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  • Author or Editor: István Deák x
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Abstract

Linear correlation between the temperature and measured δ18Owater of Budapest thermal karst water system presents an opportunity to estimate both the temperature and δ18O of the depositing water if only the δ18Otravertine is known.

Our observations on several Hungarian groundwaters and travertines deposited recently from them resulted that δ18O data of travertines originating from cold karst water and thermal water of porous aquifer are close to the “experimental“ curve presented by Friedman and O'Neil (1977). Conversely, the calculated fractionation factors of thermal karst waters significantly deviate from the experimental curve following an “empirical-curve“ (R2 = 0.99) as: 1000*lnα = (2.76*106)/T2 − 1.31.

The empirical equations calculated by this “empirical-curve“ as Twater = (25 − δ18Otrav)/0.22 and δ18Owater = 0.186*δ18Otrav − 14.22 are usable only for the Budapest thermal karst regime and only for recent travertines. Extrapolation of these equations to the past and use them to estimate the deposition temperature of paleo-travertines needs detailed information of the paleoclimate and age of travertine.

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Abstract

The isotopic compositions of the Hungarian warm and cold water samples are spread in a wide range along the Global Meteoric Water Line (GMWL), which is a result of the significant change in the climate (mainly temperature) during infiltration (Last Glaciation and Holocene) and of the mixing process along the fault zone. The thermal karst water is isotopically lighter as it was infiltrated in a 7 to 9 °C cooler climate in the Ice Age. However, in the Denizli Basin isotopic composition of all of the thermal, lukewarm and cold waters varies in a relatively narrow range, with the exception of some warm waters whose d18O values have been shifted as a result of water-rock interaction.

Isotope data prove that all the waters in the Denizli Basin infiltrated in the Holocene under more or less the same climate, so these waters are young indicating much shorter transit time from the recharge to the discharge areas because of faster flow under the surface or shorter path of the subsurface flow.

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