Europium anomaly variation under low-temperature water-rock interaction: A new thermometer
- 153 Downloads
The positive europium (Eu) anomaly, enrichment of Eu abundance relative to the neighboring elements, is often observed for water interacted with the rocks. Not only high temperature (~400°C) water-rock interaction such as seafloor hydrothermal fluids, but also relatively lower temperature interaction, less than 100°C, cause positive Eu anomaly. However, relationship between the degree of Eu anomaly and interaction temperature has not been investigated. Water-rock interaction experiments at three different reaction temperatures were performed in this study to reveal the cause of positive Eu anomaly. Comparison of the results under different solution chemistry and temperature conditions showed that the basalt containing plagioclase released larger abundances of REEs than the basaltic glass. The degree of Eu anomaly assessed by Eu/Eu* value was smaller when 0.7 M NaCl solution was used for liquid phase for both solid phases. On the other hand, the Eu/Eu* became larger with increasing reaction temperature for basalts interacted with ultra-pure water. Therefore, it is suggested that the Eu anomaly is potentially used as a fluid-rock interaction thermometer under low salinity condition.
Keywordseuropium (Eu) anomaly rare-earth element (REE) water-rock interaction basalt XANES
Unable to display preview. Download preview PDF.
- M. Bau, A. Usui, B. Pracejus, N. Mita, Y. Kanai, W. Irber, and P. Dulski, “Geochemistry of low-temperature water–rock interaction: evidence from natural waters, andesite, and iron-oxyhydroxide precipitates at Nishiki-numa iron-spring, Hokkaido, Japan,” Chem. Geol. 151, 293–307 (1998).CrossRefGoogle Scholar
- M. F. Hochella, Jr. and J. F. Banfield, “Chemical weathering of silicates in nature: A microscopic perspective with theoretical considerations,” in Chemical Weathering of Silicate Minerals, Ed. by A. F. White and S. L. Brantley, Mineral. Soc. Am. 31, 353–406 (1995).Google Scholar
- P. Kralj, “Trace elements in medium-temperature (40–80oC) thermal waters from the Mura basin (North-Eastern Slovenia),” Environ. Geol. 46, 622–629 (2004).Google Scholar
- F. C. Loughnan, Chemical Weathering of Silicate Minerals (Elsevier, New York, 1969).Google Scholar
- T. Shibuya, M. Tahata, K. Kitajima, Y. Ueno, T. Komiya, S. Yamamoto, M. Igisu, M. Terabayashi, Y. Sawaki, K. Takai, N. Yoshida, and S. Maruyama, “Depth variation of carbon and oxygen isotopes of calcites in Archean altered upper oceanic crust: implications for the CO2 flux from ocean to oceanic crust in the Archean,” Earth Planet. Sci. Lett. 321–322, 64–73 (2012).CrossRefGoogle Scholar
- T. Shibuya, M. Yoshizaki, Y. Masaki, K. Suzuki, K. Takai, and M. J. Russell, “Reactions between basalt and CO2-rich seawater at 250 and 350°C, 500 bars: implications for the CO2 sequestration into the modern oceanic crust and the composition of hydrothermal vent fluid in the CO2-rich early ocean,” Chem. Geol. 359, 1–9 (2013).CrossRefGoogle Scholar
- S. T. Taylor and S. M. McLennan, “The significance of the rare earths in geochemistry and cosmochemistry,” Handbook on the Physics and Chemistry of Rare Earth, Ed. by K. A. Gschneidner, Jr. and L. Eyring, (Elsevier, Amsterdam, 1988), pp. 485–578.Google Scholar
- J. E. Welton, SEM Petrology Atlas. Methods in Exploration Series (Am. Ass. Petrol. Geol., Tulsa, 1984).Google Scholar