Fluid evolution and ore deposition in the Harz Mountains (Germany)
Lüders, Volker; Möller, Peter
European Journal of Mineralogy Volume 4 Number 5 (1992), p. 1053 - 1068
published: Oct 14, 1992
manuscript accepted: Feb 27, 1992
manuscript received: Jun 12, 1991
ArtNo. ESP147050405023, Price: 29.00 €
Abstract Quartz-stibnite, Pb-Zn, Ba-, and F-vein mineralization developed in the Harz Mts. over a long span of time from the Late Carboniferous to the Late Cretaceous. The economically most important quartz-sulphide and subsequent carbonate-sulphide ore deposits were deposited during the Jurassic. The homogenization temperatures of primary two-phase fluid inclusions in vein quartz lie between 120 and 180 °C on average. Secondary two-phase inclusions in calcite and fluorite show approximately the same range, whereas only few primary fluid inclusions have homogenization temperatures between 210 and 300 °C. Since boiling and effervescence can be excluded, precipitation of calcite may have been achieved from fluids when cooling from 300-200 °C as indicated by the positive δ13C vs. δ18O relationships in calcite. The evolution of chlorinity in the fluid inclusions reveals that, at different times, fluids from different sources were drained and mixed. Sulphides in the quartz-sulphide and carbonate-sulphide mineralizations were deposited by mixing of an ascending metal- and carbonate-bearing H2S-free metamorphic fluid with a H2S-bearing formation water. By contrast, the gangue minerals precipitated by simple cooling of the ascending fluid. Subsequently, barite was deposited by the mixing of a probably similar metamorphic fluid with descending SO42--bearing fluids from residual evaporites of the Mesozoic cover. Finally, fluorite locally precipitated from ascending brines originating from deeper sources than the carbonate-rich metamorphic fluid.