Protracted Paleoproterozoic partial melting recorded in the Taihua Complex, southern North China Craton: Insights from zircon U-Pb ages of leucosomes within migmatites

Understanding the origin of different types of leucosome may provide important information about the occurrence and processes of crustal melting. Leucosomes are widespread in migmatites and occur as irregular layers, lenses, veins, and blocks in the Taihua Complex of the southern North China Craton (NCC). The leucosomes are oriented subparallel or oblique to the foliations of their host rocks at various scales. However, the chronological framework and relationship of different types of the leucosomes has not yet been established. Here we present zircon U-Pb ages, and trace-element compositions of eight leucosomes within migmatites from the Taihua Complex in the Xiaoqinling area. On the basis of field relationship and mineral assemblage, three types of leucosome are identified: plagioclase-rich leucosomes, K-feldspar-rich leucosomes, and leucocratic veins (pegmatites). The ages of inherited zircons suggest that early Paleoproterozoic (2376-2305 Ma) magmatic rocks are major protoliths of the migmatites. Anatectic zircons from the three types of leucosome yield formation ages of 1906 +/- 10 to 1821 +/- 15 Ma, 1823 +/- 14 to 1814 +/- 14 Ma, and 1828 +/- 9 to 1797 +/- 11 Ma, respectively, indicating prolonged partial melting that took place intermittently over a period of -110 Myr. Combined with the result of previous studies, our data suggest that the -1.91-1.82 Ga partial melting events may have occurred intermittently during the slow exhumation of a thickened crust, whereas the -1.82-1.80 Ga event may have been related to post-collisional extension. Our results provide new insights into late Paleoproterozoic partial melting in the southern NCC.