DETERMINATION AND GEOLOGICAL IMPLICATION OF THE GRANITIC MYLONITE IN NENJIANG-HEIHE TECTONIC BELT

In the Nenjiang-Heihe tectonic belt, which is the northeastward extension of the Erenhot-Hegenshan-Zhalantun tectonic belt, a metamorphosed and deformed intrusive body is identified in the metamorphic stratum of former Xinkailing group. The rock is lithologically dominated by granitic mylonite, with high silicon and rich potassium, generally weak negative anomaly to locally positive anomaly of Eu, notable P, Ti and Nb negative anomalies, with Nb/La ratio of 0.02-0.4 and Nb/Ta ration of 0.19-16.22, showing the characteristics of crustal anatectic magma. The zircon LA-ICP-MS U-Pb age testing results show that the rock formed at 324.5±2.1 Ma, with mylonitized metamorphism time of 184±1 Ma. The granitic mylonite is the product of collision-collage of the Xingan and Songnen massifs along the Nenjiang-Heihe in Early Carboniferous. It is also suggested that the Nenjiang-Heihe tectonic belt experience a long and complex evolution history.