Hf isotopic mapping of the Paleozoic-Mesozoic granitoids from the Jiamusi and Songnen blocks, NE China: Implications for their tectonic division and juvenile continental crustal growth

Abstract

The long-standing controversies in tectonic boundary, the nature of basement rocks, and the Phanerozoic continental crustal growth in the eastern Central Asian Orogenic Belt (CAOB) in NE China have been the key barriers in the understanding of the regional tectonic evolution. In this paper, we integrated published and new zircon U–Pb and Hf isotopic data of the Phanerozoic granitoids from the Jiamusi Block and the Lesser Xing'an-Zhangguangcai Range (LXZR) for a zircon Hf isotopic mapping of the region. The mapping results outlined three Hf isotopic provinces on the basis of TDMC ages: Province I (TDMC = 2.0–1.6 Ga, εHf(t) = −7.0 to −5.2) and Province II (TDMC = 1.6–1.1 Ga, εHf(t) = −4.6 to +3.9) represent the ancient basements in the Jiamusi Block; Province III (TDMC = 1.1–0.4 Ga with εHf(t) = +2.1 to +13.1) represents the juvenile crustal components in the LXZR. Province I (total area ~ 6000 km2) is sporadically exposed within Province II (~121,000 km2); the latter is bounded to Province III (~144,000 km2) along a sharp SE-NW boundary ~130 km west of the Mudanjiang Fault. This suggests that at least the part of the Songnen Block to the east of this boundary was in the same tectonic unit with the Jiamusi Block in the Paleozoic. Province III spatially accounts for about 53% of the study area, indicating a significant Mesozoic growth of continental crustal in the easternmost CAOB.