Reply to the comment by F. Tornos et al.

We welcome the discussion of our paper by Tornos et al. The epithermal character of the Hiendelaencina veins might have been an assumption in the early to mid 1980s, however, this early idea has been reaffirmed after many years of research involving fieldwork and mineralogical, sulphur isotopes, and fluid inclusions studies. The same applies to the alleged extensional frame, a tectonic episode now well documented not only in central Spain (Spanish Central System: Doblas 1987; Doblas et al. 1988; Doblas 1991) but in France (French Central Massif: Ménard and Molnar 1988; Malavieille et al. 1990; Munoz et al. 1992).The deposits are hosted by metamorphic rocks and the nearest volcanic outcrops to Hiendelaencina are those of Atienza (andesites; some 12 km northward). This is the reason why the relationships between the Atienza volcanics and the Hiendelaencina veins were initially regarded as obscure. These Stephanian-Permian volcanic outcrops are only local evidence of the late Variscan magmatism, which in the case of Hiendelaencina remained concealed. It is evident that the geologic environments of Hiendelaencina and Atienza are very different (see Discussion, p. 88 of the paper). As a direct consequence of this, the local structural conditions led to contrasted expressions of the late Variscan magmatism i.e. subaereal at Atienza and hypabyssal at Hiendelaencina.     

“Geothermal mineral equilibria”. Reply to a comment by M. A. Grant

The dominant process limiting CO₂-contents of fluids in high temperature (>240°), liquid-dominated systems consists of the conversion of primary plagioclase by CO₂ to calcite and clay according to log P_CO2 = 15.26 ? 7850/(t + 273.2), temperature t in °C, with a likely error in log P_CO2 due to variations in the activities of the anorthite and kaolinite components of the mineral phases involved of around ± 1 log unit. Secondary processes such as adiabatic expansion, conductive cooling and mixing with cooler groundwaters are largely responsible for subsequent variations in P_CO2 at lower temperatures (>240°).