Petrogenesis and significance of early Yanshanian syenite-granite complex in eastern Nanling Range
Science in China Ser. D Earth Sciences 2005 Vol. 48 No.7 912-924，-0001，（）：
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±2.2Ma 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 (δ Eu=0.63-1.82), relatively low (87Sr/86Sr)i (0.70412-0.70543), and relatively high ε Nd (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 451.03μg/g), strong negative Eu anomalies (δ Eu=0.27-0.33), relatively high (87Sr/86Sr)i (0.70805-0.70912), and relatively low ε Nd (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.