Chronology of metasedimentary rocks from Kuanping Group Complex in North Qinling Belt and its geological significance

Kuanping Group Complex is located in North Qinling orogenic belt and consists chiefly of amphibolite of Guangdongping Formation, mica-quartzose schist of Sichakou Formation and marble of Xiewan Formation. According to recent dating of the LA-MC-ICPMS U-Pb zircons from Kuanping Group Complex in Tanghe area of Henan, their ages of detrital zircons of mica-quartzose schist from Xiewan Formation Complex range from 400Ma to 3502 Ma with a group of youngest ²⁰⁶Pb/²³⁸U ages between 380 and 418 Ma. Combined with(370.9±2.0) Ma metamorphic age of ⁴⁰Ar/³⁹Ar of the biotite, it is concluded that Xiewan Formation Complex was formed in the Late Devonian. And the ages of detrital zircons from Sichakou Formation Complex range similarly from 512 Ma to 3598 Ma with a group of youngest ²⁰⁶Pb/²³⁸U ages between 512 and 549Ma, and its metamorphic age is (370.4±1.8) Ma from biotite ⁴⁰Ar/³⁹Ar. It is thus held that Sichakou Formation Complex was formed between Middle Cambrian and Late Devonian of early Paleozoic. So Kuanping Group Complex needs further disintegration due to great difference of stratigraphic ages. The sediments were probably derived from the North China Block, the Qinling orogenic belt and the Yangtze block. The ages of biotite ⁴⁰Ar/³⁹Ar show that Kuanping Group Complex was deformed in Late Devonian, indicating the end of collision orogeny of the North Qinling Belt during Paleozoic.