Sulfide-free and sulfide-bearing waters in the Northern Apennines, Italy

摘要

The investigated waters include Ca-carbonate, Ca-sulphate, Na-carbonate and Na-chloride types. Ca-carbonate waters, which circulate in fractured calcite-bearing quartz-feldspathic sandstones outcropping along the Apennine watershed, are dominated by Ca-carbonate dissolution; Ca-sulphate waters are always related to gypsum-bearing lithotypes; the Na-carbonate, strongly reduced group is involved in intensive interaction with clay minerals dominated by Na-Ca exchange and silicate dissolution, and by O_2 and CO_2 progressive consumption. The Ca-sulphate waters from Tabiano baths have unusual composition among the investigated S(-II)-bearing waters: low pH and very high S(-II) content. In these waters, there is bacteria-mediated reduction of sulphate, which is derived from Ca-sulphate minerals.