Title
Mangerite-charnockite
Identifier
AD-20
Description
This specimen is typical of the metaigneous charnockitic rocks associated with the massif anorthosites in the Adirondacks. With variation in the quantity of modal quartz, the rock qualifies as either a charnockite or a mangerite. Quartz content is sufficiently variable to result in both rock types in a single outcrop. These rocks are part of the Mt. Arab complex (earlier referred to as the Tupper Lake Complex (Buddington 1939 p. 116)). The average modes of the mangerite (pyroxene syenite gneiss) and the associated charnockites are:
Thin section shows K-feldspar, plagioclase and hypersthene.
|
 |
Pyroxene syenite gneiss (1) |
Charnockite (2) |
|
Microperthite |
46 |
46 |
|
Oligoclase |
42 |
24 |
|
Quartz |
3.3 |
16 |
|
Ferrohypersthene |
2.0 |
6 |
|
Ferroaugite |
3.6 |
1.4 |
|
Hornblende |
1.8 |
2.8 |
|
Garnet |
- |
0.5 |
|
 |
 |
 |
|
(1)Â Â Â McLelland average of 5 (2)Â Â Â Analysis 112, Table 32, Buddington, 1939 |
Date
1980
Contributor
Western Minerals Inc.
Spatial Coverage
Adirondack Highlands-collected from a road cut on NY Route 30 approximately 3 miles southwest of Tupper Lake.
Temporal Coverage
Precambrian
Accrual Method
Purchased from Western Minerals Inc.
Number of Thin Sections
1