Geochemical characteristics and zircon U-Pb age of the Paleoproterozic S-type granite in Wulashan region and its geological significance

Wulashan area, located in the north part of the North China craton, has well-developed Paleoproterozoic granites, with the Nuoeryin S-type granites as the typical one. The investigation of Nuoeryin granites shows that the granites have high SiO₂ (w(SiO₂)=70.03%~75.43%), high Al₂O₃ (w(Al₂O₃)=13.04%~14.87%), and high K₂O values (w(K₂O)=5.36%~6.58%), low Mg^# (< 10) and high A/CNK values, indicating that they belong to peraluminous S-type granites. They are enriched in LREE with significant differentiation between LREE and HREE (La_N/Yb_N=22.3-300.5), and REE patterns of the samples are of right-oblique type, with strong negative Eu anomalies(δEu=0.16-0.55). The primitive mantle-normalized trace element diagrams show enrichment of K, Rb, Th, Pb and depletion of Sr, Ba, Nb, Ta, P, Ti. The Nuoeryin granites have similar geochemical characteristics to the Paleoproterozic knondalites in Wulashan area and, and the reason is probably that Nuoeryin granites were generated by the knondalites anatexis while the Yinshan blocks and Ordos blocks experienced collision in Paleoproterzoic. The LA-ICP-MS zircon U-Pb ages of Nuoeryin granites are 1891±14 Ma and 1863±17 Ma, which represent the crystallization age of the Nuoeryin S-type granites, and the age is also contemporaneous with magmatic-metamorphic events in Khondalite belt.