Chlorine-Deficient Analog of Taseqite from Odikhincha Massif (Russia): Genesis and Relation with Other Sr-Rich Eudialyte-Group Minerals

Eudialyte-group minerals are important accessory of peralkaline rocks nepheline-syenite massifs and alkaline–ultramafic complexes. Here, we report the complex study a eudialyte-group mineral (EGM) from pegmatite alkaline-ultrabasic Odikhincha massif (Polar Siberia). The chemical composition studied EGM is intermediate between those taseqite eudialyte, with small admixtures other members eudialyte group. crystals EGMs were formed during postmagmatic stage in temperature range 300–350 °C partly replaced by late eudialite along cracks zeolite (~230 °C). compositions, structural features association similar to Sr-Nb-dominant found massifs, such as Khibiny, Lovozero Pilansberg. this work Cl-deficient variety (“monochlore taseqite”), which differs “dichlorotaseqite” (found only Ilimaussaq massif) lower amount chlorine.