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Rio Tinto Mines - San Antonio, Planes, Cerro Colorado, Salomon, Pozo Alfredo, Corta Atalaya, San Dionisio, Filon Norte, Filon Sur, Dehesa, Lago, Mass Valle |
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Huelva, Spain |
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Cu S Ag Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
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The Rio Tinto group of cupriferous pyrite deposits in Huelva, Spain, are the best known ores in the 230 km long Hispano-Portuguese (Iberian) Pyrite Belt and have been exploited for more than 3000 years. They are located just to the west of the town of Nerva, 65 km NE of the Atlantic port of Huelva in the province of Huelva, Andalucia #Location: 37° 42' 2"N, 6° 34' 44"W.
History - The Rio Tinto mines date back to the Tartessians and the Iberians who were known to have started mining for silver during the latter part of the Bronze Age before 1000 BCE, possibly as early as 2000 BCE. It has been suggested spectacularly coloured copper oxides may have been mined as early as 3000 BCE. The Phoenicians, who founded the port of Gadir, now Cádiz, in 1100 BCE, traded with the Tartessians, including for silver suspected to have originated from Rio Tinto. They are known to have also overseen the mining of silver at Rio Tinto after 800 BCE. By 700 BCE, the silver exported from the Rio Tinto mines had become so abundant that it depressed the value of silver bullion in the Assyrian world. However, in 573 BCE, after the Babylonian king Nebuchadnezzar's 13-year siege and the eventual fall of Tyre, the Phoenician trade with Tartessos was severed. They were replaced by the Phoceans from Ionian Greece, who traded wine and olives for silver from Rio Tinto.
In 535 BCE, the surviving Phoenician outpost at Gadir was defeated in battle by the Carthaginians, who set about extending their own empire, and destroyed the city of Tartessos. In 205 BCE, at the end of the second Punic War, the Romans had ousted the Carthaginians from what was to become the Roman province of Baetica, roughly corresponding to the current Andalucia. Prior to taking control of Baetica, the Romans had paid 'over the odds' for copper, gold and silver from Phoenician, Greek and Carthaginian traders who in turn were sourcing the metals from the Tartessians. When the Romans arrived, the Rio Tinto mines were already ancient, having been exploited for up to 2000 years, but even so only a small amount of the available ore had been exploited. Mine workings were only superficial, mainly exploiting the oxide zone and were seldom more than a few metres deep, although hundreds, possibly thousands of these primitive workings are said to be evident in the region. The Romans set about systematic prospecting, overseeing extensive organised mining, and developing new mining and smelting technology, all of which greatly increased the size, efficiency and output of the mines. Mining and dewatering via elaborate water wheel systems was undertaken to depths of >80 m. Within a few years of arrival, over 50 working mines had been established within 100 km to the west and north of Rio Tinto. Prior to the Roman's arrival, silver had been the sole product, but during their occupation copper production was important, although the slags suggest the tonnage of Ag versus Cu ore was ~15:1. However, following the death of Marcus Aurelius in 180 CE, Roman influence and activity in Andalucia declined until 410 CE when the Visigoths sacked Rome and the Romans withdrew from the Iberian peninsular (Hispania). Under the Visigoths, there was only very limited mining activity at Rio Tinto. This was largely because the engineers with the expertise to run the mines were part of the army which had departed, leaving behind nobody with the necessary skills to maintain the systems or technology installed by the Romans. In the ~600 year Roman period, slag heaps covering an area of ~2500 x 200 m and averaging 6 m in thickness, totalling ~6 Mt of slag, were accumulated (Rothenberg and Palomero, 1986). Two types of slag have been differentiated, the first attributed to the silver ore, contains <300 ppm Cu but ~1.2% Pb, and the second, from copper ore has >1000 ppm Cu. The silver ores were from the lower gossan oxide zone, whilst the copper ore was from a supergene sulphide zone below the gossan (Rothenberg and Palomero, 1986), as described below. Sampling of the slag dumps and underlying bedrock below has shown that copper and some silver and gold has been strongly leached over the last 1400 years, with the Au and Ag redeposited in the upper 2 to 4 m below the base of the dumps, whilst Cu has migrated to greater depths.
