Geochemical, mineralogy, and Sr–Nd–Pb isotopic compositions of the gold-related lamprophyre in the Bengbu–Wuhe Area, southeastern North China Craton: Implications for gold mineralization

Abstract

Besides granite porphyries, many mafic dikes also have a close temporal and spatial relationship with orebodies in the BWGB. However, compared with the granite porphyries, no detailed attempt has been made to determine the petrogenesis of these mafic dikes or to elucidate their relationships with the gold mineralization. Here, we present comprehensive bulk-rock geochemical data; pyrite, apatite, and amphibole compositions; Sr-Nd-Pb isotopes, and U-Pb zircon data for the lamprophyres to provide constrains on their petrogenesis, magmatic properties, geodynamic setting, and metallogenic implications. We obtained zircon U-Pb ages, which reveal that the lamprophyres were emplaced ~ 130 Ma. The lamprophyres are characterized by pronounced light rare earth element (LREE) enrichment, heavy rare earth element (HREE) depletions ((La/Yb)N > 10). They also have low SiO2 (<51 wt%) and high MgO (>4.1 wt%) contents; low Rb/Sr (0.01–0.04), Th/La (0.1–0.12), and Lu/Yb (0.13–0.16) ratios; high Ba/Rb ratios (>18), low Sr-Nd values (87Sr/86Sr(t) = 0.7060–0.7076; εNd(t) = –8.8 to –12.5); and a wide range of radiogenic Pb isotopic ratios (206Pb/204Pb(t) = 16.37–17.35), indicating an enriched mantle source metasomatized by the upper crust of the subducted South China Block (SCB). Their low apatite MnO contents and high apatite SO3 contents, high apatite molar OH/F ratios, and high amphibole Mg* and VIAl* values suggest that the mafic magmas were more highly oxidized and hydrated. Taken together, the lithospheric mantle source was initially metasomatized by the SCB and was further hydrated by the subducted Paleo-Pacific Plate, resulting in a mafic melt with a high H2O content and oxygen fugacity value, which are favorable conditions for gold transportation.