A review of niobium and tantalum metallogenic regularity in China

Niobium and tantalum are critical mineral resources in the world. Although they have coherent geochemical behavior, they can be separated to some degree during ore-forming processes. The alkaline property of the host rock is one main factor to control the separation of Nb-Ta. As a result, niobium and tantalum resources can be divided into tantalum-dominated deposits in a peraluminous granitic magma system, including granite-type and granitic pegmatite-type deposits, and into niobium-dominated deposits in alkaline and carbonate magmatic systems, including carbonate-type, carbonate-weathering crust-type and alkaline rock-type deposits. In China, tantalum and niobium resources are mainly present in granite (e.g., the Yichun deposit in Jiangxi), granitic pegmatite (e.g., the Renli deposit in Hunan), alkaline rock (e.g., the Ba’erzhe deposit in Inner Mongolia), and carbonate (e.g., Miaoya in Hubei); however, currently, there are no occurrences of carbonate-weathering crust niobium resources. In China, tantalum deposits of the peraluminous granitic magma system are primarily located in the tantalum-metallogenic belts of Altay, Songpan-Ganze, Jiangnan paleocontinent, Nanling, southern Tibet-western Yunnan with mineralizations in the Caledonian, Indosinian and Yanshanian, and few cases in the Himalayas. The niobium deposits of alkaline and carbonate magma systems are primarily located in the niobium-metalogenic belts of Talimu-Northern China, Qinling, and western Yangtze block with mineralizations from Hercynian to Indianian with a few cases from the Proterozoic. Deposits of the peraluminous granitic magma system are primarily located in flysch sedimentary formations with a huge thickness that can be melted into rare metal-rich granitic magma during the orogenic process in a compressional tectonic environment. However, deposits of the alkaline and carbonate magma systems are primarily distributed along deep fractures or rift regions, bearing features of ore-forming material sourced from the mantle. These features show niobium and tantalum mineralization separation and alternation with spatial and temporal distributions, which can be controlled via compression-extension histories of different blocks in China. Although the reserves of niobium and tantalum in China are huge, most niobium and tantalum deposits in China usually bear low grades of Ta5O2 and Nb2O5 and are difficult to utilize. Therefore, in the exploration of niobium and tantalum resources in China, we should pay attention to high-grade granitic pegmatite-type tantalum deposits in the Songpan-Ganze, Jiangnan, Qinling, southern Tibet, and western Yunnan regions. Additionally, we can explore carbonate-type niobium deposits in Talimu-Northern China. The associated niobium and tantalum resources in tungsten and tin deposits may have great potential for exploration in the Nanling, western Yunnan, and Qinling regions.