Hydrochemical Groundwater Evolution in the Bunter Sandstone Sequence of the Odenwald Mountain Range, Germany: A Laboratory and Field Study

Abstract

Field and laboratory investigations were performed to identify the principal mechanisms of the hydrochemical groundwater evolution among low mineralised groundwater in the Triassic Bunter sandstone aquifer of the Odenwald low mountain range, central Germany. Hydrochemical composition comprises low pH, SO 4 -rich shallow groundwaters issued by springs (Ca-Mg-SO 4 -type) grading to SO 4 -poor deep groundwaters with near-neutral pH (Ca-HCO 3 -type). Batch experiments of the original rock were run to determine primary mineral alteration reactions and the origin of dissolved ions. Principal experimental reactions comprise the decomposition of anorthite, K-feldspar, biotite and jarosite as mineral components of the original sandstone rock and the formation of clay minerals of the smectite group (Ca-montmorillonite, beidellite), and iron hydroxides as secondary minerals. Mobilisation of fluid inclusion in quartz grains contributes to Na and Cl concentrations in the leachates. The evolution of deep groundwater circulation proceeds by mineral alteration reactions calculated by the inverse modelling of both primary and secondary minerals to produce low-T mineral phases. The dissolution of K-feldspar converts Ca-montmorillonite to illite (illitisation). The formation of Na-beidellite correlates with decreasing concentration of Na in solution. Mineral reactions further proceed to the formation of kaolinite as stable mineral phase. As indicated by modelled adsorption curves, the decrease of SO 4 concentrations during groundwater evolution relates to the adsorption of SO 4 on iron hydroxides. The leaching of calcite indicated for individual groundwaters relates to the distribution of loess in the appropriate catchment areas.

Groundwater Evolution and Mineral Alteration Reactions in the Basaltic Rock Sequence of Mt. Wasserkuppe, Germany: A Case Study

“…and Fe total of the basaltic leachates are significantly higher than expected with regard to the mobility of dissolved Al-and Fe-species at near-neutral pH. However, these findings correlate with results of comparable leaching experiments on silicate minerals (Zhu 2001;Ludwig et al 2011). The mobility of an ion is referred to its non-conservative transport in the aquifer system with possible effect by chemical (e.g.…”

“…With regard to groundwater recharge, groundwaters related to catchment areas partly covered with forest are affected by bulk deposition as throughfall under the forest canopy (S1, S10, S11, S17, SX2, SX3). As delineated in a companion study by Ludwig et al (2011), the concentration of NO 3 -in bulk deposition significantly exceeds the values in grassland rainfall and, thus, may effect higher concentrations of NO 3 -in the associated groundwaters. Consequently, as NO 3 appears to predominantly derive from rainfall input and was excluded from the hydrochemical modelling approach.…”

Oligocene–Miocene arc magmatic activities associated with the giant Reko Diq porphyry Cu–Au deposit, western Chagai arc, Balochistan, Pakistan

“…3.15), followed by the method of Andersen (2002). Concordia ages and diagrams were obtained using Isoplot (4.15) (Cavosie and Wilde, 2006; Ludwig et al, 2011). Some of the zircon U–Pb data are concordant, while others show Pb loss.…”

Mineral, thermal and deep groundwater of Hesse, Germany

“…In south-eastern Hesse, clastic rocks of the Buntsandstein form a fractured multilevel aquifer divided by clayey intercalations which is used for drinking-water production (Ludwig et al, 2011). In the eastern Odenwald, the Buntsandstein overlies the Zechstein and the basement with increasing thickness towards the east.…”