GEOLOGY OF THE HADAYANG TECTONIC MELANGE IN INNER MONGOLIA:Discovery significance

The Hadayang tectonic melange is outcropped in the Nenjiang-Heihe tectonic belt. According to its regional geological setting and rock geological and geochemical characteristics, the tectonic melange is divided into three parts:matrix, autochthonous blocks and allochthonous blocks. The matrix is dominated by epidote-biotite-chlorite tectonic schist. The autochthonous blocks are composed of epidote-chlorite-biotite tectonic schist and possible conglomerates from outer slope of trench. The allochthonous blocks are mainly hornblendite, hybrid diorite and meta-acidic volcanic rocks. The lithogeochemical characteristics show that the hornblendite and hybrid diorite were formed in a marginal ocean expansion environment related to subduction, while the meta-acidic volcanic rocks have the characteristics of island arc calc-alkaline volcanic rocks. The characteristics above indicate that the Hadayang tectonic melange is related to the subduction-collision of plates. Combined with the feature that glaucophane appears in the Early Carboniferous meta-acidic volcanic rocks of Hongsanliang area and Paleozoic strata outcropped along the Hongsanliang-Hadayang-Yikete area are fault contact relationship between each other, the authors conclude that there is a tectonic melange belt of late Early Carboniferous along this line. The discovery of Hadayang tectonic melange belt is of important significance for understanding the NenjiangHeihe tectonic belt and its structure.