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Published April 15, 2009 | public
Journal Article

Cosmogenic ^(3)He and ^(21)Ne production rates calibrated against ^(10)Be in minerals from the Coso volcanic field

Abstract

This study calibrates the production rate of cosmogenic ^(3)He in pyroxene, olivine, garnet, zircon and apatite as well as ^(21)Ne in quartz and pyroxene against the known production rate of ^(10)Be in quartz. The Devil's Kitchen rhyolite from the Coso volcanic field in southeastern California (elev. ~ 1300 m) was chosen for this study due to its young age (~ 610 ka) and diverse mineral assemblage. Based on ^(10)Be, our two rhyolite samples have apparent exposure ages of ~ 49 and 93 ka, indicating substantial erosion after eruption. Combining data from the two samples, we estimate sea level high latitude ^(3)He spallation production rates of 145 ± 11, 141 ± 16, and 144 ± 30 at g^−1 a−^1 (2σ) for pyroxene, olivine and spessartine garnet respectively. For zircon and apatite, we estimate apparent 3He spallation production rates of 114 ± 8 and 149 ± 28 at g^−1 a^−1 (2σ) respectively. The rates for zircon and apatite are reported as apparent production rates because we do not explicitly address the redistribution of spallation produced ^(3)He from adjacent minerals. These estimates quantitatively account for production of ^(3)He from both cosmogenic and radiogenic neutron reactions on ^(6)Li within the analyzed phases and also implanted from nuclear reactions in neighboring minerals; the high U, Th and Li content of this rhyolite provides a particularly rigorous test of this correction. We estimate ^(21)Ne production rates of 17.7 ± 1.6 and 34.1 ± 3.2 at g^−1 a^−1 (2σ) in quartz and pyroxene (Fe/Mg = 0.7 by mass) respectively. Although high U and Th contents create the potential for significant production of nucleogenic ^(21)Ne, this component is small due to the young eruption age of the rhyolite.

Additional Information

© 2009 Elsevier B.V. Received 11 November 2008; revised 16 January 2009; accepted 21 January 2009. Editor: R.W. Carlson. Available online 25 February 2009. Thanks to Don Burnett, P.H. Blard, and Frank Monastero. Thanks to Samuel Niedermann and an anonymous reviewer for greatly improving this manuscript. This work was supported by National Science Foundation Grant 0511053. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.epsl.2009.01.031.

Additional details

Created:
August 22, 2023
Modified:
October 18, 2023