Geochronology and geochemistry of Liaohe Group and Liaoji granitoid in the Jiao-Liao-Ji Belt, North China Craton: Implications for petrogenesis and tectonic evolution

摘要

Zircon U-Pb geochronological, whole-rock geochemical, and Hf isotopic studies were carried out on Liaohe Group and Liaoji granitoid within the central part of the Liaodong peninsula, NE China, to understand the Paleoproterozoic evolutionary history of Jiao-Liao-Ji Belt, North China Craton. Zircon U-Pb dating indicates the studied metavolcanic rocks from Dashigiao Formation in South Liaohe Group had protolith ages of 2170 +/- 29 Ma, 2170 +/- 11 Ma, 2166 +/- 17 Ma, and 2137 +/- 9 Ma, with one showing a metamorphic age of 1866 9 Ma. These metavolcanic rocks are dacite-andesite in compositions, belonging to calc-alkaline series. They are characterized by light rare earth elements (LREEs)-enriched patterns, and enriched in large ion lithophile elements (LILEs) relative to high field strength elements (HFSEs), with significant negative Nb-Ta-Ti-P anomalies, showing arc affinities. Combined with their epsilon(Hf)(t) values (-4.36 to +8.38), we suggest that the intermediate-acidic magma were derived from partial melting of Meso-Neoarchean juvenile lower continental crust, with a possible contribution of ancient materials. In addition, the studied monzonitic gneiss from Liaoji granitoid had a protolith age of 2167 26 Ma, with a metamorphic age of 1883 10 Ma. Based on previous studies of Liaohe Group and related meta-mafic rocks, as well as Liaoji granitoid, these Paleoproterozoic rocks not only share statistically indistinguishable Paleoproterozoic magmatic and metamorphic history for the Jiao-Liao-Ji Belt, but also collectively formed in an active continental margin or volcanic arc. These data, combined with previous studies within the Jiao-Liao-Ji Belt, suggest that an arc-continent collision model was favored for the Paleoproterozoic tectonic evolution of the Jiao-Liao-Ji Belt, and the significant arc-continental collision was probably at ca. 1.9 Ga.