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 ^143^Nd/^144^Nd 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 ^87^Sr/^86^Sr ratios at 2.10 Ga ranging from 0.7017 to 0.7076. In the ε~Nd~ versus ^87^Sr/^86^Sr 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.