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

• Published in: Di xue qian yuan. 2012-09, Vol.3 (5), p.635-646
• Main Authors: Zhang, Jinyang, Ma, Changqian, She, Zhenbing
• Format: Article
• Language: English
• Subjects: A-type granite; Early Cretaceous; East Qinling Orogen; Garnet; 东秦岭造山带; 中部地区; 地球化学制约; 岩石学; 早白垩世; 石榴子石; 矿物学; 铝质A型花岗岩
• ISSN: 1674-9871
• DOI: 10.1016/j.gsf.2011.11.011

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 SiO2, alkalis, FeOt/ MgO, TiO2/MgO and low A1203, CaO with w（Na2O）/w（K20）〉 ]. 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 Erlang- miao 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 878r/S6Sr ratios （0.706--0.708）, low and negative εNd （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.