期刊
GEOCHIMICA ET COSMOCHIMICA ACTA
卷 73, 期 7, 页码 1890-1900出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2009.01.002
关键词
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资金
- NSF [05-39109]
- W.M. Keck Foundation
- Carnegie Institution for Science
- Deutsche Forschungsgemeinschaft [Mu 40/911]
Understanding the partitioning of aqueous boron species into marine carbonates is critical for constraining the boron isotope system for use as a marine pH proxy. Previous studies have assumed that boron was incorporated into carbonate through the preferential uptake of tetrahedral borate B(OH)4(-). In this study we revisit this assumption through a detailed solid state B-11 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic study of boron speciation in biogenic and hydrothermal carbonates. Our new results contrast with those of the only previous NMR study of carbonates insofar as we observe both trigonal and tetrahedral coordinated boron in almost equal abundances in our biogenic calcite and aragonite samples. In addition, we observe no strict dependency of boron coordination on carbonate crystal structure. These NMR observations coupled with our earlier re-evaluation of the magnitude of boron isotope fractionation between aqueous species suggest that controls on boron isotope composition in marine carbonates, and hence the pH proxy, are more complex that previously suggested. (c) 2009 Elsevier Ltd. All rights reserved.
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