These 40Ar/39Ar experiments were measured using a GV Instruments 5400® mass spectrometer at Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. The mass spectrometer is equipped with a high Faraday and an electron multiplier. The Faraday feedback resistor is 1011Ω. The source trap current is set at 200 μA during measurement. The signal intensity ratio of the multiplier to the Faraday is about 0.84. The argon isotopes are listed in volt. The multiplier sensitivity of this 5400® mass spectrometer is 1.64×10-15 mol/mV. A COHERENT© 50W CO2 laser (spot size 3mm) is used for stepwise heating. Data marked with "" were included in the calculations for the isochron ages.