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Carbonate-Hosted Zn-Pb Deposits in Upper Silesia, Poland: Origin and Evolution of Mineralizing Fluids and Constraints on Genetic Models

Wouter Heijlen and Philippe Muchez

Fysico-chemische Geologie, K.U. Leuven, Celestijnenlaan 200C, B-3001 Leuven, Belgium

David A. Banks

School of Earth Sciences, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom

Jens Schneider

Institut für Geowissenschaften und Lithosphärenforschung, Justus-Liebig-Universität Giessen, Senckenbergstrasse 3, D-35390 Giessen, Germany

Henryk Kucha

University of Mining and Metallurgy, al. Mickiewicza 30, 30-059 Kraków, Poland

Eddy Keppens

Isotopengeologie en evolutie van de paleo-omgeving, V.U. Brussel, Pleinlaan 2, B-1050 Brussels, Belgium

Corresponding author: email,wouter.heijlen{at}geo.kuleuven.ac.be

Microthermometric and crush-leach analyses of fluid inclusions in ore and gangue minerals of the Upper Silesian Zn-Pb deposits, Poland, along with first results of Rb-Sr geochronology on sulfides, provide important constraints on the paleohydrogeologic and metallogenetic models for the origin of these ores. The analyzed samples comprise two generations of dolomite, two generations of sphalerite, galena, and late calcite. The two dolomite generations and the late calcite were also analyzed for their oxygen and carbon isotope compositions, allowing a characterization of the mineralizing fluids. The ore-forming fluids represent highly saline (20–23 wt % CaCl₂ equiv) Na-Ca-Cl brines, episodically introduced into the Triassic host carbonates. They had an oxygen isotope composition of ~0 per mil V-SMOW. Their Na-Cl-Br content (molar Na/Br and Cl/Br ratios between 99 and 337 and between 248 and 560, respectively) suggests that they originated by evaporation of seawater, which most likely occurred in the Permian-Triassic. The relative concentrations of potassium (molar K/Cl between 0.0147 and 0.0746) and lithium (molar Li/Cl between 0.0004 and 0.0031) further indicate that the fluids significantly interacted with siliciclastic rocks. The ionic and calculated oxygen isotope compositions of the fluids indicate that they were more evolved than present-day brines in the Upper Silesian coal basin, and the present-day brines show more extensive mixing with low-salinity fluids.

The first results of direct Rb-Sr dating of ore-stage sulfides yield an isochron model age of 135 ± 4 Ma for the mineralizing event. This is consistent with hydrothermal activity and ore formation in Upper Silesia occurring in response to Early Cretaceous crustal extension preceding the opening of the northern Atlantic Ocean.

The data presented support a model in which bittern brines migrated down into the deep subsurface and evolved into mineralizing fluids owing to extensive water-rock interaction. They were episodically expelled along deeply penetrating faults during the Early Cretaceous to form Zn-Pb deposits in the overlying Mesozoic carbonate rocks.

This article has been cited by other articles:

				J. SRODON, N. CLAUER, M. BANAS, and A. WOJTOWICZ K-Ar evidence for a Mesozoic thermal event superimposed on burial diagenesis of the Upper Silesia Coal Basin Clay Minerals, June 1, 2006; 41(2): 669 - 690. [Abstract] [Full Text] [PDF]