In 711 CE, Islamic Moors of Berber descent from northern Africa crossed the Strait of Gibraltar, and by 756 CE had conquered Christian Visigothic Hispania, which then became known as al-Andalus. The Moors were more interested in arts, science and architecture and allowed the abandonment of the mines, including Rio Tinto. From ~1030 CE, internecine warfare for power over the Caliphate in al-Andalus led to the decline of the Moors and by 1492 most of their territories had been lost to the Catholic Castile-Aragón alliance that would become Spain.
In 1556, the newly crowned King Felipe II of Spain ordered Francisco de Mendoza, a member of the Council of Finance, to mount an expedition to locate inspect and report on the Rio Tinto and other abandoned Roman mines in southern Spain which might be resurrected to generate revenue for the crown which was in finacial difficulty. During the expedition, while investigating old workings to which they had been directed by local inhabitants "they cleared a ridge and saw ahead of them a network of valleys in which great mounds of slag stood in dark contrast to the green shrub-covered hillsides. As they rode on they recognised ... the signs of ancient Roman occupation: carved columns, the dressed stone of tumbling walls and immense drainage adits emerging from the hill-face. They had rediscovered some of the greatest mines of the ancient world" (Avery 1974). Never-the-less, bureaucacy and its relatively remote location stifled any development. Over the next 170 years, although a number of concessions were granted for mining at Rio Tinto by the Council of Mines, all came to nothing. The river draining the deposit, known as the Rio Tinto because of its red colour, was reported in 1556 by one of Mendoza's subordinates, a priest, Diego Delgado, to dissolve any iron put into it, and to replace it with copper (Avery 1974). In 1727 a small operation was initiated to produce blister copper from scrap iron placed in vats which were filled with water pumped from the Roman workings. Various attempts were made to dewater the Roman mines to restart operations by companies granted rights by the the Spanish crown. However, amidst long running litigation between those parties, little was achieved, other than sporadic continuation of small vat-leach operations. By 1783, the Spanish government took over management of the mines, and at the end of the century, the mines were producing >10 000 tonnes of copper sulphides per annum. However, production declined due to poor management and were halted from 1808 to 1814, during Spain's War of Independence against Napoleon. Following that war, the Spanish government granted a 20-year lease from 1829 to 1849 to the Marquis de Remisa, a Catalan banker. On the expiry of this lease in 1850, when annual production was 25 000 tons of sulphides per annum, the Spanish government resumed management of the mines. Production continued to increase for a number of years, but by 1870, after multiple problems, operations ceased and the Spanish crown sought new investors. A London based syndicate, the Rio Tinto Company, led by Hugh Matheson, was formed in 1873, to purchase the rights to the Rio Tinto concession, which were granted by the Spanish government. Major investment was put into developing underground operations, a large scale open pit, associated infrastructure, smelters and a rail line to Huelva on the coast. By the end of the 1880s, Rio Tinto was the world's leading producer of copper, providing 8% of world supply in 1887. Initial mining had included underground operations at Filón Norte between 1880 and 1894, with subsequent work concentrated on open pit mining at Salomón, and at Lago and Dehesa at Filón Norte. In 1940 underground open-stoping commenced in the Quebrantahuesos zone and continued until 1970. The Spanish Civil War, between 1936 and 1939 saw the mine occupied by insurgent forces led by General Francisco Franco who used copper production to secure arms from the Axis powers. Control over the the Rio Tinto Company's Spanish assets had been lost, and was never effectively regained. In 1954, after lengthy negotiations through Franco, the Rio Tinto Company sold its interest to a new Spanish company, Compañia Española de Minas de Riotinto, S.A., in which it retained a minority one third share. In 1966 a reorganisation of operations and structure resulted in a change of name to Río Tinto Patiño, while Minas de Riotinto was the operating entity. Between 1964 and 1967 an exploration campaign was carried out to delineate the large low grade stockwork that constitutes the Cerro Colorado copper deposit, with mining commencing in 1968 (see below). In 1977, after a further shareholder reorganisation, Río Tinto Patiño became Rio Tinto Minera SA. and the operating company. Mining continued until 1987 when low copper prices forced the closure of the copper plant and a reduction of mining operations. The Cerro Colorado operation was restricted to mining and treating gossans for gold and silver, at a rate of 2 Mtpa of oxides, before all production was temporarily halted in 1990. In 1992, the British based Rio Tinto Company, now RTZ plc, sold its residual interest to Freeport McMoRan Inc. The latter closed the mine in 1995 and focussed investment on the smelter in Huelva, while the mine was purchased by a workers' cooperative, Minas de Rio Tinto SAL. However, the mine was closed once more in 2001, again due to the low copper price, and placed on care and maintenance. Two attempts to restart the operation by Spanish and Australian companies in 2004 and 2006 respectively were unsuccessful, before EMED Mining Public Limited was successful in 2008 in receiving the necessary regulatory approvals and finance. In 2015, EMED became Atalaya Mining plc, and in 2016 commercial mining commenced and continues (2022). Since Roman times, more than 140 Mt of copper ore is estimated to have been mined (Acheson et al., 2013).
