Zirconium-bearing amphiboles from the Igaliko dyke

• Main Author: N. J. G. Pearce
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: Mineral. Monatsh 1989
• Subjects: Zr-bearing amphiboles; amphiboles; Igaliko Dyke Swarm; Greenland; Igaliko
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.599.6369; http://www.minersoc.org/pages/Archive-MM/Volume_53/53-369-107.pdf

Sodic-calcic and alkali amphiboles from benmoreitic members of the Igaliko Dyke Swarm contain up to 4.13 wt. % ZrO2. It is proposed that Zr enters the amphiboles by a coupled substitution of Zr 4+ +AI~. + ~ Fec 3+ + Si 4+ (where C = octahedral site and T = tetrahedral site) to produce the richest Zr-bearing amphiboles so far identified, with compositions ranging up to " 3+ 2+ Ko.48Na2.30Cao.32[Tlo.ooFeo.3 sFe3.9 sMno.14Mgo.zsZro.33] S17.58Alo.36022(OH)2. These amphiboles crystallize at a late stage from magmas which were Zr-rich, highly peralkaline and hydrous, with anfo ~ close to the synthetic QMF buffer. The incorporation of Zr in to the amphibole is a consequence of the failure of other Zr-bearing phases (such as zircon, baddeleyite, udialyte) to crystallize.