Survey of Greenland. References
occur together in approximately equal propor-tions, indicating an original Fe Ti oxide of the composition UspssMt15. Graphical pyroxene thermometers (e.g. Saxena et aL, 1986) suggest a very wide range of crystallisation temperatures (around 1350 to 1000 ~ for the S.E. Greenland dykes, for which the...
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.617.8915 http://www.minersoc.org/pages/Archive-MM/Volume_52/52-368-705.pdf |
| Summary: | occur together in approximately equal propor-tions, indicating an original Fe Ti oxide of the composition UspssMt15. Graphical pyroxene thermometers (e.g. Saxena et aL, 1986) suggest a very wide range of crystallisation temperatures (around 1350 to 1000 ~ for the S.E. Greenland dykes, for which the late-stage precipitation of near end member ulv6spinel indicates fo2 con-ditions of- log fo ~ = 13 (cf. Lindsley, 1976). In contrast to the Proterozoic dolerites, the pyroxenes in the Tertiary olivine-dolerite dykes of S.E. Greenland are relatively chemically uniform pigeonite-augite pairs (Fig. l f) , which suggest a crystallisation temperature of between 1100 and 900 ~ These dykes contain early precipitated titanomagnetite, and their chilled margins carry microphenocrysts of ilmenite and magnetite. The combination of this pyroxene assemblage and the composition and early precipitation of the Fe Ti oxide phases in these Tertiary rocks clearly indicate that they crystallised under slightly higher fo~ conditions than did the neighbouring Proterozoic dykes. |
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