MINERAL RESOURCES OF PORTUGAL Text prepared by Luís Plácido Martins CONTENTS 4 PREAMBLE 6 GEOLOGICAL AND MINING BACKGROUND 10 HISTORICAL OVERVIEW OF MINING IN PORTUGAL 25 PRECIOUS METALS 26 Galicia - Trás-os-Montes Zone 27 Central – Iberian Zone 29 South – Portuguese Zone 30 Secondary Deposits 32 BASE METALS 32 Ossa Morena Zone 35 South – Portuguese Zone 45 OTHER METALS 45 Tungsten and Tin 49 Uranium 52 Iron and Manganese 52 Lithium and High Tech Metals 54 Rare Earths 54 Nickel, Cobalt and Chrome 55 NON METALLIC MINERALS 55 1 - Rocks 60 2 - Industrial Minerals 66 LEGAL FRAMEWORK 67 Prospecting and Exploration Contract, and Mining Contract Regime 69 Mining Contracts 70 Doing Business in Portugal 71 KEY REFERENCES 3 PREAMBLE A complex and diversified geology endows Portu- zones, placers, etc.). gal with a considerable mineral potential, leading to the occurrence of considerable number of ore, The general framework of the activity has favour- industrial and ornamental stone deposits. able characteristics, which is considered one of the reasons, linked with the recognised mineral po- Mineral exploitation has a present considerable tential, of the present level of activity. Institutional high level originated from world class deposits, as stability, mineral rights granting mineral property, Neves-Corvo (Cu, Sn) and Panasqueira (W), but also good infrastructure, incentives to investment, af- from a lot of some other deposits producing salt, fordable qualified work for European standards, a feldspar, kaolin, ball clay and fire clay, ornamental light fiscal burden are several others reasons why stones and some other mineral substances. Portu- activity is so interesting. gal is presently one of the main UE producers of copper, tin and tungsten concentrates and an im- This publication lies in the framework of the public portant world producer of ornamental stones. mission of the Direcção-Geral de Energia e Geolo- gia of promoting corporate investment, both na- Exploration activity is also at a high level consider- tional and foreign, which may be complemented ing the relative small extent of the territory (rough- to all those interested with the provision of all the ly 90 000 Km2). Several international companies basic information about geology, hydrogeology, conduct exploration mainly focused on base and geophysics, geochemistry and drilling data in ar- precious metals. chive or assistance in defining exploration targets and strategies. Portuguese territory covers half of the Iberian Py- rite Belt (IPB) which is considered the main met- You are welcome! allogenic province of the European Union, where occurrences of polymetallic massive sulphide de- posits like Neves-Corvo and Aljustrel, in Portugal, Rio Tinto, Sotiel, Los Frailes, Las Cruces, etc., in Spain. The IPB is the main primary source of base metals in the EU. Hesperian granites and associated metamorphics in the north and central part of the country are as- sociated with tungsten and tin mineralisations. Carlos A. A. Caxaria The potential in precious metals is well known since ancient times and is spread out geographically all over the country, occurring in diverse forms and Deputy General Director different geological settings (veins, skarns, shear Area of Geological Resources 4 5 The Hesperian Massif, in which predominantly tin, normally associated with the contact be- metallic mineral resources occur, can in turn tween the granite and the metasediments, and be divided into various geotectonic units, as the existence of precious metals, frequently as- described below (Ribeiro et al., 1979; Quesada, sociated with arsenic and antimony, as in the 1992): Valongo/Gondomar Gold-Antimony Belt, for example. There are also important mineralisa- Galicia - Trás-os-Montes Zone - This is character- tions of uranium, many of which have been ex- ised mainly by the existence of two mafic and ploited, related with late tectonic and metal- ultramafic polymetamorphic massifs known as logenetic phenomena that have affected the Bragança and Morais. The surrounding forma- post-tectonic “calcalkali” granite. tions date chiefly from the Silurian period and are characterised by the existence of acid and Ossa - Morena Zone - This is an extremely com- basic volcanic rock, which make contact with plex and diverse unit which begins with a poly- the massifs via larger thrust systems. Binary metamorphic Precambrian, followed by Cam- granite, “alkali” and porphyritic granite, biotite brian and Silurian formations, and ends with a and “calcalkali” granite also occur. The chrome, flysch sequence from the Late Devonian period. platinum and, possibly, copper, nickel and co- balt potential of the Morais and Bragança mas- Contact with the Central Iberian Zone is carried sifs is worth stressing, as is