Volcanic feldspars anomalous fading: Evidence for two different mechanisms

This study presents measurements of anomalous fading of feldspars extracted from volcanic units from the Auvergne (France) and Patmos Island (Greece). We measured the fading rate for samples stored at ambient temperature, and also at liquid nitrogen temperature. A strongly different behaviour is then observed, the fading is reduced to values usually obtained and explained by pure tunnelling recombination of charges to near enough luminescence centres, which is athermal. We suggest that the temperature dependent or “frozen” part of the fading is relevant to a different mechanism, which is “hopping”, already proposed in the mid-sixties, which preserves the experimental logarithmic fading decreasing law.