Cross Lake Project (1983-86)


Geologist    P.G. Lenton     Year    83     STATION    5041
EASTING   570986     NORTHING   6041657     ZONE   14     DATUM   NAD83
Date of mapping    06/23/1983

STRUCTURAL DATA

Planar Structures:
Structure type Strike Dip Separation
schistosity 220 0

Dikes and Sills:
Rock Number Type Width (m) Strike Dip
3 diabase 1.55 142 80

Linear Structures
Type Plunge Azimuth
rodding 60 115

PETROLOGIC DATA

Rock Number: 1

Rock Type: tonalite
Descriptors:
schlieric or schlieren present
leucocratic
biotite lenses
weakly megacrystic
light grey
weakly deformed

Field Description:

-grey tonalite/granodiorite
- appears to be the older unit but not as severly deformed or sheared as at other locals. Weathers pale greyish-white with a well defined lensoid BO segregation visible on fresh surface.
-weakly megacrystic-felspars 2 to 3 mm in an average 1 to 1.5 mm grain size

Textural Features
Type Mineral Min. Size Max. Size Abundance (%) Unit
phenocryst plagioclase 2.0 3.0 mm
mafic mineral biotite 0.0 0.0
groundmass grainsize 0.0 1.5 mm

Rock Number: 2

Rock Type: basalt
Descriptors:
pillowed
selvages present on pillows
occurs as a raft
epidote veins

Field Description:

-first convincing pillowed volcanic seen in Clearwater Bay.
-black weathering massive amphibolite with anastomosing veinlets of hornblende + plagioclase +/- epidote that look like selvages

Minerals of Note
Mineral Abundance (%)
hornblende
plagioclase
epidote

Rock Number: 3

Rock Type: diabase
Descriptors:
massive
Molson dike
155 cm wide
diabasic
dark green

Field Description:

-155 cm maximum width with 10 cm chill margin
-sample A 40 cm into dike
-sample B lower contact chill margin
-weathers dark green with some remnant plagioclase lathesd; diabasic texture

PHOTOS


Fine grained greenish black diabase dike. The unfoliated nature, clean sharp contacts and strike of 142° suggests this may be a Mackenzie dike rather than an offshoot of the Molson dikes.


Flattened and stretched amphibolite raft that still has convincing characteristics of pillowed basalt.


Manitoba Geological Survey, 2017