Fig. 5

Variations of the weathering trends of the source regions and the calculations of R_AK, R_ACN and R_KCN. Major elemental Al₂O₃–(CaO^* + Na₂O)–K₂O (A–CN–K) diagram of bulk and clay-fraction sediments in a surrounding fluvial drainage systems (modified from Liu et al. 2016), b sites DLW3101, MD12-3429, ZHS-176, MD12-3432, as well as c ODP sites 1144 (Wei et al. 2003), 1146 (Wan et al. 2010b) and 1148 (Wei et al. 2006). CaO^* represents the CaO in the silicate fraction (Nesbitt and Young 1982). The three sectors (I, II and III) in (a) represent the ranges of weathering trends. And the diagram presents the calculated positive and negative values of R_AK, R_ACN and R_KCN in the three regions. R_AK, R_ACN and R_KCN are the correlation coefficients between the chemical index of alteration (CIA), K^* and CN^*. CIA = Al₂O₃/(Al₂O₃ + CaO^* + Na₂O + K₂O) × 100; K^* = K₂O/(Al₂O₃ + CaO^* + Na₂O + K₂O) × 100; CN^* = (CaO^* + Na₂O)/(Al₂O₃ + CaO^* + Na₂O + K₂O) × 100. R_AK: Pearson’s r between CIA and K^*; R_ACN: Pearson’s r between CIA and CN^*; R_KCN: Pearson’s r between K^* and CN^*. The range of Pearl River samples (> 2.5 ka) is estimated based on Hu et al. (2016). The black polylines show the weathering trends. UCC: Upper continental crust