Sample Description

Sample Location
All seven samples (collected by S. Moorbath) are from well-localised garnet-mica schist
horizons in the eastern sector of the Isua greenstone belt, close to various expedition base
camps of 1978, 1993 and 1997. No GPS coordinates are available, but the sample sites are
easily located on aerial photographs, and on the geological map of the Isua region published
by the Geological Survey of Greenland in 1986 (Bull. Gronlands geol. Unders. No.154).
Further details of sample localities can be obtained from S. Moorbath (Oxford).
Note that sample SM/GR/97/22 was collected from the same (complex) outcrop as sample IE
715 28 (collected by R.F.Dymek), which was used by Jacobsen and Dymek (J. Geophys. Res.
93, 1988, 338-354) for
728-732) for
Sm-143Nd studies, and by Harper and Jacobsen (Nature 360, 1992,
Sm-142Nd studies, from which the latter authors claim to have discovered the
presence of excess 142Nd.
Sample description
SM/GR/93/13 Porphyritic garnet set in equigranular groundmass of plagioclase, biotite,
quartz, muscovite, epidote, zoisite, tourmaline.
Banded, granular, intergrown aggregate of garnet, plagioclase, quartz,
hornblende, biotite, with minor ore and calcite.
SM/GR/93/57 Foliated schist with porphyritic garnet, quartz, plagioclase, biotite, muscovite,
epidote, tourmaline.
SM/GR/93/76 Porphyritic garnet, large staurolite grains, with strongly foliated groundmass
of quartz, muscovite, plagioclase.
SM/GR/97/22 Equigranular, slightly foliated schist, with quartz, plagioclase, biotite, calcite,
tourmaline, apatite.
248484 Porphyritic garnet (not abundant) set in foliated, folded groundmass of quartz,
plagioclase, biotite, muscovite.
248443 Identified in the field as garnet-hornblende-mica-feldspar schist, but thin section
currently unavailable.