Geology and VMS Deposits of the Iberian Pyrite Belt

Abstract

This Guidebook contains information to support the three SEG field trips included in the SEG Neves Corvo Field Conference 1997 (Lisbon, May 11–14, 1997). Collectively, these field trips cover the whole Iberian Pyrite Belt and beyond. Given that the Conference is aimed primarily at participants unfamiliar with the geology of the Belt, it was considered appropriate to introduce the subject prior to the field guides. Many studies have presented the overall characteristics of the geology and mineral deposits of the IPB (e.g. Carvalho et al., 1976; Strauss et al., 1977; Carvalho, 1979; Routhier et al., 1980; Barriga, 1990). Very recently, Carvalho et al. (1997) have summarized rather thoroughly the present state of the art concerning the IPB geology and metallogenesis. The present introduction is drawn largely from this. The Iberian Pyrite Belt (IPB) corresponds to an area of Devonian-Carboniferous volcanic and sedimentary rocks containing massive polymetallic sulfide deposits. This area forms an arcuate belt, about 250 km long and up to 60 km wide, trending westwards from near Seville in Spain to west-northwest in South Portugal. Both the eastward and westward extents of the belt are covered by Tertiary sedimentary rocks (Figure 1). The IPB is arguably the largest and most important volcanogenic massive sulfide (VMS) metallogenic province in the world. Some of its mineral deposits have been known and mined since the Chalcolithic era such as the Rio Tinto deposit, renowned for its historical role in the study of ore deposits. Only after the discovery of the large and rich copper-tin ore body of Neves Corvo (Southern Portugal) in 1977 has the true importance and potential of the IPB become fully appreciated. The original, pre-erosional amount of sulfides concentrated in about 90 known deposits are estimated at more than 1. 7 billion tons. Of this amount, about 20 percent has been mined, and 10-15% lost to erosion. This impressive amount of metals, in concentrations that range from small lenses with thousands of tons to giant bodies with hundreds of million tonnes, in such a relatively small area, represents an outstanding global geochemical anomaly of S, Fe, Zn, Cu, Pb, Sn and several other metals. The Iberian Pyrite Belt is located in the Southwest of the Iberian Peninsula, and comprises a large part of the Setubal and Beja districts in Portugal, and Huelva and Seville provinces in Spain (Figure 2). The region is an eroded peneplain, plunging gently to the