The Pre-Cambrian Structure of Missouri 125 
mineralization to be quite late but still pre-Cambrian inasmuch 
as it must have occurred at considerable depths and therefore 
have taken place before the erosion at the end of the pre-Cam- 
brian and beginning of the Cambrian. Mineralization in the 
granite southwest of Coldwater is of a lower temperature type 
but may belong to the same period as that at Silver Mine. If 
it does, the mineralization may have been later than any of 
the granitic intrusions so far recognized, If the Silver Mine 
mineralization is of older age than that near Coldwater, it may 
be related to the Graniteville granite as it is younger than the 
granite at Silver Mine. 
Description of Structures 
Pre-Cambrian 
Primary structures. Haworth believed that the granite was 
only a deeper phase of the felsite and it followed that the gran- 
ite was continuous under the felsite throughout the whole region. 
While the intrusive nature of the granite is now generally recog- 
nized, it is still thought by some to be continuous beneath the 
felsite with the exposures merely cupolas on the top of a batho- 
lith. Relations to structure, however, indicate that generally each 
area must be considered as a separate instrusion. 
The large igneous mass of the Central Granite area is ap- 
Parently a stock. While the granite within the area varies con- 
siderably, it may all be part of the same intrusion and probably 
is of the same age as the Graniteville granite. The Silver Mine 
§ranite, which is older than the Graniteville, outcrops only along 
the southern boundary of the main granite area and probably is 
part of the country rock into which the younger granite was 
intruded, 
The contact of the granite of the Central area with the 
felsite in the Iron Mountain quadrangle is relatively straight and 
independent of countour lines, indicating it is nearly vertical. 
€ mass seems to be elongated in a northeast-southwest direc- 
tion with its northeast and southwest sides parallel to the prin- 
cipal Structural trends of the region. The northeast end of the 
§tanite body is buried under sedimentary rocks, but the granite 
