IRIB IO) QUE “IMIS, IDI DC ANOUK, | IOZr2, 147 
source of Vein Filling 
It might be supposed that because of the proximity of this vein 
to the nearby syenites, gneisses and their pegmatities that the 
source of the main constituent of this vein could be assigned to 
igneous action but in as much as silica-bearing solutions, which 
were in large part responsible for the vein filling as well as for 
the silicification of the gneisses and pegmatites on the hanging 
wall side, seem to be of a later date a different source will neces- 
sarily have to be found. 
The shallow position of the vein in the earth’s crust, the 
nature of the fracture as well as its structural and mineral con- 
tents all bespeak influences at work in the belts of cementation 
and weathering where solutions were in active circulation. 
Under these conditions, a well-known source for silica is the 
decomposition of the silicates of the nearby rocks by carbonic 
acid, where not only quartz but carbonates are produced simul- 
taneously (Van Hise), 9). With such conditions, solution silicifi- 
cation, cementation, replacement, carbonization, oxidation and 
hydration would be effective for producing the essential minerals 
of the vein. 
Age of Vein 
As has been shown in the foregoing paragraphs both the frac- 
ture and its contents are evidently of shallow origin and the age 
of the break is certainly post-Archaeozoic. The most important 
mountain-making disturbances which have in all likelihood 
effected the Adirondack region or province were those which 
occurred at the close of the Paleozoic and the Mesozoic, at least 
these two orogenic periods were of the fault-making types accord- 
ing to Cushing (7) and Miller (2b), but the former known as the 
Appalachian revolution was responsible for the major faulting 
of the region (2b). Ifthe break occurred during the Appalachian 
revolution the once overlying Paleozoic would in all probability 
have been involved, but not so if the post-Cretacic disturbance or 
elevation were responsible for it because by that time all or most 
of the Paleozoic cover would have been eroded. 
Just how soon after the fissuring of this rock the infilling took. 
place we have no definite knowledge. Possibly a clue to the age 
of this infilling might be obtained were we to know when such 
minerals as sphalerite, galena and chalcopyrite were introduced 
in their several deposits as found in the foothills of the Adiron- 
dacks and in the region south of the Mohawk. At Martinsburg, 
