Acta Petrologica et Mineralogica

The Houhe Complex is an important part of the early Precambrian basement rocks in northern margin of the Yangtze Block. However, its genesis and tectonic setting are still unclear, which restricted our understanding on the geological evolution of northern margin of the Yangtze Block and even the entire Yangtze Block during the Paleoproterozoic period. In this study, analyses of whole-rock major and trace elements, Sm-Nd isotopes, zircon U-Pb geochronology and in-situ Lu-Hf isotopes are performed on trondhjemite and monzogranite from the Houhe Complex in Beiba area, northern margin of the Yangtze Block. The U-Pb dating results show that the crystallization ages of trondhjemite and monzogranite are 2 101±10 Ma and 2 072±15 Ma, respectively. The trondhjemite samples exhibit the characteristics of high silicon and sodium, low potassium and magnesium. Most samples belong to metaluminous to weakly peraluminous and calc-alkaline I-type granitic rock series and exhibit characteristics of island arc granite. Their zircon εHf(t) values range from -0.8 to + 4.6, with whole-rock εNd(t) values ranging from +0.1 to +1.1 and two-stage Hf model ages (t_DM2) ranging from 3 005 Ma to 2 469 Ma. In contrast, the monzogranite rocks show low silicon, but high magnesium, aluminum and potassium, belonging to weakly peraluminous and high-K calc-alkaline I-type granite. Their total rare earth element concentrations are relatively high. The differentiation between light and heavy rare earth elements is obvious, accompanied by weak negative Eu anomalies. The monzogranite rocks are also enriched in large ion lithophile elements (Rb, Ba and Th), and depleted in high field strength elements (Nb, Ta and Ti). They have high Mg^# values, and Cr and Ni contents, with zircon εHf(t) values of - 2.9~+ 2.4, and whole-rock εNd(t) values of +0.1~+0.9 and two-stage Hf model ages (t_DM2) of 2 939~2 604 Ma. All these data indicate that the trondhjemite was mainly produced by partial melting of Neoarchean basaltic rocks in the lower crust, with a certain degree of fractional crystallization. The monzogranite was generated by partial melting of ancient Neoarchean continental crust caused by underplating of mantle-derived magma, with addition of lithospheric mantle material. Considering the temporal and spatial distribution, and petrogenesis of the late Paleoproterozoic (2.1~2.0 Ga) mafic-felsic magmatic rocks reported in northern margin of the Yangtze block, it is supposed that the Paleoproterozoic (2 101~2 072 Ma) granitoid rocks from the Houhe Complex in Beiba area, northern margin of the Yangtze block, were formed under an active continental margin arc setting, related to convergent process of global Paleoproterozoic Columbia supercontinent.

Northern margin of Yangtze Block; Houhe Complex; Paleoproterozoic; granitoids; active continental margin arc