Open AccessA new type of interpenetration twin of labradorite from East Greenland
Author(s) -
E. Wenk,
A. Glauser,
E. Wenk,
A. Glauser
Publication year - 1986
Publication title -
bulletin of the geological society of denmark
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.674
H-Index - 28
eISSN - 2245-7070
pISSN - 0011-6297
DOI - 10.37570/bgsd-1986-35-04
Subject(s) - geology , basalt , albite , echelon formation , geochemistry , quartz , paleontology , fault (geology)
Labradorite phenocrysts of basaltic rocks collected from the moraine of Daugaard-Jensen Gletscher in Scoresby Sund, East Greenland, have been studied by U-stage methods. lnterpenetrating fourlings after (010) have the axis [001) in common. The (010) planes of the two fourlings form an angle of 38° ± 1° in the example illustrated. Two rectangular planes of symmetry between the two systems intersect in [0(ll], but are not developed as morphological boundary planes. These symmetry planes bring the twin axes of the Albite, Carlsbad and Albite-Carlsbad laws of one fourling into the position of those of the second fourIing. The same mirror reflection brings the vibration directions na, nf3, ny of each individual of the first fourling into the position of corresponding indicatrix axes of an individual of the second fourling. As a second interpenetration with common [001) but with an angle of 52° between the planes (010) has been found, we conclude that the coinciding axis [001) is the characteristic feature of this new type of intergrowth. A geological implication from this study is the proof for the occurrence of basalt in the bed-rock below the ice cap west of Daugaard-Jensen Gletscher, 150 km north of the northernmost extension of the thick pile of plateau basalts of the Brito-Arctic province along the East Coast of Greenland.