GEOLOGY OF THE INNER EARTH—GREGORY. 325 
The ore body at Kiruna outcrops along the crest of a ridge 2 miles 
long, and it is continued beneath Lake Luossajarvi to the smaller but 
still immense ore body of Luossavaara. At Kiruna the ore rises to 
the height of 816 feet above the surface of the lake, and it varies in 
thickness from 30 to 500 feet, with an average thickness of about 
230 feet. According to the report by Prof. Walfrid Petersson,* 
submitted this year to the Swedish Parliament, Kirunavaara contains 
200 million tons of ore above lake level, and Luossavaara another 
224 million tons. The ore is high grade. According to Lundbohm 
60 per cent of the trial pits showed a yield varying from 67 to 71 per 
cent of iron, and 21 per cent of them showed a yield of from 60 to 67 
per cent of iron. The average of nineteen analyses published in 
Professor Petersson’s recent report gives the contents of iron as 64.15 
per cent. Unlike the Taberg and Routivaara ores, the percentage 
of titanium is very low; thus in nineteen analyses given by Petersson 
the average of titanic acid is only 0.23 per cent, and it varies in the 
specimens from 0.04 to 0.8 per cent. 
The ore les between two series of acid rocks, which have been very 
differently interpreted, but will no doubt be fully explained by the 
‘researches now in progress under the direction of Mr. Lundbohm. 
The rocks were first called halleflinta, as by Fredholm, and regarded 
as of sedimentary origin. They are now accepted as an igneous series, 
associated with some conglomerates, slates, and quartzites. ‘The ore 
body itself is bounded on both sides by porphyrites, of which that on 
the lower or western side is more basic than that overlying the ore to 
the east. The basic western porphyrite is in contact with a soda- 
wugite syenite of which the relations are still uncertain. Interbedded 
with the overlying eastern porphyrite are rocks that appear to be 
volcanic tuffs, and both in the tuffs and in the upper porphyrite are 
fragments of the Kiruna ore. 
Three main theories of the genesis of the Kiruna ores have been 
proposed., Their sedimentary origin was urged on the ground that 
they occur regularly interstratified in a series of altered sediments, 
and that the ores, therefore, are also sedimentary. This view may be 
promptly dismissed, since the adjacent rocks are igneous. 
The second theory has been advanced independently by Professor De 
Launay and Dr. Helge Bickstrém. According to them the porphy- 
rites above and below the iron ores are lava flows, and the ore was 
2 superficial formation deposited in an interval between the volcanic 
eruptions. According to De Launay the iron was raised to the surface 
as emanations of iron chloride and iron sulphide; the iron was depos- 
ited as oxide, and most of it subsequently reduced to magnetite during 
the metamorphism of the district. 
4 Bihang till Rikd. Prot., 1907, 1 Saml., 1 Afd., 84 Hift, No. 107, pp. 218, 217. 
