This paper is the result of mineral exploration engineering.

Objective Clay−hosted REE (rare earth element) deposit mainly occurs in low altitude, low elevation above sea level, and rolling topography, and is associated with Caledonian or Yanshanian highly fractionated granitoids. Can they be formed in high elevation, middle mountain, and/or associated with much older granite?

Methods By means of geological mappings and boreholes,

Results A medium−sized clay−hosted REE (rare earth element) deposit, i.e. the Kuanyu deposit, has been identified within the weathering crusts of the Mosuoying granite in the Panzhihua−Xichang district, Sichuan, SW China. The Kuanyu deposit is generally LREE−enriched and low grade, with leachable REE concentration. Orebodies are very shallow, and concentrate between 1427 and 2153 m above sea level. They predominantly occur in the uppermost part of the completely weathered zone of laterite-type weathering profiles, and could be further grouped into three types, named ridge−type, slope−toe−type and valley−type, according to local geomorphology. Such features are significantly different from the clay-hosted REE deposits in South China, where the orebodies are much deeper and tend to locate on ridge of low hills (mostly with an elevation of <500 m).

Conclusions We propose that, the unique climate, regional geomorphology (slope gradient), bedrock compositions are three key factors controlling the formation of the Kuanyu REE deposit. The case study presented in this article would be significantly helpful in understanding of the ore-forming mechanism and further exploration of clay-hosted REE deposits.