Silicon (Si) is known as an important regulator of the global carbon cycle via its effect on silicate weathering in continents and phytoplankton productivity in the oceans. It is also beneficial to plants by improving their resistance to biotic and abiotic stresses. Detailed analysis of geological record of Si in sediments underpins our understanding of ecosystem evolution over geological time. Here, we unravel the mystery of low Si content in Permo-Carboniferous shales from the central North China and link the terrestrial Si fluxes to the thriving forest ecosystems at that time. Provenance fluctuations as indicated by Zr/TiO are well explained by episodic volcanic input which are identified by elevated Zr/TiO and lowered V/AlO and Cr/AlO. CIA and Ga/Rb and KO/AlO ratios imply cyclic changes of climate in an overall warm and humid condition. The covariation between the volcanic indicators and climatic proxies indicates that the volcanism forced the climate cycles. Despite the felsic sources (high Zr/TiO and Th/Sc ratios and low Zr/Sc ratios), the Si-poor shales are universal in Permo-Carboniferous across the North China Block. The enhanced continental weathering of mineral silicates and the hydrolysis of volcanic materials released silica into the environment and led to the eventual deposition of Si-poor shales. The shales lacking in Si tend to have larger TOC contents except for the most distal shales. It implies that the sufficient supply of dissolved-Si in environments may benefit the expansion of terrestrial plants in Permo-Carboniferous and therefore the accumulation of organic matter in the shales. This work provides new insight into feedback linking volcanism, climates, terrestrial dissolved silica flux, and terrestrial ecosystems in Permo-Carboniferous North China Block.

中文翻译：

---

火山和气候对页岩中硅丰度的影响：对华北二叠纪-石炭系陆地植物扩张的影响

硅（Si）因其对大陆硅酸盐风化和海洋浮游植物生产力的影响而被认为是全球碳循环的重要调节剂。它还可以提高植物对生物和非生物胁迫的抵抗力，从而对植物有益。对沉积物中硅地质记录的详细分析巩固了我们对地质时期生态系统演化的理解。在这里，我们揭开了华北中部二叠纪-石炭系页岩低硅含量的神秘面纱，并将陆地硅通量与当时繁荣的森林生态系统联系起来。 Zr/TiO 所显示的物源波动可以通过间歇性火山输入很好地解释，火山输入可通过 Zr/TiO 升高和 V/Al2O 和 Cr/Al2O 降低来识别。 CIA、Ga/Rb 和 KO/Al2O 比值表明总体温暖湿润条件下气候的周期性变化。火山指标和气候代理之间的协变表明火山活动迫使气候循环。尽管存在长英质来源（高 Zr/TiO 和 Th/Sc 比以及低 Zr/Sc 比），但贫硅页岩在整个华北地块的二叠系-石炭系中普遍存在。矿物硅酸盐的大陆风化增强和火山物质的水解将二氧化硅释放到环境中，最终导致贫硅页岩的沉积。除最远端页岩外，缺乏 Si 的页岩 TOC 含量往往较高。这意味着环境中溶解硅的充足供应可能有利于二叠-石炭系陆生植物的扩张，从而有利于页岩中有机质的积累。这项工作为华北二叠纪-石炭系火山活动、气候、陆地溶解硅通量和陆地生态系统之间的反馈提供了新的见解。