Study on ⁴He Isotope Extraction and Quantitative Measurements in Minerals

As an effective low-temperature thermochronometer method, the (U-Th)/He dating technique is currently widely applied in geological research. The efficient extraction and accurate content determination of ⁴He in minerals are key for the (U-Th)/He dating technique. This paper introduces the laboratory extraction methods of ⁴He in minerals and the ⁴He content-determination method in Chengdu Institute of Geology and Mineral Resources. Apatite and zircon are the most common minerals for (U-Th)/He dating, while magnetite, olivine, goethite and garnet are used less for (U-Th)/He dating. There are some routine methods for ⁴He extraction and U, Th content determination. The resistance furnace heating method and laser heating method ⁴He extraction from minerals are introduced, and the latter method being more commonly applied because of the fast analysis and low He background. In Chengdu Institute of Geology and Mineral Resources, the laser heating method and the quadrupole mass spectrometer are used to extract and determine the ⁴He content in apatite. This paper describes the ⁴He content determination process, calculation and correction method adopted for apatite samples. Furthermore, the alternative minerals should be tested for (U-Th)/He dating to attempt to improve the routine analysis methods.