碩士 / 國立成功大學 / 地球科學系 / 102 / In present study, we investigated the boron isotopic distributions in various specimens, including marine carbonates, inorganic precipitated calcite and adsorbed B on oxide surface, and the associating isotopic fractionation under different pH conditions. The δ11B values in the biogenic calcium carbonates were 24.2‰ and 16.2‰ in corals JCp-1 and giant clam JCt-1, respectively. The distinct δ11B values in the two specimens suggest that biogenic effects strongly influence the boron isotopic fractionation factor in carbonates under similar seawater pH conditions. Our batch experiment was conducted under peroxidic conditions. The δ11B in the performed carbonate was distinct with that of theoretical calculations. It indicates that the boron isotopic compositions are significantly influenced by the peroxoborate rather than the borate during the carbonate formation. The equilibrium constant and potential boron isotopic fractionation during the sorption processes onto oxide surface was evaluated as well. The maximum boron sorption occurs at 8〈pH〈10 with a Kd up to 55.3. The boron isotopic compositions of the adsorbed to varied as a function of solution pHs. Thus, the δ11B associated in the oxide fraction serves as a sensitive tracer to reconstruct the pH conditions in the paleo-environments. Accordingly, the determination of δ11B in multi-geochemical fractions, i.e. carbonates and iron-oxides, provides an opportunity to evaluate the paleo-pH conditions without the conventional assumption of paleo- seawater boron isotopic compositions.
| Identifer | oai:union.ndltd.org:TW/102NCKU5135140 |
| Date | January 2014 |
| Creators | Yen-PoLin, 林彥伯 |
| Contributors | Chen-Feng You, 游鎮烽 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 49 |
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