Rare-metal mineralization potential and petrogenesis of Early Cretaceous I-type granitic rocks in the Lizikeng volcanic basin of Jiangxi Province, South China: evidence from mineralogy, geochemistry, and geochronology

Abstract

The North Wuyi area is an important metallogenic belt in South China and hosts many Pb–Zn–Ag deposits within the Jurassic–Cretaceous volcanic basins. These deposits are mostly genetically associated with Late Jurassic magmatism. The Cretaceous granitic rocks in the Lizikeng basin, at the eastern part of the North Wuyi area, were investigated for their mineralogical and geochemical characteristics in this study. Three types of granitic rocks, quartz monzonite, granite porphyry, and monzogranite, occur, and zircon U–Pb dating reveals that they all formed during the short period of 133–129\xa0Ma, corresponding to the early Cretaceous volcanic-intrusive activities in South China. The whole-rock geochemistry indicates that all three granitic rocks have I-type affinity. The quartz monzonite and granite porphyry have consistently low whole-rock ε Nd ( t ) values of −\u200910.4 to −\u20099.6 and zircon ε Hf ( t ) values of −\u200914.2 to −\u20098.2, and they were likely derived from Proterozoic crustal sources without any significant contribution of mantle-derived material. The monzogranite, which shows also negative but slightly higher ε Nd ( t ) and ε Hf ( t ) values of −\u20097.6 to −\u20097.1 and −\u20099.3 to −\u20097.0, respectively, might also be derived from a major Proterozoic crustal source but with some input of mantle magma. The geochemical data show that the monzogranite belongs to tungsten-bearing granite with highly evolved characteristics, and with high Nb and W contents similar to the typical rare-metal and W-bearing granites in South China. A large number of typical hydrothermal rare-metal minerals are identified in the monzogranite, such as W-bearing rutile, niobian rutile, and columbite-group minerals as well as ferberite. The discovery of the early Cretaceous granitic rocks with tungsten mineralization potential indicates that the North Wuyi area is prospective for rare-metal mineralization, which opens a new window for rare-metal prospecting in the volcanic basins, as this type of ore deposit was previously thought to occur in granites from mountain range areas in South China, such as the Nanling Range.