Single-zircon dating of Precambrian strata in the west sector of the northern Qilian Mountains and its geological significance

Single-zircon evaporation method was employed in the present study to determine the age of the iron-bearing rock series in Precambrian strata in the western sector of the northern Qilian Mountains. Three zircon ages from the diabase of the Aoyougou ophiolite previously put into Upper Lithologic Formation of the Zhulongguan Group are (1 840 ± 2), (1 783 ± 2) and (1 784 ± 2) Ma respectively, whereas the zircon ages from the welded breccias in the Zhulongguan Group are (733 ± 71, (738 ± 4) and (604 ± 6) Ma respectively. These results show that they should belong to the bottom of the middle Proterozoic and the upper part of upper Proterozoic respectively.