The Hispano-Portuguese (Iberian) Pyrite Belt lies within the Herecyinian Fold Belt of the southern Iberian Peninsula, and extends for some 230 km in a generally east-west strike direction, from Seville in Spain to the east, to Casa Verde in Portugal to the west, with a width ranging from 35 to 50 km. It embraces around 85 known deposits containing a mined + reserve tonnage of some 1.75 Gt of ore with 14.6 Mt Cu, 13 Mt Pb, 34.9 Mt Zn, 46 188 t Ag and 887 t Au. The massive sulphide deposits are part of a Devonian to Carboniferous (Famennian to early upper Visean) volcanogenic-sedimentary complex comprising calc-alkaline felsic volcanic rocks (three sequences of dacitic-rhyolite pyroclastics, lavas and reworked tuffs dated at 385±40 Ma) and intercalated tholeiitic-alkaline mafic volcanics (basic lavas, dykes and sills), sedimentary rocks (purple-blue shale, pelitic black shale and sandstone), sedimentary 'exhalites' (chert and jasper) and manganese rich beds. This whole complex is overlain by thick Carboniferous Culm Formation turbidite facies slates and greywackes. The basement is an apparently conformably underlying succession of Upper Devonian slates, quartzites, sandstone, limestone and conglomerate.
The massive sulphides of the Iberian Pyrite Belt occur within two mineralised stratigraphic levels (the lower or middle of the three dacitic-rhyolite sequences of the volcanogenic-sedimentary complex) and are found either directly in the black shale unit of the volcanogenic-sedimentary complex, or resting on rhyolitic volcanic facies, commonly separated from the felsic volcanics by a thin pelitic layer. Mineralisation appears to be within shallow submarine facies.
The Rio Tinto orebodies are associated with an anticlinal core of volcanic rocks framed by the surrounding overlying Culm Beds. The deposit occurs at the transitional contact between i). a lower mafic volcanic unit composed of andesitic and spilitic pillow lavas and dolerite sills intercalated with bands of slate and chert of Lower Carboniferous (Tournaisian) age, and ii). the overlying felsic volcanic unit composed of quartz-keratophyre and/or rhyolite lavas and pyroclastic rocks, formed by submarine volcanic activity in the Lower Carboniferous (Visean) period. The felsic volcanics grade upwards into hematitic volcanic dust, sedimentary rocks and carbonaceous slates of the Upper Visean Culm Formation (Dunning, 1989).
The exploited sulphide deposits are found in the eastern half of this east-west trending volcanic anticline, centred on what is now the main Cerro Colorado pit, on the flanks of which are the historic mine workings. This anticline was formed during the Hercynian orogeny, and has steep limbs and an axis that plunges at 10° to the east. The ores of the district are interpreted to have originally formed an almost continuous unit of massive to semi-massive sulphides some 5 km long, by 750 m wide and ~40 m thick, accounting for an estimated 500 Mt of ore. All bar the small carbonaceous slate hosted Mass Valle ores are stratigraphically related to felsic pyroclastics, associated with underlying 'chimneys' defined by stockworks of small sulphide veins within a halo of chloritic, sericitic and silica alteration. Weathering over an extended period formed a goethite-limonite gossan, an oxidised cap and an underlying 20 to 30 m thick layer of supergene sulphides, mainly gold and silver-bearing chalcocite-covellite, overlying massive, semi-massive and irregular pyrite and chalcopyrite stockworks. The hill on which the main red pre-mining gossan cap outcropped was named 'Cerro Colorado' (i.e., 'Red Hill').
