Granite-type lithium deposits in China: Important characteristics, metallogenic conditions, and genetic mechanism

Due to the rapid development of the electric vehicle and the continuous innovation of controllable nuclear fusion, the competition of lithium supply capacity is happening all over the world. China has the most quantity of granitic-type lithium deposits in the world and this type of lithium deposits accounts for 1/4 of the total lithium supply in the country at present. So it is very important that the breakthrough not only the theoretical study but also the mineral exploration is crucial to enhance the self-sufficiency of lithium resources in China. In this work, by integrating the geology characteristics, rock sequence, mineral evolution, geochemistry and lithium independent minerals of 40 granitic-type lithium deposits in China, we found that: (1) They mainly formed in Late Jurassic to Early Cretaceous and focused in South China, especially in the Nanling range; (2) There are 1/3 of ore-forming granitic plutons are buried underground and the outcrop areas are commonly small with 0.07 similar to 5.7km(2); (3) The plutons generally evolved from dark biotite-bearing monzogranite to light lepidolite-bearing albite granite from bottom to top in a vertical direction, with greisen and pegmatite at the top; (4) Li with other rare-metal elements including Rb, Cs, Be, Nb, Ta, W and Sn highly enriched in the albitie granite and greisen; (5) Biotite granite -> Li-bearing albite granite -> greisen, the crystal fractionation of magmas gradually inceased and the magma system gradually evolved towards melt-fluid coexistence. Moreover, the whole-rock SiO2 contents and values of A/CNK, Nb/Ta, Zr/Hf and delta Eu changed regularly; (6) Various types of dykes such as lamprophyre, gabbro, diabase, granite porphyry, aplite, and felsite are associated with the ore-bearing plutons in most cases. Based on above characteristics, we concluded that: (1) The pegmatite shell was the product generated the earliest by cooling and consolidation of magma batches, which were injected earlier in the magma reservoir by contacting with the cold wall-rock, so it formed a barrier between the magma reservoir and the outside to prevent escaping of the volatile components of Li, F, P, H2O, and so on; (2) The later batches of magma injected into the magma reservoir experienced a long process of crystal mush-residual melt segregation leading to the increasing enrichment of Li and other rare-metal elements in the residual magma forming ultimately the Li-rich granites and greisens; (3) Various types of dykes are the evidence of continuous heat supply under the magma reservoir, allowing the residual ore-bearing melt to be gradually extracted upwards: the mafic dykes came from the high-temperature mantle magmas; Ore-free intermediate-acidic porphyritic dykes were the product of the cumulate remelting from the bottom of magma reservoir; Ore-bearing acidic porphyritic dykes and aplitic dykes generated from the ore-rich magma from the top of the magma reservoir. This is because that the close system produced by the overlying pegmatite shells and underlying heat below the magma reservoir, the magmas in the magma could keeping crystal fractionation to finally evoled into the granitic-type lithium deposits.