|Abstract||Till sample surveys were conducted near the headwaters of the Mackenzie River in 2007, 2008, and 2012, as part of the Northwest Territories Geological Survey's Protected Area Strategy surveys. Numerous
sphalerite, galena, chalcopyrite, and arsenopyrite grains were recovered from many of the till samples. No proximal, up-ice mineralized bedrock source for these sulphide grains has been found to date, with the nearest known outcropping bedrock source
of sphalerite and galena being the Qito Pb-Zn showing (~274 km to the northeast) and the Pine Point Mississippi Valley-type (MVT) Pb-Zn deposit (~400 km to the east). The sulphide indicator mineral grains were analysed via electron probe micro
analysis and laser ablation-inductively coupled plasma-mass spectrometry to determine their major, minor and trace elemental composition to elucidate their potential bedrock source and to characterize the potential host mineralization type.
Sphalerite grains are Fe-poor, having up to 5.07 wt% (6.38 mol% FeS) with Cd abundances up to 2.21 wt% (0.97 mol% CdS); they also have variable Cu, Ga, Ge, In, Ag, Sn, As, Te, Sb, and Bi. Most trace elements in galena are below the limit of detection
with the exception of Ag, Cd, In, Sn, Sb, Te, and Bi. Similarly, most trace elements in chalcopyrite are in low abundance, with the exception of Zn, Ge, As, Se, Ag, In, Sn, and Bi. Arsenopyrite grains contain Co, Ni, Cu, Ge, Se, Ag, In, Sb, Te, Au,
and Bi; all other elements analysed are below the detection limit. The trace element compositions of sphalerite and galena are indicative of deposition in a low temperature (and low aS2) environment, such as carbonate-hosted MVT Pb-Zn mineralization.
Chalcopyrite and arsenopyrite mineral chemical data do not provide signatures that are diagnostic of a specific deposit type. |