Hydrothermalism in the Tyrrhenian Sea: Inorganic and microbial sulfur cycling as revealed by geochemical and multiple sulfur isotope data

The Palinuro volcanic complex and the Panarea hydrothermal field, both located in the Tyrrhenian Sea (Italy), are associated with island arc magmatism and characterized by polymetallic sulfide mineralization. Dissolved sulfide concentrations, pH, and Eh measured in porewaters at both sites reveal a variable hydrothermal influence on porewater chemistry.Multiple sulfur isotopic measurements for disseminated sulfides (CRS: chromium reducible sulfur) extracted from sediments at Palinuro yielded a broad range in δ³⁴S range between ?29.8 and + 10.2‰ and Δ³³S values between + 0.015 and + 0.134‰. In contrast, sediments at Panarea exhibit a much smaller range in δ³⁴S_CRS with less negative values between ?11.3 and ?1.8‰. The sulfur isotope signatures are interpreted to reflect a mixture between hydrothermal and biogenic sulfide, with a more substantial biogenic contribution at Panarea.Multiple sulfur isotope measurements were performed on sulfides and elemental sulfur from drill core material from the Palinuro massive sulfide complex. δ³⁴S and Δ³³S values for pyrite between ?32.8 and ?1.1‰ and between ?0.012 to + 0.042‰, respectively, as well as for elemental sulfur with δ³⁴S and Δ³³S values between ?26.7 and ?2.1‰ and between + 0.035 and + 0.109‰, respectively, point to a microbial origin for much of the sulfide and elemental sulfur studied. Moreover, data suggest a coupling of bacterial sulfate reduction, sulfide oxidation and sulfur disproportionation. In addition, δ³⁴S values for barite between + 25.0 and + 63.6‰ are also in agreement with high microbial turnover of sulfate at Palinuro.Although a magmatic SO₂ contribution towards the formation of the Palinuro massive sulfide complex is very likely, the activity of different sulfur utilizing microorganisms played a fundamental role during its formation. Thus, porewater and multiple sulfur isotope data reveal differences in the hydrothermal activity at Palinuro and Panarea drill sites and underline the importance of microbial communities for the origin of massive sulfide mineralizations in the hydrothermal subsurface.     

Ökotechnologischer Einsatz von höheren Wasserpflanzen in stehenden und gestauten Gewässern — Möglichkeiten,Grenzen

Species of macrophytes which are suitable for the biogenic aeration of the hypolimnion by macrophytes must reach positive balances of the net primary production at a high development of populations also at low light intensities and temperatures (winter). Elodea canadensis, Juncus bulbosus and Littorella uniflora from suitable sites were exposed after holding at different water depths, and the biomass development was investigated in relation to the radiation intensity. Parallel to that, the net primary production was determined in dependence on the light intensity in the bottle experiment by air-conditioned laboratory experiments (oxygen method). Elodea canadensis has been found to be suitable for the ecotechnological application to more eutrophic waters with neutral pH, especially because of the low light compensation point of the net primary production. Colonization with Juncus bulbosus, however, seems to be possible only in the acidophilic range (pH<7), whereas Littorella uniflora is not suitable for floating vegetation covers because of the higher light compensation point for a hypolimnetic colonization and the linkage to the substrate.     

Identifying sources of salinization using hydrochemical and isotopic techniques, Konarsiah, Iran

Konarsiah salt diapir is situated in the Simply Folded Zone of the Zagros Mountain, south Iran. Eight small permanent brine springs emerge from the Konarsiah salt body, with average total dissolved solids of 326.7 g/L. There are numerous brackish to saline springs emerging from the alluvial and karst aquifers adjacent to the diapir. Concerning emergence of Konarsiah diapir in the study area, halite dissolution is the most probable source of salinity in the adjacent aquifers. However, other sources including evaporation and deep brines through deep Mangerak Fault are possible. The water samples of the study area were classified based on their water-type, salinity, and the trend of the ions concentration curves. The result of this classification is in agreement with the hydrogeological setting of the study area. The hydrochemical and isotopic evaluations show that the groundwater samples are the result of mixing of four end members; Gachsaran sulfate water, Sarvak and Asmari carbonate fresh waters, and diapir brine. The molar ratios of Na/Cl, Li/Cl, Br/Cl, and SO₄/Cl; and isotopic signature of the mixed samples justify a groundwater mixing model for the aquifers adjacent to the salt diapir. The share of brine in each adjacent aquifer was calculated using Cl mass balance. In addition, concentrations of 34 trace elements were determined to characterize the diapir brine and to identify the possible tracers of salinity sources in the mixed water samples. B, Mn, Rb, Sr, Cs, Tl, and Te were identified as trace elements evidencing contact of groundwater with the salt diapir.     

Eolian dust deposition on the Giara di Gesturi basalt plateau,Sardinia

Mineralogical study of samples from depression fills on an isolated basalt plateau in Central Sardinia showed that, although the basalt is free of quartz and mica, fair amounts of these minerals occur in the finer fractions. Results from X-ray analyses of silt fractions and morphoscopical analyses of sand fractions indicate that the bulk of the quartz and mica is of eolian origin. The eolian quartz is predominantly of medium and coarse silt size and, in the upper 10 cm of the depression fills, constitutes about 20 per cent of the soil mass (approx. 20 kg/m²). Eolian mica is present in smaller amounts and is of medium silt or smaller size. The provenance of the eolian material could not be established with certainty, although a local origin can be excluded.