Abstract Pore-filling and carbonate-replacing silica is exceedingly common in carbonates, but the fundamental geochemical mechanisms that drive these silicification reactions during diagenesis remain poorly understood. An existing model has proposed that carbonate silicification proceeds through an interface-coupled dissolution-precipitation reaction, but it lacks a mechanism that enables pore fluids to reach the requisite level of supersaturation with respect to silica to allow nucleation and growth. Here, we present a sequence of batch experiments ranging in duration from 7 to 49 days designed to test the hypothesis that these reactions are facilitated by the formation and destruction of organo-silica complexes during diagenesis. Our results illustrate that the stability of organo-silica complexes is dependent upon the concentration of organic molecules in solution, as well as pH, salinity, and solution redox state. Together, these results allow us to present the following scheme for organo-silica complex mediation of silicification reactions: Firstly, the breakdown of organic matter in the presence of siliceous material creates organo-silica complexes, leading to silica-enriched pore fluids, a process which is enhanced by the anoxic conditions accompanying sediment burial. Then, as environmental conditions evolve (fO2, salinity, light, fCO2, pH…), the stability of the organo-silica complexes diminishes, and the organo-silica complexes break down. Simultaneously, the pore fluids become intensely silica-supersaturated, in direct proportion to the amount of organic material remaining in solution. The resulting supersaturation drives carbonate silicification via the precipitation of silica minerals, a process which is aided by the presence of silica “nuclei” (such as sponge spicules). This study contributes new data and a conceptual model that will aid in the ongoing quest to understand carbonate silicification reactions and their potential applications in hydrocarbon exploitation and geologic CO2 storage. Moreover, it helps to explain the common association between silica precipitates and organic mineral in the sedimentary rock record.

中文翻译：

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儿茶酚-二氧化硅水溶液对碳酸盐岩成岩过程中硅化作用的贡献

摘要 孔隙填充和碳酸盐替代二氧化硅在碳酸盐岩中极为常见，但在成岩过程中驱动这些硅化反应的基本地球化学机制仍知之甚少。现有模型提出碳酸盐硅化通过界面耦合的溶解-沉淀反应进行，但它缺乏使孔隙流体达到所需的相对于二氧化硅的过饱和水平以允许成核和生长的机制。在这里，我们提出了一系列持续时间为 7 到 49 天的批量实验，旨在测试这些反应是由成岩过程中有机二氧化硅复合物的形成和破坏促进的假设。我们的结果表明，有机硅复合物的稳定性取决于溶液中有机分子的浓度，以及 pH、盐度和溶液氧化还原状态。总之，这些结果使我们能够提出以下硅化反应中有机硅复合物介导的方案：首先，有机物在硅质材料存在下的分解产生有机硅复合物，导致富含二氧化硅的孔隙流体，这是一个过程伴随沉积物掩埋的缺氧条件增强了这一点。然后，随着环境条件的变化（fO2、盐度、光照、fCO2、pH...），有机硅复合物的稳定性降低，有机硅复合物分解。同时，孔隙流体变得高度二氧化硅过饱和，与残留在溶液中的有机物质的量成正比。由此产生的过饱和通过二氧化硅矿物的沉淀推动碳酸盐硅化，这一过程得益于二氧化硅“核”（如海绵针状体）的存在。这项研究提供了新的数据和概念模型，将有助于对碳酸盐硅化反应及其在碳氢化合物开采和地质 CO2 封存中的潜在应用的持续探索。此外，它有助于解释沉积岩记录中二氧化硅沉淀物与有机矿物之间的共同关联。这项研究提供了新的数据和概念模型，将有助于对碳酸盐硅化反应及其在碳氢化合物开采和地质 CO2 封存中的潜在应用的持续探索。此外，它有助于解释沉积岩记录中二氧化硅沉淀物与有机矿物之间的共同关联。这项研究提供了新的数据和概念模型，将有助于对碳酸盐硅化反应及其在碳氢化合物开采和地质 CO2 封存中的潜在应用的持续探索。此外，它有助于解释沉积岩记录中二氧化硅沉淀物与有机矿物之间的共同关联。