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• The granodiorites and monzonitic diorites were originated from slab melts and slab melts-metasomatized mantle source, respectively. • The alkali feldspar granites were produced by partial melting of a crustal source in an extension background. • The gabrros were generated by partial melting of mantle wedge metasomatized by slab-derived fluids. • A slab window was likely happened at 2.46–2.44 Ga in the south margin of the Yinshan Block. The earliest Paleoproterozoic magmatic rocks have recorded the transition from the Neoarchean cratonization of the NCC to its post-Archean tectonic evolution, which will provide insight into the onset of the modern-style subduction. This study focuses on the early Paleoproterozoic granodiorite, monzonitic diorite, alkali feldspar granite and gabbro in the Guyang area to decipher the early Paleoproterozoic tectonic evolution of the Yinshan Block. Zircon U–Pb dating indicates that these rocks were emplaced at ca 2.46 – 2.41 Ga. The ∼ 2.46 Ga granodiorite samples have high Sr contents, low Y and Yb contents with high Sr/Y ratios, similar to the characteristics of adakitic rocks. Based on their high Mg# values, Na 2 O/K 2 O ratios, Cr, Co and Ni concentrations, and positive ε Nd (t) values, we propose that the granodiorite was likely produced by partial melting of subducting oceanic slab. The contemporary monzonitic diorite samples are characterized by high Nb concentration, which are similar to those of Nb-enriched basalt/andesite. The monzonitic diorite samples are characterized by LREE-enriched patterns with negative Eu anomalies and have negative ε Nd (t) values (-0.4 – −1.4), which suggest that they were derived from partial melting of fertile mantle peridotite metasomatized by adakitic melts. The ∼ 2.44 Ga alkali feldspar granite samples have negative ε Nd (t) values (-4.0 – −1.9) and show geochemical characteristics of A-type granites, indicating an extension background. The distinct geochemical characteristics of ca. 2.46 – 2.44 Ga Guyang adakatic granodiorite, Nb-enriched monzonic diorite and A-type alkali feldspar granite suggest that a slab window was opened in the southern margin of the Yinshan Block. The gabbros were emplaced at ∼ 2.41 Ga revealed by U-Pb dating. The enriched LREEs and relatively flat HREEs patterns with negative Nb-Ta anomalies of gabbros indicate a subducting tectonic setting. Their high Ba/Th and low Nb/Y ratios imply that the mantle source was metasomatized by slab-derived fluids. This special rock association not only constrains the tectonic evolution in the southern margin of the Yinshan Block, but also indicates modern-style subduction operated already in the early Paleoproterozoic. [ABSTRACT FROM AUTHOR]

Dioritic--trondhjemitic gneisses of Neoarchean age are widely distributed throughout the Gualanyu--Shangying area in Eastern Hebei, North China Craton. These orthogneisses consist of dioritic, trondhjemitic, and quartz-rich trondhjemitic gneisses, which were subjected to amphibolite- to granulite-facies metamorphism. LA-ICP-MS zircon U--Pb isotopic dating reveals that the magmatic precursors of these rocks were contemporaneously emplaced from 2535 ± 23 to 2513 ± 8 Ma, reflecting an important Neoarchean dioritic--trondhjemitic magmatic event followed by sequential Proterozoic tectonothermal events between 2472 ± 60 and 2307 ± 50 Ma. Dioritic and trondhjemitic gneisses exhibit similar zircon ɛHf(t) values of +1.5 to +5.2 and +2.9 to +5.3, respectively, indicating their depleted mantle affinity. Geochemical analysis reveals that the dioritic gneisses have low SiO2 contents (55.4-63.0%), various MgO contents (2.07-4.78%) and Mg# (36.07-63.56), and high (La/Yb)N ratios (5.45-15.19). In contrast, the trondhjemitic gneisses exhibit higher SiO2 contents (67.4-73.8%) and (La/Yb)N ratios (12.86-76.73), and lower MgO contents (0.66-2.67%), although their Mg# (36.29-61.41) are similar to those of dioritic gneisses. These geochemical and zircon Lu--Hf isotopic features, together with geochemical modeling, suggest that the dioritic magmas were derived mainly from the partial melting of a depleted mantle wedge that was metasomatized by slab-derived melts or fluids, and that the trondhjemitic magmas were formed by fractional crystallization of the dioritic magmas. Quartz-rich trondhjemitic gneisses exhibit extremely high SiO2 contents (77.4-84.6%) with zircon ɛHf(t) values ranging from -3.4 to +4.1, suggesting that their precursors formed after the partial melting of a mixed magmatic source. It is suggested that the precursors comprised a mafic member derived from a mantle wedge altered by oceanic slab melts or fluids, and a felsic member derived from the partial melting of ancient crustal material. These new data, combined with previous studies of contemporaneous metavolcanic rocks in Gualanyu-Shangying area and surrounding areas, suggest that the magmatic precursors of these Neoarchean dioritic--trondhjemitic gneisses formed in a subduction-related tectonic environment at an E-W strike convergent plate margin. Furthermore, the Eastern Block of the North China Craton had a major lateral accretion of crustal growth in the north margin in the Neoarchean, whereas vertical crustal growth and recycling under plume tectonic backgrounds occurred in the interior of the Eastern Block. [ABSTRACT FROM AUTHOR]