Iron Ores The iron deposits are intimately connected with the anorthosite and gabbro, and are located not far from the granite area which parallels the northwest shore of Bad Vermilion lake and Seine bay of Rainy lake. Near Bad Vermilion lake two workable bodies of ore are present, and occasionally a smaller third one is found; but in the covered region near Seine bay it has not been definitely shown that there is more than one. The ore appeared to be magnetite, though a portion of it was stated by Dr. Goodwin, who was developing the properties, to contain a considerable percentage of titanium and some vanadium. Through Dr. Goodwin's courtesy the writer was enabled to make a microscopic examination of one of the drill cores with a view to determining the relations existing between the ore and the adjoining rock. Several schistose bands were cut by the drill, and it was thought desirable to ascertain whether these represented different types of original rock, or were merely shear zones in the anorthosite-gabbro. Unfortunately, none of the drill holes started in the pure anorthosite, but the relationships are such that there is little doubt that the gabbro is merely a more basic marginal phase of this rock. With the exception of two slides in which the minerals could not be definitely identified by the microscope, the core appears to be divided mineralogically into three distinct portions which are still genetically related, and with the exception of the richer ores all the rock showed plagioclase feldspar or some of its alteration products. A further exception is made of the afore-mentioned two samples where the minerals could not be identified. The first 67 feet appears to be normal gabbro, and schist derived from gabbro, and is characterized by the presence of plagioclase, calcite and hornblende or biotite, with minor quantities of pyrite and magnetite. In the next 173 feet the character of the rock differed in two respects: augite was the predominant dark mineral, and ilmenite with its decomposition product leucoxene was present as a rock-forming mineral. Pyrite and biotite were present rather uniformly. From this point to the bottom of the hole at 384 feet, augite was lacking, though biotite or chlorite was present in nearly every section. Magnetite1 was present in every section but one, and ilmenite and leucoxene were not found. A mineral which came as a surprise in connection with the ore bodies was apatite, which was in well formed crystals surrounded by magnetite. The microscopic examination would tend to the supposition that the ore would be rather high in phosphorus. It is also possible that when more material for examination can be secured, the apatite may prove to be the source of the vanadium that has been reported from these ores. This seems probable, as there is no other source indicated by the minerals present in the sections, and vanadium and phosphorus have similar chemical relations. "The analyses made later and given in the text indicate that the mineral recognized as magnetite is in nearly every case ilmenite. In the ore body leucoxene was absent, so that it was not possible to make a distinction between the two minerals, magnetite and ilmenite. The analyses strengthen the supposition that the ore is due to magmatic segregation. On account of the lack of definite chemical formulae for the minerals hornblende, augite, biotite, and chlorite. it has been impossible to make a calculation showing the percentages of these minerals in the rocks. The ore is in many respects similar to the celebrated Kiruna ores in Sweden, but the associated rocks are very different; the Kiruna ores being immediately associated with syenite porphyry and quartz porphyry. Another more nearly related series is found in Nelson county, Virginia, where ilmenite and apatite form a rock or ore mass which appears much the same in hand specimens as the Kiruna ores. Origin of Iron Ores The iron ores of this range have a peculiar interest among Canadian ores, as they furnish a type of deposit which is important in other regions but has not been noted before in Canada. Being associated with great masses of anorthosite, and containing neither siderite, hematite nor limonite, it appears to owe its origin to igneous causes. The one feature favouring a sedimentary origin is the great length of a comparatively narrow band of iron ore. So far as microscopic examination has shown, there is no accompanying rock to which a sedimentary origin could reasonably be assigned. When other similar deposits are recalledmagnetite and titaniferous magnetite containing more or less apatite associated with anorthosite-it seems reasonable to look upon the ore as a magmatic segregation. Representative samples were taken from the drill core for analysis to show not only the quality of the ores, but to get further light on the genesis of the rocks and ores. The analyses have been made by W. K. McNeill, Provincial Assayer with the following results. Pyrite Deposits at Mokomon About a mile from Mokomon station on the Canadian Northern railway extensive development work was in progress during the past season in proving the extent of some pyrite deposits on lot B, concession V, Conmee township. The work consisted principally of trenching and diamond drilling. Over a large portion of the property there is a very deep overburden, so that geological boundaries could not be readily seen, and the writer was informed by the former owner of the property that he traced these deposits by means of a dip needle where they were not in evidence on the surface. This use of the dip needle at first seems surprising, as pyrite is one of the minerals which does not affect the dip needle to any extent. It is, however, worthy of note that in most places where pyrite is present there is also some pyrrhotite and possibly magnetite, both of which are magnetic, so that it may be desirable to give more attention to dip needle reading in prospecting even for sulphide ores. In trenching it was found necessary in many places to sink to a depth of forty feet through a hard boulder clay which required very little timbering. By means of the trenches and the diamond drilling five deposits were proven, and as a result the property was taken over by the Nichols Chemical Company during the winter. The rocks on the property appear to be principally Keewatin greenstones with some rhyolitic portions, and in a few places a conglomerate was uncovered which is probably to be correlated with the Seine conglomerate. These rocks containing the pyrite deposits rise quite abruptly from the Kaministiquia valley, along which may be seen a comparatively level terrace which appears in part to be connected with the flat-lying Animikie deposits that are better exposed a few miles nearer Port Arthur. Details of the extent of the deposits could not be given at the time of the writer's visit, but the accompanying photograph (fig. 16) of a quarry face on one of the deposits will give some idea of size. Lake of the Woods In view of the scarcity of platinum and the consequent extremely high price of this metal, the writer was instructed by the Provincial Geologist to examine any known serpentine deposits in the western part of the Province to ascertain whether there might be a source of platinum in this region. Two deposits of serpentinous rock had been observed by the writer in his earlier work on Lake of the Woods, both of which are easily accessible, one being a copper-bearing rock on Allie island, and the other a serpentinized dike in the Welcome channel. These were both visited the latter part of August and samples of about 100 pounds were taken from each place. The samples were sent to W. K. McNeill, Provincial Assayer, but both yielded negative results. |