THE EFFECTS OF U-TH-RICH GRAIN BOUNDARY PHASES ON APATITE HELIUM AGES |
We document a source of apatite He age variability amongst single apatite grains from the same sample: U-Th-Sm-bearing phases precipitated on apatite grain boundaries. These phases interfere with the key assumptions made when we apply the alpha-ejection correction to apatite He ages. We model these effects and demonstrate strategies for retrieving useful information from otherwise problematic apatite He datasets.
Most importantly, in routinely collected apatite He datasets GBP effects result in ages that are 'too old' and manifest as negative-slope age-[eU] patterns. See the data repository for my Henry Mountains paper for an example. Published in Chemical Geology. |