ZIRCON U-Pb DATING AND GEOCHEMISTRY OF THE RHYOLITES FROM XINMIN FORMATION IN SANGENHE FOREST FARM, NORTHERN DAXINGANLING MOUNTAINS
LI Zhong-hui1, LI Yang2, LI Rui-jie1, LI Kai1
1. Heilongjiang Institute of Geological Survey, Harbin 150036, China; 2. Qiqihar Institute of Geological Exploration, Qiqihar 161006, Heilongjiang Province, China
Abstract:The volcanic rocks of Xinmin Formation in Sangenhe forest farm are mainly composed of rhyolites and rhyolitic ignimbrites. The U-Pb dating results indicate the rhyolites were formed in Middel Jurassic, with the age of 165.71±0.83 Ma. The petrogeochemical analysis shows that the rhyolites are characterized by relatively high silicon, alkali and peraluminous, with the SiO2 content of 71.05%-76.77%, Na2O+K2O of 6.66%-8.49% and A/CNK of 1.02-1.17. The rocks present medium total REE content, significant fractionation of HREEs and LREEs, strong negative Eu anomaly (δEu=0.39-0.66) and negative Dy anomaly, relative depletion of LILEs (Ba and Sr), enrichment of HSFEs (Th and U) and relative depletion of Nb, Dy and Ti, with the characteristics of A-type rhyolites. The study shows the magma is derived from partial melting of crustal materials. The Xinmin Formation is spatially distributed along the middle-north section of Daxinganling volcanic belt, revealing the volcanic belt was in a tensional tectonic environment in Middle Jurassic.
李中会, 李阳, 李睿杰, 李凯. 大兴安岭北段三根河林场新民组流纹岩锆石U-Pb定年及地球化学特征[J]. 地质与资源, 2020, 29(4): 310-318.
LI Zhong-hui, LI Yang, LI Rui-jie, LI Kai. ZIRCON U-Pb DATING AND GEOCHEMISTRY OF THE RHYOLITES FROM XINMIN FORMATION IN SANGENHE FOREST FARM, NORTHERN DAXINGANLING MOUNTAINS. GEOLOGY AND RESOURCES, 2020, 29(4): 310-318.
Liu Y S, Hu Z C, Zong K Q, et al. Reappraisement and Refinement of zircon U-Pb isotope and trace element analyses by LA-ICP-MS[J]. Chinese Science Bulletin, 2010,55(15):1535-1546.
[13]
Ludwig K R. User's manual for isoplot (ver.3.0):A geochronological toolkit for Microsoft Excel[M]. Berkeley:Berkeley Geochronology Center, 2003:1-55.
Whalen J B, Currie K L, Chappell B W. A-type granites:Geochemical characteristics, discrimination and petrogenesis[J]. Contributions to Mineralogy and Petrology, 1987,95(4):407-419.