Temperature dependence of oxygen- and clumped isotope fractionation in carbonates: A study of travertines and tufas in the 6-95°C temperature range

Kele, Sándor and Breitenbach, Sebastian F. M. and Capezzuoli, Enrico and Meckler, A. Nele and Ziegler, Martin and Millan, Isabel M. and Kluge, Tobias and Deák, József and Hanselmann, Kurt and John, Cédric M. and Yan, Hao and Liu, Zaihua and Bernasconi, Stefano M. (2015) 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, 168. pp. 172-192. ISSN 0016-7037 DOI https://doi.org/10.1016/j.gca.2015.06.032

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Abstract

Conventional carbonate–water oxygen isotope thermometry and the more recently developed clumped isotope thermometer have been widely used for the reconstruction of paleotemperatures from a variety of carbonate materials. In spite of a large number of studies, however, there are still large uncertainties in both δ18O- and Δ47-based temperature calibrations. For this reason there is a need to better understand the controls on isotope fractionation especially on natural carbonates. In this study we analyzed oxygen, carbon and clumped isotopes of a unique set of modern calcitic and aragonitic travertines, tufa and cave deposits from natural springs and wells. Together these samples cover a temperature range from 6 to 95 °C. Travertine samples were collected close to the vents of the springs and from pools, and tufa samples were collected from karstic creeks and a cave. The majority of our vent and pool travertines and tufa samples show a carbonate–water oxygen isotope fractionation comparable to the one of Tremaine et al. (2011) with some samples showing higher fractionations. No significant difference between the calcite–water and aragonite–water oxygen isotope fractionation could be observed. The Δ47 data from the travertines show a strong relationship with temperature and define the regression Δ47 = (0.044 ± 0.005 × 106)/T2 + (0.205 ± 0.047). The pH of the parent solution, mineralogy and precipitation rate do not appear to significantly affect the Δ47-signature of carbonates, compared to the temperature effect and the analytical error. The tufa samples and three biogenic calcites show an excellent fit with the travertine calibration, indicating that this regression can be used for other carbonates as well. This work extends the calibration range of the clumped isotope thermometer to travertine and tufa deposits in the temperature range from 6 °C to 95 °C.

Item Type:	Article
Uncontrolled Keywords:	2015AREP; IA69; weekly list
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title:	Geochimica Et Cosmochimica Acta
Volume:	168
Page Range:	pp. 172-192
Identification Number:	https://doi.org/10.1016/j.gca.2015.06.032
Depositing User:	Sarah Humbert
Date Deposited:	08 Jan 2016 19:23
Last Modified:	08 Jan 2016 19:23
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3531

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