Cross Lake Project (1983-86)

Geologist P.G. Lenton Year 83 STATION 5075
EASTING 571567 NORTHING 6038885 ZONE 14 DATUM NAD83
Date of mapping 06/27/1983

STRUCTURAL DATA

Planar Structures:
Structure type | Strike | Dip | Separation
fault | 237 | 74 |

Dikes and Sills:
Rock Number | Type | Width (m) | Strike | Dip
0 | pegmatite | 0.03 | 105 | 80

30-55 cm ultramylonite
-photos
1 Tonalite-granodiorite contact
2 Amphibolite raft with dike of mafic tonalite
3 agmatite of amphibolite in tonalite
4 schlieric termination of inclusions in tonalite
5 deformation associated with cataclasis in granodiorite
6,7,8 minor structures associated with mylonite

PETROLOGIC DATA

Rock Number: 1

Rock Type: tonalite
Descriptors:
grey - white
leucocratic
young phase / unit
has unit 2 to 4 as inclusions
Field Description:

-Dominant rock type is grey-white weathering quartz rich leucocratic tonalite.
-appears to be the youngest rock in the outcrop
-it is intrusive into all others except late pegmatites
-quartz 30-35 %

Textural Features
Type | Mineral | Min. Size | Max. Size | Abundance (%) | Unit
mafic mineral | biotite | 0.0 | 0.0 | 4.0 | %
groundmass grainsize |  | 0.0 | 1.0 |  | mm

Minerals of Note
Mineral | Abundance (%)
quartz | 33.0

Rock Number: 2

Rock Type: granodiorite
Descriptors:
grey
dark grey
augened
cataclastic
porphyritic
occurs as a raft
pegmatite lit
has unit 1 as inclusions
Field Description:

-coarser grained less quartz rich (quartz 20 %) grey weathering intrusive granodiorite. Slightly plagioclase megacrystic.
-occurs as inclusions in leucotonalite.
-is crossed by deformed pegmatite and late undeformed pegmatite

Textural Features
Type | Mineral | Min. Size | Max. Size | Abundance (%) | Unit
mafic mineral | biotite | 0.0 | 0.0 | 10.0 | mm
groundmass grainsize |  | 1.0 | 3.0 |  |
phenocryst | plagioclase | 0.0 | 0.0 |  |

Minerals of Note
Mineral | Abundance (%)
quartz | 20.0

Rock Number: 3

Rock Type: tonalite
Descriptors:
salt and pepper texture
homogeneous
weakly foliated
massive
has unit 4 as inclusions
has unit 1 and 2 as inclusions
pegmatite lit
occurs as a raft
Field Description:

-massive poorly foliate mafic tonalite (looks quartz diorite but has 20 to 25 % quartz) with salt and pepper texture and even grained homogeneous appearance.
-Intrusive into the volcanics and contains amphibolite inclusions
-Occurs as large rafts in Rock 1 and 2 but dominantly in 1.
-cut by old and young pegmatites.

Textural Features
Type | Mineral | Min. Size | Max. Size | Abundance (%) | Unit
mafic mineral | hornblende | 0.0 | 0.0 | 25.0 | %
groundmass grainsize |  | 1.0 | 2.0 |  | mm

Minerals of Note
Mineral | Abundance (%)
quartz | 22.0

Rock Number: 4

Rock Type: amphibolite
Descriptors:
layered
hornblende - diopside bearing
occurs as a raft
has unit 3 as inclusions
possible volcanic rock
Field Description:

-large inclusions highly deformed mafic amphibolite.
-probable massive and possibly pillowed flows with minor sediments of volcanic origin

PHOTOS

Contact between leucotonalite and the old augen granodiorite.

Amphibolite raft cut by dike of mafic hornblende tonalite.

Agmatite of amphibolite in the mafic hornblende tonalite

Schlieric termination of a mafic inclusion in tonalite

Deformation associated with cataclasis in older granodiorite.

Minor structures associated with mylonite zone in augen grandiorite

Minor structures associated with mylonite zone in augen grandiorite

Mylonite produced classic straight gneiss in augen granodiorite.

Manitoba Geological Survey, 2017