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540321 
Journal Article 
Petrogenesis and significance of the Hongshan syenitic pluton, South Taihang : zircon SHRIMP U-Pb age, chemical compositions and Sr-Nd isotopes 
Zhou, L; Chen, B 
2006 
16 
2 
192-200 
English 
The Hongshan syenitic pluton (South Taihang) is mainly made up of hornblende syenite and minor granite. SHRIMP zircon dating yields a U-Pb age of 135 +/- 2.7 Ma for the emplacement of the pluton, while biotite Rb-Sr isotopic data give an isochron of 120.3 +/- 2.4 Ma. Hongshan syenites show low silica, high alkalis and LILE such as Sr, and exhibit negligible Eu anomalies or slightly positive anomalies in the REE patterns. The syenites show quite enriched isotopic compositions with I-Sr from 0.7052 to 0.7102 and epsilon(Nd)(t) from -7.5 to -11.1. Petrogenesis of the pluton can be that partial melting of an enriched lithospheric mantle gave birth to an alkali basaltic magma, which subsequently underplated in the lower crust and experienced a coupled fractionation of ferromagnesian phases like pyroxene and hornblende and minor (< 10%) contamination of lower continental crust, producing the Hongshan syenites that partially evolved into granite through combined fractionation of hornblende and feldspar. Our data are not in agreement with a previous model that the syenites originated from melting of lower crust in a thickened crust circumstance, and thus do not support the speculation of "East China Plateau" in the Mesozoic. 
syenite; zircon SHRIMP; Nd-Sr isotopes; Taihang; North China craton; north china craton; sino-korean craton; crustal evolution; liaoning; province; lithosphere; mantle; complex; constraints; magmatism; beneath