LA-ICP-MS zircon U-Pb dating of Nanshan subduction type intrusion in Qinghai Province and its geological significance

The Nanshan intrusion consists of monzonitic granite, granodiorite and tonalite, geochemically belonging to subduction type granite. The high precision LA-ICP-MS denudation plasma mass spectrometry (laser) single particle zircon micro area U-Pb isotopic dating yielded 446.1±3.5Ma, 447.2±5.3Ma, and 443.6±8.6Ma for monzonitic granite, granodiorite and tonalite, respectively, which indicates the Caledonian movement in the Qilian orogenic belt in the geological record. The rock-forming ages of the three different types of rocks may represent southward subduction of the Lajishan orogenic belt. The determination of the rock-forming epoch and tectonic environment of the Nanshan subduction type intrusion is of great significance for the tectonic evolution and dynamics mechanism of the Lajishan orogenic belt.