Archean to Paleoproterozoic continental crust growth in the Western Block of North China: Constraints from zircon Hf isotopic and whole-rock Nd isotopic data

This study presents new zircon Hf isotopic data, which, combined with previous zircon U-Pb geochronological, in-situ Hf and whole-rock Nd isotopic data from the Western Block of the North China Craton (NCC), provide a new insight into global-scale continental crustal growth and evolution of early Earth. In particular, igneous zircons and detrital zircons from the Yinshan Block yield Pb-207/Pb-206 ages of 2446-2733 Ma, with an age peak at 2524 Ma. Of those, 86% have positive s (H)/t) values and Archean Hf model ages (T-DM(c)) (2.6-2.9 Ga) peaking at 2840 Ma. This indicates that those basement rocks of the Western Block are most likely derived from a depleted mantle source, implying a crust-mantle differentiation event at 2.8-2.7 Ga followed by extensive reworking at similar to 2.5 Ga. More than 95% detrital zircons from the Khondalite Belt have ages converging on 2.2-2.0 Ga and their epsilon(Hf)(t) values vary from-5.43 to +9.54, of which 80% are positive and yield Hf model ages (T-DM(c)) peaking at 2250 Ma. These characteristics of s epsilon(Hf)(t)values in the Khondalite Belt are also documented in the basement rocks of the Ordos Block under same age frame of 2.2-2.0 Ga. This suggests that the Ordos Block may be a juvenile crust with addition of older materials. The initiation of subduction under the southern margin of the Ordos Block leads to the formation of a 2.2-2.0 Ga magmatic arc, which is likely related to the assembly of the supercontinent Columbia. (c) 2017 Elsevier B.V. All rights reserved.