Open AccessMargarite pseudomorphs after corundum, Qôrqut area, Godthåbsfjord, West Greenland
Author(s) -
R. F. Dymek
Publication year - 1983
Publication title -
rapport
Language(s) - English
Resource type - Journals
eISSN - 2597-2944
pISSN - 0418-6559
DOI - 10.34194/rapggu.v112.7816
Subject(s) - muscovite , plagioclase , gneiss , biotite , epidote , geochemistry , geology , corundum , mineral , mineralogy , pseudomorph , metamorphic rock , chemistry , quartz , chlorite , paleontology , organic chemistry
Margarite (end member CaAI2Si2AI2O1O) is reported as nodular aggregates of fine-grained material partly replacing corundum and as fine dispersed material replacing biotite in an inclusion of migmatitic plagioclase-rich gneiss within the Qôrqut granite. Muscovite replaces biotite in the same sample. A retrograde reaction in the presence of volatiles is suggested in which biotite + plagioclase + corundum go to an assemblage containing margarite + muscovite + epidote. Cell parameters and chemical data are presented. A maximum temperature for the reaction of - 5800 at 5 Kb is suggested.