3he cosmogenic nuclide age dating
existing cosmogenic 3He calibration sites) will help to refine estimates of the reference production rate. (AM) Accepted Manuscript First Live Deposit - 01 November 2018 Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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: Relatively high diffusivity of He in apatite (and some other phases) to near-surface temperatures at geologic timescales provides low bulk or intragrain closure temperatures (Dodson, 1973, 1979, 1986).
This makes apatite He dating uniquely suited to providing low-temperature cooling ages and constraining low temperature thermal histories in the uppermost few kilometers of crust.
Improving the viability of in situ10Be for geological applications in mafic domains requires increased analytical precision beyond current levels.Uncertainty associated with the correction depends on uncertainties in measurements of crystal dimensions, the correspondence of analyzed and original crystal morphologies, and the distribution of parent nuclides both within the crystal and within the ~20- m external environment during He accumulation in the rock.The latter two factors are difficult to quantify a priori, and may be largely responsible for the fact that the observed reproducibility of He ages for most crystals (typically Ar ages on the same samples (e.g., Blondes et al., 2007). alpha dating by some authors) stretches farther back than any other radioisotopic dating technique (Rutherford, 1905).It can arguably be interpreted as an allegory for the history of thermochronology in general, in which early, presumably nonsensical or inconsistent ages are later interpreted as geologically meaningful cooling ages in the context of additional kinetic and geologic constraints (e.g., see review in Reiners et al., 2005).