Which minerals control the Nd–Hf–Sr–Pb isotopic compositions of river sediments?

River sediments naturally sample and average large areas of eroded continental crust, making them ideal for provenance studies based on isotopic compositions, while also establishing average isotopic values of continental crust. However, in large fluvial systems, mineral sorting processes can significantly alter the mineralogy and geochemistry of transported sediments, yet the extent to which this mineral sorting affects the isotopic compositions remains poorly quantified. This study focuses on the role of various mineral species in shaping the bulk isotopic compositions of bedloads and suspended loads from the Ganga River, which drains the Himalayas. We conducted isotopic analyses of Nd, Hf, Sr, and Pb, along with trace element contents from numerous pure mineral fractions, including K-feldspar, plagioclase, muscovite, and others. These findings were combined with mineral proportions typical of Ganga sediments to perform Monte Carlo simulations, enabling us to quantify the contributions of individual mineral species to the isotopic budgets of the river sediments. Our results reveal that few minerals dominate the isotopic systematics of river sediments, with zircon and monazite/allanite, despite their low abundances, playing crucial roles in controlling Hf and Nd isotopes respectively.