300 Million years of episodic hydrothermal activity: stable isotope evidence from hydrothermal rocks of the Eastern Iberian Central System

The Eastern Iberian Central System has abundant ore showings hosted by a wide variety of hydrothermal rocks; they include Sn-W, Fe and Zn-(W) calcic and magnesian skarns, shear zone- and episyenite-hosted Cu-Zn-Sn-W orebodies, Cu-W-Sn greisens and W-(Sn), base metal and fluorite-barite veins. Systematic dating and fluid inclusion studies show that they can be grouped into several hydrothermal episodes related with the waning Variscan orogeny. The first event was at about 295Ma followed by younger pulses associated with Early Alpine rifting and extension and dated near 277, 150 and 100 to 20Ma, respectively (events II-IV). The δ^sup 18^O-δD and δ^sup 34^S studies of hydrothermal rocks have elucidated the hydrological evolution of these systems. The event I fluids are of mixed origin. They are metamorphic fluids (H^sub 2^O-CO^sub 2^-CH^sub 4^-NaCl; δ^sup 18^O=4.7 to 9.3[per thousand]; δD ab.-34[per thousand]) related to W-(Sn) veins and modified meteoric waters in the deep magnesian Sn-W skarns (H^sub 2^O-NaCl, 4.5-6.4wt% NaCl eq.; δ^sup 18^O=7.3-7.8[per thousand]; δD=-77 to -74[per thousand]) and epizonal shallow calcic Zn-(W) and Fe skarns (H^sub 2^O-NaCl,