College of Earth Sciences��Jilin University��Changchun 130061��China

This paper reports lithologic features��K--Ar age and geochemical data of riebeckite granophyres from Aliwula area in the southern Da Hinggan Mts����aiming to reveal the petrogenesis of riebeckite granophyres�� K-- Ar age of riebeckite granophyres is 126 ± 2 Ma��implying that the riebeckite granophyres formed in the Early Cretaceous�� The granophyres are rich in riebeckites and with a lot of melt-fluid inclusion in its quartz phenocrysts�� The granophyres are characterized by extensive enrichment in SiO2 ��FeO��and ( Na2O + K2O) and depletion in MgO and CaO��strong negative Eu anomalies and strong positive Ce anomalies�� Additionally��the riebeckite granophyres not only have high total REE contents and display enrichment of HFSEs ( for example Zr�� Hf��Nb��Ta) ��but also are strong in depletion of LILEs ( e�� g�� Ba��Sr) as well as high Ga /Al ratios�� Primitive mantle-normalized REE pattern significantly displays REE M--W tetrad effect�� REEs fractionate evidently and highly enrich in LREE��but are uneven distribution in the rocks�� Taken together��we conclude that the riebeckite granophyres are similar to typical A-type granite��which could be derived from stretching environments in the Early Cretaceous�� The granophyres originated from residual melt which underwent highly differentiation process�� and were formed in magmatic-hydrothemal transition stage at last��