Source-rock, grain-size, weathering, and recycling controls on the feldspar/quartz ratio in silt-sized sediments

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 660; p. 112700
• Main Authors: Fu, Hanjing, Jian, Xing, Zhang, Zhihua, Pan, Hanqing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.02.2025
• Subjects: Chemical weathering; Lithology; River sediments; Sediment recycling; Silt-sized minerals; Sediment recycling; River sediments; Silt-sized minerals; Lithology; Chemical weathering
• ISSN: 0031-0182
• DOI: 10.1016/j.palaeo.2024.112700

Numerous chemical weathering indices have been proposed based on analyses of weathering products and/or residues from siliciclastic sediments to reconstruct paleoclimate. The subjects of weathering studies often concentrate on the bulk-sample, clay and sand components, neglecting the study of silt mineral composition and its potential applications in weathering and provenance analysis. In this study, we investigate the variability of the plagioclase/quartz (Pl/Qtz), feldspar/quartz (F/Qtz), K-feldspar/quartz (Kfs/Qtz), plagioclase/K-feldspar (Pl/Kfs) ratios in silt-sized fractions of siliciclastic sediments of East Asian rivers to understand superimposed controlling factors of lithology, climate, recycling and grain size. Results indicate that the Pl/Qtz and F/Qtz ratios of silt-sized sediments from representative rivers in East Asia show significant correlations with climatic factors (R2: 0.48–0.82), with a Pl/Qtz ratio of 0.3 differentiating dry-cold climates (Pl/Qtz > 0.3) and wet-warm climates (Pl/Qtz < 0.3). Given the substantial influence of felsic-mafic parent rock lithology and polycyclic quartz enrichment on silt-sized mineral ratios, along with the intricate geological context of the global river data collected, it follows that the silt-sized mineral composition in global river sediments exhibits a limited climate-weathering control and a weak correlation with temperate and precipitation. Grain size bias is evident in silt component, with compositional differences between the 2–32 μm and 32–63 μm fractions mainly attributed to the varying chemical-physical abrasion properties of quartz, K-feldspar, and plagioclase, and potentially linked to size inheritance from parent rocks. To enhance the accuracy of weathering and provenance analysis, we recommend conducting sediment grain size differentiation and multi-grain size studies, focusing on the extent of weathering and provenance signals in mineral composition, and emphasizing the integrated application of various chemical weathering indices. •Silt-sized F/Qtz ratio in East Asian rivers show strong climate correlations.•Pl/Qtz of 0.3 differentiates dry-cold from wet-warm climates in East China.•Grain size dependence of silt mineral stems from chemical-physical abrasion.•Source rock lithology and recycling significantly impact silt mineral indices.