Cosmogenic 10Be in pyroxene: laboratory progress, production rate systematics, and application of the 10Be-3He nuclide pair in the Antarctic Dry Valleys

• Main Authors: Balter-Kennedy, Allie, Schaefer, Joerg M., Schwartz, Roseanne, Lamp, Jennifer L., Penrose, Laura, Middleton, Jennifer, Tibari, Bouchaïb, Blard, Pierre-Henri, Winckler, Gisela, Hidy, Alan J., Balco, Greg
• Format: Text
• Language: English
• Published: 2023
• Subjects: Antarctic; The Antarctic; McMurdo Dry Valleys; Antarc*; Antarctica
• Online Access: https://doi.org/10.5194/egusphere-2022-1379; https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1379/

Here, we present cosmogenic- 10 Be and cosmogenic- 3 He data from Ferrar dolerite pyroxenes in surficial rock samples and a bedrock core from the McMurdo Dry Valleys, Antarctica, with the goal of refining the laboratory methods for extracting beryllium from pyroxene, further estimating the 10 Be production rate in pyroxene and demonstrating the applicability of 10 Be– 3 He in mafic rock. The ability to routinely measure cosmogenic 10 Be in pyroxene will open new opportunities for quantifying exposure durations and Earth surface processes in mafic rocks. We describe scalable laboratory methods for isolating beryllium from pyroxene, which include a simple hydrofluoric acid leaching procedure for removing meteoric 10 Be and the addition of a pH 8 precipitation step to reduce the cation load prior to ion exchange chromatography. 10 Be measurements in pyroxene from the surface samples have apparent 3 He exposure ages of 1–6 Myr. We estimate a spallation production rate for 10 Be in pyroxene, referenced to 3 He, of 3.6 ± 0.2 atoms g −1 yr −1 . 10 Be and 3 He measurements in the bedrock core yield initial estimates for parameters associated with 10 Be and 3 He production by negative-muon capture ( f 10 ∗ = 0.00183 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="67pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="b8d80758c5229555d2f87ecc0009ae48"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-5-301-2023-ie00001.svg" width="67pt" height="14pt" src="gchron-5-301-2023-ie00001.png"/></svg:svg> and f 3 ∗ f C f D = 0.00337 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="83pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="9948fc960df7c711666d09b5b9e12773"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-5-301-2023-ie00002.svg" width="83pt" height="14pt" src="gchron-5-301-2023-ie00002.png"/></svg:svg> ). Next, we demonstrate that the 10 Be– 3 He pair in pyroxene can be used to simultaneously resolve ...