Petrogenesis and significance of early Yanshanian syenite-granite complex in eastern Nanling Range
In the eastern Nanling Range there exists the early Yanshanian syenite-granite assemblage. A representative example is the Pitou-Tabei complex composed of the Tabei syenite pluton and the Pitou syenogranite pluton in southern Jiangxi Province. U-Pb zircon dating yields ages of 188.6±2.2 Ma for the Tabei pluton and 186.3±1.1 Ma for the Pitou pluton. The Tabei syenite is characterized by relatively low SiO2 content (62.40%- 68.75%), high alkalis (K2O+Na2O = 10.56%- 11.96%), low percent K2O/Na2O ratios (0.56-0.93), metaluminous feature (A/CNK = 0.80-1.00), enrichment in LILE (Rb, Ba, K) and HFSE (Th, U, Nb, Ta, Zr, and so on), weakly negative to positive Eu anomalies (δEu = 0.63-1.82), relatively low (87Sr/86Sr)i (0.70412-0.70543), and relatively high εNd(t) (3.14-3.52). The Pitou syenogranite is characterized by high silicon content (SiO2 = 71.06%-76.28%), relatively low alkalis (K2O+Na2O =8.10%-9.80%), high percent K2O/Na2O ratios (1.22-1.94), metaluminous feature (A/CNK =0.94-1.07), enrichment in Rb, Th (U), K, depletion in Ba, Nb, Ta, Sr, P, Zr, Ti, high ΣREE (averaging 451.03 μg/g), strong negative Eu anomalies (δEu = 0.27-0.33), relatively high (87Sr/86Sr)i (0.70805-0.70912), and relatively low εNd(t) (-5.35--6.29). The Tabei syenite and Pitou syenogranite both have the characteristics of A-type granites. The former is considered to be from the asthenosphere mantle, and the latter was the product of the crust-mantle mixture.They both were probably formed in a rifting setting.
作 者： CHEN Peirong ZHOU Xinmin ZHANG Wenlan LI Huimin FAN Chunfang SUN Tao CHEN Weifeng ZHANG Min 作者单位： CHEN Peirong,ZHOU Xinmin,ZHANG Wenlan,FAN Chunfang,SUN Tao,CHEN Weifeng,ZHANG Min(State Key Laboratory of Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China)LI Huimin(Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin 300170, China)
刊 名： 中国科学D辑（英文版） SCI 英文刊名： SCIENCE IN CHINA (EARTH SCIENCES) 年，卷(期)： 2005 48(7) 分类号： P5 关键词： syenite-granite assemblage single zircon U-Pb age rifting environment Nanling Range