Petrogenesis of the ca. 2.5 Ga dioritic-TTG and granitic gneisses from the Huai'an Complex and its implications for crustal evolution and tectonic settings of the North China Craton

Abstract

The diversity and petrogenesis of Archean granitoid rocks, including tonalite-trondhjemite-granodiorite suites (TTGs), sanukitoids, and K-rich granites, is essential to understanding the geodynamic process of crust-mantle interaction and the origin and evolution of the continental crust. In this study, we investigate the petrogenesis, geochronology, and Sr-Nd-Hf isotopes of Neoarchean granitoids from the Huai'an Complex in the North China Craton (NCC) to gain insight into the crustal evolution during the Late Neoarchean–Early Paleoproterozoic. Five groups of plutonic gneisses of dioritic-tonalitic-trondhjemitic (DTT) and granitic gneisses in the Huai'an Complex are distinguished by their compositions. LA-ICP-MS zircon U-Pb dating constrains their emplacement ages from ca. 2.53 to 2.47 Ga and metamorphic ages at ca. 2.46 Ga and 1.86–1.82 Ga. The ca. 2.5 Ga DTT gneisses have consistent Sr-Nd-Hf isotopic compositions with positive whole-rock ɛNd(t) (+1.0 to +5.1), zircon εHf(t) (0.0 to +6.2) values, and older two-stage Hf model ages of 2.7–3.0 Ga, indicating they are cogenetic and derived from the partial melting of preexisting mafic crust. The dioritic gneisses with elevated MgO (3.09–4.94 wt%) and compatible element compositions (e.g., Cr and Ni) originated from a mafic crustal source modified by mantle-derived melts. The high Sr/Y values (104–661) and positive Eu anomalies (Eu/Eu⁎ = 1.05–2.76) of trondjemitic gneisses are controlled by plagioclase accumulation. The granitic gneisses are slightly peraluminous with high K2O (5.00–6.29 wt%) and low FeOT and MgO contents, indicating they were formed from the remelting of preexisting tonalitic crusts. The DTT and granitic plutonic gneisses in the Huai'an Complex were likely derived from crust-mantle interaction and crustal reworking in a subduction-related arc setting. The diverse geochemistry of these ca. 2.5 Ga granitoids is significantly controlled by source compositions, magmatic mixture, and accumulation. The prominent ca. 2.5 Ga TTG and granitic magmatism in the NCC likely represent a dominated internal reworking of the continental arc crust with subordinate crustal growth involving a subduction environment.