Abstract:Ages and tectonic implications of the Eraly Cretaceous rhyolites in the west of the Songliao Basin and Da Hinggan Mountains were obtained using zircon UPb dating, petrography analyses and geochemical researche methods. The zircon UPb dating by LAMCICPMS and SHRIMP techniqu, indicate that the crystallizing age of the rhyolites, was from 131.6±06Ma to 123.9±1.7Ma, which belongs to Early Cretaceous. Geochemical researches indicate that the rhyolites from Manduhu area are rich in silica (SiO2=69.08%~79.58%), alkali (K2O+Na2O 5.93%~9.76%, average=8.14), K (K2O/Na2O>1.0, average=2.14), poor in calcium (average=0.60), magnesium (average=0.27) and have high FeOT/MgO (average=6.77) ratio, which is a typical highK calcalkaline to shoshonitic series with the character of metaluminous (A/CNK=1.35~1.78). Early Cretaceous rhyolites are classified as two major types in terms of rare earth element and trace elements geochemistry: I type rhyolites and II type rhyolites. The rocks have high contents of rare earth elements with ∑REE=149.04×10-6~213.18×10-6(average=172.35×10-6), enriched in LREE \[(La/Yb)N=4.89~11.87\], LILEs (Rb, Ba, Th, K) and depleted in HFSE, especially Nb, Ta, Sr, P and Ti. The δEu values vary from 0.54to 0.88 (average=0.70) and most rocks have moderate negative Eu anomalies. Similar REE distribution pattern imply that the rhyolites come from the same magma source. Compared with I type rhyolites, the II type rhyolites, with strong negative Eu anomalies (δEu=0.05~0.46, average=0.27),have lower ∑REE(average=142.60×10-6) and depleted in HFSE (Nb, Ta, Sr, P and Ti). The types (I, II) rhyolites with the characteristics of postcollision granites, have lower Sr(<206×10-6), high Yb(>2) and well geochemical correlation. Combining with previous studies, we suggest that the rhyolitic magma, which caused by Mongolia Okhotsk postcollisional action, was ogigrinated from partial melting of crustal materials and suffered fractional crystallization, and the rhyolites formed in the interpolateextending settings. The conclusions have most important significance for studying the volcanic action and tectonic settings of Early Cretaceous volcanic rocks.