Lei Gao

High-purity quartz is a critical raw material for high-tech industries such as semiconductors and photovoltaics, yet its purity is severely constrained by gas–liquid inclusions within quartz crystals that are difficult to eliminate. The calcination–water quenching process is a key pretreatment step for removing inclusions and achieving deep purification, but its underlying mechanisms and the influence of process parameters on removal efficiency remain insufficiently understood. In this study, systematic calcination–water quenching experiments at different temperature gradients (500 °C, 700 °C, 900 °C, and 1100 °C) were conducted on high-purity quartz samples from Inner Mongolia and Angola. Comprehensive analytical techniques, including X-ray diffraction (XRD), major and trace element analyses, and polarizing microscopy, were employed to investigate the microstructural evolution, inclusion morphology, impurity element concentration changes, and phase transformation behavior before and after treatment. With increasing temperature, the quartz samples exhibited pronounced whitening and pulverization, accompanied by a significant reduction in the number of internal linear inclusions. Elemental analysis revealed that calcination–water quenching effectively removed certain alkali metals, alkaline-earth metals, and iron impurities, with 900 °C identified as the optimal calcination temperature; moreover, the sand-sized samples consistently showed better impurity removal efficiency than the lump-sized counterparts. XRD analysis was used to verify the phase transformation of quartz during calcination. Excessive temperatures (e.g., 1100 °C) led to a rebound in the content of some impurity elements. The calcination–water quenching process promotes inclusion decrepitation, exposure, and subsequent removal through the combined effects of volumetric strain induced by quartz phase transitions, thermal pressurization of inclusions, and thermal-shock stress from water quenching. This study establishes the optimal process window (hold at 900 °C for 2 h, sand-sized morphology) for the specific ore samples, elucidates the multi-factor synergistic mechanism of inclusion rupture, and provides both experimental and theoretical bases for the industrial purification of high-purity quartz.

During the Ediacaran–Cambrian transition, a series of stratal continuous and well-preserved siliceous rock and phosphorite assemblages developed in Qingzhen, Guizhou Province, China, facilitating research on the biological evolution, marine chemistry, and palaeoecological environment of this period. Therefore, we investigated the paleontology, trace and rare earth elements, total organic carbon, total sulfur content, and Zn isotopes of the phosphorus-bearing rock series in the Taozichong Formation of the Cambrian period in Qingzhen. Geochemical analysis reveals that the sedimentary rocks in this area were formed in the oxygen-rich seawater environment and were not affected by high-temperature hydrothermal activity. The upwelling ocean current provided abundant rare earth elements and other nutrient elements, as well as conditions for the prosperity of biota in Qingzhen. In addition, the δ⁶⁶Zn value (−0.21‰–0.41‰ range and 0.17‰ mean) in the Qingzhen phosphorous rock series was much lower than that in seawater, indicating a strong level of biological productivity. The variation trend of δ¹³C, δ¹⁸O, and δ⁶⁶Zn exhibited four stages and three obvious drift events. The results suggest that climate change during this period led to the intermittent flourishing and extinction of organisms, which triggered the negative drift of δ¹³C and δ¹⁸O in the ocean, resulting in a coordinated response of δ⁶⁶Zn. The unique ecological environment of the Taozichong Formation in Qingzhen also provides favorable conditions for the population continuation of Ediacaran-type benthic soft-bodied metazoon dominated by discoid fossils, Shaanxilithes, worm fossils, and sponge fossils in the Cambrian strata, as well as participation in the global biological explosion events. The study area provides new insights for rebuilding the global Ediacaran–Cambrian ecosystem during the transition period.