The main deposits exploited represented two main forms of mineralisation. The San Dionisio orebody, for example, is composed of both types, namely a tabular massive pyritic sulphide body which has a 1200 m strike length and is 50 to 60 m thick, and a stockwork mass which has a 600 to 700 m east-west surface dimension, is 200 m thick and extends down plunge for 600 m. The stockwork is in the footwall of the stratabound massive pyrite body.
In 1990 there were four mines exploiting the Rio Tinto orebodies, two open pits and two underground operations. The open pits were the Cerro Colorado - Salomon and Corta Atalaya, while Pozo Alfredo and San Antonio - Planes are underground. The open pit Corta Atalaya and underground Pozo Alfredo are both developed on the San Dionisio orebody. Corta Atalaya (in the late 1980's) extracted ore with 48% S and 0.8% Cu from the stockwork ores. Pozo Alfredo ore averaged around 1.35% Cu. San Dionisio is to the west of the Cerro Colorado - Salomon open pit.
The Cerro Colorado-Salomon pit was started in 1968 on a reserve of 39 Mt @ 0.8% Cu, plus the gossans that formed the top of Cerro Colorado, above the sulphides, containing 18 Mt @ 2.4 g/t Au, 42 g/t Ag. Remaining reserves in 1990 were 200 Mt @ 0.52% Cu. Mining since 1995 was focused on the Cerro Colorado - Salomon open pit and the adjacent San Lucas pit, with 25 Mt @ 0.57% Cu having been mined between 1995 and 2001. The final pit in 2001 was 1560 m long, 850 m wide and 230 m deep and covered an area of about 200 ha. Within this pit, altered, grey, felsic volcanics host a major pyrite-chalcopyrite stockwork, part of which extends below the felsites into mafic volcanics. Alteration closest to the stockworks is chloritic passing to sericitic and distal silicic. The Cerro Colorado and Salomon (or Cerro Colorado West and Cerro Colorado East respectively) sections of the combined pit have differing mineralogical characteristics. At Cerro Colorado West, chalcopyrite is the dominant copper mineral, associated with pyrite and some covellite, with arsenic present in arsenopyrite and tennantite. It is also characterised by lower copper and sulphur grades, higher metallurgical recoveries and concentrate grade, and lower contaminant element grades. Historic plant feed grades were 0.46% Cu 0.12% Zn, 5.11% S, 139 ppm As, 42 ppm Sb, 8 ppm Bi. In contrast, Cerro Colorado East (Salomon) also contains chalcopyrite, but has significantly more pyrite and covellite. Contaminants are present in arsenopyrite, tennantite, sphalerite, galena and stibnite, with some mercury in the pyrite. Resources in tis section of the deposit are characterised by their higher copper and sulphur, lower metallurgical recoveries and concentrate grade, and higher contaminant element grades. Historic plant feed grades were 0.78% Cu 0.17% Zn, 34.5% S, 711 ppm As, 94 ppm Sb, 60 ppm Bi.
The Planes ores, which are on the eastern end of Cerro Colorado have been worked almost continuously since Roman times, with the 600 m eastern extension - San Antonio - having been discovered in 1962. This mineralisation is hosted by silicified, chloritised and sericitised pyroclastics with a few bands of tuffaceous sediments. It is composed of brecciated colloform pyrite, and unlike the other deposits of the belt is laterally separated from any underlying related stockwork zone.
The steeply dipping Filón Norte (North Lode) and Filón Sur (South Lode), which are located on the northeastern and southeastern margins respectively of the mineralisation mined in the Cerro Colorado - Salomon open-pits, were previously exploited underground by the Rio Tinto Company. Filon Norte (which included the old Dehesa, Lago and Salomon mines) produced 2.75 Mt of pyrite from underground between 1881 and 1895, followed by 22.93 Mt from an open-pit between 1892 and 1937. At Filon Sur, 18.22 Mt of pyrite were mined from underground between 1873 and 1967, whilst 24.2 Mt were extracted by open-pit between 1874 and 1949. Prior to the arrival of British miners in 1873, mining activity mainly consisted of underground workings in the Filón Sur area.
