Geochronology and geochemistry of Neoarchean granitoids from the western Shandong Province, North China Craton, implications for crustal evolution and cratonization

Based on the SiO2 contents and REE patterns, the late Neoarchean granites exposed in Wande, Sishui, Qixingtai and Menglianggu areas can be subdivided into three groups. Group 1 exhibits, low SiO2 (68.6-69.2 wt%), high ΣREE (345.4-475.3 ppm) contents, moderate negative Eu anomalies (0.55-0.73) and depletion in U, Nb, Ta and Sr contents. Group 2 is composed of most of the studied samples and show moderate SiO2 (70.1-75.7 wt%) and ΣREE (135.8-357.1 ppm) content with obvious negative Eu anomalies (0.33-0.58) (excluding an outlier sample TS1310) and pronounced depletions in Ba, Sr, Nb and Ta contents. Group 3 displays high SiO2 (74.9-76.3 wt%) and low ΣREE (18.6-71.6 ppm) abundance. They are characterized by lack of negative Eu and Sr anomalies. Geology and Geochemical comparisons suggest that the major part of the granitic magma originate from re-melting of TTG type rocks at low pressure. The negative U anomalies of Group 1 granite are inherited from the source which is different from the case of TTGs. The correlation of Sr vs. Ba and Rb suggests fractional crystallization of K-feldspar, plagioclase and minor hornblende in the precursor magmas of Group 2. These geochemical features are similar to those associated with crustal stabilization in other cratons. Our studies on the WSP also suggest that the coeval to slightly earlier regional anatexis is also an important process during cratonization.