Analytical methods and reproducibility of reference material dates for (U-Th)/He thermochronology at the geochronology laboratory of IGGCAS China

Abstract

The (U-Th)/He dating technique has been widely used for several decades to constrain the timing of low temperature geological processes. In this contribution, we describe the detailed procedures developed and dating results of reference materials for over more than a decade in low-temperature thermochronological laboratory at Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS), which allow (U-Th)/He age to be obtained with an analytical uncertainty of 1-3%. (U-Th)/He geochronological data of U, Th-bearing minerals at IGGCAS laboratory are obtained through a combination of crystal selection, helium extraction by laser heating and measurement by noble gas quadrupole mass spectrometry (QMS), and U, Th measurement by isotope dilution using inductively coupled plasma mass spectrometry (ICP-MS). More specifically, (U-Th)/He geochronological data of widely used reference materials such as Durango apatite and Fish Canyon tuff (FCT) zircon and titanite were reported, which were consistent with previously published results. Moreover, newly developed potential reference minerals such as MK-1 apatite, Penglai zircon (PL) and M6635 vesuvianite were also reported with considerable precision of 1-3 % for single crystal/fragment of uncorrected (U-Th)/He date.