College of Earth Sciences��Jilin University��Changchun 130061��China

In order to understand the tectonic evolution of Fujin uplift�� the authors studied the unconformity of conglomeratic sandstone- quartz sandstone with its underlying granitic gneiss in Fujin uplift of northeastern Jiamusi Massif�� Based on the LA��ICP��MS zircon dating�� granitic gneiss weighted mean age is 495 ±5 Ma�� The U�� Pb ages for zircons from quartz sandstone are all more than 480 Ma��of which are mainly concentrated in the age of 480 �� 520 Ma��and just a small amount of ages are more than 800 Ma�� The evidence of unconformity and geochronology indicates that the Fujin uplift is a part of Jiamusi Massif�� Due to the Jiamusi Massif lacking of the Ordovician and Silurian sediments��it suggested that the forming time of the conglomeratic sandstones and quartz sandstone is Devo- nian�� Combined with the regional research data��it is considered that after the formation of metamorphic crystalline basement��the Jiamusi Massif was undergone long- time uplift and erosion until Early Devonian��then the eastern part of the Massif was whole turning into passive continental margin��