Final assembly of Gondwana enhances crustal metal (HREE and U) endowment

Abstract

The South China Block hosts a variety of U and HREE mineralisation styles. The Yushui Cu deposit is located at a sedimentary unconformity and is enriched in HREEs and U. U-Pb ages of uraninite and xenotime indicate that the HREE mineralisation is epigenetic and formed at ca. 223 ± 1 Ma. Ore petrography, elemental mapping, and Nd isotope data suggest that HREEs and U were leached from the footwall sandstone and transported to the Cu deposit via oxidised basinal brines. U-Pb ages of detrital xenotime and zircon from the sandstone show that this sedimentary sequence was mainly derived from Silurian S-type granites, which were emplaced during Gondwana amalgamation. Rapid erosion formed clastic sedimentary rocks that contain accessory HREE-U minerals which could be remobilised by younger mineralising events. S-type granite magmatism during the final assembly of Gondwana established the crustal metal reservoir which was repeatedly tapped over geological history, including the modern formation of regolith hosted HREE deposits in South China. Given the global distribution of analogous S-type granites in other terranes globally, our study has exploration implications outside of China. This will be enlightening for finding new HREE deposits, which is vital to support the transition to a low carbon footprint energy.