monde et Minéraux . tape 72 , 1986, pp. 20-22 .
- Marcoux, E. and Lescuyer, JL: Les minerais sulfo-arsénisées aurifères de Salsigne - Aude - France . In: Canadian Mineralogist . tape 32 , no. 1 , 1994, p. 159-178 .
- Forner, H. et al .: La mine d'or de Salsigne (Aude) . In: Le Régne Minéral . n ° spécial, 1997, p. 36-60 .
Individual evidence
- ↑ "Salsigne, une Pollution sans répit" (Salsigne, a merciless environmental pollution) Archive link ( Memento of the original from April 28, 2010 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ geze, B .: Languedoc Méditerranéen Montagne Noire . In: Guides géologiques régionaux . Masson, Paris 1979, ISBN 2-225-64120-X .
- ↑ Demange, M. et al .: The Salsigne Au-As-Bi-Ag-Cu deposit, France . In: Economic Geologist . tape 101 , no. 1 , 2006, p. 199-234 , doi : 10.2113 / gsecongeo.101.1.199 .
- ↑ Tollon, F .: Le district aurifère de Salsigne - Aude . Édition de la Société des Mines et Produits Chimiques de Salsigne, 1970, p. 175 .
- ↑ Drouhot, S. et al .: Responses of wild small mammals to Arsenic pollution at a partially remediated mining site in Southern France . In: Science of the Total Environment . tape 470-471 , 2014, pp. 1012-1022 .
