Zircon U–Pb ages of the metamorphic supracrustal rocks of the Xinghuadukou Group and granitic complexes in the Argun massif of the northern Great Hinggan Range, NE China, and their tectonic implications

Abstract

The basement of the Argun massif in the northern Great Hinggan Range consists of the metamorphic supracrustal rocks of the Xinghuadukou Group and associated granitic complexes. The metamorphic supracrustal rocks were previously interpreted as Paleoproterozoic, while the granitic complexes were considered Mesoproterozoic in age. This paper presents new zircon LA-MC-ICP-MS U–Pb ages of biotite-plagioclase leptynite and biotite schist from the Xinghuadukou Group in the Lulin Forest area, Heilongjiang Province; zircon SHRIMP U–Pb ages of biotite-plagioclase gneiss from the Xinghuadukou Group in Lulin Forest; and quartz diorite and monzogranite from the granitic complexes in Mohe County, Heilongjiang Province. New geochronological data from the three metasedimentary rock samples of the Xinghuadukou Group can be preliminarily divided into five groups: (1) 2017–2765Ma, (2) 1736–1942Ma, (3) 1359–1610Ma, (4) 749–1239Ma, and (5) 448–716Ma. Except for the zircons of the 448–716Ma group belonging to a metamorphic origin, the other age groups had the youngest age of 749±17Ma, indicating that the Xinghuadukou Group formed during the Neoproterozoic era (at least <749Ma). These detrital zircon ages cluster at ca. 2.0–1.8Ga and ca. 1.0–0.80Ga, suggesting that the Argun massif had connections with both Columbia and Rodinia and implying that the provenance of the Xinghuadukou Group metamorphosed sediments must be characteristic of felsic–intermediate igneous rocks with ages of ca. 2.0–1.8Ga and ca. 1.0–0.80Ga. The quartz diorite and monzogranite from the granitic complexes of the basement within the Argun massif yielded weighted mean ages of 516±10Ma and 504±9Ma, respectively, indicating that these rocks emplaced in the Early Paleozoic. Considering the geochemical and chronological data together, we propose that the Xinghuadukou Group was most likely deposited in a back-arc basin environment, whereas the granitic complexes emplaced in a post-collisional setting. A wide age spectrum of detrital zircons ranging from 749±9 to 2765±11Ma with ages clustering approximately 2.0–1.8Ga and 1.0–0.80Ga suggests that the basement rocks of the Argun massif are chiefly composed of the Neoproterozoic metasedimentary sequence and Early Paleozoic granitic complexes, with a few Meso- to Paleoproterozoic and even Neoarchean metamorphic rocks.