The ∼2.3 Ga magmatic event in tectonic quiescent period: Geochronological and geochemical constraints from the Xiaohe granite in the Xiaoqinling Terrane at southern North China Craton.

[Display omitted] • The Xiaoqinling area is widespread of the ∼2.3 Ga Xiaohe granitic plutons. • The REE patterns and Sr/Y and δEu values of granites vary with source depth of magmas. • The Xiaohe granite is A-type granite emplaced in an extensional setting. • The Xiaohe granite was intruded by the ∼1.8 Ga granite. The early Paleoproterozic is generally considered as a worldwide tectonic quiescent period. It is unusual that widespread early Paleoproterozoic magmatism has been identified in the North China Craton (NCC), especially in the Xiaoqinling Terrane at the southern NCC. The Xiaohe granite occurs along the southern margin of the Xiaoqinling Terrane and intrudes the lower portion of the Taihua Supergroup (gneisses). Previous data suggest the emplacement time of the Xiaohe granite ranging from the early to late Paleoproterozoic, leaving a controversy over 500 Ma. To accurately constrain the age, genesis and tectonic setting of the Xiao granite, we have carried out a comprehensive study and here present new petrographical, geochronological, and isotope and element geochemical data. It is confirmed that the Xiaohe granite is dominated by the ca. 2.3-Ga monzogranite and locally intruded by the Guijiayu granites at 1.82 ± 0.05 Ga. Three samples from the Xiaohe granite yield consistent zircon U − Pb ages of ca. 2.3 Ga, and ɛ Hf (t) values showing mixing of juvenile and recycled continental crust sources. The Xiaohe granite are characterized by high SiO 2 (70.7–79.6 %) and high alkali (5.67–10.15 %), belong to calc-alkaline to shoshonite series and show weak peraluminous feature with A/CNK values around 1.1. Its geochemical characteristics are similar to those of A-type granites formed involcani arc or syn- to post-collision tectonic settings. Samples also display eastward decrease of Sr/Y, (La/Yb) N and δEu values, and weakening REE fractionation, indicating an eastward increase of plagioclase in residue during partial melting of the crust, and the magma sources become shallow eastwardly. Hence it is concluded that the Xiaohe granite was formed in a widespread granitic event associated with continental collision or terrane amalgamation. [ABSTRACT FROM AUTHOR]