Alavuden ja Kuortaneen kartta-alueiden kalliopera - Geologian ...

3 4map-sheet area (2223), there occurs a massif that is possibly the only notable graniteformation belonging to the younger, or late orogenic, intrusive rocks . In appearance,it is mainly massive, porphyritic or somewhat coarse- and even-grained . Thelast-mentioned includes, as the youngest of all, aplite granites as well . They aremainly composed of massive and fine-grained material (0 = 0 .5-2 mm) . Examplesof the mineral composition of the granites are given in Table 3, Nos . 25-27, and ofthe chemical composition in Table 5, No-38 .In the largest pegmatite occurrences in the western and northwestern parts of thearea of the Kuortane map sheet (2224), there lies a rather fine-grained muscovitegranite, in which the pegmatite material takes the form of knobs or irregular dikelikeparcels . The principal minerals of both the granite and the pegmatite are potashfeldspar, albitic plagioclase, quartz and muscovite . In addition, there are present invarying amounts biotite and chlorite as well as opague and apatite as accessories . Themuscovite occurs frequently as sheaflike or fanshaped accretions together with quartz(Fig . 13) .Smaller, mainly dikelike pegmatites located in the southwestern part of theKuortane map-sheet area (2224) and in the area of the Alavus map sheet (2223) havebeen dealt with in detail in a study made by I . Haapala (1966) . According to thisresearcher, the pegmatites are granite pegmatites, the main minerals of which aremicrocline, plagioclase (from albite to andesine), quartz and micas . Tourmaline also ispresent in many places . Accessories are apatite and garnet . In some places, there occurberyl and columbite, and, further, numerous minerals characteristic of complexpegmatite are to be met with here and there . The pegmatites of the area studied areregarded (Saksela 1935, Haapala 1966) as being connected genetically, at least for themost part, with the local quartz-granodiorite complex .Tectonics and stratigraphyAs regards the course of the waterways and river beds in both map- sheet areas,two directions can be perceived that represent the fault and fracture trends of thelatest block movements . The one is 330' + 15' and the other an average of 40' . Thelineation and fold-axis trends resulting from earlier tectonic activity and representingthe tectonic b-axis run predominantly in both map- sheet areas toward the southeast,the dip being 20-80* . An exception is the part of the Kuortane map-sheet area(2224) located in the north-northwest, which is separated from the rest of the area bythe culmination zone of the fold axes running approximately southwest-northeast ; andthe trends on its northwest side dip toward the west and northwest .The primary structures have generally disappeared from the supracrustal rocks, andno sure observations indicating the direction of stratification have been made .