U-Pb ZIRCON GEOCHRONOLOGY AND GEOCHEMISTRY OF JIANGGOUSHAN INTRUSION IN BEIPIAO AREA, LIAONING, CHINA

The Jianggoushan intrusive body in Beipiao area, Liaoning Province, mainly monzogranite, belongs to highpotash calc-alkalic series. It is characterized by high SiO₂ (71.4%-73.78%), rich alkali and relative high Na₂O ((Na₂O/K₂O=1.17), with low Mg^# (averagely 0.18) and high A/CNK (1.09-1.14). Normative minerals commonly include corundum (1.36-3.01). These data prove that the intrusion is of S-type granite. The rocks have relative low abundance of REE (average 96.99×10^-6) with variable differentiation between LREE and HREE and medium negative Eu anomalies (δEu=0.77-0.87). The rocks are enriched in LILE (Rb, Ba) but depleted in HFSE (Ti). The Jianggoushan intrusion formed in syn-collision environment according to R₁-R₂ diagram. The U-Pb isotopic ages of zircon from two samples are 239±2 Ma and 233±4 Ma, respectively, suggesting an emplacement during Triassic. Previous study shows that the S-type granite of Middle Triassic (229.2-237.5 Ma) in the west of the area is from the collision of Siberia plate and North China plate. This paper agrees with the previous study and provides new information for the research on the evolution of continental lithosphere in the plate's margins.