Geochemistry, LA-ICP-MS Zircon U-Pb Dating and Geological Significance of Middle Cambrian Monzogranite in Yichun, Heilongjiang Province

LA-ICP-MS zircon U-Pb age of 504.1±5.4Ma was obtained for the fine-medium grained monzogranite from southern Yichun, which suggests the monzogranite formed in Middle Cambrian. Geochemical data for the monzogranite reveal K₂O+Na₂O contents of 7.41%~8.70%, K₂O/Na₂O ratios of 1.80%~2.28%,and low TFeO abundances, indicating it belongs to shoshonite to high K calc-alkaline series. While A/CNK>1.1 suggests peraluminous feature of S-type granite. Trace element geochemistry of the monzogranite also shows LILE enrichment and HFSE depletion. Most of the samples are concentrated on syn-collision and late orogenic tectonic settings in R₁-R₂ diagram, fall into syn-collision and post-collision settings in Rb- Hf -Ta diagram, plot into areas of volcanic arc and syn-collision in Nb-Y diagram, and cluster in syn-collision setting in Rb- (Y+Nb) diagram. Based on above-stated petrological and geochemical data it is inferred that the monzogranite of Yichun might be derived from a syn-collision setting, the Jiamusi and Songnen massifs amalgamated together in Middle Cambrian, and the amalagamation may be responsible for the crustal derived syn-collisional granites.