Temperature dependence of oxygen-and clumped isotope fractionation in carbonates: a study of travertines and tufas in the 6-95°C temperature range, Geochimica et Cosmochimica Acta (2015), doi: http://dx.doi.org/10.1016/j.gca. 2015.06.032 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. calibrations. For this reason there is a need to better understand the controls on isotope 25 fractionation especially on natural carbonates. In this study we analyzed oxygen, carbon and 26 clumped isotopes of a unique set of modern calcitic and aragonitic travertines, tufa and cave 27 deposits from natural springs and wells. Together these samples cover a temperature range 28 from 6 to 95°C. Travertine samples were collected close to the vents of the springs and from 29 pools, and tufa samples were collected from karstic creeks and a cave. The majority of our 30 vent and pool travertines and tufa samples show a carbonate-water oxygen isotope 31 fractionation comparable to the one of Tremaine et al. (2011)

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We have studied environmental isotopes and noble gases in groundwater samples from various locations in the Great Hungarian Plain along two selected hydrogeological cross-sections of ca 100km. The 14C groundwater ages were corrected hydrochemically and compared with age information derived from excess helium due to 4He from α-decay of U and Th and their daughter nuclides within the aquifer and to He accumulation from the crustal (and mantle) He flux. In correcting the 14C groundwater ages, we considered carbonate dissolution under open and closed system conditions in the infiltration areas. Non-radioactive reduction of the 14C/12C isotope ratio also plays an important role due to the addition of “dead” carbon species to groundwater along its subsurface pathway. High (corrected) 14C ages, which fall into the last global cold period, are supported by significantly lower heavy stable isotope values as well as lower temperatures derived from the noble gases Ne, Ar, Kr and Xe.

3H, He, 4He, and Ne data were obtained from a shallow ground‐water system being recharged by bank infiltration from the Danube River in northwestern Hungary. After correting for excess air, 4He and Ne concentrations reflect a recharge temperature of about 9° C., close to the mean annual temperature of the Danube (10.4° C). Values of H plus 3Hetrit (“initial tritium”) as a function of the tritium/He age are consistent with time series measurements of tritium in the Danube. Tritium/ He ages increase linearly as a function of distance from the Danube along ground‐water flow lines. A horizontal flow velocity of about 530 m yr1 was derived from the age gradient. Most of the deviations between measured Danube tritium data and ground‐water tritium/He data can be explained by dispersive mixing.