Cross Lake Project (1983-86)
Geologist P.G. Lenton
Year 83
STATION 5006
EASTING 572150
NORTHING 6040039
ZONE 14
DATUM NAD83
Date of mapping 06/18/1983
STRUCTURAL DATA
Structure type | Strike | Dip | Separation |
---|---|---|---|
cataclastic foliation | 65 | 75 | |
mylonitic fabric | 311 | 68 | dextral |
PETROLOGIC DATA
Rock Number: 1
-Very old highly gneissic unit that has undergone extensive deformation, mainly shearing.
-Whiskey Jack Augen unit
Type | Mineral | Min. Size | Max. Size | Abundance (%) | Unit |
---|---|---|---|---|---|
mafic mineral | biotite | 0.0 | 0.0 | 5.0 | mm |
Mineral | Abundance (%) |
---|
plagioclase |
chlorite |
biotite |
Rock Number: 2
-Dikes of homogeneous charcoal grey plagioclase porphyritic quartz diorite
-it intrudes an already highly deformed and sheared TNLT but has undergone extensive deformation
-exists now as a series of boudins
Type | Mineral | Min. Size | Max. Size | Abundance (%) | Unit |
---|---|---|---|---|---|
mafic mineral | biotite | 0.0 | 0.0 | 15.0 | mm |
Mineral | Abundance (%) |
---|
plagioclase |
chlorite |
biotite |
Rock Number: 3
Apparent history
1- oldest unit leucocratic tonalite
2- leucocratic tonalite is extensively intruded by old lit-par-lit veinlets or mobilizate
3- tonalite gneiss highly deformed and sheared
4- dikes of grey porphyritic granodiorite intrude the tonalite gneiss
5- grey granodiorite is intruded by leucocratic tonalite stringers
6- Tonalite and granodiorite intruded by an E-W set of pegmatite dikes of 3-5 cm thickness
7- Extreme deformation of all rocks, mainly cataclastic in nature broke the granodiorite dikes into agmatitic blocks and large boudins
8- Intrusion of N-S zones pegmatites (pegmatitic borders and aplitic cores) with 2 m sinistral offset
9- Continuation of cataclasis imposes fracture cleavage in late pegmatites with attendant pinch - and - swell and undulous folding. Deformation is still in the main shearing plane
10- Everything is crosscut by late, undeformed mylonites with pseudotachylitic margins with 120cm of dextral offset
PHOTOS
Large block boudin of grey porphrytic granodiorite in old sheared schlieric augen leucocratic tonalite. Notice how the laering/fabric in the old gneiss wraps around the boudin ends.
Detail of marginal deformation on grey porphyry boudin.
Overview of outcrop showing the schollen structure of the complex.
Younger cross cutting pegmatite containing small inclusion of grey porphyry granodiorite.
Late dextral mylonite with quartz filled extension veins.
Overview of t he schollen migmatite with the late mylonite zone central in the picture.
Manitoba Geological Survey, 2017