Abstract: Determination of K-Ar Ages on Some Young Basalts by IDMSSang Haiqing;Qiu Ji;Wang Songshan;Hu Shiting(Institute of Geology,Chinese Academy ofSciences,Beijing 100029,China)Received Abstract:The present paper reports some results of K-Ar ages in young basalts from northwest and northeast region of China.These results are determined by 38Ar isotope dilutien mass spectrometry(IDMS).The particle size of samples analysed sanes in a range from 0.20 to 0.63 mm in diameter is selected.We use an ultra-high vacuum system for argon extraction and a RGA-10 mass spectrometer operated in static mode for isotopic measurement.The isotopic ratios of argon for spike are40Ar/38Ar=7.4364×10-3,36Ar/38Ar=5.0868×10-5.All argon isotopes has been corrected for memory effect.Using flame photometry the potassium is determined.Finally,we use following contants λe=0.581×10-10/year,λβ=4.962×10-10/year,λ=5.543×10-10/year and 40Ar/K=1.167×10-104(mole/mole)for age calculation.The age range of all basalts is from 0.116 to 2.101 Ma.Also,the standard diviation is given for every measured age.The measurement precision of most samples is within ±5%.The results indicate well for young samples.Keywords:young basalt,K-Ar age,IDMS