Zircon Hf isotopes and geochemistry of the early paleoproterozoic high-Sr low-y quartz-diorite in the Quanji massif, NW China : Crustal growth and tectonic implications

The metamorphosed Early Paleoproterozoic granitoids in the Quanji massif, Northwestern China provide constraints for relationship between the Tarim Craton and North China Craton. Among granitoids batholiths, rocks of the Mohe quartz-diorite show typically adakitic geochemical characteristics, with medium K₂O/Na₂O ratios (0.56-1.17) and high Sr (519-619 ppm) low Y (9.37-20.40 ppm) and Yb (0.97-1.77 ppm) concentrations. The rocks have e{open} _Nd(t) values between +2.4 and +4.4 and depleted mantle Nd model ages of 2.43-2.59 Ga. The magmatic zircons have positive e{open} _Hf(t) values ranging from +0.40 to +7.60 and depleted mantle Hf model ages of 2.43-2.70 Ga, with major peaks at ∼2.54 and ∼2.65 Ga. The geochemical and Nd-Hf isotopic characteristics indicate that the Mohe quartz-dioritic rocks might be formed by partial melting of high-pressure metamorphosed juvenile crustal rocks in post-orogenic extensional regime in the Early Paleoproterozoic. It suggests that important crustal growth occurred in the Quanji massif and the Tarim Craton at ∼2.4 and 2.5-2.7 Ga. The Quanji massif and Tarim Craton might share a similar crustal evolution history with the North China Craton in the Neoarchean.