Cross Lake Project (1983-86)


Geologist    P.G. Lenton     Year    83     STATION    5187
EASTING   573569     NORTHING   6056802     ZONE   14     DATUM   NAD83
Date of mapping    08/05/1983

STRUCTURAL DATA

Planar Structures:
Structure type Strike Dip Separation
schistosity 45 87

Dikes and Sills:
Rock Number Type Width (m) Strike Dip
0 diabase 0.25 217 88

-several photos of hydrothermal alteration of granite

PETROLOGIC DATA

Rock Number: 1

Rock Type: granodiorite

Field Description:

-grey weathering mottled intrusive, possibly derived from a marginal phase of the granite
-has a strange mottled appearance caused by irregular anastomosing web work or coarser quartz, feldspar, biotite and chlorite
-these coarse areas resemble the epidotized margins of alteration veinlets in the granite
-my impression is that this rock has undergone considerable hydrothermal alteration, probabl as a late magmatic feature related to the de-gassing of the pluton
-there are textural remnants that resemble the porphyritic nature of the granite but converted to fine grained quartz, feldspar, chlorite, epidote leaving only vague outlines of pre-existing phenocrysts

Sample 1B - alteration of granite by hydrothermal vein system

Minerals of Note
Mineral Abundance (%)
muscovite
magnetite

PHOTOS


Photo of alteration in margin of granodiorite.


Detail of alteration.


Alteration may be a hornfels effect.


Manitoba Geological Survey, 2017