| dc.description.abstract | As part of the greater Slave Province geophysical, surficial materials and permafrost
study, a Northwest Territories Geological Survey (NTGS) led government-academic-industry
research program, this study is intended to identify and interpret indicator mineral glacial
dispersal trains using publicly available mineral chemistry data and discuss the uses of the NTGS
kimberlite indicator mineral chemistry database (KIMC) for diamond exploration in the
southern Slave Province.
In addition to the database, 21 till samples were collected from the southern Slave
Province national topographic system map sheets 075M and 075N during the 2017 field season
(17-DECS sample suite). Kimberlite indicator minerals (KIM) were recovered from the till
samples and selected grains were subsequently analyzed using scanning electron microscopy
and laser ablation techniques to identify mineral chemistry that is representative of KIMS in
surficial sediment samples in the KIMC for the southern Slave. Mineral chemistry data collected
during this study were evaluated and compared to those published in a database of the Slave
Province by the NTGS. The database was created as a collaborative effort between the NTGS
and exploration companies in order to compile an all-encompassing kimberlite indicator
mineral database with raw mineral chemistry data. Mineral chemistry data retrieved from the
NTGS database and from analysis of the 17-DECS sample suite were used to interpret kimberlite
potential of the region. Ilmenite, chromite, Cr-diopside, olivine, and garnet grains in surficial
sediment samples were assessed in terms of their chemistry and areal distribution in the Slave
Province. The raw mineral chemistry data for garnets were classified according to their Gnumbers and chromite, ilmenite, olivine, and Cr-diopside were classified as kimberlitic or nonkimberlitic. Data from indicator minerals in till samples collected during this study were
classified using the same criteria.
Indicator minerals distribution patterns were mapped based on the classification of
individual mineral grains. These maps show disparity in the amount of data contained in the
database and the variation in kimberlite indicator mineral dispersal train direction, length, and
composition between the north and south Slave. Kimberlite indicator mineral dispersal trains in the southern Slave Province are disjointed with highly variable indicator concentrations per
sample location, and trend approximately westward. These trains are near monomineralic,
often exclusively consisting of garnet. Trains in the northern Slave Province are more consistent
in concentration (concentration increases with increasing distance down ice) and trend
northwest and west. These trains have greater variety of kimberlitic mineral species. The
direction, length, and composition of the trains reflects glacial processes (erosion, entrainment,
transportation, deposition), permafrost conditions, and the nature of the source kimberlites. Of
the kimberlite indicator minerals identified, garnet was the most abundant and informative
mineral recovered from surficial sediment samples in the southern Slave Province. Overall,
there was little variation in abundance of garnet G-number classes which could not be
contributed to variations in sample density. However, garnet grains recovered from till samples
in the southern Slave Province have lower sodium concentrations than till samples in the
northern Slave. It has been proposed that the concentration of sodium in certain garnets is
indicative of kimberlite diamond potential. Sodium concentrations of the southern Slave
Province are below the diamond indicator threshold (Na2O>0.07%). Although this may be
indicative of a lower diamond potential, it may also be a result of differing geochemical
compositions of the subcontinental lithospheric mantle. | en_US |
