Origin and migration of fluids during the evolution of sedimentary basins and the origin of Zn [sbnd]Pb deposits in Western and Central Europe

Abstract

Numerous major Zn Pb deposits in Western and Central Europe formed as the result of the migration of highly saline fluidsthrough sedimentary basins during several stages of their evolution. The mineralising fluids originated as seawater or as evaporated seawater and migrated downwards into the sedimentary basin and often into the basement. In regions characterised by pronounced extension and elevated heat production, the fluids did not remain in the subsurface but migrated back upwards along extensional faults. This circulation pattern caused the formation of the deposits of Meggen and Rammelsberg and the Irish-type deposits. The latter could have formed during a prolonged period of fluid circulation. In Belgium, Germany and Poland, the fluids remained in the deeper subsurface for several tens to more than one hundred million years. During subsequent periods of tectonic activity, the fluids were tapped from this reservoir to form base metal deposits, hosted by overlying carbonate rocks and clastics.