LA-ICP-MS zircon U-Pb age and geochemical characteristics of Neoarchaean metamorphic plutonic rocks in Kaiyuan area of northern Liaoning Province

Located in the Kaiyuan area of northern Liaoning Province on the northern margin of North China, the Neoarchaean metamorphic plutonic rocks are mainly composed of monzonitic granitic gneiss, granodioritic gneiss and quartz dioritic gneiss.According to LA-ICP-MS zircon U-Pb dating, they were formed in Neoarchaean, with the ²⁰⁷Pb/²⁰⁶Pb age of 2489.6±9.1 Ma.Neoarchean metamorphic plutonic rocks belong to high-K calc-alkaline-potassium basalt, quasi-aluminium-peraluminous rock series, and are enriched in LREE and relatively depleted in HREE, characterized by partial melting of the lower crust or Archean sedimentary rocks.Based on an analysis of petrology, petrogeochemistry, tectonic environment and emplacement mechanism, and combined with the study of tectonic evolution in adjacent areas, it is considered that the metamorphic plutonic magma in Kaiyuan area of northern Liaoning came from relatively shallow local melting of basic paleocontinental crust.Geotectonic location was in the contact zone between oceanic crust and continental crust, which indicates that there might have been collision and accretion of continental crust near Qinghe fault in Neoarchean.The diorite-quartz diorite-granodiorite-monzogranitic gneiss body shows that the continental crust has undergone a long period of accretion and continental activity, and has changed from the early basic continental crust to the present silica-alumina continental crust.