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首页> 外文期刊>Earth Surface Dynamics Discussions >Linking mineralisation process and sedimentary product in terrestrial carbonates using a solution thermodynamic approach
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Linking mineralisation process and sedimentary product in terrestrial carbonates using a solution thermodynamic approach

机译：使用溶液热力学方法将矿化过程与陆相碳酸盐中的沉积产物联系起来

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Determining the processes which generate terrestrial carbonate deposits (tufas, travertines and to a lesser extent associated chemical sediments such as calcretes and speleothems) is a long-standing problem. Precipitation of mineral products from solution reflects a complex combination of biological, equilibrium and kinetic processes, and the different morphologies of carbonate sediment produced by different processes have yet to be clearly demarked. Building on the groundbreaking work of previous authors, we propose that the underlying control on the processes leading to the deposition of these products can be most parsimoniously understood from the thermodynamic properties of their source solutions. Here, we report initial observations of the differences in product generated from spring and lake systems spanning a range of temperature–supersaturation space. We find that at high supersaturation, biological influences are masked by high rates of physico-chemical precipitation, and sedimentary products from these settings infrequently exhibit classic "biomediated" fabrics such as clotted micrite. Likewise, at high temperature (>40 °C) exclusion of vascular plants and complex/diverse biofilms can significantly inhibit the magnitude of biomediated precipitation, again impeding the likelihood of encountering the "bio-type" fabrics. Conversely, despite the clear division in product between extensive tufa facies associations and less spatially extensive deposits such as oncoid beds, no clear division can be identified between these systems in temperature–supersaturation space. We reiterate the conclusion of previous authors, which demonstrate that this division cannot be made on the basis of physico-chemical characteristics of the solution alone. We further provide a new case study of this division from two adjacent systems in the UK, where tufa-like deposition continuous on a metre scale is happening at a site with lower supersaturation than other sites exhibiting only discontinuous (oncoidal) deposition. However, a strong microbiological division is demonstrated between these sites on the basis of suspended bacterial cell distribution, which reach a prominent maximum where tufa-like deposits are forming. We conclude that at high supersaturation, the thermodynamic properties of solutions provide a highly satisfactory means of linking process and product, raising the opportunity of identifying water characteristics from sedimentological/petrological characteristics of ancient deposits. At low supersaturation, we recommend that future research focuses on geomicrobiological processes rather than the more traditional, inorganic solution chemistry approach dominant in the past.
机译：确定产生陆上碳酸盐沉积物（石灰石，钙华和在较小程度上与相关的化学沉积物（如石灰石和蛇皮草）有关的过程）是一个长期存在的问题。从溶液中沉淀出的矿物产品反映了生物学，平衡和动力学过程的复杂结合，并且由不同过程产生的碳酸盐沉积物的不同形态尚未明确描述。在先前作者的开创性工作的基础上，我们建议可以从其源解决方案的热力学性质最简约地理解导致这些产品沉积的过程的基本控制。在这里，我们报告了对温度和过饱和空间范围内春季和湖泊系统产生的产品差异的初步观察。我们发现，在较高的过饱和度下，高物理化学沉淀速率掩盖了生物学影响，并且来自这些环境的沉积产品很少显示出经典的“生物介导的”织物，例如凝结的微尘。同样，在高温（> 40°C）下，维管植物和复杂/多样的生物膜的排斥会显着抑制生物介导的沉淀，从而再次阻碍了遇到“生物型”织物的可能性。相反，尽管在广泛的凝灰岩相关联和空间上较不广泛的沉积物（如类瘤质床）之间在产品上有明确的划分，但在温度过饱和空间中，这些系统之间没有明确的划分。我们重申先前作者的结论，这些结论表明不能仅根据溶液的理化特性来进行此划分。我们进一步提供了一个来自英国两个相邻系统的这种划分的新案例研究，在该区域中，米粉状连续沉积发生在米级，其过饱和度低于其他仅表现出不连续（盘状）沉积的位置。然而，基于悬浮的细菌细胞分布，在这些位点之间表现出强烈的微生物学分裂，在形成类似石灰华的沉积物的情况下达到了显着的最大值。我们得出的结论是，在高过饱和度下，溶液的热力学性质为连接过程和产物提供了非常令人满意的方法，从而增加了从古沉积物的沉积学/岩石学特征中识别水特征的机会。在过饱和度较低的情况下，我们建议未来的研究重点是地球微生物学过程，而不是过去占主导地位的更传统的无机溶液化学方法。

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