MASS-SPECTROMETRIC IDENTIFICATION OF COSMIC-RAY-PRODUCED NEON IN TERRESTRIAL ROCKS WITH MULTIPLE NEON COMPONENTS

Studies of cosmic-ray-produced nuclides in terrestrial rocks are expec ted to provide important geomorphological and glaciological informatio n, such as surface exposure ages, erosion rates and extent of glacial cover. In the case of the stable nuclide Ne-21, the cosmic-ray-produce d component may represent but one of several components, and a compone nt resolution based on three-isotope correlations is essential. We dev eloped analytical techniques which permit accurate corrections for all interfering ions. We show (for OUT modified Nier source) that correct ions for doubly charged species based on constant charge state ratios are not satisfactory. The improved techniques permit isotopic studies of < 10(6) atoms of Ne-21. The spallation ratio (Ne-22/Ne-21)c from Si was calibrated using a quartz separate from an Allan Hills sandstone and yields a value of 1.243 +/- 0.022. This ratio is expected to be es sentially constant for terrestrial quartz samples and should be useful in component resolutions. The stepwise release of Ne at increasing te mperatures shows that cosmic-ray-produced Ne is released from quartz a t rather low temperatures. This permits an estimate of the activation energy for Ne diffusion in quartz (90 +/- 10 kJ/mol).