Fast, microscale-controlled weathering of rhyolitic obsidian to quartz and alunite

摘要: Abstract Six-year experiments of volcanic glass reacting with waters different chemistry (two freshwaters, seawater and brine) at ∼22 °C have produced the thorough transformation mm-size chips into quartz, minor alunite calcite. These results contradict current thinking about weathering quartz formation. The reaction from to took place an estimated velocity ranging 300–2000 times 10 6 faster than accepted values for precipitation, depending on how rates were assessed. most likely process taking is rapid cation-depleted quartz. In addition, formed very efficiently low-S (40±15 ppm). Such effective in absence conditions formation attributed high Al K content combined generation low pH microscale. Local, low-pH may arise due proton-for-Na substitution earliest stage followed by liberation protons as later corroded. surprising show a new pathway point towards reactions controlled microscale producing activities locally. be common mineral–fluid interface saline waters, immobile or systems water:rock ratios. precipitation temperature relevant origin silica budget variety sedimentary environments prompts their reconsideration.