The northern Hebei single tower subgroup Phoenix mouth geochronology of the rocks

The study of the basement of the northern Heibei Province plays an important role in understanding the Early Precambrian evolution of the North China Craton. In this paper, detailed geochronological study on Fenghuangzui complex of the Dantazi Group was reported, which indicate at least two tectonic events between Late Archean and Early Proterozoic. The Fenghuangzui complex of Dantazi Group, occupies the northern Hebei Province, is mainly composed of granitic mylonite gneiss and is intruded by metamorphic dyke. Zircons from the granitic mylonite gneiss show typical core-rim structure, and the age of magmatic core is 2. 45Ga and the metamorphic rim 1. 95 Ga. However, zircons from the metamorphic dyke occur as only single grains and cathodoluminescence images constrain their metamorphic origin. Their concordant age of 1. 9Ga, similar to metamorphic age of the granitic mylonite gneiss, indicate the granitic gneiss and the dyke underwent Paleoproterozoic orognic event together. Though the original age of the dyke is unknown, prominent Paleoproterozoic extension in the study area, occurred between 2.45 ∼ 1.9Ga, can be deduced by existence of large-scale massive dykes.