A REEVALUATION OF IN SITU COSMOGENIC HE-3 PRODUCTION RATES

³He is among the most commonly measured terrestrial cosmogenic nuclides, yet robust interpretation of terrestrial ³He concentrations requires a more accurate understanding of its sea level high latitude (SLHL) production. We present new measurements of the terrestrial cosmogenic ³He production rate in olivine from a well-dated lava flow at Tabernacle Hill, Utah, USA. The new ³He measurements (n=8) show excellent internal consistency and yield a SLHL production rate of 123±4 at g^-1 yr^-1 following the Lal (1991)/Stone (2000) scaling model [Lal, D., 1991. Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and erosion models. Earth and Planetary Science Letters, 104, 424-439.; Stone, J.O., 2000. Air pressure and cosmogenic isotope production. Journal of Geophysical Research, 105, 23753-23759.]. We then combine our new measurements from Tabernacle Hill with a compilation of published production rate determinations to characterize the mean global SLHL production rates (e.g. 120±10 at g^-1 yr^-1 with Lal (1991)/Stone (2000)). The results show that the internal consistency of the global ³He production rate dataset is as high or higher than for the other commonly used cosmogenic nuclides. Additionally, ³He production rates in olivine and pyroxene are within experimental error, which constrains the compositional dependence of helium production. The new production rates are implemented in an age and erosion rate calculator forming part of the CRONUS-Earth effort to develop an easily accessible and internally consistent platform for cosmogenic nuclide data interpretation. The calculator is made available online at http://www.cronuscalculators.nmt.edu/.