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

详细信息    查看全文

• 作者：Sá ; ndor Kele^a ; ^b ; ^{keles@geochem.hu" class="auth_mail" title="E-mail the corresponding author} ; Sebastian F.M. Breitenbach^a ; ^c ; Enrico Capezzuoli^d ; A. Nele Meckler^a ; Martin Ziegler^a ; Isabel M. Millan^a ; Tobias Kluge^e ; ^f ; Jó ; zsef Deá ; k^g ; Kurt Hanselmann^a ; Cé ; dric M. John^e ; Hao Yan^h ; Zaihua Liu^h ; Stefano M. Bernasconi^a
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：2015
• 出版时间：1 November 2015
• 年：2015
• 卷：168
• 期：Complete
• 页码：172-192
• 全文大小：6548 K

文摘

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 未¹⁸O- and 螖₄₇-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 螖₄₇ data from the travertines show a strong relationship with temperature and define the regression 螖₄₇ = (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 螖₄₇-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.