摘要
Abstract
Zircon U-Pb dating,petrogeochemistry and Hf isotopic were analyzed on late Triassic acid intrusive rocks in the Maying area,northern margin of North China.The late Triassic acid intrusive rocks in Maying area mainly include fine-grained,medium-grained and coarse-grained monzogranites.The results reveal that the monzogranites in Maying area were formed in 232～236.2 Ma,with SiO2 content ranging from 74.26%～76.54%,aluminum index A/CNK=1.04～1.14,with K2 O/NaO of 0.76～1.44,which belongs to peraluminous high potassium calc-alkaline granite.The differentiation of light and heavy rare earth is obvious,with LREE/HREE ratios of 8.89～18.28 and(La/Yb)N ratios of 10.35～29.33.There are negative to positive Eu anomalies with δEu ranging from 0.59 to 1.22.The rocks are enriched in large-ion lithophile elements such as Rb,Ba,Th,U,and K,while depleted in Nb,P,and Ti.The composition of monzogranite is controlled by fractional crystallization,and some of their geochemical characteristics are close to A-type granite,but the content of Zr+Nb+Ce+Y is range of 99.8～184.5×10-6,10 000 Ga/Al is 2.2～2.8,and TZr is 724℃～814℃,which is a typical non-A-type granite.The P2 O5 content shows a decreasing trend with the SiO2 content increasing,and the samples with SiO2 content greater than 75%,the P2 O5 content ranges from 0.01%to 0.04%,which is consistent with the characteristics of highly differentiated I-type granite.The trace elements characteristics combined with previous results show that the monzogranites in Maying area were formed in the post-collision extensional environment,mainly originated from the ancient crust with a minor contribution from mantle material,indicating that except for the post-collision thinning process,the deep magmatic system also played an important role.关键词
华北北缘/晚三叠纪/马营二长花岗岩Key words
northern margin of the North China craton/late Triassic/monzogranite of Maying area分类
天文与地球科学
