Limited Zn and Ni mobility during simulated iron formation diagenesis
Limited Zn and Ni mobility during simulated iron formation diagenesis
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模拟铁形成岩作用过程中锌和镍的流动性有限
DOI：
10.1016/j.chemgeo.2015.02.037
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发表时间：
2015
期刊：
影响因子：
3.9
通讯作者：
Robbins L
中科院分区：
文献类型：
--
作者：
Robbins L
铁层是在前寒武纪沉积的富含铁和硅的化学沉淀物。最近的几项研究表明，IF中的痕量金属丰度可以作为古代海水中痕量金属生物利用度的指标；最终目标是了解古代生物圈组成的一阶控制。然而，IF作为代理的效用取决于在成岩过程中微量金属的固定化。在模拟成岩过程中（170°C, 1.2 kbar），在没有有机物（葡萄糖）的情况下，我们评估了锌和镍在三氧化二铁（水合铁）中的迁移率；类似于一些前寒武纪生物的经历。定量浓度数据，结合x射线衍射分析和电子探针元素测绘，表明这两种金属在模拟成岩过程中相对不动。此外，利用x射线吸附光谱对镍的初始吸附机理进行了研究。对于非生物水合铁初始吸附微量元素，初始吸附Zn为93.38%，Ni为65.95%。利用生物源水合铁进行实验，初始吸附Zn为97.03%，Ni为93.38%。在不同的成岩胶囊处理条件下，锌和镍的含量分别保持在99%以上和91.9%以上。胶囊实验表明，在非生物或生物成因的水合铁成岩作用后，锌和镍都有很强的保留。总的来说，我们的研究结果表明，古海洋Zn和Ni浓度可能被忠实地记录在保存完好的IF矿床中。
Iron formations (IF) are iron- and silica-rich chemical precipitates that were deposited during the Precambrian. Several recent studies have demonstrated how the trace metal abundances in IF can be used as proxies for the bioavailability of trace metals in ancient seawater; with the ultimate goal being to understand first-order controls on the composition of the ancient biosphere. However, the utility of IF as proxies depends on the immobilization of trace metals during diagenesis. Here, we assess the mobility of Zn and Ni from ferric oxyhydroxides (ferrihydrite) in the absence and presence of organic matter (glucose) during simulated diagenesis (170 °C, 1.2 kbar); similar to what some Precambrian IF experienced. Quantitative concentration data, coupled with X-ray diffraction analysis and electron microprobe element mapping, demonstrate that both metals are relatively immobile during simulated diagenesis. Additionally, the mechanism for initial Ni sorption is examined using X-ray adsorption spectroscopy. For the initial sorption of trace elements in abiotic ferrihydrite experiments, 93.38% Zn and 65.95% Ni were initially sorbed. In experiments utilizing biogenic ferrihydrite, 97.03% of Zn and 93.38% of Ni were initially sorbed. Following the diagenetic capsule treatments, more than 99% of Zn and more than 91.9% of Ni were retained under the varied conditions considered here. Capsule experiments suggest the strong retention of Zn and Ni following the diagenesis of either abiotic or biogenic ferrihydrite. Overall, our results indicate that paleomarine Zn and Ni concentrations are likely to be faithfully recorded in well-preserved IF deposits.
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DOI：
--
发表时间：
1981
期刊：
The Journal of geology
影响因子：
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DOI：
10.1103/physrevb.48.9825
发表时间：
1993-10
期刊：
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影响因子：
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