Halogene (Cl, Br, I) in Böden und Verwitterungszonen von Erzlagerstätten

01/02/2016 to 31/01/2019

The heavier halogens Cl, Br and I are commonly regarded as inert tracers in fluid-involving processes in soils and upper crustal rocks. We challenge this traditional view and propose to investigate a carefully chosen site in the Schwarzwald, SW Germany, for the geochemical evolution of halogens from meteoric water input through soil into the uppermost crustal rocks and into a Pb-bearing ore deposit, where Cl-bearing minerals (pyromorphite) form in response to weathering.
This ideally suited locality allows to sample all compartments of this fluid pathway in unusual detail, and we will be able to distinguish between organically and inorganically bound Cl, Br and I in the various soil, mineral, rock and fluid fractions occuring in the upper 50 m of the Earth’s surface. A combination of state of the art techniques (combustion IC with SIMS and microprobe, soil leaching and water flow experiments at the site of interest) will allow to quantitatively assess the halogen budget in surface processes and during oxidation of an ore deposit. Preliminary data show that considerable fractionation of halogen occurs in the critical zone.