EGU22-10824
https://doi.org/10.5194/egusphere-egu22-10824
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

10Be analysis in pyroxene - a method for routine chemical extraction

Allie Balter-Kennedy1,2, Joerg Schaefer1,2, Roseanne Schwartz1, Laura Penrose1,2, Jennifer Lamp1,2, and Gisela Winckler1,2
Allie Balter-Kennedy et al.
  • 1Lamont-Doherty Earth Observatory, Columbia University, New York, United States of America (abalter@ldeo.columbia.edu)
  • 2Department of Earth and Environmental Science, Columbia University, New York, United States of America

We have developed a method for routine processing of pyroxenes for cosmogenic 10Be analyses, offering a multi-nuclide (3He/10Be) approach for mafic terranes. Analyzing multiple cosmogenic nuclides from the same rock/mineral (most commonly, 26Al/10Be and 10Be/21Ne in quartz) enables quantification of complex exposure histories, including burial times, and erosion and denudation rates. This requires measurement of at least two cosmogenic nuclides whose production ratios and systematics are well known. For example, in quartz-bearing lithologies, the 26Al-10Be pair is routinely used because the production ratio of ~7 is relatively well constrained. In mafic lithologies, the 3He-10Be pair is a viable candidate for multi-nuclide studies because 3He is routinely measured in pyroxenes, and preliminary studies demonstrate that beryllium extraction from pyroxene grains is possible. Despite the potential of this nuclide pair, there is not yet a simple method for extracting beryllium from pyroxenes given that this mineral has high elemental concentrations and retains meteoric 10Be within the crystal lattice. 

Here, we present a method for beryllium extraction from pyroxenes, modified from the extraction method in quartz, that will enable routine use of the 3He-10Be pair. We demonstrate that hydrofluoric acid leaching not only allows for separation of large amounts of clean pyroxene, even from fine-grained lithologies such as Ferrar Dolerite, but also successfully removes meteoric 10Be. The addition of a simple precipitation step prior to ion exchange chromatography adequately reduces the cation load, allowing us to proceed with the same beryllium extraction chemistry used for quartz. Together, this approach allows for routine processing for 10Be analyses in pyroxene. Using our 10Be measurements, we present a preliminary 10Be production rate in pyroxene, referenced to 3He, for the McMurdo Dry Valleys, Antarctica, meaning that the 3He-10Be pair can already be used to evaluate complex exposure histories. With this result, we are optimistic that the presented extraction method opens new opportunities for multi-nuclide applications in mafic lithologies. 

How to cite: Balter-Kennedy, A., Schaefer, J., Schwartz, R., Penrose, L., Lamp, J., and Winckler, G.: 10Be analysis in pyroxene - a method for routine chemical extraction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10824, https://doi.org/10.5194/egusphere-egu22-10824, 2022.

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