The potential medium- and large-scale Be ore deposit in Altai, Xinjiang: A case study of pegmatites from Chonghur

Rare metals such as lithium and beryllium are strategic resources, and the supply risk in beryllium resource is higher than lithium for China. The Altai Orogen, Xinjiang, is the largest pegmatite province and mineral resource base for Be and other rare metals in our country. However, it is urgent to seek increasing reserves of resources because of the closure of many existing mines due to long-term mining and resource exhaustion. Besides, previous exploration, study and utilization of rare metal resources in the Altai Orogen were mainly limited to the Central Altai terrane, while the resource potential in other areas was less concerned. Several beryl rich pegmatites in Chonghur area in the Qiongkur terrane have been identified by the authors after long term field works, and the typical one was chosen to study on whole rock rare metal content, chronology and mineralogy, aim to evaluate the Be ore -forming potential in pegmatites from the Chonghur area. Results show that monazite grains yield a weighted mean age of 250. 5 +/- 3. 6Ma, indicating the formation of pegmatite in the end of Permian to the Early Triassic coeval with many other rare metal pegmatites in the Chinese Altai. Beryls are rich in alkali metals such as Cs Na and Li, with high enrichment levels equal to the beryl from the Koktokay No. 3 pegmatite, indicating a high degree of differentiation and evolution of the pegmatite -forming melt after emplacement. Combined with the consistent isotope composition of the studied pegmatite with the Late Triassic medium-superlarge rare metal ore deposits, the pegmatite is believed to meet the source and differentiation requirements for significant mineralization. Be mineralization was mainly developed in the quartz -muscovite zone of the pegmatite, with high BeO grades of 0. 321% similar to 0.999% and average grade of 0. 590%. The inferred BeO resource of the pegmatite reach to a medium scale at least after a preliminary calculation. With consideration of other Be -rich pegmatites juxtaposed with the studied pegmatite, a large scale Be ore deposit is expected to form in the Chonghur area in the Chinese Altai.