An ice-free greenhouse interval (ca. 660 ∼ 650 Ma) occurred between the global Sturtian (ca. 717 Ma ∼ 660 Ma) and Marinoan glaciation (ca. 650 Ma ∼ 635 Ma) during the Cryogenian. While volcanic CO₂ emissions have been suggested as a trigger for this ice-free interval, evidence for volcanism has been lacking. In this study, spikes in both Hg concentration (76 to 366 ppb) and Hg to total organic carbon ratio (Hg/TOC: 114 to 717 ppb/wt.%) were observed in the Wuhe section of South China, suggesting that extensive volcanic emissions of Hg occurred during the Cryogenian interglacial period. Positive ${\mathrm{\Delta }}^{199}$Hg (0.02 to 0.18‰) values were observed in these Hg-rich shales, indicating that the volcanic Hg was cycling in the atmosphere, deposited in seawater, and sequestered to sediment via organic matter burial. Combined with other geochemical proxies (e.g., organic carbon isotope and chemical index of alteration), our results provide the first direct evidence that volcanism played a key role in forming the brief Cryogenian interglacial period.

在低温时代，全球斯图里特人（约717 Ma〜660 Ma）和马里诺期冰河融化（约650 Ma〜635 Ma）之间发生了无冰温室间隔（约660〜650 Ma）。虽然有人建议将火山的CO ₂排放触发为无冰期，但仍缺乏火山活动的证据。在这项研究中，在华南五合地区观察到了汞浓度（76至366 ppb）和汞与总有机碳比（Hg / TOC：114至717 ppb / wt。％）的峰值，这表明火山活动广泛汞的排放发生在冰晶期间冰期。积极的${\mathrm{\Delta }}^{199}$在这些富含汞的页岩中观察到Hg（0.02至0.18‰）值，表明火山Hg在大气中循环，沉积在海水中，并通过有机物埋藏而被隔离为沉积物。结合其他地球化学代理（例如有机碳同位素和化学变化指数），我们的结果提供了第一个直接证据，表明火山作用在形成短暂的低温冰晶间期中起了关键作用。