Secondary alteration minerals like clays accompanied by volcanic activity can provide an important information on eruption cycle. Representative volcanic tuffs and seabed sediments were collected from the Dokdo volcanic island in East Sea, South Korea, to interpret eruption cycle based on clay mineral characteristics and other geochemical proxies (sulfur isotope composition, Si/Al, K/Al, among others). Tuffs are mainly composed of volcanic glass and hydrothermally altered phenocrysts. Secondary minerals such as clay mineral species in volcanic tuffs mostly were identified as smectite comprising dioctahedral sheets, based on expanding to 15.8 Å after treatment with 1 M MgCl₂ solution, and 060 reflections near at 1.48 Å. Moreover, the results of infrared bands, based on (Al, Al)–OH (904–912 cm⁻¹), (Al, Fe)–OH (865–877 cm⁻¹), (Fe, Mg)–OH (778–798 cm⁻¹) indicate the presence of dioctahedral sheets in clay mineral structure. Partially, occurrence of kaolinite and relatively low pH values and K/Al ratios at the Eolgulbawi tuff support chemical flexibility of clay mineral species. The δ³⁴S value of Dongdo tuff (H₂O–S: 15.3‰) is close to water leached sulfate, whereas Seodo tuff II including pyrite and native sulfur (− 5.5‰) shows a value of H₂S-bearing volcanic gases. The similarity of chemical compositions between clay fractions and surrounding volcaniclastic rocks suggests that the smectite formed in low-temperature hydrothermal environments, where alkali elements were supplied under reducing conditions. Clay fractions separated from seabed sediments include diatom frustule with higher SiO₂/Al₂O₃ ratios, and clay minerals contain mineral nitrogen originated from organic-rich seafloor sediments. Moreover, the δ³⁴S values of seabed sediments (1.8‰, 8.4‰) indicate that the different origin of clay mineral species between tuffs and seabed sediments. It can be concluded that the alteration types and clay mineral characteristics are similar to the Surtseyan volcano, generally known as shallow-marine phreatomagmatic eruption and deposits. It further suggests that clay minerals sensitive to environmental change will be useful to interpret the volcanic environment characterized by explosive hydrovolcanic activities that occurred at the time of magma in contact with water before erupting into the atmosphere.

伴随火山活动的次生蚀变矿物（如粘土）可以提供有关喷发周期的重要信息。从韩国东海的独岛火山岛收集了代表性的火山凝灰岩和海底沉积物，以根据粘土矿物特征和其他地球化学代理（硫同位素组成，Si / Al，K / Al等）解释喷发周期。凝灰岩主要由火山玻璃和水热蚀变的隐晶组成。次级矿物，例如火山凝灰岩中的粘土矿物种类，大多被鉴定为包含八面体薄片的蒙脱石，其基于在用1 M MgCl ₂溶液处理后扩展至15.8Å ，并在1.48Å附近产生060反射。此外，基于（Al，Al）–OH（904–912 cm ^-1），（Al，Fe）-OH（865-877 cm ^-1），（Fe，Mg）-OH（778-798 cm ^-1）表示粘土矿物结构中存在八面体片。部分地，在Eolgulbawi凝灰岩中高岭石的出现以及相对较低的pH值和K / Al比值支持了粘土矿物种类的化学柔韧性。的δ ³⁴ Dongdo凝灰岩的S值（H ₂ O形S：15.3‰）靠近水硫酸浸出，而Seodo凝灰岩II包括黄铁矿和原生硫（ - 5.5‰）所示的H值₂含S的火山气体。粘土组分与周围火山碎屑岩之间化学成分的相似性表明，蒙脱石是在低温热液环境中形成的，在该环境中，在还原条件下提供了碱金属元素。从海底沉积物中分离出的粘土馏分包括具有较高SiO ₂ / Al ₂ O ₃比的硅藻壳，并且粘土矿物中的矿物氮来源于富含有机物的海底沉积物。此外，δ ³⁴海床沉积物的S值（1.8‰，8.4‰）表明凝灰岩和海床沉积物的黏土矿物种类不同。可以得出的结论是，蚀变类型和黏土矿物特征与Surtseyan火山相似，通常被称为浅海相岩浆喷发和沉积。它进一步表明，对环境变化敏感的粘土矿物将有助于解释火山岩环境，其特征是在岩浆与水接触之前，喷发到大气中之前发生了爆炸性的火山活动。