By conducting a chemical investigation that addressed both major and trace elements dissolved in the mineral waters that discharged on the slopes of the recently extinct (ca. 27-35 ka ago) Ciomadul volcano (East Carpathians, Romania), specific processes undergone by the concerned hydrochemical system have been documented.In terms of trace elements concentrations, it was noticed that the concentrations of Ti, V, Co, Ni and Zn never exceed several tens of ppb in near-neutral waters, while in acid waters they could reach, alternatively, several hundred ppb. Similarly, As, Cr and Pb reached up to several tens of ppb in acid waters, while in near-neutral waters their concentrations never exceeded 5 ppb. As for Cu, it was detected only in some of the acid waters, in concentrations up to almost 100 ppb.It was next possible to refine the image suggested by this pattern, by noticing that between acid and near-neutral outlets that occurred very close (ca. 20 m) to one another, the concentration ratios were similar for most of the major components (Ca, Mg, K), as well as for some of the trace elements (Sr, Rb, Ba), being thus suggested that in both types of discharges, a common parent-water was involved. The near-neutral outlets however appeared to be strongly depleted in base-metals (Ti, V, Co, Ni, Cr, Zn, Pb) as "compared to the acid fluids. The latter likely originate in the oxidation of the H2S fraction contained in gas outflows (rich mostly in CO2) released by a still cooling magma body: the H2S oxidation actually occurs when those magma-derived gas outflows finally reach superficial aquifers of essentially meteoric origin.

In the surroundings of Ciomadul Mountain, located in the southern extremity of the Harghita Mountains, Romania, intense discharge of dry (predominantly CO2, H2S) and wet emissions are known to occur, being an evidence of a deeply settled geothermal system.In this post-volcanic environment, an inventory of the water outflows was recently performed, aiming to update the old existing databases and to better document the permanent sources. The appearance of new (spontaneous) sources as well the dryness of other sources was observed during the monitored period extended over one year, being a phenomenon related to both internal (geological) and external (climate) factors.Despite the fact that Harghita Mountains also host the strongest heat-flow anomaly in Romania and hydrogeological records state the presence of a geothermal aquifer located at 800m depth (intercepted by a borehole in andesitic formations), only 2 sources (tapped water) monitored by the authors were identified to have a temperature overpassing 19 degrees C during the whole year. The highest value (28.5 degrees C) was recorded in the SNAM borehole, whose water upflows from similar to 300m depth.A total number of 37 sources, considered as permanent sources, were selected in order to analyse the time and space variability of post-volcanic activities in the area of Tusnad-Bicsad and Balvanyos. According to their spatial position they were divided into 5 groups: Tusnad area (formed by a group of 6 sources), Hammas-Vallato (grouping 11 sources), Balvanyos I (6 sources), Balvanyos II (5 sources) and Csiszar Cold Baths (9 sources).In terms of pH, the groundwater sources from the analysed area1 are classified as moderate to high acid waters, displaying values from 1.53 (u. pH) to 6.86 (u. pH), while the electrical conductivity parameter shows a wide range of values, between 139 and 50600 mu S/cm. The extreme value of 50600 mu S/cm was reported for a wet mofett, loaded with dissolved salts and with intense CO2 emissions.Physical parameters were further used to analyse the influence of the local tectonic on the area1 spreading of the sources (deployment on preferential alignments) and the possibility of interconnection between the sources upflow paths (based on physic-chemical parameters correlation).