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