Late Jurassic Intracontinental Extension and Related Mineralisation in Southwestern Fujian Province of SE China: Insights from Deformation and Syn-Tectonic Granites

Late Mesozoic igneous intrusions and extensional structures in Carboniferous to Permian sequences in the SW Fujian region acted as important controls on the localisation of Fe-polymetallic deposits. Here we document the identification of extensional deformation at shallow crustal levels and syn-tectonic granites related to normal faults. Based on spatial distribution and structural features, the extensional deformation can be divided into cover-only and basement-intersecting styles. A series of syn-tectonic plutons were emplaced into the footwall of normal faults. Representative samples of the Tangquan Granite have high Si O2(66.4 wt.%–73.9 wt.%) assays and Mg~# values(37–59). The samples also have relatively homogenous initial87Sr/86Sr(0.708 3–0.708 9) and εNd(-9.2–-10.2) values. Geochemical and isotopic evidences indicate that the Tangquan granite originates from a hybrid source including lower crustal-derived felsic and lithospheric mantle-derived mafic magmas. Zircon U-Pb dating indicates that the granodiorite phase from the pluton crystallised at 161±4 Ma and the monzogranite phase crystallised at 159±1 Ma. Combined with the granitic rocks in a wider region of SE China, the widespread granitic magmatism and polymetallic mineralisation have been synchronous during the Late Mesozoic, probably resulting from extensional tectonics related to the lithospheric thinning.