GEOCHEMISRY OF THE MYLONITIZED SILICEOUS BANDED LIMESTONE IN CENTRAL LANGSHAN AREA, INNER MONGOLIA

The Langshan tectonic belt is an important part of the giant orogenic belt in the north margin of North China Platform, with ductile shear zone as one of the major structural styles, reflecting deep structure of the crust. The geochemical characteristics of the mylonitized siliceous banded limestone in the southwest of Langshan Ⅱ ductile shear zone are discussed to study the composition changes of the mylonitized rock from protolith in different deformation strength. The analysis results show that, compared with the content of the protolith, there are differences of major and trace elements in the siliceous banded limestone by deformation strength. Among the major elements of deformed rocks, only CaO is the exported component, all the others are imported ones. The trace elements such as Rr, Sr, Ba, Pb, Ti, Cr, Cu, Nb, Ta, Zr and Hf are enriched and Ni relatively deficient. The REE distribution patterns of deformed siliceous banded limestone and protolith are basically consistent, which are characterized by right-dipping curves with enrichment of LREEs and depletion of HREEs, and obvious negative Eu anomaly, indicating the REEs have relative stability and homology during ductile shearing.