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:

 

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)    McLelland average of 5

(2)    Analysis 112, Table 32, Buddington, 1939

Thin section shows K-feldspar, plagioclase and hypersthene.

Date

1980

Contributor

Temporal Coverage

Accrual Method

Purchased from Western Minerals Inc.

Number of Thin Sections

1

Geolocation