Hi Pawan, please check the following articles: Jansen et al. (2017): Journal of Luminescence 186: 205-211; Nikolaev et al. (2017) Journal of Molecular Structure 1149: 323-331; and references therein. Cheers Daniel
The positive Eu anomaly can be can be interpreted as: (1) Change in crystallization setting from reduced to oxidized conditions ; (2) or Eu-enriched hydrothermal fluid rather than the setting itself