78 IRON ORES OF IRON SPRINGS DISTRICT, UTAH. 
solution above hypothesized for the carrying of the iron. Lindgren 
finds salt in inclusions in vein quartz with a probable igneous origin. 
This most volatile of all the common mineral compounds is an 
abundant emanation product of volcanoes. It may be noted that 
sodium chloride would be decomposed by reaction with silicic acid 
undoubtedly met in the limestone contact, precipitating the sodium 
in its present silicate combination. 
The introduction of apatite, garnet, amphibole, and pyroxene, all 
of them containing lime, and the greater abundance of these minerals 
nearer the limestone than elsewhere, suggests reaction between the 
hot solution and the limestone. It is not certain, however, that 
the limestone was necessary as a precipitating agent for the reason 
that these minerals are also found in fissures in the andesite entirely 
awa} T from the limestone. The deposition of silicates may equally 
well have been a function of the change of temperature of the solu- 
tions. The order of deposition of the principal minerals of this first 
concentration seems to have been: (1) Magnetite (and other oxides), 
pyrites, and amphibole, apatite, and garnet; (2) diopside. 
Interlay ered with the magnetite and closely associated with glass 
is amorphous iron carbonate, the genetic relations of which to the 
other minerals are not known. 
SOURCE AND CONDITIONS OF THE ORE-BEARING SOLUTIONS. 
Judging from records available elsewhere as to flow of meteoric 
waters with depth, the 4,000 feet of rock covering the laccolith 
probably prevented ready access of abundant meteoric waters. Such 
as were present in the rocks may have reached high temperatures 
adjacent to the laccolith, and may have aided in the ore-depositing 
processes. But that the principal source of the solutions was the hot 
andesite magma seems to be implied by the nature of the minerals 
deposited and their association, and manner of association, with the 
laccolith. These solutions were ejected after at least the outer parts 
of the laccolith had crystallized. 
That the temperature of the solutions was high is clearly shown by 
the nature of the materials deposited. The temperature was above 
the critical temperature of water — 365° — judging from experi- 
mentally determined temperatures necessary for the crystallization of 
certain silicates similar to those here found. A temperature higher 
than the critical temperature is further indicated b} r the presence of 
glass in the ores locally. From the fact that the fusion of the contact 
phase of limestone probably took place at temperatures 'ranging 
upward from 1,000° (see p. 36) and that the ore is in veins in this 
a Allen, E. T.. Wright, F. E., and Clement, J. K., Minerals of the composition MgSiOs; a case of 
tetramorphism: Am. Jour. Sci., 4th ser., vol. 22, 1906, p. 399. 
