Mechanisms of inorganic silicification of early Precambrian (older than 750 Ma) carbonate rocks remain equivocal. A quantitative model is presented here that captures the essence of ancient inorganic silicification of the carbonate rocks and is based on the hypotheses that carbonate silicification, a volume-conservative replacive process, is driven by crystallization stress induced by the growth of the guest mineral. Results of the quantitative model for silicification of calcitic limestone and dolostone are compared and validated against available independent observations and are found to be geologically reasonable. The quantitative model suggests that silicification of carbonate rocks is dependent on the host-rock composition and that calcitic limestones will be readily silicified compared to dolostone and/or aragonitic limestone. Results also show that silicification rate of carbonate rocks—irrespective of their composition—increases with increase in silica supersaturation and reactive surface area. Porosity and permeability of the host rock also increases the silicification rate of the carbonate rocks. Results also predict that substantial volume of silica-saturated fluids is required for inorganic silicification of a one-meter cube of carbonate rock. The quantitative model presented here has its limitations and should not be viewed as a unique and truly realistic representation of the carbonate silicification mechanism. The quantitative model presented here is unable to explain the formation of porosity and subsequent volume reduction of the parent material during the replacement process as observed in replacement experiments. Also, the effect of pH on silicification of carbonate rocks cannot be quantitatively estimated in this study. The quantitative model presented here should be viewed as one of the possible mechanisms of carbonate silicification that has to be tested further with experimental data and by model refinement.

中文翻译：

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古代碳酸盐岩的无机硅化作用

早前寒武纪（大于750 Ma）碳酸盐岩的无机硅化机理仍然不明确。这里提出了一个定量模型，该模型捕获了碳酸盐岩石古老的无机硅化作用的本质，并基于以下假设：碳酸盐硅化作用（一种体积守恒的置换过程）是由客体矿物的生长引起的结晶应力驱动的。将钙质石灰石和白云石硅化的定量模型的结果进行了比较，并根据可得的独立观测结果进行了验证，发现其在地质上是合理的。定量模型表明，碳酸盐岩的硅化作用取决于基质岩的组成，与白云岩和/或钠钙质石灰石相比，钙质石灰岩将很容易被硅化。结果还表明，碳酸盐岩石的硅化速率（无论其成分如何）随着二氧化硅过饱和度和反应表面积的增加而增加。基质岩石的孔隙度和渗透率也增加了碳酸盐岩的硅化率。结果还预测，要对一米长的碳酸盐岩进行无机硅化，需要大量的二氧化硅饱和流体。这里介绍的定量模型有其局限性，不应被视为碳酸盐硅化机理的唯一且真实的代表。此处提供的定量模型无法解释置换实验中观察到的置换过程中母体材料的孔隙形成和随后的体积减小。还，在这项研究中，不能定量估计pH对碳酸盐岩石硅化作用的影响。此处介绍的定量模型应被视为碳酸盐硅化的可能机制之一，必须通过实验数据和模型完善对其进行进一步测试。