Subaerial volcanism and atmospheric volcanic ash deposition have been recognized as factors that can greatly affect the nutrient content of the surface ocean and the redox conditions of the water column. Black siliceous, organic-rich mudstone and shale containing numerous volcanic ash layers were deposited in the South China Block during the Ordovician-Silurian transition. Although this association has been observed in other regions, whether there is a relationship between volcanic ash and the organic carbon contents and the effect of volcanic ash remains unclear. Based on analysis of the concentrations of major elements, trace elements, and total organic carbon in the volcanic ash and shale, we found that anoxic and high-productivity environments existed during the Ordovician-Silurian transition and that organic matter was preferentially preserved under these conditions. For the volcanic ash, we quantitatively estimated the depletion of the nutrient elements Fe, Si, and P (in percentages). The calculated results show that leaching removed 25–75% of the Fe, Si, and P in most of the ash samples in the study area, potentially leading to high marine primary productivity in the surface water. Redox conditions also played a major role in the preservation of organic matter. The trace element analysis results show that although productivity was high during the Ordovician-Silurian transition, organic matter was preferentially preserved in the Lower Silurian strata. Therefore, high organic matter flux and good preservation conditions both contributed to the formation of the organic-rich shale, and volcanic ash was the dominant source of nutrients for primary productivity.

中文翻译：

---

火山灰是页岩中有机碳富集的原因吗？奥陶纪-lur陵系过渡带富含有机质页岩的定量表征

航空火山作用和大气火山灰沉积已被认为是可以极大影响表层海洋营养成分和水柱氧化还原条件的因素。在奥陶纪-lur留纪过渡期，华南地块沉积了黑色硅质，富含有机质的泥岩和页岩，含大量火山灰层。尽管在其他地区也观察到这种关联，但尚不清楚火山灰与有机碳含量之间是否存在关系，以及火山灰的影响。通过分析火山灰和页岩中主要元素，微量元素和总有机碳的浓度，我们发现，在奥陶纪-西柳纪过渡期存在缺氧和高产环境，并且在这些条件下有机质得到了优先保存。对于火山灰，我们定量地估算了营养元素铁，硅和磷的消耗（百分比）。计算结果表明，浸出去除了研究区域大部分灰分样品中25-75％的铁，硅和磷，可能导致地表水的海洋初级生产力较高。氧化还原条件在有机物的保存中也起着重要作用。微量元素分析结果表明，尽管奥陶纪-西陆纪过渡期生产力较高，但下志留统地层仍优先保留有机质。所以，