The generation and evolution of Archean continental crust in the Dunhuang block, northeastern Tarim craton, northwestern China

• TTG in the interior of the Dunhuang blocks was formed at ∼2.7–2.6 Ga.
• Tarim experienced two-stage (∼2.7–2.6 and ∼2.5 Ga) intrusion of Archean TTG.
• Tarim was characterized by episodic generation of juvenile continental crust.
• Paleoproterozoic and Paleozoic tectonothermal events were prevail in the Tarim craton.
• Paleoarchean continental crust as old as ∼3.4 Ga may have existed in the Dunhuang block

Tonalite–trondhjemite–granodiorite (TTG) preserved in Archean cratons can provide insights into the generation and evolution of the early continental crust. In this study, typical TTG gneisses from the Dunhuang block in the northeastern Tarim craton were studied in detail regarding their geochemistry and geochronology to constrain the generation and evolution of the Archean continental crust in this region. These TTG gneisses are characterized by high contents of SiO2 (68.3–71.6%), Al2O3 (15.3–16.9%), Na2O (4.43–4.85%), low K2O/Na2O ratios (0.20–0.37) and a very low HREE content (Yb < 1 ppm) and show two-stage Nd isotope model ages of ∼3.06–2.84 Ga. Zircon U–Pb analyses reveal that these TTG gneisses were formed ∼2.7–2.6 Ga ago, as shown by inherited magmatic zircon cores, and were later altered by Paleoproterozoic (∼2.0–1.9 Ga) and early Paleozoic (∼430 Ma) high-grade metamorphic events. Two samples show positive ɛHf (t) values of 1.5–5.4 for magmatic zircons with ages of ∼2.7–2.6 Ga and give a two-stage Hf isotope model age of ∼2.95 Ga, while one sample exhibits negative ɛHf (t) values of −3.4 to −7.2 for magmatic zircons with ages of ∼2.7–2.6 Ga and gives a two-stage Hf isotope model age of ∼3.4 Ga, suggesting that the Paleoarchean and Mesoarchean Eras were important periods for the generation of juvenile continental crust in the Dunhuang block. Lastly, based on analyses of previous studies, we speculate that the Tarim craton has been subjected to episodic crustal growths at ∼3.4 Ga, ∼3.2 Ga, ∼2.95 Ga, ∼2.8 Ga and ∼2.6 Ga and reworking events at ∼2.7–2.6 Ga and ∼2.5 Ga