Geochronology And Geochemistry Of Early Permian And Cretaceous Igneous Rocks In The North Margin Of The North China Craton

In the present paper, Our samples are located in the northern margin of North China Craton and the southeastern area of Inner Mongolia, where a large scale of Late Paleozoic and Mesozoic plutons outcropping. Combined with regional geological background, this paper integrates studies of petrology, geochemistry, LA-ICP-MS U-Pb geochronology with zircon Hf isotopic.Early Permian granitites samples, containing rich SiO₂, alkali-rich features, and can be classified into high-K calc-alkaline. Yuanbaoshan monzonite diorite and syenite-diorite with a medium level of SiO₂. Early Permian alkaline granites average age is 292.7 Ma, and the average age of the granites rock is 280.6 Ma, meanwhile diorites’ s average age is 283.9 Ma. Their εHf（t） are negative, and the difference of Hf isotope composition suggesting that their source characteristics are different, the area where a strong crust-mantle interaction. Hf model ages variation range, with a peak in 2.6-2.8 Ga.Zircon Hf model ages ranges from 1.8².6 Ga and the peak appears in 2.5².6 G indicating a crustal accretion event, with widely ranging εHf（t） values which are mostly negative, implying that the melting of Archaean lower crust beneath the North China Craton contributed to their origin whereas there may be depleted mantle material mixed into the source for granitoids.Cretaceous Shuiquanzi pluton has SiO₂ content of 75.97%, the poor potassium and calcium content, belonging to high potassium calc-alkaline- alkaline granite. Tangyuchang pluton has SiO₂ content of 71.05 percent, high sodium content, potassium-rich, belong to high-K calc-alkaline- alkaline series aluminum prevail. Wujiabao pluton has SiO₂ content of 73.26%, the poor potassium and calcium content, A / CNK, A / NK are in the 1.0 to 1.1. Belong to high-K calc-alkaline series, with volcanic arc granite features. Xigouyaocun pluton, high silicon, calcium poor, poor sodium, potassium, are alkaline rhyolite. Shuiguankoucun pluton has SiO₂ content of 69.08%, high potassium, high alkali content, high-K calc-alkaline series, whichever aluminum rock. Shuiquanzi pluton age is 140.8 ± 1.6 Ma, Tangyuchang pluton age is 133.7 ± 3.0 Ma, the age of Wujiabao pluton is 134.4 ± 2.6 Ma, each rock has negative εHf（t）, Hf model ages as 1.8-2.1 Ga. Lower crust or simply Paleoasian subducted slab remelting is not enough to form such a large number of igneous rocks, the middle of the northern margin of the North China Early Permian, Cretaceous magmatic activity in large-scale mantle component had to play a role in that, given the geochemical evidence also supports this conclusion. And almost simultaneously upwelling mantle and crustal remelting causing widespread igneous events, was a response to tectonic events and mantle activities. This paper states that the Middle North Margin of North China Early Permian in non-orogenic inner plate – post-collision tectonic setting, Cretaceous crustal was thickening while lithospheric was thinning in the extensional tectonic backgroud. That granites are the mainly from the North China Craton ancient crust, and also the depleted mantle substance.