Abstract Silica-rich coatings of up to 660 μm thickness were found on the juvenile volcanic lapilli and blocks of the 1783 CE pyroclastic flow deposits 1.9–3.6 km northeast of the Maekake crater of Asama volcano in Central Japan. These coatings are composed of fine-grained volcanic ash particles with silica-rich cement. Raman spectroscopic measurements revealed that the interstitial silica-rich phase is hydrous amorphous silica and is considered to be a reaction product of ash particles with acidic volcanic rain and fog like volcanic smog (vog) as it has been recorded in Hawaii. The formation of amorphous silica without jarosite and the preferential alteration of plagioclase compared with pyroxene indicate that the reaction occurred with a sulfuric acid solution of pH

中文翻译：

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公元 1783 年浅间火山喷发的侧面沉积物上的无定形二氧化硅涂层

摘要 在日本中部浅间火山 Maekake 火山口东北部 1.9-3.6 公里处的 1783 CE 火山碎屑流沉积物的幼年火山碎屑和块体上发现了厚度高达 660 μm 的富含二氧化硅的涂层。这些涂层由细粒火山灰颗粒和富含二氧化硅的水泥组成。拉曼光谱测量表明，富含二氧化硅的间隙相是含水无定形二氧化硅，被认为是火山灰颗粒与酸性火山雨和雾如火山烟雾 (vog) 的反应产物，因为它已在夏威夷记录。不含黄钾铁矾的无定形二氧化硅的形成和斜长石与辉石相比的优先改变表明反应发生在 pH 值的硫酸溶液中