500 PETROLOGICAL ABSTRACTS AND REVIEWS 



gneiss, mica-schist, conglomerate-gneiss, quartzite, and limestone, with some 

 leptites. All but the latter are of sedimentary origin. Even the plagioclase- 

 gneiss, which in chemical composition approaches certain igneous rocks, is 

 sedimentary. The rocks have been formed, to a considerable extent, of 

 unweathered volcanic material (volcanic ashes, as well as mechanically dis- 

 integrated materials from tuffs and lava beds) partly assorted and deposited in 

 water. Associated with these rocks are certain intrusives and extrusives, 

 mainly plagioclase-porphyrites, uralite-porphyrites, and amphibolites. The 

 post-Bothnian rocks form a comagmatic series, chiefly abyssal but in part 

 hypabyssal in character. The rocks are granite, syenite, granodiorite, quartz- 

 diorite, diorite, gabbro, diabase, hornblendite, and peridotite. In the south- 

 western part of the area there were apparently two periods of intrusion from a 

 magma differentiated in situ. In the parish of Haapavesi to Kivijarvi, there 

 is no evidence of two periods of intrusion but the rocks, from granite to grano- 

 diorite and gabbro, grade into each other. The northern and eastern part of 

 the area is an area of migmatites. Here the magma has been differentiated to 

 a certain extent, but the different rocks have not been separated to form large 

 homogeneous masses. The older rocks have undergone fairly complete assimi- 

 lation by the magma. In the reviewer 's modified classification the ortho-gneiss 

 is 227' (a granodiorite-gneiss), the plagioclase-porphyrite is 228 (quartz-diorite 

 porphyry or tonalite-porphyry), four granodiorites are all 227' (granodiorites 

 in the broad sense, but quartz-monzonites if this group is included in the 

 classification), twelve microcline-quartz-diorites are 227' (monzotonalites nar- 

 row, or granodiorites in the broad sense), three tonalites are 228 (tonalite), a 

 tonalite-gneiss is 227' (monzotonalite-gneiss), three quartz-diorites are 228 

 (tonaUte), a quartz-diorite is 328 (mela-tonalite), a diorite is 227' (monzo- 

 tonalite), two biotite-granites are 227" (adamellites in the narrow, or grano- 

 diorites in the broad sense), an olivine-gabbro is 2312, and two soda-syenites are 

 21 11' (an albite-monzodiorite in the narrow, or albite-syenodiorite in the broad 

 sense. The latter is the rock to which Laitakari compares his albite-epidote 

 rock which he calls helsinkite. Laitakari 's rock is given above in the reviews 

 as 21 1 2, from definition, but he says it may in some cases have a little micro- 

 dine. The present rocks contain enough microcline,one 11 and one 7 per cent, 

 to throw them into the next family.) 



