Zircon U-Pb Dating and Metamorphism of Granitoid Gneisses and Supracrustal Rocks in Eastern Hebei, North China Craton

Granitoid gneisses dominated by tonalitic-trondhjemitic-granodioritic (TTG) compositions, with metamorphic supracrustal rocks consisting of sedimentary and volcanic rocks, are widely exposed in the Eastern Hebei terrane, North China Craton (NCC). This study presents systematic zircon U-Pb geochronological and whole-rock geochemical data of the Neoarchean granitoid gneisses and supracrustal rocks in Eastern Hebei. Zircon U-Pb isotopic dating for the representative samples reveals that magmatic precursors of granitoid gneisses were emplaced between 2524 +/- 7 and 2503 +/- 12 Ma, and the protoliths of the pelitic granulites were deposited in the Late Neoarchean era. Both of them have been subjected to granulite facies metamorphism during 2508 +/- 10 to 2468 +/- 33 Ma, coeval with the intrusion of syenogranitic pegmatite (2488 +/- 5 Ma). Zircon ages of 2.45-2.01 Ga obtained from the analyzed samples were considered mixed data from 2.53-2.48 Ga and 1.9-1.8 Ga and were chronologically meaningless. Paleoproterozoic metamorphic zircon ages of 1.9-1.8 Ga were usually neglected because of hardly being obtained from TTG gneisses and supracrustal rocks. The tectonic regime during the Neoarchean era was considered to be dominated by vertical tectonism in the Eastern Hebei terrane.