The Cerro Colorado gossan represents the relict basal portions of the massive sulphide zone that occupied the crest of the anticline before being removed by erosion. These massive sulphides were only preserved and exploited on the steeply dipping northern and southern limbs of the anticline as the high grade Filón Norte and Filón Sur massive sulphide ores. The bulk of the remaining mineralisation between these two zones, and below the gossan and supergene zone, is composed of lower grade stockwork mineralisation as the Cerro Colorado - Salomon (or Cerro Colorado West and Cerro Colorado East) deposits. Both stratabound massive sulphides and underlying stockwork mineralisation has been mined at San Dionisio and the San Antonio deposits on the anticlinal axis to the west and east. The remaining hypogene massive sulphide mineralisation relicts beneath the supergene enrichment zone at Cerro Colorado and at Filón Norte and Filón Sur on its flanks, is mostly composed of pyrite, with minor chalcopyrite, sphalerite, tetrahedrite and sulphosalts of antimony and arsenic. Chalcopyrite frequently occurs within small fractures in the massive pyrite, although it also occurs on its own. The hypogene massive sulphides are interpreted to have been deposited in two distinct events, an initial intense pyrite mineralisation, followed by a second phase when the copper minerals appear to have been deposited.
The gossan on Cerro Colorado ranges from a few to >40 m in thickness, averaging 20 to 30 m throughout, though it is locally up to 100 m (Findlayson 1911) where water percolated through faults and fractures, particularly along the footwall shale contacts. Silver and gold were leached and concentrated toward the base of the gossan and are deposited in combination with ferric sulphate as argento-jarosite, one of an isomorphous series of jarosites (González 1981; Amoros, Lunar and Tavira 1981; Dutrizac et al., 1983), or as cerargyrite. A layer at the base of the gossan described by Williams (1950) was 1.5 m thick carrying 25 g/t Au and up to 2100 g/t Ag, although actual recoveries were ~150 g/t Ag. It was earthy, multicoloured, sometimes banded, but mainly yellow or red and partly grey to black. Such bands are found elsewhere in the deposit, cemented by dark brown limonite or reddish clay (Willies, 1997). A grade of 600 g/t Ag has been suggested as a minimum for Roman period extraction (Tylecote 1987).
Beneath the gossan, a leached horizon after massive pyrite, represented by a barren white quartzitic or clay layer, separates the gossan from the underlying supergene mineralisation characterised by black chalcocite overprinting primary chalcopyrite. At Filón Norte, this supergene enrichment extends to the base of the deposit at ~100 m below the surface, and at San Dionisio, chalcocite encapsulates hypogene chalcopyrite to a depth of 250 m (Findlayson, 1911). These gossan/oxide and supergene sulphide zones were the basis of much of the historic mining at Riotinto, with the lower grade hypogene stockwork mineralisation only becoming significant in the more recent bulk tonnage open pit operations of the last 50 years.
The operation was closed in 2002 due to falling copper prices, and was placed on care and maintenance, but was secured by EMED Mining Public Limited in 2008 with the aim of restarting the operation. In 2015, EMED became Atalaya Mining plc, and in 2016 commercial mining commenced at Rio Tinto, initially at 5 mtpa, and following an expansion in 2019 to 15 mtpa in 2020.
JORC-compliant Mineral Resources and Ore Reserves for the Rio Tinto Copper Mine have been independently verified by consultant AMC in 2010 (EMED Prospectus, December, 2010), as follows:
Total Mineral Resources - 203 Mt @ 0.46% Cu, at a cut-off grade of 0.20% Cu, for 0.9334 Mt of contained copper; including
Ore Reserves - 123.0 Mt @ 0.49% Cu, at a cut-off grade of 0.20% Cu for 0.606 Mt of contained copper.
JORC-compliant Mineral Resources and Ore Reserves (Atalaya Mining website, viewed February 2022), were as follows:
Mineral Resources
Measured - 152 Mt @ 0.39% Cu;
Indicated - 106 Mt @ 0.40% Cu;
Inferred - 18 Mt @ 0.50% Cu;
TOTAL Measured+Indicated+Inferred Resources - 276 Mt @ 0.40% Cu, including:
Ore Reserves
Proved - 128 Mt @ 0.41% Cu;
Probable - 69 Mt @ 0.44% Cu;
TOTAL Proved+Probable Reserves - 197 Mt @ 0.42% Cu.
