476 REVIEWS 



Finally it may be said that the general scheme and mode of treatment 

 of the book follow the lead of the comprehensive treatise of Chamberlin 

 and Salisbury, and the fundamental views which give distinctive charac- 

 ter to that work find reflection in this. 



R. T. C. 



Geology of the Kiruna District (2). Igneous Rocks and Iron Ore of 

 Kurunavaara Luossovaara and Tualluvaara. Academical Dis- 

 sertation by Per A. Geijer, for the degree of Doctor of 

 Philosophy. By the permission of the philosophical faculty 

 of the University of Upsala. Stockholm, 1910. Pp. 278; 

 2 geologic maps. 

 The district is in northern Lapland. The rocks, which are generally 

 regarded as pre-Cambrian, include greenstones, conglomerates, syenite 

 porphyries, magnetite ores, quartz porphyry, phyllites, sandstones, etc. 

 They are strongly folded and in general stand nearly vertical but other- 

 wise do not show pronounced metamorphism. The textures are well 

 preserved. A typical ore body is the one of Kurunavaara which forms 

 the backbone of a mountain about 748 meters high. This ore body is 

 over 5 kilometers long and some 96 meters wide. Other ore bodies 

 are somewhat smaller. The ore zone is included between quartz por- 

 phyry and syenite porphyry. The minerals of the ore are magnetite, 

 hematite (subordinate), fluor-apatite, augite, amphibole, biotite, titanite, 

 tourmaline, zircon, etc. Generally there is enough apatite to place the 

 ore above the Bessemer limit. 



The ore minerals are intergrown like those of an igneous rock and 

 contacts between ore and country rock are in places gradational. All of 

 the minerals of the ore except tourmaline are primary constituents of 

 igneous rocks near by. Rock textures indicate that the ore mass has 

 crystallized quite in the same way as an igneous rock— these include 

 trachytoidal flow structure, skeleton forms of magnetite, and the ophitic 

 distribution of augite. The ores are believed to be of magmatic origin 

 and the writer is inclined to the view that the associated syenites are 

 effusive in character. He does not agree with De Launey, who held that 

 the ores were deposited at the surface from gases and hot solutions by 

 pneumatolytic-sedimentary processes. The writer does not feel sure 

 as to the nature of the differentiation processes which have resulted in the 

 product, but does believe that such an origin is proven. 



W. H. E. 



