Geochemistry and U‐Th‐Pb Geochronology of Monazite in the Suzhou A‐type Granite Pluton: Implications for Nb‐Ta Mineralization

The Suzhou granitic pluton is the first identified Nb‐Ta‐rich granite in China. To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb‐Ta mineralization in different intrusive phases of the Suzhou granite, whole‐rock geochemistry, geochemistry and U‐Th‐Pb dating of monazite was analyzed. The unique geochemical characteristics show that the Suzhou pluton can be discriminated as an A‐type granite. LA‐ICP‐MS U‐Th‐Pb dating of monazite in both the medium‐ and coarse‐grained biotite granite (MBG) and the fine‐grained biotite granite (FBG) indicates that the granite formed between 124 and 127 Ma. Based on geochemical characteristics and mineral textures, the MBG (Mnz‐Ia) and FBG (Mnz‐Ib) monazites are classified as magmatic monazites; another monazite (Mnz‐II) from the MBG formed during a magmatic‐hydrothermal transitional stage. Nb‐Ta in the Suzhou pluton gradually concentrated during fractional crystallization and alteration of Ti‐rich minerals and biotite. Ultimately, with the involvement of F‐Li‐rich fluid, Nb‐Ta mineralization occurred during the magmatic–hydrothermal transition. The Suzhou pluton is considered part of a 600‐km‐ and NE–SW‐trending Nb‐rich A‐type granite belt together with other Early Cretaceous A‐type granites in the Jiangnan Orogen that offers prospects of a new target for Nb‐Ta prospecting.