LA-ICP-MS zircon U-Pb age of the intrusive rocks in Longyangxia area of Qinghai Province and its geological significance

The intrusive rock types of Longyangxia area in Qinghai Province include syenogranite, monzonitic granite and granodiorite, The rocks have the data Al₂O₃=11.78%~15.11%, K₂O=3.57%~5.58%, A/NK=1.14~1.63, A/CNK=0.87~0.97, and TFeO/(TFeO + MgO)=0.74~0.91, exhibiting the characteristics of metaluminous intermediately high-K calc-alkaline granite. The LAICP-MS detection shows that the ²⁰⁶Pb/²³⁸U ages of zircon in syenogranite and monzonitic granite are respectively 243.5 ±2.9Ma (MSWD=5.20) and 247.2±1.7Ma (MSWD=0.97), which are interpreted as the rock emplacement age and represent the geological record of Indosinian Movement's tectonic evolution in the Gonghe aulacogen located in the conjugating and transferring part between the western section of West Qinling orogenic belt and the east Kunlun orogenic belt. The determination of the formation epoch and tectonic environment of the intrusive rocks in Longyangxia area of Qinghai plays a crucial role in the research on the tectonic evolution and dynamics mechanism of Gonghe aulacogen.