Geochemical characteristics and tectonic significations of Paleoproterozoic strongly peraluminous granitoids in the central segment of the northern margin of the North China craton

Paleoproterozoic strongly peraluminous granitioids are distributed in large amount along the line of JiningLiangcheng-Qianlishan in the central segment of the northern margin of the North China craton. Most of them are characterized by lower SiO_2 content (<74%), Al_2O_3/TiO_2 ratio (<100), Rb/Sr ratio and Rb/Ba ratio but higher CaO/Na_2O ratio (>0.3) than normal strongly peraluminous granitoids. The REE is very complex: samples have positive, negative or normal Eu anomalies. However, two types may be distinguished based on Eu/Eu *: the first type has intermediate LREE enrichment and flat HREE patterns, and the second type has the same LREE features as the first type but shows highly varied HREE. The inconsistency of the REE features of the two types suggests that the REE inherited from different source rocks. The granitoids are relatively enriched in HFLE (such as K, Rb and Ba) and depleted in HSFE (such as Nb, Ti and P). These geochemical characteristics imply that the strongly peraluminous granitioids were sourced from graywacke with high melting temperature and deep source and that their tectonic environment was similar to that of the Lachlan orogenic belt, Australia, belonging to a high-temperature collision zone. They should be the product of the lithospheric extension after the Paleoproterozoic collision of the west block and northeast block of the North China craton.