Zirconium-bearing amphiboles from the Igaliko dyke
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...
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| Language: | English |
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Mineral. Monatsh
1989
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| 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 |
| Summary: | 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. |
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