OKIGIN OF THE IRON ORES. 
85 
Mineral associations of ores. 
1. 
2. 
3. 
4. 
5. 
6. 
7. 
Minerals de- 
Minerals of 
Minerals in 
Minerals of 
Minerals of 
Minerals in 
Weathering 
veloped in 
first ore 
veins in 
late ore 
same age 
veins and 
minerals. 
limestone 
concentra- 
contact 
concentra- 
and origin 
amygdules 
at contact 
tion under 
limestone 
tion under 
as 4 but 
in lavas. 
of andesite 
influence of 
and ande- 
influence of 
occurring 
intrusive. 
andesite 
intrusive. 
site. a 
effusives. 
in late 
veins in 
limestones. 
Quartz 
Quartz 
Quartz 
Quartz, chal- 
cedony, etc. 
Quartz, chal- 
cedony, etc. 
Quartz, chal- 
c e d o n y, 
opal, etc. 
Calcite 
Calcite 
Calcite 
Calcite 
Calcite 
Calcite 
Diopside 
Diopside 
Diopside. 
Andradite. 
A n d r a - 
Andradite. . . 
dite(?). 
Apatite (?).. 
Actinolite 
Apatite 
Apatite 
Actinolite 
Actinolite. 
Magnetite . . . 
Magnetite . . . 
Magnetite . . . 
Magnetite . . . 
Magnetite. 
Hematite 
Hematite 
Hematite 
Hematite 
Hematite. 
Limonite 
Albite. 
Orthoclase. 
W o 1 laston- 
ite (?). 
Phlogopite... 
Biotite 
Phlogopite. 
Serpentine. 
Kaolin 
Kaolin. 
Kaolin. 
Andalusite. 
Epidote. 
Pyrite. 
Titanite. 
Chlorite, b 
Copper car- 
Copper car- 
bonates. 
bonates. 
Siderite. 
Siderite. 
Barite. 
Galena. 
Chalcopyrite. 
a Slightly later than those of column 1 and of about the same age as ores, but containing no ore. 
b Found in one locality to depth of 80 feet in porous ore, but probably still due to action of effusives. 
CONCLUSIONS AS TO THE ORIGIN OF THE ORES. 
If the foregoing reasoning is correct, the events leading up to the 
completion of the ore deposits in their present form are in outline as 
follows: 
(1) Intrusion of andesite laccoliths in Paleozoic and Mesozoic 
sediments, with consequent tilting of the strata in quaquaversal 
manner about the laccolith and contact metamorphism of the zone 
adjacent to it, accompanied and followed by fissuring, jointing, and 
faulting. 
(2) Entrance of hot ore-bearing solutions through fissures in the 
andesite into the adjacent sediments, depositing ore as dikelike 
masses in fissures in the andesite, as fissure fillings and replacements 
in the limestone, and as cements in breccias of andesite, limestone, 
and quartzite. The solutions introduced also garnet, diopside, am- 
phibole, phlogopite, apatite, calcite, quartz, and pyrite. Most of 
these minerals had also been developed in the. limestone by the pre- 
ceding contact metamorphism. Soda was conspicuously increased 
in the wall rocks. It is thought that the solutions were pneuma- 
tolytic after-effects of the andesite intrusion. 
