Title
Tennantville gabbroic anorthosite
Identifier
AD-14
Description
This medium grained facies is one of a number of anorthositic sheets that intrude throughout the stratigraphic section of the southern Adirondacks. A chemical analyses of specimens from this outcrop yield results that are almost identical with Buddington's (1939) average gabbroic anorthosite.
The existence of these instrusive sheets of gabbroic anorthosite argues strongly against the proposition that the anorthositic rocks constitute part of an older, pre-Grenvillian basement complex. Rocks similar to the Tennantville gabbroic anorthosite commonly occur as border facies surrounding larger, coarser bodies of anorthosite. Spongy, brick-red garnets are common in these rocks.
Thin section shows plagioclase and clinopyroxene.
|
 |
|
Average Gabbroic |
|
SiOâ‚‚ |
52.36 |
52.37 |
|
TiOâ‚‚ |
1.14 |
- |
|
Al₂O₃ |
23.75 |
24.68 |
|
Fe₂O₃ |
1.11 |
1.24 |
|
FeO |
3.96 |
3.49 |
|
MnO |
.07 |
- |
|
MgO |
1.53 |
2.0 |
|
CaO |
10.63 |
10.57 |
|
Naâ‚‚O |
3.69 |
4.02 |
|
Kâ‚‚O |
.90 |
.86 |
|
Pâ‚‚Oâ‚… |
.16 |
- |
|
Hâ‚‚O+ |
.69 |
.90 |
|
Total |
99.99% |
100.13% |
Thin section shows plagioclase and clinopyroxene.
Date
1980
Contributor
Western Minerals Inc.
Spatial Coverage
Adirondack Highlands-collected from a low road cut on Military Road at the north edge of the Edinburg Quadrant.
Temporal Coverage
Precambrian
Accrual Method
Purchased from Western Minerals Inc.
Number of Thin Sections
1