the potential for out via an important shear zone which stretches tungsten, tin, precious metals, uranium and, from Oporto to Cordoba in Spain (Blastomylo- probably, polymetallic sulphides in the sur- nitic Belt). rounding formations (Goínhas et al., 1992). With regard to magmatism, the NE sector has a Central Iberian Zone - This is mainly character- predominance of granitic rocks, chiefly “calcal- ised by the predominance of the formations of kali”, porphyritic, biotitic, similar to those in the the so-called Schist-Greywacke Complex, con- north and centre. sisting of a flysch-type series dating from the Cambrian and Late Precambrian period. There To the south, the basic character of the intru- are also large areas of “alkali” and “calcalkali” sions gradually increases, with “calcalkali” be- granitoids, in which various types of granite coming predominant: gabbros, diorites, ser- can be distinguished. Worth highlighting is pentinites and anorthosites (which form the the occurrence, in the Douro-Beiras sector, of recently named Beja ophiolite complex), vari- continental formations from the Carboniferous ous different porphyries, and later intrusions period, where various coal mines have been ex- comprising gabbrodiorites, granodiorites, to- ploited (Douro Carboniferous Belt). nalites and granites (which constitute what is known as the Évora Massif). Also worth mentioning in this geotectonic unit are important mineralisations of tungsten and 8 MINERAL RESOURCES OF PORTUGAL The most important mineral occurrences are base period, overlain by a Culm flysch sequence; under- metals, which are associated with the Cambrian- lying this complex is the so-called “Phyllite-Quartz- Ordovician volcanic sedimentary complex, pre- ite Group”. The oldest formations in this zone date cious metals, chiefly related with the Precambrian from the Early Devonian period and belong to the formations, and tungsten and tin in the Sta. Eulália “Pulo de Lobo” Formation, which includes phyllites, granitic complex, not to mention the potential for quartzites and rare acid and basic volcanic rocks. chrome, nickel, cobalt and platinum in the basic The acid volcanic rocks in the volcanic sedimentary and ultrabasic rocks on the north and south mar- complex constitutes the metallotect of the massive gins of this zone. polymetallic sulphides that are characteristic of the Iberian Pyrite Belt, the most important metal- With regard to non-metallic minerals, this geotec- logenetic province in Portugal in which the Lousal, tonic unit is rich in ornamental rocks, particularly Aljustrel, Neves Corvo and S. Domingos mines are marble. located. South Portuguese Zone - The Ossa - Morena Zone We shall not go into the geological aspects of the and this unit are joined by the Ferreira - Ficalho Epi-Hercynian Covering, but shall touch on its non- thrust (partially over the Beja-Acebuches complex), metallic resources, namely sands, gypsum, clay, which runs approximately E-W to the east and NW- kaolin, limestone, diatomite and salt, further on. SE to the west. The South - Portuguese Zone is characterised by the existence of a volcanic sedimentary complex (VS) from the Late Devonian - Early Carboniferous 9 HISTORICAL OVERVIEW OF MINING IN PORTUGAL The mining of mineral resources in Portugal was The two world wars, particularly the Second World initially carried out by the Phoenicians, but was in- War, led to a great demand for tungsten, which in tensely and mainly developed by the Romans. turn led to increased exploration and exploitation of not only this element but tin as well, as these The first mining operations would have taken place two elements are generally related spatially and/ in “gossan” type oxidation zones (for copper, zinc, or structurally. Production of the concentrates of lead, gold and silver) and gold-bearing placers these substances peaked during 1942 at 5700 tons (Carvalho, 1994). The Romans would later intensely for tungsten, the main producing mines being Pa- exploit gold and polymetallic sulphide vein depos- nasqueira, Borralha, Argozelo, Montesinho, Vale its. To better comprehend the size of the work in- das Gatas and Ribeira. volved, one need look no further than Três Minas, to the north of Vila Real, from which approximately The country also possesses important uranium de- 10 million tons of material was extracted; and in posits, with approximately 4200 tons of U3O8 pro- Aljustrel (southwest of Beja), mine shafts reached a duced between 1950 and 1990. depth of 120 metres. From the start of the fifties but mainly in the eight- Then followed a lengthy break in the mining of ies, exploration underwent somewhat of a boom in mineral resources in Portugal which was only oc- Portugal, at first including tungsten and tin in the casionally interrupted,