Petrogenesis and Tectonic Setting of Late Mesozoic Felsic Magmatic Rocks in the Wangmushan Mining District, Northern Fujian, South China

ABSTRACT

The Wangmushan mining district (WMD) in the Southeast Coastal Volcanic Belt (SCVB) of South China provides an excellent natural laboratory to constrain Late Mesozoic crustal architecture and tectonomagmatic evolution. Here, we present zircon U–Pb geochronology, whole‐rock geochemistry and Sr–Nd–Pb–Hf isotopic data for ore‐bearing rhyolitic ignimbrite (RI) and barren K‐feldspar granite porphyry (KGP) from the WMD to explore their petrogenesis and tectonic setting. Zircon U–Pb dating yields ages of 173.8 ± 0.8 Ma for the RI and 102.6 ± 0.4 Ma for the KGP, recording two distinct magmatic episodes. Both suites show enrichments in large‐ion lithophile elements (Rb, U, Th, K, Pb) and light rare earth elements, coupled with depletions in Nb, Ta, Ti, P and heavy rare earth elements, indicating subduction‐zone/arc geochemical affinities. The Middle Jurassic RI displays enriched Sr–Nd–Pb–Hf isotopes ( ε _Nd (t) = −13.3 to −11.3; zircon ε _Hf (t) = −22.5 to −10.8) with crustal Pb isotopic signatures. In comparison, the Early Cretaceous KGP has less negative ε _Nd (t) (−9.2 to −8.3) and zircon ε _Hf (t) (−9.6 to −6.5), alongside more radiogenic Pb isotopes trending toward EMII. The RI originated mainly from partial melting of Early Paleoproterozoic Cathaysia basement under continental extension, whereas the KGP formed via melting of Paleo–Mesoproterozoic basement mixed with significant juvenile lower‐crustal melts in a comparable extensional regime. Combined with the spatial–temporal pattern of Jurassic–Cretaceous arc magmatism across the SCVB, we suggest that RI magmatism relates to the breakup and foundering of a Middle Jurassic flat slab, and the KGP formed during enhanced lithospheric extension driven by Paleo‐Pacific slab rollback.