An Early Cretaceous garnet-bearing metaluminous A-type granite intrusion in the East Qinling Orogen, central China: Petrological, mineralogical and geochemical constraints

摘要

The Erlangmiao granite intrusion is located in the eastern part of the East Qinling Orogen. The granite contains almost 99 vol.% felsic minerals with accessory garnet, muscovite, biotite, zircon, and Fe-Ti oxide. Garnet is the dominant accessory mineral, shows zoned texture, and is rich in w (FeO) (14.13%–16.09%) and w (MnO) (24.21%–27.44%). The rocks have high SiO 2 , alkalis, FeO t /MgO, TiO 2 /MgO and low Al 2 O 3 , CaO with w (Na 2 O)/ w (K 2 O)> 1. Their Rb, Ga, Ta, Nb, Y, and Yb contents are high and Sr, Ba, Eu, Zr, P, and Ti contents are low. These features indicate that the Erlangmiao granite is a highly evolved metaluminous A-type. Garnet crystallized at the expense of biotite from the MnO-rich evolved melt after fractionation of biotite, plagioclase, K-feldspar, zircon, apatite, and ilmenite. The relatively high initial 87 Sr/ 86 Sr ratios (0.706–0.708), low and negative ? Nd (120 Ma) values (?6.6 to ?9.0), and old Nd model ages (1.5–1.7?Ga) suggest that the rocks were probably formed by partial melting of the Paleoproterozoic granitic gneisses from the basement, with participation of depleted mantle in an extensional setting. Graphical abstract Display Omitted Highlights ? FeO-, MnO-rich garnet crystallized at the expense of biotite from MnO-rich granitic magma. ? Granite formed from a highly evolved metaluminous A-type magma. ? Granite magma derived through the melting of Paleoproterozoic granitic gneisses.