Strontium in coral aragonite: 3. Sr coordination and geochemistry in relation to skeletal architecture
Strontium in coral aragonite: 3. Sr coordination and geochemistry in relation to skeletal architecture
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DOI：
10.1016/j.gca.2005.01.026
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发表时间：
2005-08-01
影响因子：
5
通讯作者：
Sutton, SR
中科院分区：
文献类型：
--
作者：
Allison, N;Finch, AA;Sutton, SR
珊瑚Sr古温度计的使用假设珊瑚骨架中的Sr随机取代文石结构中的Ca。Sr在附加相中的存在，锶石或Sr在文石中金属位置的非随机分布将使Sr/Ca-海面温度关系复杂化。我们已经使用Sr K-边缘microEXAFS（扩展X射线吸收精细结构），以确定Sr的结构状态，在选定的微体积的四个珊瑚骨骼（滨珊瑚裂叶珊瑚，鹿角珊瑚，孔雀，Montastrea annularis）。我们使用5 X 3 Am光束分析珊瑚骨骼结构的特定区域，即，钙化中心、纤维束和隔膜。所有EXAFS分析完善，误差范围内，一个理想的取代锶文石，我们没有发现证据的锶矿或部分有序的结构状态。各向异性的第一壳响应的结果，分析的微体积不一定是平均的文石中的所有晶体取向的响应的事实。虽然二次离子质谱证实，Sr/Ca组成可以有很大的不同骨架成分之间，我们没有发现任何证据的Sr结构状态的对比。锶异质性可能是由于动力学效应，反映复杂的不平衡过程中的晶体沉淀，或生物效应，导致生物介导的钙化液的组成的变化。版权所有（c）2005 Elsevier Ltd.
Use of the coral Sr palaeothermometer assumes that the Sr in coral skeletons is substituted randomly for Ca in the aragonite structure. The presence of Sr in additional phases e.g., strontianite, or the non random distribution of Sr across metal sites in aragonite, would complicate the Sr/Ca-sea surface temperature relationship. We have used Sr K-edge microEXAFS (extended X-ray absorption fine structure) to determine the structural state of Sr across selected microvolumes of four coral skeletons (Porites lobata, Acropora palmata, Pavona clavus, and Montastrea annularis). We used a 5 X 3 Am beam to analyse specific areas of the coral skeletal architecture, i.e., centres of calcification, fasciculi, and dissepiments. All EXAFS analyses refine, within error, to an ideally substituted Sr in aragonite, and we found no evidence of strontianite or partly ordered structural states. Anisotropy in the first shell responses results from the fact that the analysed microvolumes are not necessarily averaged for the responses of all crystal orientations in the aragonite. Although secondary ion mass spectrometry confirmed that Sr/Ca composition can vary substantially between skeletal components, we find no evidence for any contrast in Sr structural state. Sr heterogeneity may result from kinetic effects, reflecting complex disequilibrium processes during crystal precipitation, or biological effects, resulting from variations in the composition of the calcifying fluid which are biologically mediated. Copyright (c) 2005 Elsevier Ltd.