where the variables represent the molecular proportions of each major element oxide and Ca O* denotes the silicate-bound Ca O. The CIA is an index based on the changes in chemical compositional associated with the decomposition of feldspar and formation of clay minerals. Given that feldspar is a major constituent of the continental crust, the CIA has been widely used to investigate continental chemical weathering (e.g., Hayashi et al., 1997). However, the approach based on decomposition of unstable minerals has limitations, with the main one being the assumption that the chemical composition of the source rock does not change for the studied sediments. When applying this type of weathering index to sediments with an unknown source rock, there is always the possibility that a change in the CIA value reflects a change in the source rock composition and not the degree of weathering in the hinterland (e.g., Meunier et al., 2013). In fact, CIA values of silicic igneous rocks generally vary from 45 to 55, whereas those for mafic igneous rocks generally range from 25 to 45.

where the variables represent the molecular proportions of each major element oxide and Ca O* denotes the silicate-bound Ca O. The CIA is an index based on the changes in chemical compositional associated with the decomposition of feldspar and formation of clay minerals. Given that feldspar is a major constituent of the continental crust, the CIA has been widely used to investigate continental chemical weathering (e.g., Hayashi et al., 1997). However, the approach based on decomposition of unstable minerals has limitations, with the main one being the assumption that the chemical composition of the source rock does not change for the studied sediments. When applying this type of weathering index to sediments with an unknown source rock, there is always the possibility that a change in the CIA value reflects a change in the source rock composition and not the degree of weathering in the hinterland (e.g., Meunier et al., 2013). In fact, CIA values of silicic igneous rocks generally vary from 45 to 55, whereas those for mafic igneous rocks generally range from 25 to 45.