Recognition of the A-type granites from the Huangling granite batholith in western Hubei

The A-type granites were discovered for the first time from the Huangling granite batholith in western Hubei. This kind of granites consisting of K-feldspar and monzonitic granites is characterized by metaluminous rocks (A/CNK=0.95 -1.09), high SiO₂(72.64%-75.64%), high alkali (K₂O + Na₂O ranging between 8.23% and 8.46%), low CaO and MgO contents, and high FeO^*/MgO ratios (12.49 -23.07), depletion of the elements Ba, Sr, P, Ti and Eu, enrichment of the high field strength elements Nb, Th, Zr and Y, and higher Ga/Al ratios, implying that the granites in the study area are typical of A2 granites differing greatly from the I-type granites. The ages of 800 -770 Ma for the A-type granites from the Huangling granite batholith indicate that the northern margin of the Yangtze landmass was in the extension phases during the Neoproterozoic, and may be related with the breakup of the suppercontinent Rodinia.