Annual report . th concession. There is a gradualtransition between the two types, and both facies are in places amygdaloidal, Fig. 29,and contain agglomerate and tuff, showing the volcanic character of the rocks. Theandesite variety, which, at times, contains much hornblende, is a massive, greenish,brown to grey colored rock, fine or medium in grain, and at times strikingly sections show it to be made up of plagioclase, microcline, hornblende, biotite, andquartz. The amygdules, which are filled with calcite or quartz, are not seen in allparts of the mass, but good examples ma
Annual report . th concession. There is a gradualtransition between the two types, and both facies are in places amygdaloidal, Fig. 29,and contain agglomerate and tuff, showing the volcanic character of the rocks. Theandesite variety, which, at times, contains much hornblende, is a massive, greenish,brown to grey colored rock, fine or medium in grain, and at times strikingly sections show it to be made up of plagioclase, microcline, hornblende, biotite, andquartz. The amygdules, which are filled with calcite or quartz, are not seen in allparts of the mass, but good examples may be observed on the north part of lot 5 in the * Vol. 13, part 2, pp. 59 et seq. 64 Bureau of Alines No. 4 fifth concession of Madoc, to the south of the bend in the road,of analyses will show the composition of the andesite facies. The following results (1) SiO, ALO, Fe203 FeO CaO MgO 05 Na,0 K20 H20 C02 (2) Fig. 29. Am> jfdaloidal facies of Madoc andesite. Lot 4. concession 5,iModoc Township, Hastings County. The rhyolitic variety, which is fine in grain, has a peculiar light grey or pinkishcolor, and consists essentially of quartz, feldspar and sericite. Its composition is asfollows: Si02 Al2Os Fe203 FeO CaO MgO 2 54 KX> .................... Loss on ignition 1913 The Pre=Cambrian Geolojjy of Southeastern Ontario 65 It may be noted here that the andesite and rhyolite both show evidence of altera-tion and metamorphism in various parts of their masses. The rhyolite is slightlyschistose at times, and the andesite appears to have in part recrystallized. A good contact of the andesite with the peculiar limestone conglomerate is tobe seen on the northwest part of lot 4 in the fifth concession of Madoc township, nearthe western end of section, A B. At the contact the andesite rises with steep faceagainst the conglomerat
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectminesandmineralresou
