The Grønnedal–Ika carbonatite–syenite complex, South Greenland: carbonatite formation by liquid immiscibility
The Grønnedal-Ika complex is dominated by layered nepheline syenites which were intruded by a xenolithic syenite and a central plug of calcite to calcite–siderite carbonatite. Aegirine–augite, alkali feldspar and nepheline are the major mineral phases in the syenites, along with rare calcite. Temper...
| Main Authors: | , , |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2005
|
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.538.476 http://petrology.oxfordjournals.org/content/46/1/191.full.pdf |
| Summary: | The Grønnedal-Ika complex is dominated by layered nepheline syenites which were intruded by a xenolithic syenite and a central plug of calcite to calcite–siderite carbonatite. Aegirine–augite, alkali feldspar and nepheline are the major mineral phases in the syenites, along with rare calcite. Temperatures of 680–910C and silica activities of 028–043 were determined for the crystallization of the syenites on the basis of mineral equilibria. Oxygen fugacities, esti-mated using titanomagnetite compositions, were between 2 and 5 log units above the fayalite–magnetite–quartz buffer during the magmatic stage. Chondrite-normalized REE patterns of magmatic calcite in both carbonatites and syenites are characterized by REE enrichment (LaCN–YbCN 10–70). Calcite from the carbonatites has higher Ba (5490 ppm) and lower HREE concentrations than calcite from the syenites (54–106 ppm Ba). This is consistent with the behavior of these elements during separation of immiscible |
|---|