Technical note: Analytical protocols and performance for apatite and zircon (U–Th) ∕ He analysis on quadrupole and magnetic sector mass spectrometer systems between 2007 and 2020

Gautheron, Cécile; Pinna-Jamme, Rosella; Derycke, Alexis; Ahadi, Floriane; Sanchez, Caroline; Haurine, Frédéric; Monvoisin, Gael; Barbosa, Damien; Delpech, Guillaume; Maltese, Joseph; Sarda, Philippe; Tassan-Got, Laurent

Apatite and zircon (U–Th) inline-formula M3inlinescrollmathml / 8pt14ptsvg-formulamathimge653eaf840568ee76bb20ba3bf368ae0 gchron-3-351-2021-ie00004.svg8pt14ptgchron-3-351-2021-ie00004.png  He thermochronological data are obtained through a combination of crystal selection, He content measurement by crystal heating with analysis using noble gas mass spectrometry, and measurement of U, Th, and Sm contents by crystal dissolution as well as solution analysis using inductively coupled plasma mass spectrometry (ICP-MS). This contribution documents the methods for helium thermochronology used at the GEOPS laboratory, Paris-Saclay University, between 2007 and the present that allow apatite and zircon (U–Th) inline-formula M4inlinescrollmathml / 8pt14ptsvg-formulamathimg57ee8123d9c9aefcf23d9c7f6463c158 gchron-3-351-2021-ie00005.svg8pt14ptgchron-3-351-2021-ie00005.png  He data to be obtained with precision. More specifically, we show that the He content can be determined with precision (at 5 %) and accuracy using a calibration of the He sensitivity based on the Durango apatite, and its use also appears crucial to check for He and U–Th–Sm analytical problems. The Durango apatite used as a standard is therefore a suitable mineral to perform precise He calibration and yields (U–Th) inline-formula M5inlinescrollmathml / 8pt14ptsvg-formulamathimg93e47eb16cb371fe6916d3191efc4f1d gchron-3-351-2021-ie00006.svg8pt14ptgchron-3-351-2021-ie00006.png  He ages of 31.1 inline-formula± 1.4 Ma with an analytical error of less than 5 % (1inline-formulaσ). The (U–Th) inline-formula M8inlinescrollmathml / 8pt14ptsvg-formulamathimgfb147fccdcf98a9911cf3d26a8f6dc33 gchron-3-351-2021-ie00007.svg8pt14ptgchron-3-351-2021-ie00007.png  He ages for the Fish Canyon Tuff zircon standard yield a dispersion of about 9 % (1inline-formulaσ) with a mean age of 27.0 inline-formula± 2.6 Ma, which is comparable to other laboratories. For the long-term quality control of the (U–Th) inline-formula M11inlinescrollmathml / 8pt14ptsvg-formulamathimg165b352473919034209a9d51d0eaf41d gchron-3-351-2021-ie00008.svg8pt14ptgchron-3-351-2021-ie00008.png  He data, attention is paid to evaluating the drift of He sensitivity and blanks through time as well as that of (U–Th) inline-formula M12inlinescrollmathml / 8pt14ptsvg-formulamathimg6bfc4ae3491d603d986b6e1d0e6866cf gchron-3-351-2021-ie00009.svg8pt14ptgchron-3-351-2021-ie00009.png  He ages and Th inline-formula M13inlinescrollmathml / 8pt14ptsvg-formulamathimg8550e2e9970f84100ffbfa4da4f4f543 gchron-3-351-2021-ie00010.svg8pt14ptgchron-3-351-2021-ie00010.png  U ratios (with Sm inline-formula M14inlinescrollmathml / 8pt14ptsvg-formulamathimg539a58614ea8688159b8effbc6d3da8d gchron-3-351-2021-ie00011.svg8pt14ptgchron-3-351-2021-ie00011.png  Th when possible), all relying on the use of Durango apatite and Fish Canyon Tuff zircon as standards.

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Gautheron, Cécile / Pinna-Jamme, Rosella / Derycke, Alexis / et al: Technical note: Analytical protocols and performance for apatite and zircon (U–Th) ∕ He analysis on quadrupole and magnetic sector mass spectrometer systems between 2007 and 2020. 2021. Copernicus Publications.

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