Iberian Projects

ProExMin will be abroad by end of July 2016 to conduct an extensive regional reconnaissance survey of Spain and Portugal. The Iberian Peninsula is a prolific metal producing region, and ProExMin believes that there are other excellent mineral development opportunities for precious (gold) and critical and specialty metals (tungsten, tin, antimony, bismuth, lithium) in the region.

 

The Iberian Peninsula has a complex and diversified geology with a considerable mineral potential, therefor it has always been an area with a variety on mining activities and operations. The Hercynian orogeny formed the basement of the Iberian Peninsula and most of western and central Europe. The Hercynian cycle and the formation of the Hercynian Massif, starting in Late Precambrian times by the collision of Gondwana and Laurussia and terminated at the end of the Palaeozoic, is linked throughout Europe with the deposition of a wide variety of metallic and nonmetallic mineral resources. In Iberia, the most important deposits are the base-metal sulphides of the Iberian Pyrite Belt (IPB), tin and tungsten, gold, mercury, and fluorite besides numerous showings and geochemical anomalies.

 

A range of different minerals has been mined by a culture of metalworkers in Spain and Portugal since at least 5,000 years and maybe there are some mineral deposits that have been known and mined afore. Gold, silver, copper, cinnabar and lead were exploited by the Phoenicians, Greeks, Carthaginians and the Romans. After millennia-long mining activities it was the Fall of the Roman Empire that stopped step by step the exploitation. At the last from the fifth century A.D., the Vandals spread into Europe and terminated this illustrious period. During the occupation of the Iberian Peninsula by the Moors, just alluvial gold in small extent has been mined. While the exploration and colonization of the Americas has occured, mining activities in Iberia failed due to the vast amount of wealth that spills over the Atlantic.

Las Medulas mine, an UNESCO World Heritage site, NW Spain. In the 1st century A.D. the Romans began to exploit the sedimentary gold deposits hosted in conglomerates, using a technique based on hydraulic power. After two centuries of working, the Romans withdrew, leaving a devastated landscape. The grade in the auriferous layer ranged from 0.5 g/t Au at its base to 0.01 - 0.06 g/t (!!!) Au in the upper parts. The Romans moved about 160 Mt overburden and auriferous gravel and recovered 3.5 to 5 t Au.

Intense mining activities did not commence until the mid of the 19th century, at which time English and French companies began with the exploitation of volcanogenic massive sulphide deposits (VMS) in the IPB and numerous copper, lead-zinc, antimony, tin, tungsten and gold-silver deposits. The innumerable traces of mining activities that can be seen anywhere in Iberia testify to these period and the beginning of modern mining. By the last years of that century and up to the time in between the two World Wars, the mostly Spanish production had reached an immense output on copper, iron and pyrite. Almost the total production was exported to Europe. Through this the industrial development of Europe mainly took part on endeavors made by Spanish mining.

 

Mine development until the early 1960's was by innumerable small operations for metals and nonmetals. By the mid-1960's, mainly in response to the restructuring of the Spanish economy, and through foreign capital by several multinational companies and new investments in existing mines led to the discovery of new prospects and deposits. Progress in exploiting techniques led to re-evaluations of already known low-grade deposits. Through modern open pit methods these deposits could be exploited economically, which led to an increase of production. The following period was characterized by less exploration and fewer major developments. However, in the past few decades, mineral production has begun to decline. The industry has been hampered by resource depletion, technological problems, low metal prices, and enivronmental problems. Before the 1980's, environmental damage was considered to be an inevitable consequence of the extractive Spanish mining industry. This has produced many environmental problems associated with pollution in water, air and soils.

Environmental problems due to dumped pyrite-bearing materials (weathered and decomposed rocks with grey colour), former Tharsis mine, Spain.

The situation in Portugal was slightly different. There was a first prospecting and mining boom for tungsten in the World War I, but most of the ventures could not adapt to post-war industrial conditions and crashed. The Word War II produced a second boom for tungsten and other minerals. The demand for tungsten increased considerably, which led to ruthless exploitation. Most production came from underdeveloped mines which were mined for rapid extraction and who could not made efforts to determine and establish proven reserves and long-term resources. Due to the lack of enduring and sustainable supply, the development of the mines were short-lived and most of the ventures failed. From the start of the fifties but mainly in the eighties, exploration underwent somewhat of a boom in Portugal at first including tungsten and tin in the centre and north of the country and later concentrating to precious metals and base metals, the latter sought principally in the Pyrite Belt in the south, where a remarkable number of mineral bodies have been discovered.

 

While mining in Spain and Portugal has been declining in recent decades, the opening of new mines and several other deposits waiting to be developed and the increasing number of exploration projects has heralded a resurgence in this sector in Iberia. There is a large number of national and foreign companies investing in exploration in Portugal and Spain.

The Hercynian Massif of Iberia with prominent metallogenic provinces and structural geotectonic boundaries.

Most of the peninsula is formed by three main stuctrual domains. The Hercynian Massif or basement of late Precambrian and Palaeozoic rocks extends from the north to the Sierra Morena in the south, and from the Atlantic coast of Portugal to the Mediterranean and central Spain. The Alpine domain is composed of Mesozoic and Tertiary formations that have suffered the thrust of Alpine movements. The Alpine domain consists of the Pyreenes, Iberian and Catalan coastal range, and the Betic and Balearic range. The Mesozoic and Tertiary basins formed by Mesozoic and Tertiary materials occupying basins and depressions and were not affected by the Alpine deformations, constituted by continental materials (Ebro, Duero, and Tajo basins) and in the case of the Betic range, of marine origin (Guadalquivir basin).

 

The Hercynian Massif is classically subdivided into granitic rocks and mainly NW-SE trending folded sedimentary complexes with different grades of metamorphism. Granitic rocks can be subdivided into two major groups namely the syn-kinematic emplaced about 340-320 Ma and the late-post-kinematic granites emplaced between 315-270 Ma. The Iberian granitoids can be classified into two main suits: a) strongly peraluminous leucogranites and two-mica granitoids of mesocrustal origin, b) calc-alkaline granodiorites and biotite monzogranites of deep crustal origin associated minor intrusions of basic and intermediate rocks. The two granitoid suites cannot be exclusively assined to any particular group.

 

During the Hercynian orogeny, a complicated series of tectonic microplate collisions occured in Iberia. The resulting crustal deformations created a variety of complex structures, which were formed by folding, metamorphism, fracturing, shearing, and magmatic activities. In the north and central part of the Hercynian Massif, granite intrusions and linked vein/hydrothermal mineralizations created tungsten, tin and gold deposits. In shear zones were gold, lead and zinc deposits created. In the south, the IPB contains several supergiant as well as minor VMS deposits that hosts copper, zinc, lead, gold, and silver.

Current mining operations at Cerro Colorado open pit (Riotinto).