A New Type of Rare Metal Deposit: The Yushishan Leptynite‐Type Nb‐Ta Deposit in Eastern Altun, Gansu Province, NW China

The Yusishan deposit is a newly found leptynite‐type niobium and tantalum (Nb‐Ta) deposit, which is located in the Eastern Altun of Gansu Province. The leptynite of the Neoproterozoic Aoyougou Formation occurs more than 10 km long and 3 km wide. In this paper, we carried out a detailed study of the leptynite and related mineralization. The U‐Pb dating of zircon reveals ages of 831 ± 5 Ma and 790 ± 5 Ma for the unmineralized leptynite and 491 ± 4 Ma and 455 ± 4 Ma for the mineralized leptynite. The petrographic and geochemical evidence identified the protolith of the leptynite as alkaline volcanic rocks that erupted during Neoproterozoic at ca. 830 Ma. At ca. 490 Ma, the tectono‐magmatic and metamorphic event triggered remobilization and enrichment of Nb‐Ta as well as other critical metals (REE, Zr, Hf etc) with the formation of industry orebodies in the leptynite strata. The Yushishan deposit presents many similarities with the alkaline volcanic rocks related rare metal deposits in the south Qinling of China and the Brochman, Toogni and Southern Peak Range deposits in Australian. We therefore propose that the Yushishan deposit is a new type (sub‐type) of Nb‐Ta deposit and termed as leptynite type that represents the metamorphic counterpart of the alkaline volcanic rocks related rare metal deposits.