Evidence of NeoArchean/PaleoProterozoic Crustal Reworking

Detrital zircon U-Pb ages and Hf isotopes of the metasedimentary rocks from the Jiaodong Group, Jiaobei terrane: Provenance and implications for the crustal evolution in the North China Craton

Authors:

Shan et al

Abstract:

Clastic sedimentary rocks can be a very powerful tool to gain insights into the crustal evolution history of many terranes. Here we present detrital zircon U-Pb ages and Hf isotopic data for the metasedimentary rocks in the Jiaobei terrane in the North China Craton (NCC), with a view to constrain the provenance of the protolith and depositional age, and to discuss implications for crustal evolution. The metasedimentary rocks in this study are similar to the sedimentary sequence of the Jiaodong Group in age populations of detrital zircons, petrology and mineralogy, and metamorphism and deformation, indicating that the studied samples belong to the sedimentary sequence of the Jiaodong Group. Detrital zircon U-Pb ages and Hf isotopic data of the metasedimentary rocks from the Jiaodong Group show similarity to those of the zircons from the Meoarchean-late Neoarchean granitoid gneisses in the Jiaobei terrane, suggesting that the Meoarchean-late Neoarchean granitoid gneisses in the Jiaobei terrane possibly provided the major source for the metasedimentary rocks of the Jiaodong Group. In combination with the previous studies, the detrital zircon populations in the Jiaobei terrane can place a good constraint on the depositional age of the Jiaodong Group. The youngest U-Pb age population of the magmatic detrital zircons (peak at 2489 Ma) is considered to constrain the maximum depositional age of the Jiaodong Group to 2.49 Ga. A major phase of metamorphism (late Paleoproterozoic) has been identified in the metasedimentary rocks of the Jiaodong Group, which mirrors the high-pressure granulite-facies regional metamorphism in the Jiaobei terrane. The magmatic detrital zircon Hf isotopes suggest that the zircons crystallized in magmas formed from the mixing of juvenile crustal components, including magmas derived from the depleted mantle, with ancient crustal materials. Therefore, our data suggest juvenile crustal growth and contemporaneous crustal reworking during the Neoarchean-Paleoproterozoic transition in the Jiaobei terrane.