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

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) 2017-2765 Ma, (2) 1736-1942 Ma, (3) 1359-1610 Ma. (4) 749-1239 Ma. and (5) 448-716 Ma. Except for the zircons of the 448-716 Ma group belonging to a metamorphic origin, the other age groups had the youngest age of 749 +/- 17 Ma, indicating that the Xinghuadukou Group formed during the Neoproterozoic era (at least <749 Ma). These detrital zircon ages cluster at ca. 2.0-1.8 Ga and ca. 1.0-0.80 Ga, 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. 2.0-1.8 Ga and ca. 1.0-0.80 Ga. The quartz diorite and monzogranite from the granitic complexes of the basement within the Argun massif yielded weighted mean ages of 516 +/- 10 Ma and 504 +/- 9 Ma, 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 +/- 11 Ma with ages clustering approximately 2.0-1.8 Ga and 1.0-0.80 Ga 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. (C) 2011 Elsevier Ltd. All rights reserved.