SOME CHARACTERISTICS OF THE MYLONITE ZONE IN THE MIDDLE SECTOR OF THE LIANHUASHAN TECTONIC BELT

The myonite zone in question occurs in the right-lateral echelon form between two E-W-trending major faults.It includes the Yangmeishui,Zhongding and Yingpingshan subzones.It strikes NE 45°—65° and dips NW at an angle of 25°—45°.A single subzone is generally 150—300m wide and may be up to 1000 m wide near the major faults. The intensity of deformation of the mylonite increases gradually along the cross section.The center of the granite te（?）ane is represented by ultramylonite, flanked successively by granitic mylonite,mylonitized granite and gneissic crystalloblastic granite.In the volcanic terrane the rocks are successively quartz mylonite,quartz-mica mylonite,banded mylonite and mylonitized volcanic rocks from the center outwards. The strike of the foliation of the mylonite makes an angle of 30°—40° with the metamorphic zone.The microstructures of plastic deformasion are developed;for example,quartz exhibits wavy,banded and echelon extinctions. Some quartz is flattened and stretched due to stresses.The ratio is generally 1:5 and up to 1:50 at maximum,occurring in the wire-drawing or pseudorhyolitic form.The petrochemical composition of ultramylonite and flaky mylonite,is highly variable.The Si and Fe coneents increase markedly,while the K,Na, Ca and Al contents decrease as compared with the protoliths.