Abstract:

The electron spin resonance dating method (ESR) has been widely used in the world for active tectonic research. However, in Vietnam this method has not been widely applied. In this paper, 03 gouge faults samples were taken in NE - SW trending fault systems occurred in the central portion of Vu Gia Thu Bon river basin. The samples were processed to collect quartz grains, which were then separated into 4 different grain sizes: 125÷250 μm, 75÷125 μm, 45÷75 μm and 01÷45 μm. There grainswere analyzed at the University Okayama of Sciences. The results of the ESR analysis in this research show that the age range from large grain size to the smaller grain size decreases gradually from 33577 to 10282 (Late Pleitocene to Early Holocene). This result shows that the size of quartz particles used for ESR analysis affects determinination of the real age of the fault activities. The age recorded in the larger grain size were older than those in the smaller one. This is explained by the fact that larger grain size particles were not completely ‘’zeroing compare with the small particles during the latest phase of major movement along the faults. In this case, the age of smallest quartz grains generally indicate the lattest age of the fault movements, whereas the age of coarser quartz grains may reflect the older movements along the faults in the study area