Diamond Potential in Alberta: Reinterpretation and Distribution of Kimberlite-Indicator Minerals Outside Known Kimberlite Fields

This report accompanies the Alberta Geological Survey’s (AGS) Alberta Kimberlite Indicator Mineral Microprobe Analyses digital file (AER/AGS Digital Data 2020-0009), which is a compilation of microprobe analytical data for kimberlite-indicator-mineral grains from samples collected by government agencies and industry in Alberta and released to the public between 1993 and 2012. This compilation involved a revision and reclassification of the interpreted kimberlite-indicator-mineral mineralogy, and this report describes the methodology used to complete the mineral reclassifications. Additionally, this report presents the results of a preliminary assessment of the data to identify areas of interest for diamond exploration outside of the known kimberlite and ultramafic fields of Mountain Lake, Birch Mountains, and Buffalo Head Hills in northern Alberta, which have already been assessed by industry for their diamond content.
Kimberlite-indicator minerals (KIMs) include garnet, clinopyroxene, ilmenite, chromite, and olivine. The classification schemes that were applied to KIMs in this work allowed for the identification of minerals that may be associated with kimberlite and diamonds, and could potentially lead to identifying an undiscovered diamond-bearing kimberlite.
Seven areas outside of known kimberlite fields have been identified as having higher potential to contain diamond-bearing kimberlite. The assessment was based on the presence of (1) alluvial diamonds, (2) garnet or clinopyroxene grains with chemistry associated with diamonds, (3) a high number of interpreted KIMs with mineral chemistry related to kimberlite, and (4) a high number of species of interpreted KIMs with mineral chemistry related to kimberlite. These areas are
• Buffalo Head Hills north,
• Buffalo Head Hills west,
• Calling Lake,
• Hinton,
• Peace River,
• St. Paul, and
• Utikuma Lake.
Additional areas that contain fewer KIMs with favourable chemistry for the presence of diamonds are classified as having moderate potential. These include the Birch Mountains east, Chain Lakes, Chinchaga, Cold Lake, Hay–Zama lakes, Kakwa River, Lesser Slave Lake, Mary Lake, Peerless Lake, Ram River, Swan Hills, Sweet Grass Hills, West Edmonton, and Whitecourt areas.
Two areas that have KIMs with favourable chemistry for the presence of kimberlite, but without favourable chemistry for diamonds (i.e., an absence of either diamonds or garnet/clinopyroxene grains with chemistry related to diamonds), are considered to have a lower potential. These are the Clear Hills and Pembina areas.
In addition, the study of clinopyroxene geothermobarometry indicated that the lithosphere most favourable for diamonds is in the northeastern portion of the province, north of 54°N latitude and east of 116°W longitude. This quadrant of the province has the coolest geotherm relative to the rest of the province with an associated lithospheric thickness of ~200 km. 
The work described herein preceded the Mineral Grant (provided by the Government of Alberta dated June 22, 2021) and the Mineral Mapping Program (initiated by the Government of Alberta, Alberta Energy Regulator, and Alberta Geological Survey in 2021). This special report does not include any new data collected during the Mineral Mapping Program.