Abstract

In the Little Long Lac Area gold occurs in two main types of orebodies. The first, exemplified by the Number 2 and Number 30 vein systems at Hard Rock, and the North and West ore zones at MacLeod-Cockshutt, consists of massive sulphide replacement bodies in iron formation. The second consists of silicified zones associated with intrusive acid porphyries, found in the South ore zone at MacLeod-Cockshutt, and in the orebodies at Magnet Consolidated, Bankfield, Tombill, and Jellicoe. Gold-quartz veins associated with acid porphyries, a variety of the second type, are found in the Number 1 vein system at Hard Rock, and the 210 quartz vein at MacLeod-Cockshutt. The orebodies at the Little Long Lac mine are confined to shear zones in arkose, and do not conform to the above general classification.Hand specimens and polished sections typical of these orebodies have been studied. Composite diagrams representing the mineral paragenesis in each orebody or mine have been drawn up and are discussed in this paper. These eleven diagrams are combined in a table representing a generalization of the mineral relations over the entire area. In addition, the sequence of mineralization is presented in terms of radicles.From the evidence of mineral sequences, and certain other investigations, it is apparent that the ore deposits of the Little Long Lac area may be correctly placed in Lindgren's upper hypothermal, or lower mesothermal, zone. Possible sources of the ore-depositing solutions are discussed, but no final statement made.

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