Geotectonic Implications Of The Hongqiyingzi Complex From Within The Chicheng, North Hebei Province, China

The Hongqiyingzi Complex occurred to the north side of the Chongli-Chicheng fault belt and consisted of biotite plagioclase gneiss derived from the original terrigenous clastic rocks in the continental margin. Retrogressive eclogite and metamorphosed peridotite of tectonic origin developed within the gneiss. Zircon SHRIMP dating from the gneiss revealed that the age of the original classic rock ranged from 369 to 1855 Ma and the igneous rock in the gneiss from 414 to 482Ma. Later, the sedimentary clastic rocks were metamorphosed into biotite plagioclase gneiss with an amphibolite facies in the late Paleozoic period. Therefore, Hongqiyingzi Complex in the Chicheng area belonged to the sedimentary- metamorphic rock series formed in the late Paleozoic, which is different from the Hongqiyingzi Complex in the Chongli-Pingquan area which consisted of volcanic-metamorphic rock series formed in the late Proterozoic period (2000-2450 Ma).As an allochthnous tectonic block, four tectonic evolutional stages have been recognized within the Hongqiyingzi Complex in the Chicheng area. First is the formation of sedimentary clastic rocks. The second stage was characterized by the diving of the basalt and the intrusion of peridotite followed by metamorphism of original clastic and igneous rocks into biotite plagioclase gneiss. When to the third stage ,the basalt transformed into eclogites unrde the high pressure metamorphism and return into the the Hongqiyingzi complex, and sedimentary rock into biotite plagioclase gneiss. Finally, there was a tectonic event characristic of overthrust of Hongqiyingzi Complex from the north to the south. Through the difference of the lithology combination between the wall rock and the Hongqiyingzi complex and the difference of the shaping age , it was recognized that the original Hongqiyingzi Complex in the Chongli, Chicheng and Chengde areas should be dismembered into 3 different tectonic blocks. This recognition played an important role in the study of tectonic evolution in the northern margin of north China craton.We use the geochemistry characteristic analysis to restore the original clastic rocks types .and we adopt the Zircon SHRIMP dating to obtain the original rocks characteristic ,shaping age , metamorphosing age and the tectonic evolution history. All above all ,we can recognize four evolving stage and judge the geotectonic implications of the hongqiyingzi complex from within the Chicheng ,north Hebei Province, China.