Palaeozoic magmatic-related hydrothermal activity in the Almadén syncline, Spain: A long-lasting Silurian to Devonian process?

Abstract

Almadén (central Spain) is the most remarkable mercury-mining district in the world, having produced one-third of the total world output of this element. The mercury orebodies are hosted by sedimentary and volcanic rocks belonging to a Lower Palaeozoic sequence that unconformably overlies the pre-Ordovician basement of the Central Zone of the Iberian Variscan Chain2,3 (Fig. 1). The Almadén rocks and mineralization pose an intriguing problem because in addition to the classic Lower Silurian strata-bound mineralization (e.g. Almadén and El Entredicho) other deposits are found higher in the stratigraphic sequence in both Silurian and Devonian been carried out in conjunction with re-evaluation of the already available isotopic and stratigraphic data in the hope of providing new insights into the genetic environment in which the alteration and mineralization processes took place. It is suggested that the persistent submarine magmatic activity in the Almadén basin may have sustained long-lasting submarine hydrothermal activity through most of the Silurian and Devonian, i.e. a time-span of about 70 m.y.