La evolución isotópica de los fluidos ligados a los Sistemas Hidrotermales tardi y postvariscos del Sistema Central Español

Abstract

The late to postvariscan hydrothermal activity of the Spanish Central System extends almost from ca. 300 Ma to the present. It consists of several Independent stages that can be grouped in two different hydrothermal regimes. There Is a first hydrothermal event (295±15 Ma) spatially related with minor intrusions of Late Variscan peraluminous granitoids. Here, highly confinated hydrothermal cells dominated by lithostatic pressure involve local fluids of complex composition and likely metamorphic origin; modified low-saline meteoric waters occur in the more distal manifestations only. Three recorded younger hydrothermal pulses (ca.274±6, 150±5 and 100 Ma) involving low-saline waters were channelized along regional structures. Here, waters of meteoric origin that infiltrate to a great depth into the basement, leading to a B1B0-shift of the fluids and a leaching of sulphur and metals from the host rocks. During upwelling, hydrothermal rocks are generated by fluid-rock interaction and boiling. In the shallow section of the system, the mixing with surficial complex brines led to the formation of fluoritebarite (Zn-Pb-Ag) veins, but no ffsO- 8D variation could be detected