This paper is the result of mineral exploration engineering.

Objective The Mianning−Dechang rare earth element (REE) metallogenic belt in the Panxi area is one of China's important light REE metallogenic belts, hosting the giant Maoniuping deposit, the large−scale Dalucao deposit, the medium−small Muluozhai and Lizhuang deposits, and a series of other mineral occurrences. Previous studies have identified clues of weathering crust−type REE mineralization in areas such as Cida (Dechang), Banshantian (Huili), and extending south to Pingdi (Panzhihua). However, research within this metallogenic belt remains insufficient, and no industrial−grade ore bodies have been reported. This paper aims to discuss the metallogenic characteristics and spatiotemporal distribution of the weathering crust−type REE occurrence in Tongchanggou and propose potential prospecting target areas.Research.

Methods Supported by a provincial science and technology project, a comprehensive analysis was conducted on the geochemical data of the weathering crust and bedrock REEs from Tongchanggou. This was based on summarizing results from 1∶50,000 stream sediment surveys and verification by manual percussion drilling.

Results The study revealed the following: The chondrite−normalized REE distribution patterns of the weathering crust show a significantly left−leaning trend, indicating pronounced fractionation between light and heavy REEs in the rock, which are enriched in an almost linear fashion. The total content of whole−phase rare earth oxides (TREO) ranges from 0.083% to 0.39%, with an average of 0.21%. The total content of ion−adsorbed rare earth oxides (SREO) ranges from 0.0025% to 0.056%, with an average of 0.022%. The thickness of the weathering crust meeting or exceeding the industrial grade for weathering crust−type REE deposits is between 1 and 5 meters.

Conclusions The Tongchanggou weathering crust−type REE occurrence is identified as a high−ytrium heavy rare earth deposit. The degree of REE enrichment shows a certain negative correlation with the cerium anomaly. Based on the exposure characteristics of granites in the Panxi area and related geographical and geological conditions, the belt along Mianning−Dechang−Huili−Miyi is indicated to have the potential to become another key metallogenic belt for weathering crust−type REE deposits.