Reply to comments of T. Yalcin and F. Suner (Environmental Geology 39(5): 433–436) – "More on the Jelenia Góra-Cieplice thermal waters"

Abstract

Yalcin and Suner (2001) made important and pertinent remarks concerning the content of the paper by Dowgiallo (2000). The necessity for some clarifications is obvious. It is, of course, true that K in the formula (a) on page 436 should be within square brackets. This printing error, however, did not influence the computational results, as K was in this case given in mol/dm. The observation of the above-mentioned authors concerning the silica (chalcedony) geothermometer (Arnorsson and others 1983) is not quite clear. After recalculation, the results appear the same as in the discussed paper, except the C-1 samples from depths of 1,790 and 2,002 m, where the values should be rounded. The differences, however, are less than 1 C, and not 3 C. For geothermometric temperature estimates, such differences do not play any important role. As far as the silica concentrations are concerned, analytical errors suggested by Yalcin and Suner (2001) regarding some samples from the C-1 borehole (depths 1,605, 1,700, 2,002, and perhaps 1,790 m) cannot be excluded. Samples were taken during drilling and they did not always immediately reach the chemical laboratory. However, results (expressed in ppm) from another drilled well (C-2) and from spring no. 5 providing thermal water do not arouse doubts but serve as a sound basis for temperature estimation. Pang Zhong-he (1992) states that the chalcedony geothermometer applied to low-temperature granitic geothermal areas in southeast China (thus, to conditions analogous to the Cieplice area) is one of the most suitable for this type of geothermal systems. The pH values of the Cieplice undiluted thermal waters measured in the field do not exceed 8.2 (Leśniak and Nowak 1993). However, pH in samples taken from borehole C-1 during drilling was measured only in the laboratory with a certain delay. Obtained pH values vary between 8.4 and 8.9, and are presumably higher than if pH were measured directly at the outflow. It has to be emphasized that the dependence of silica solubility on pH shown on the graph by Krauskopf (1956) concerns low-temperature solutions. In more recent papers dealing with silica geothermometers (e.g., Rimstidt and Barnes 1980; Arnorsson and others 1983), both temperature and pH as well as the contribution of H3SiO 4 to alkalinity are taken into account. Yalcin and Suner (2001) correctly point out that waterminerals equilibria in reservoirs are the basis of chemical geothermometry. However, partial equilibria shown by the water may also be used as an indicator of temperature at depth. It can be shown that thermal waters at Cieplice have reached partial (although far from full) equilibrium with rock-forming minerals containing K, Na and Mg (Fig. 1), and that calculated temperatures are in most cases realistic and close to those observed in well C-1.