Thermal links between crustal radiogenic heating and peraluminous granites: a case study in Wuyi terrain, southeastern China

Peraluminous granites are widely regarded as products of crustal reworking in continental interiors and are genetically linked to Sn–W–rare metal mineralization (e.g., Li, Be, Nb, Ta, Cs, Rb). However, the mechanisms of heat transfer responsible for generating peraluminous magmas, as well as the role of the mantle in these processes, remain debated. To address these questions, we investigated the origin of the Xingluokeng granite—a peraluminous granite in the Wuyi terrain of the Cathaysia Block that hosts large-scale tungsten mineralization—through zircon U–Pb and Hf isotopic analysis and numerical modeling of heat transfer. The modeling incorporates geologically plausible ranges of ancient crustal thickness and crustal heat production.

Autocrystic zircons from the granite (~150 Ma) exhibit strongly negative εHf(t) values (–25.72 to –7.01), which fall within the range of inherited zircons (600–1000 Ma) and the highest-density values of Neoproterozoic detrital zircons in the Cathaysia Block. This suggests no detectable mantle-derived mass contribution. The Mesozoic upper crust in the Wuyi terrain and other regions in the Block, represented by fine-grained clastic sediments, has an average heat production of ~2.9 μW m⁻³, while amphibolite- to granulite-facies rocks, representing the middle–lower crust, range from ~0.6 to 4 μW m⁻³. These values exceed present-day global averages for continental crust (upper crust: ~1.68 μW m⁻³; middle–lower crust: ~0.19–1 μW m⁻³). When combined with moderate crustal thickening (~50 km) and a normal mantle heat flux, such elevated crustal heat production can drive partial melting of metasedimentary rocks in the middle–lower crust over a thermal relaxation period of ~30–50 Ma.

Crustal radiogenic heating also warms the upper mantle, facilitating partial melting of mafic rocks and giving rise to volumetrically minor mafic dykes coeval with peraluminous granites in the same region. Consequently, the presence of such dykes does not necessarily imply that the mantle supplied significant heat or material for the associated peraluminous magmas. High crustal heat production coupled with crustal thickening appears to be a common feature in other parts of the Cathaysia Block, suggesting that the above conclusions may also apply to other Mesozoic peraluminous granites in South China.