Early Precambrian rare-metal mineralization in the North China Craton

Most of the major cratons in the world are characterized by pegmatite type of rare metal mineralization during the Early Precambrian. However, the North China Craton (NCC) in China seems to be an exception since this stage of rare metal pegmatite with significant industrial value is not identified so far in the area. After a comprehensive summary for the valuable data, it is found that Early Precambrian pegmatites were widely developed in the NCC, and these pegmatites can be further divided into two stages. Late Archean pegmatite is mostly distributed in the area of northern Liaoning-eastern Hebei-western Shandong, and is closely related to the early cratonization at 2.5 billion years ago. It is found that this Late Archean pegmatite is mainly distributed in the metamorphosed mafic-ultramafic volcanics in the greenstone belts, with lithium (Li) and tantalum (Ta) as the major mineralization types, represented by the Shipeng spodumene-bearing pegmatite in Xintai of Shandong Province, and the Lijiapuzi niobium (Nb)-Ta pegmatite in Xinbin of Liaoning Province. Therefore, the Archean pegmatites in the NCC are characterized by Li-Cs-Ta rare metal mineralization. Paleoproterozoic pegmatites with an age of ~1.8Ga are widely distributed in the NCC, such as in the Liaoning-Jilin mobile belt in the northeastern China, the khondlite belt in Inner Mongolia, and the collisional zone in the central NCC, closely related to the terrane assemblage and collision, and subsequent later cratonization. It is recognized that this Paleoproterozoic pegmatites are mainly occurred in the metamorphosed supracrustal rocks, and the mineralization types are characterized by beryllium (Be), Nb, Ta, uranium (U) and rare earth elements (REE). The typical representatives include the Nb/U-bearing pegmatites in Haicheng, Liaoning, and the Be-bearing pegamatites in Wulashan, Inner Mongolia. No Li mineralization has been identified for this stage of pegmatites, indicating that the rare metal mineralization is dominated by NYF type. By comparison, it was found that the NCC has the similar rare metal mineralization to other major cratons in the world (such as Australia, Africa, Baltic, North America, etc.). It is suggested that the scarcity of Early Precambrian rare metal pegmatite deposits in the NCC is partly due to its high degree of metamorphism or a strong erosion later. Another factor might be the less research and low level of exploration. It is suggested, therefore, that a more comprehensive comparison in the near future with other cratons in the world might be necessary to better understand their difference. Meanwhile, more attention should be paid on the background, source characters, and evolutionary history of the different stage of magmatism in the NCC, in order to better understand the differences between the Archean LCT and Paleoproterozoic NYF type pegmatites. It is expected that the above studies can provide a solid theoretical basis for breakthroughs in the pegmatite type rare metal resources formed in the Early Precambrian of the NCC.