The information in this summary is partly drawn from Acheson, D., Fletcher, R.J., Bennett, J. and Francis, A.D., 2013 - EMED’s Rio Tinto Copper Project Huelva Province, Spain; an NI 43-101 Technical Report prepared by Behre Dolbear International Ltd., Ashford, Kent, UK, for EMED Mining Public Limited, 88p.
The most recent source geological information used to prepare this decription was dated: 2010.
Record last updated: 5/2/2022
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Rio Tinto - Cerro Colorado
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Barrie C T, Amelin Y, Pascual E 2002 - U-Pb geochronology of VMS mineralization in the Iberian Pyrite Belt: in Mineralium Deposita v37 pp 684-703
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Chauvet, A., Onezime, J., Charvet, J., Barbanson, L. and Faure, M., 2004 - Syn- to Late-Tectonic Stockwork Emplacement within the Spanish Section of the Iberian Pyrite Belt: Structural, Textural, and Mineralogical Constraints in the Tharsis and La Zarza Areas: in Econ. Geol. v.99, pp. 1781-1792.
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de Mello, C.B., Tornos, F., Conde, C., Tassinari, C.C.G., Farci, A. and Vega, R., 2022 - Geology, Geochemistry, and Geochronology of the Giant Rio Tinto VMS Deposit, Iberian Pyrite Belt, Spain: in Econ. Geol. v.117, pp. 1149-1171.
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Leistel J M, Marcoux E, Thieblemont D, Quesada C, Sanchez A, Almodovar G R, Pascual E, Saez R, 1997 - The volcanic-hosted massive sulphide deposits of the Iberian Pyrite Belt. Review and preface to the Thematic Issue: in Mineralium Deposita v33 pp 2-30
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Leistel J M, Marcoux E, Deschamps Y, 1997 - Chert in the Iberian Pyrite Belt: in Mineralium Deposita v33 pp 59-81
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Luz, F., Mateus, A., Ferreira, E., Tassinari, C.G. and Figueiras, J., 2022 - Pb-Nd-Sr Isotope Geochemistry of Metapelites from the Iberian Pyrite Belt and Its Relevance to Provenance Analysis and Mineral Exploration Surveys: in Aguas Tenidas (Cu-Zn-Pb), Sotiel-Coronada (Cu-Zn-Pb), and La Magdalena Econ. Geol. v.117, pp. 423-454.
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Mathur R, Ruiz J, Tornos F 1999 - Age and sources of the ore at Tharsis and Rio Tinto, Iberian Pyrite Belt, from Re-Os isotopes: in Mineralium Deposita v34 pp 790-793
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Nehlig P, Cassard D, Marcoux E 1997 - Geometry and genesis of feeder zones of massive sulphide deposits: constraints from the Rio Tinto ore deposit (Spain): in Mineralium Deposita v33 pp 137-149
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Pasava J, Vymazalova A and Tornos F, 2007 - PGE distribution in massive sulfide deposits of the Iberian Pyrite Belt : in Mineralium Deposita v42 pp 309-314
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Saez R, Almodovar G R and Pascual E, 1996 - Geological constraints on massive sulphide genesis in the Iberian Pyrite Belt: in Ore Geology Reviews v11 pp 429-451
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Sanchez-Espana J, Velasco F, Boyce A J, Fallick A E 2003 - Source and evolution of ore-forming hydrothermal fluids in the northern Iberian Pyrite Belt massive sulphide deposits (SW Spain): evidence from fluid inclusions and stable isotopes: in Mineralium Deposita v38 pp 519-537
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Soriano C, Marti J 1999 - Facies analysis of volcano-sedimentary successions hosting massive sulfide deposits in the Iberian Pyrite belt, Spain: in Econ. Geol. v94 pp 867-882
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Tornos F, 2006 - Environment of formation and styles of volcanogenic massive sulfides: The Iberian Pyrite Belt: in Ore Geology Reviews v28 pp 259-307
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Vazquez Guzman F 1989 - Spain (Extracts): in Dunning F W, Garrard P, Haslam H W, Ixer R A (Eds.), Mineral Deposits of Europe IMM, London v 4/5: Southwest and Eastern Europe, with Iceland pp 105-127, 194-196
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Willies, L., 1997 - Roman mining at Rio Tinto Huelva, Spain: in The Bulletin of the Peak District Mines Historical Society, v.13, 29p.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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