170 THE ROYAL SOCIETY OF CANADA 



either in intimate mixture, with a relatively small amount of country 

 rock in evidence (the "solid" sulphides of the Mandy and Flin-Flon 

 orebodies), or somewhat coarsely crystallized in the greenstone schist 

 and not closely intergrown (the "disseminated" sulphides near the 

 wall rock in the orebodies, and in the sulphide occurrences through- 

 out the district). In general, the exposures are found in the valleys 

 which represent lines of shearing or faulting. An unmineralized 

 "horse" in the orebodies, or a lens of rich chalcopyrite, stands out 

 prominently in sulphide bodies which are otherwise much below the 

 average level of the Pre-Cambrian surface in that area. In this 

 respect the sulphide mineralization in greenstone may be contrasted 

 with gold mineralization in quartz veins in the same mineral area where 

 the veins not infrequently occupy positions of marked relief. Only 

 in one type of sulphide mineralization are the exposures found normally 

 on the higher rock ridges, and with this type of deposit we are not 

 concerned in this study. On the northeast arm of Lake Athapapus- 

 kow, veinlets of bornite and chalcopyrite traverse a greenstone which 

 has been to such a degree hardened by epidotization during the process 

 of mineralization that it has proved more resistant than the un- 

 mineralized greenstone. 



Oxidation and Reduction Processes 



Except where they occur in the epidotized basalt, the sulphides of 

 iron and copper have suffered very considerable oxidation and subse- 

 quent reduction. The changes are most pronounced in the dissemin- 

 ated ore, and of less importance in the massive ore, particularly when 

 rich in copper. In the pools which rest on the low hollows in the 

 mineralized areas, ochres are precipitated, and a capping of limonite 

 or haematite forms a red gossan on the sulphide bodies, visible from 

 considerable distance. Trenches dug in the valleys underlain by 

 disseminated sulphides pass through (1) limonite, (2) haematite, 

 (3) loose unoxidized sulphide, before reaching solid rock- No samp- 

 ling is possible unless at the bottom of trenches at least 15 feet deep. 

 With "solid" sulphide ore, oxidation is unimportant. In the case 

 of the lens of rich chalcopyrite ore in the Mandy orebody (20% Cu), 

 the ore was discovered underneath the moss, practically unaltered, 

 forming part of the highest ridge on the property. 



Taking the sulphide bodies as a whole, the primary mineralization 

 consists of pyrrhotite, pyrite, chalcopyrite, sphalerite, galena, bornite, 

 and probably chalcocite. Oxidation products are limonite, haematite, 

 melanterite, chalcanthite, azurite, and malachite. Reduction min- 



