Cross Lake Project (1983-86)

Geologist P.G. Lenton Year 83 STATION 5164
EASTING 575820 NORTHING 6048276 ZONE 14 DATUM NAD83
Date of mapping 07/29/1983

STRUCTURAL DATA

PETROLOGIC DATA

Rock Number: 1

Rock Type: pegmatite
Field Description:

-shallow SW dipping dike very irregular in form
-dike is probably 2.5 to 3.0 m thick although only the lower 1/3 to 1/2 is exposed
-the form of the lower contact appears to be controlled by 2 fracture sets--the main fracture at approx. 135 degrees dipping variably from 10 to 30 degrees gives a general undulous S westward shallow attitude that is the main trend of the dike
-this is modified by the strong 110/82 degree fracture that causes boot heel structures in the lower contact
-at the west end the dike wraps around into a more northerly attitude with a west dip
-thin screens at 8+ indicates down warp into gully.
(see cross section)
CHECK FIELD NOTES FOR VARIOUS MAPS AND CROSS SECTIONS
-this is the first dike noted with significant amounts of triphylite
EXOMORPHISM
Slight tourmineralization of contact. Inclusions are completely tourmineralized--see photos. The contact comprises 1 to 3 m tourmaline rind.
BORDER ZONE
1 cm fine grained. albite + quartz with acicular tourmaline-constant around all contact
WALL ZONE
Quartz poor-mainly clevelandite with traces of tourmaline, triphylite, spessartine, microcline to 5 cm. Arsenopyrite (on edge of triphylite), very little muscovite. Zone averages 15 to 20 cm thick. Transition into lower intermediate is quite sharp. Traces of columbite
INTERMEDIATE ZONE
-clevelandite slowly dies out upward
-sudden drastic increase in grain size accompanied by greatly increased quartz content
-microcline increases in abundance upward into blocky zone near top
-muscovite slowly increases in abundance and grain size
-tourmaline slowly increases in abundance and grain size
-beryl first appears in middle of intermediate zone
-spessarite dies out rapidly--triphylite is grain size increase to 30 to 50 cm blocky microcline zone just below core
-Saccharoidal albite common at to of intermediate zone
CORE ZONE
-grain size again increases with 15 cm muscovite appearing 50 to 70 cm blocky microcline, rare 5 to 10 cm beryl and sudden appearance of spodumene as large cumulus blocky crystals along bottom of core zone
-rare saccharoidal albite veins
-tourmaline very coarse up to 20 cm across
PHOTOS
1 triphylite near lower contact
2 & 3 tourmalinized inclusions in lower wall zone
4 general view of upper blocky portion of lower intermediate

PHOTOS

Triphylite masses near lower contact.

Tourmalinized inclusions of country rock in lower wall zone.

General view of upper blocky portion of lower intermediate zone.

Structural overview of dike

General geology map of occurrence 5164. Grid is in metres.

Manitoba Geological Survey, 2017