Late Neoarchean magmatism identified in Daqingshan, Inner Mongolia: SHRIMP zircon U-Pb dating

This paper reports SHRIMP zircon U-Pb dating results of Late Neoarchean granitoids in Daqingshan, western North China Craton. Three samples dated in this study are taken from the south of Shiguai, include biotite monzogranitic gneiss, hypersthene quartz dioritic gneiss and dioritic gneiss. Based on mineral association, the biotite monzogranitic gneiss and hypersthene quartz dioritic gneiss underwent upper amphibolite-granulite facies metamorphism whereas the dioritic gneiss underwent amphibolite facies metamorphism. The zircon grains commonly show core-mantle-rim or core-rim textures. Dating on magmatic zircon domains yielded ages of 2484 7Ma, 2494 +/- 12Ma and 2495 +/- 10Ma, which is younger than real ages of the magmatic zircon because of later metamorphic recrystallization, and may be formed at Late Neoarchean. The rocks also recorded metamorphic zircon ages at 2441 +/- 7Ma to 2481 +/- 10Ma and 1847 +/- 35Ma to 1919 +/- 73Ma, respectively. Combined early work, main conclusions can be drawn as follows; 1) There are different types of Neoarchean magmatic rocks, including monzogranite, quartz diorite and diorite, in the south of Shiguai, Late Neoarchean magmatism may extensively occur in the entire Daqingshan area. Late Paleoproterozoic khondalite Belt was developed on Archean basement or its adjacent area. 2) Similar to other geological bodies of the Early Paleoproterozoic in the Daqingshan area, the Late Neoarchean intrusive rocks commonly underwent tectono-thermal events at the early and late Paleoproterozoic, respectively.