Intensified and apace bauxitization over the paleo-karstic surface linked to volcanism

Recent studies indicate that volcanism may be a potentially important factor in the formation of karstic bauxite, but more evidence is needed. Six billion tons bauxite formed upon paleo-karstic terrain within short time Late Carboniferous North China Basin (NCB) and Permian Youjiang (YB) China. The factors trigger their apace remain unclear. Herein, we proposed extensive volcanic eruptions have accounted for this large-scale based on mineralogy, Hg isotopes, concentration enrichment proxies samples bauxitic sequence NCB YB. generally has three layers, namely bottom Fe-bearing claystone, intermediate ore, top while claystone usually absent YB which directly covers carbonate rocks. mineral assemblages confirm they were deposited superficial alkaline reducing environment. Strong peaks with corresponding near-zero ?199Hg, signal excess volcanogenic Hg, discovered upper sequences, overlaid Ordovician substrate. It denotes occurred immediately subsequent to deposition terrestrial weathered Al-rich remnants depressions during Carboniferous. This volcanism, occurring northern margin NCB, considered triggered bauxitization after its long exposure weathering. In YB, remarkable ?199Hg observed entire sequences as enhanced inputs throughout whole process Permian. episode associated Emeishan large igneous province contemporaneous arc system resulted term weathering source materials Volcanism suggested aggravate surface acidic oxidizing conditions, rapid decomposition release Al3+ precipitate diaspore above physiochemical barrier underlying carbonate.