Abstract:

Foziling group of North Huaiyang is a set of lower metamorphic rocks which had undergone multiple deformations and metamorphism. The average contents of Foziling Group are SiO2 75.42%, Al2O3 8.13%, MgO 1.52%, Fe2O3 3.23%, Na2O 1.61%, K2O 1.67%, TiO2 0.41%; a part of characteristic trace elements like Th, U, Hf, Sc, Zr, Y have average of 8.49×10-6, 1.47×10-6, 4.85×10-6, 170.66×10-6, 193.69×10-6 and 18.97×10-6, respectively; and the ratio of Th/U, La/Y, Th/Sc, La/Sc are respectively 4.92, 3.56, 1.51 and 1.38; the average of ∑REE is 125.3×10-6, δEu is 0.67, light REE enrichment, La/Yb is 14.99 and (La/Yb)N is 10.11. The lower part of Foziling group which named Xiangyunzhai Formation is a set of metamorphic quartz sandstone whose protolith are sandstone and greywacke rock, and it has a tectonic setting of passive continental margin and a provenance of quartzite and sedimentary rocks which indicates the Yangtze(phile) geochemical features. However, the upper part of Foziling Group metamorphic rocks including Zhufoan Formation and Panjialing Formation mainly consists of a set of quartzmica schist, micaquartz schist, mica schist and minor quartz quartzite and its protolith are greywacke, sublitharenite, litharenite and shales. Its tectonic setting is continental island arc and active continental margin and its provenance are mainly quartzite sedimentary rocks and felsic igneous provenance. That shows the characteristics of North China Plateaffinitive. The above information suggests that Foziling Group has undergone the tectonic transformation from the passive continental margin of northern Yangtze to the active continental margin of southern margin of North China.

Key words: geochemistry, protolith reconstruction, tectonic setting, Foziling Group, North Huaiyang