Retentivity of minerals for cosmogenic He and Ne

The extent to which Hcc is lost from quadz by diffusion was a matter of debate in the early nineties (e.g.. Ceding 1990 Graf et al. 1991 Trull et al. 1991 Brook and Kurz 

Discrimination of cosmogenic against trapped, radiogenic, and nucleogenic components 

To allow for an accurate determination of the concentration of a cosmogenic noble gas isotope, noble gas components from other sources must be effectively discriminated against. These components include  

On the other hand, care must be taken to avoid irreversible adsorption of atmospheric noble gases on fresh grain surfaces (e.g., Niedermann and Eugster 1992), which may not be a problem for Ne in quartz but might affect certain other minerals. 

Nucleogenic He produced by the reaction Li(n,a) H(P ) He is only important in minerals with high Li content. The He/ He ratio resulting from U/Th decay and Li neutron capture can be estimated from the chemical composition of the mineral and 

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