A well-preserved, ca 250 m.y. old, geothermal field in central Spain: shallowest traces of a much larger hydrothermal system

摘要

Preservation of a ca 250 m.y.-old palaeogeothermal field is unusual, particularly in Iberia-a region that has been subjected to major tectonic cycles, such as the Hercynian and the Alpine orogenies. The latter, although classically studied in the Betics region of southern Spain, had profound tectono-sedimentary effects in the rest of Iberia. Even so, Las Torrecillas may be explained in terms of the tectonic and structural setting in which the deposit formed-an extensional episode leading to formation of a major northeast-orientated graben. It is proposed that this graben acted as a 'fossilization site', preventing rapid erosion of the Las Torrecillas geothermal facies, which were quickly covered by sedimentary rocks (Upper Permian-Triassic). Finally, as discussed here, the geological, isotopic and fluid inclusion evidence strongly supports a hydrothermal connection between the shallow Las Torrecillas facies and the deep environment of Linares-La Carolina, which makes the area a unique site at which to study the effects and vertical extent of a large hydrothermal system.