ORES OF IRON 143 
dyke. According to Per Geijer (Geol. Kiruna, 1910, p. 269; 
he later adopted the dyke theory), the ore was discharged as 
a lava flow of magnetite. 
One essential fact is the occurrence along the base of the 
quartz-porphyry of fragments of all the varieties of the under- 
lying ore. The ore was therefore in existence before the first 
quartz-porphyry lava flow. Prof. Daly’s theory is attended 
by the difficulty that the quartz-porphyry contains only 
from 2-9 to 8 per cent. of iron oxide, and the lowest flow, 
which could alone have supplied the ore, could not have 
provided the quantity in the lode; and that porphyry still 
contains a normal amount of iron. 
SY. - 
QP CST Gi’ ow. ws’ 
Fie, 46.-—TuE ORE-SHEET OF KIRUNAVAARA, SWEDISH LAPLAND. 
Sy.P., syenite-porphyry; solid black, the ore, sharply bounded above, 
with occasional secondary spurs passing upward,” Q.P., the quartz- 
porphyry, of which the lower flow contains at the base angular 
fragments of the ore; C.S.T., conglomerate, sandstone, and tuff; S., 
quartzite. 
The iron ore pebbles in the quartz-porphyry favour the 
formation of the ore by some aqueous agency. The sheet 
of ore (Fig. 46), though sharply separated from the quartz- 
porphyry, passes down gradually into the underlying syenite- 
porphyry; the iron appears to have been dissolved from the 
underlying syenite and deposited on its surface as a sheet 
of phosphatic bog iron in a swamp, as suggested by W. H. 
Herdsman (Journ. Ir. and St. Inst., Ixxxiii, 1911, p. 480), 
Or as a deposit from hot rising water, as suggested by Bick- 
Strém (Geol. Fir. Stockholm Fork., xxvi, 1904, pp. 180-5), 
OF as a sheet of surface ironstone formed by evaporating 
water.l Backstrom described the process as pneumatolvtic 
as 
‘ De Launay, dun. Mines (10), IV, 1903, Pp. pad = 
sedimentary, A new paper by Vogt (6G. For. Bork I92 fib 153 5) 
Arges the intrusive nature of the ore, regarding the 
Segregations,