Paleoproterozoic crustal growth in the Western Block of the North China Craton: Evidence from detrital zircon Hf and whole rock Sr-Nd isotopic compositions of the khondalites from the Jining Complex

Abstract

Detrital zircons from the khondalites in the Western Block of the North China Craton were mainly derived from a 1.9 to 2.1 Ga Paleoproterozoic provenance. Most of the more than 200 detrital zircons analyzed in this study have positive initial ε Hf values and a wide range of Hf depleted mantle model ages (T DM C) that range from 2.08 Ga to 2.74 Ga, with a peak at 2.24 to 2.40 Ga. The whole rock Nd isotopic analyses for the khondalite samples give quite uniform 143Nd/ 144Nd ratios from 0.511188 to 0.511858, corresponding to initial ε Nd (2.10Ga) values ranging from -1.6 to +0.6. In contrast, Sr isotopic compositions of these samples are more varied, with initial 87Sr/ 86Sr ratios at 2.10 Ga ranging from 0.7017 to 0.7076. In the ε Nd versus 87Sr/ 86Sr correlation diagram, most samples plot near the mixing hyperbola of the depeleted mantle and crust, with the contribution of depleted mantle about 65 to 75 percent. These results suggest that a large amount of juvenile materials from the depleted mantle was accreted to the Western Block at 2.1 Ga, a period of magmatic quiescence in many cratons of the world.