Geochemical and mineralogical investigations of the Lower Permian Kemmlitz rhyolite within the NW-Saxonian Basin (Germany) and associated lithophysae (high-temperature crystallization domains) as well as agates were carried out to constrain the genesis and characteristics of these volcanic rocks and the origin of the agate-bearing lithophysae. The volcanic rocks of rhyolitic composition are dominated by quartz, sanidine, and orthoclase and most likely derive from lava flows. Agate-bearing lithophysae were exclusively formed in a glassy facies (pitchstone) of the rhyolites, which was afterwards altered to illite-smectite mixed-layer clays. The results of this study show that agate formation can be related to the alteration of the volcanic rocks accompanied by the infill of mobilized silica into cavities of lithophysae. Fluid inclusion studies point to temperatures of agate formation above 150 °C, indicating that the mobilization and accumulation of silica started already during a late phase of or soon after the volcanic activities. Remarkable high concentrations of B (29 ppm), Ge (> 18 ppm), and U (> 19 ppm) as well as chondrite-normalized rare earth element (REE) distribution patterns of the agates with pronounced negative Eu-anomalies, slightly positive Ce-anomalies and enriched heavy rare earth elements (HREE) indicate interactions of the host rocks and transport of SiO₂ with magmatic volatiles (F/Cl, CO₂) and heated meteoric water. Characteristic yellow cathodoluminescence (CL), heterogeneous internal textures as well as high defect density of micro- and macrocrystalline quartz detected by electron paramagnetic resonance (EPR) spectroscopy point to crystallization processes via an amorphous silica precursor under non-equilibrium conditions.

对西北撒克逊盆​​地（德国）内的下二叠统凯姆利茨流纹岩和相关的石泡（高温结晶区）以及玛瑙进行了地球化学和矿物学调查，以限制这些火山岩的成因和特征以及火山岩的起源。含有玛瑙的石泡。流纹岩成分的火山岩主要由石英、透长石和正长石组成，很可能源自熔岩流。含玛瑙的石泡仅在流纹岩的玻璃相（沥青岩）中形成，随后转变为伊利石-蒙脱石混合层粘土。这项研究的结果表明，玛瑙的形成可能与火山岩的蚀变有关，同时伴随着流动的二氧化硅填充到石泡的空腔中。流体包裹体研究指出玛瑙的形成温度高于 150 °C，这表明二氧​​化硅的动员和积累已经在火山活动的后期或火山活动后不久就开始了。玛瑙中 B (29 ppm)、Ge (> 18 ppm) 和 U (> 19 ppm) 浓度以及球粒陨石归一化稀土元素 (REE) 分布模式具有明显的负 Eu 异常，略为正异常Ce 异常和富集的重稀土元素 (HREE) 表明主岩和 SiO2 迁移之间的相互作用₂含有岩浆挥发物（F/Cl、CO ₂）和加热的大气水。通过电子顺磁共振（EPR）光谱检测到的微晶和宏观晶石英的特征黄色阴极发光（CL）、异质内部纹理以及高缺陷密度表明在非平衡条件下通过无定形二氧化硅前体进行结晶过程。