Origin of heavy rare earth mineralization in South China

Cheng Xu,Jindřich Kynický,Tomas Urubek,Wenlei Song,Antonin Kopriva,Yueheng Yang,Chen He,Zheng Zhao,Martin Brtnický,Martin P Smith

doi:10.1038/ncomms14598

Abstract

Heavy rare earth elements (HREE) are dominantly mined from the weathering crusts of granites in South China. Although weathering processes occur globally, no economic HREE resources of this type have yet been found outside China. Here, we report the occurrence of unidentified REE minerals in the granites from South Chinese deposits. They contain high levels of both HREE and light REE, but are strongly depleted in Ce, implying high oxidation state. These REE minerals show higher initial Nd isotope than primary REE-rich minerals (ɛNd(t)=0.9±0.8 versus −11.5±0.5). The mineralized weathering crusts inherited REE signature of the granites, but show more Ce depletion and more overall concentration of the REE. We propose, therefore, that highly oxidized, REE-rich fluids, derived from external, isotopically depleted sources, metasomatized the granites, which resulted in Ce depletion as Ce4+ and enrichment of the remaining REE, especially the HREE, contributing to formation of a globally important REE resource.

Highlights

Heavy rare earth elements (HREE) are dominantly mined from the weathering crusts of granites in South China
These deposits are currently only known in southern China, but comparable systems have been recently identified in Southeast Asia[3], Madagascar[4] and the Southeastern United States[5], where the deposits are generally enriched in light REE (LREE)
Heavy REE enrichment is commonly observed in peralkaline and alkalic granitoids, where it is related to the metasomatism of zirconosilicates[20,21]

Summary

Introduction

Heavy rare earth elements (HREE) are dominantly mined from the weathering crusts of granites in South China. The particular type of HREE ion-adsorption deposit studied here is thought to be formed by the leaching of HREE from granitic rocks, followed by fixing of the elements as ionic complexes adsorbed onto clays in the weathering crust. These deposits are currently only known in southern China, but comparable systems have been recently identified in Southeast Asia[3], Madagascar[4] and the Southeastern United States[5], where the deposits are generally enriched in LREE. Samples were collected from drill cores from the weathering profiles in Muzishan (MZS), Kaizidong (KZD) and Jiazibei (JZB) within the Zhaibei area (see Fig.[1] in ref. 15)

Methods

Results

Conclusion