Palaeohydrogeology and geodynamic framework of carbonate-hosted Zn-Pb mineralisation in Europe and North America: Insights from fluid composition and Pb isotope systematics

摘要

A comparison between the source of the mineralising fluids and the Pb isotope composition of carbonate-hosted Zn-Pb mineralisation in Europe and North America reveals remarkable patterns. Districts where the mineralising fluids originated as residual brines during seawater evaporation are characterised by homogeneous and non-radiogenic lead isotopes. On the contrary, when the mineralising fluids gained their salinity at least partly by dissolution of evaporites, the resulting Pb isotope composition of the ores is heterogeneous and very radiogenic. It is proposed that cross-formational migration of residual brines, which are generated during basin formation, results in homogeneous and only slightly radiogenic lead, while lateral flow of meteoric fluids induced by gravity or tectonic forces leads to heterogeneous and radiogenic lead.