Mineral chemistry of layered Archaean anorthosite at Majorqap qâva,near Fiskenæsset,southwest Greenland |
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| Authors: | JS Myers RG Platt |
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| Institution: | 1. John S. Myers, Geological Survey of Greenland, Oster Voldgade 10, 1350 Copenhagen K, Denmark;2. R. G. Platt, Department of Geology, Lakehead University, Thunder Bay, Ontario P7B 5E1, Canada |
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| Abstract: | Variations of mineral chemistry are described in a layered sheet of partly metamorphosed anorthosite, leucogabbro, gabbro and peridotite. The rocks appear to represent part of two major cycles of crystal deposition in which the anorthite content of plagioclases decreases upwards from An98?94 to An90?75 and hornblendes show upward iron enrichment. The composition of corona minerals formed by subsolidus reaction between plagioclase and olivine in gabbro, suggests that these coronas formed under pressures of between 6 and 9 kb and at a temperature of about 800°C during a late magmatic or early metamorphic stage. |
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