30 / 2025-03-27 09:58:39

Revisiting the provenance and formation environment of bauxite and associated riverine deposits

Bauxitization; laterization; Quaternary glaciation; weathering; U-Pb dating; zircon;

Theme 3: Earth-Life Co-evolution Through Time > Session 3c: Life-Mineral Interactions during the Plant Terrestrialization

Bauxite deposits have long been linked to intense subaerial chemical weathering, serving as an indicator of a warm and humid (paleo-)climate and a relatively stable tectonic setting. However, the formation environment of bauxite has long been a subject of debate. This study investigates the provenance and sedimentation-weathering processes of Cenozoic bauxite in South China, which features a complex provenance associated with modern river sediments. Geochronological constraints indicate the formation age of the bauxite deposits to be between 10.49 ± 0.78 ka and 439 ± 43 ka (Middle Pleistocene – Upper Holocene). The sedimentation period coincides well with interglacial periods of the Quaternary Ice Age, possibly indicating that the parent material for bauxite formation was deposited rapidly during floods under warm climate conditions. New detrital zircon U-Pb isotopic age data (803 from bauxite deposits and 455 from river sediments) reveal that the detrital zircon compositions in the river sediments are relatively uniform, minimally influenced by surrounding bedrock inputs, and represent a sustained detrital supply and transport system within a stable fluvial regime. However, significant variations in detrital zircon compositions are observed in bauxite deposits from different regions, recording age peaks from proximal bedrock, thus possibly recording rapid proximal accumulation. Analysis of the detrital zircon compositions of modern bauxite and nearby river sediments indicates that their provenance does not completely match, suggesting that deposition of the bauxite parent rock may not have resulted from sedimentation in the present river systems. This result reveals that, under conditions of rapid chemical weathering in the modern subtropical monsoonal climate, the formation of bauxite relies on a supply-limited weathering process characterized by low rates of physical erosion and surface sediment accumulation.