The Longwen tin-iron polymetallic deposit is a small skarn-type tin-iron deposit located in the northwestern end of the eastern Guangdong tin metallogenic belt.The exact mineralization age and magmatic evolution process of ore-forming intrusion are still unclear.To shed light on this,we focused on the early-stage coarse-grained gra-nite,late-stage fine-grained granite,and skarn ore containing cassiterite for geochronological and geochemical studies.The results show that the zircon U-Pb ages of the two stages of granite are(140.8±1.2)Ma and(140.7±1.4)Ma,respectively.Similarly,the cassiterite U-Pb ages are(139.8±1.3)Ma and(140.8±1.8)Ma.These ages sug-gest that both the magmatic crystallization and tin polymetallic mineralization occurred during the Early Creta-ceous period.The ore-forming granites exhibit characteristics of high silica,calc-alkaline,and peraluminous com-position.They also show slight enrichment in light rare earth element(REE)and flat heavy REE distribution pat-terns,indicating that they belong to highly fractionated I-type granites.Both stages of granite exhibit negative whole-rock εNd(t)values and zircon εHf(t)values.The Nd two-stage and Hf crustal model ages range from 1557 to 1621 Ma and 1341 to 1811 Ma,respectively.Combined with the presence of dark microgranular enclaves in the coarse-grained granite,it is inferred that the Longwen granitic magma primarily originated from partial melting of Paleo-to Meso-Proterozoic crust with minor mantle and juvenile crust involvement.In comparison to the early-stage coarse-grained granite,the late-stage fine-grained granite is depleted in TFeO,MgO,and TiO2,and has high-er Rb/Sr ratio and lower Nb/Ta and Zr/Hf ratios.These differences suggest that the late-stage granite resulted from further differentiation of the early-stage granitic magma,through the extraction of melt from a crystal mush system.The fiine-grained granite is closely related to tin mineralization in the Longwen deposit.
维普
万方数据