Processes in High-Mg, High-T Magmas: Evidence from Olivine, Chromite and Glass in Palaeogene Picrites from West Greenland |
| |
| Authors: | LARSEN LOTTE M; PEDERSEN ASGER K |
| |
| Institution: | 1GEOLOGICAL SURVEY OF DENMARK AND GREENLAND, THORAVEJ 8, DK-2400 COPENHAGEN NV, DENMARK
2GEOLOGICAL MUSEUM, ØSTER VOLDGADE 5–7, DK-1350 COPENHAGEN K, DENMARK |
| |
| Abstract: | Uncontaminated volcanic rocks from the 60 Ma Vaigat Formation,West Greenland, contain 6·5–30 wt % MgO, averaging15·5 wt % MgO. Olivine (mg-number 77·4–93·3)forms diverse assemblages of zoned phenocrysts and xenocrystsshowing evidence for equilibrium and fractional crystallization,oxidation, partial to complete re-equilibration, as well asmagma mixing. The olivine crystals contain glass inclusionsand have high contents of Ca and Cr, indicating that all olivineswith up to mg-number 93·0 crystallized from melts. Associatedchromites (mg-number 45·4–77·2) are essentiallyunzoned and in equilibrium with the olivines. Matrix glassesfrom pillow breccias have 6·7–8·8 wt % MgOand quenched close to 1200°C with oxidation states one log-unitabove the NNO (nickel–nickel oxide) buffer. Compositionaldifferences between the glasses from different volcanic membersare inherited from the primary melts. The magmas erupted ascrystal-charged melts, and liquids with more than |
| |
| Keywords: | |
| 本文献已被 Oxford 等数据库收录！ |
|
