The chevkinite group: underestimated accessory phases from a wide range of parageneses
Published Online: Jul 31, 2014
Page range: 99 - 114
Received: Apr 20, 2011
Accepted: Aug 08, 2013
DOI: https://doi.org/10.2478/mipo-2013-0006
Keywords
© by Bogusław Bagiński
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.
Chevkinite-group minerals are widespread in a very wide range of igneous and metamorphic parageneses, forming important components of accessory mineral assemblages. Their presence in a rock may be difficult to establish by standard optical techniques, which has contributed to their importance being underestimated; a combination of SEM and EMPA is recommended here. Currently, there are eleven IMAapproved members of the group but undoubtedly several more will be described in the near future. There is considerable compositional variation in the group, which can be expressed as:
REE + M2+C + M3+C = Ca2+ A + Sr + Ti4+C + Zr4+C
where A and C are structural sites. Chevkinite-group minerals strongly fractionate geochemically coherent pairs, such as LREE-HREE, Nb-Ta, Zr-Hf and Th-U, and thus play a critical role in geochemical modelling.