Rare earth elements, yttrium and H, O, C, Sr, Nd and Pb isotope studies inmineral waters and corresponding rocks from NW Bohemia, Czech Republic

The sparkling waters from the area of Kyselka near Karlovy Vary at the west ern slope of the Doupovske hory, Bohemia (Czech Republic), and CO2-poor wat ers from two underground boreholes at Jachymov, Krusne hory, Bohemia, have been studied with the aim of characterizing the distribution of rare earth elements, yttrium, and H, O, C, Sr, Nd, Pb isotopes during the low-temperat ure alteration processes of the host rocks. Additionally, leaching experime nts were performed at pH 3 on the granitic and basaltic host rocks from Kys elka and the granite of Jachymov. All REE patterns of the granite- and the basalt-derived waters From the Kyselka area are different from those of the ir source rocks and the leachates of the latter. This elucidates the inhomo geneous distribution of REE and Y among the solid phases in the altered mag matic rocks. The Eu and Ce anomalies in granite-derived waters are inherite d, the Y anomaly is achieved by fluid migration. Yttrium is always preferen tially leached by mineral waters, whereas Y/Ho ratios of rocks and their le achates are very similar. The REE abundances in waters from the wells in Ja chymov are derived from rocks intensely leached and depleted in easily solu ble REE-bearing minerals, whereas the granites and basalts from Kyselka sti ll contain soluble. REE-bearing minerals. A comparison of REE/Ca patterns o f the experimental leachates with those of the mineral waters elucidate the high retention of REE in rocks during water-rock interaction. In strongly altered rocks Sr isotope ratios of mineral waters and rocks differ widely, whereas the corresponding Nd isotope ratios are very similar. Pb-207/Pb-208 , Pb-206/Pb-208 and Pb-206/Pb-207 ratios in mineral waters are independent from U/Th ratios in the rocks. Pb-206/Pb-208 and Pb-206/Pb-207 are lower in mineral waters than in their source rocks and their leachates, which indic ates that Pb is primarily derived from solid phases that do not contain sig nificant contents of leachable U and Th. Thus, mineral waters, although CO2 rich, only interact with surface films on minerals and not with the bulk o f the minerals as in the leaching experiments. Calculation of mixing ratios of waters from the granitic and basaltic sourc es of the waters fi om the Kyselka area yield about 40% of water from the u nderlying granite in water recovered from the basalt, whereas the granite-d erived water is mixed with only about 5% of the water from the basalt. (C) 1998 Elsevier Science Ltd. All rights reserved.