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A new occurrence of musgravite, a rare beryllium oxide, in the Caledonides of North-East Greenland

Published online by Cambridge University Press:  05 July 2018

B. Chadwick
Affiliation:
Earth Resources Centre, University, Exeter EX4 4QE
C. R. L. Friend
Affiliation:
Department of Geology, Oxford Polytechnic, Oxford OX3 0BP
M. C. George
Affiliation:
Department of Physics, University, Exeter EX4 4QL
W. T. Perkins
Affiliation:
Institute of Earth Studies, University of Wales, Aberystwyth SY23 3DB

Abstract

Musgravite, Be(MgFeZn)2Al6O12, is associated with norbergite and minor chlorite in a Precambrian calcite marble within the gneissic basement in an internal part of the Caledonian mobile belt in Dove Bugt, North-East Greenland. It commonly occurs as vitreous black, idioblastic crystals (<7 mm in size) with combined rhombohedral and basal pinacoid forms. XRD data show that its space group is R3m and its unit cell dimensions are a 5.687 ± 0.002 Å and c 41.16 ± 0.02 Å. Electron microprobe and ICP-MS analyses have yielded BeO 5.51 wt.% and ranges in abundance (wt.%): Al2O3 68.74-70.63; Tot, Fe as FeO 6.76-7.89; MgO 12.17-13.98; and ZnO 3.22-4.47. ICP-MS analysis also revealed significant trace amounts of V 249 ppm, Cr 740 ppm and Ga 178 ppm. The crystallographic parameters and composition are broadly in accord with those of musgravite from the two other recorded occurrences, in Precambrian high-grade terrains in Australia and Antarctica, although mineral and rock associations in these localities differ from those in Dove Bugt. The source of beryllium in each of the musgravite occurrences is uncertain, although a metasomatic source related to granite emplacement is favoured for the occurrence in North-East Greenland.

Type
Mineralogy
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

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