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Project lOc: Compilation Geology, Pelican Narrows (63M) and Amisk Lake (63L)

by R. Macdonald

This project was commenced last year (Macdonald, 1975) as the first in a

new series of 1:250,000 scale compilation Geology maps.

Office work over the 1975/76 winter, carried out mainly by L.O. Craig,

entailed the drafting of a number of overlays to the preliminary lithological map .

These include overlays of planar and linear structural elements , major fold axial

traces, faults, metamorphic minerals and facies grades and topographic isopleths

(generalized contours). Some of this material has been placed on comput er file.

Samples of the Amisk Volcanics (Errington Lake area), and the Sahli and

Deschambault granites collected in 1975 by Dr. Keith Bell, Carleton University,

in connection with this project have yielded good Rb/Sr isochron ages and are due

for publication shortly.

The 1976 summer field work comprised re-investigation in some detail of two

ar eas (see Macdonald and Posehn, this volume) and spo t checking by the author,

mainly along the Tabbernor Lake fault zone and in the area to the west . Four

traverses were also completed (with the assistance of G. A. Posehn) to fill a

mapping gap just south of The Two Rivers (63M-11). Preparation of the fi nal draft

compilation maps awaits completion of primary mapping in 63M-14(W) and 63M-16,

scheduled for 1977.

The following summarizes some of the findings and conclusions since last

year's report:

1. The main translation in the Tabbernor Lake fault zone, in the Churchill River­

Manawan Lakes area, is contained in a narrow intensely sheared lineament (the

Tabbernor Lake fault itself, as mapped by Budding and Kirkland, 1956; Kirkland

1957, 1976)(Fig. 1).

South of Sandy Narrows, the Tabbernor Lake fault has been identified hitherto

as the fault which passes south-southeast towards Hanson Lake (Byers, 1957;

Pearson, 1972). It is apparent however, from this summer ' s investigations, that

the more important fault passes due south through the West Arm, Pelican Lake and

connects with the West and East Sarginson Lake faults south of Deschambault Lake

(Padgham, 1968; Macdonald and Posehn, this volume) (Fig. 1). This Tabbernor­

Sarginson fault lineament runs almost due north-south and separates a distinct

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•,u b~M I

I I I I I I I LI

I I I I

!\ ! • •I• 31: ~lj

LI

I I I

I I

' ,V }0

Fig . l. Sketch map of main geological f~atures, including the Tabbernor fault zone, Pe lican Narrows (63M) and Amisk

J

Lake (63L) areas . Northern edge of Ordovician limes t ones (line with dots); "gree nstone " a r eas (V); me ta sediment s

I I I

west of Tabbernor fault zone (v ertica l lines ); granitoids west of Tabbe rnor fault zone (crosses); po s tulat ed Archean greenstones (Av); Ourom me ta-arkoses and broad co rr e l at ives along east side of Tabbernor fault (dott ed patte rn); "Kiss eynew type" ro cks including associated granitoids, east of Tabbe rnor fault zone (blank); Amisk-Flin Flon volcanics, Aphebian (diagonal lines). Sahli granite (flecked patt ern). Only the main faults are indicat ed (normal line), postulated faults (pecked lined), TF Tabber­nor fault, TBr Tulabi Brook fault, SLF Sarginson Lake Faults, (E and W), S- W F Sturgeon Weir Fault.

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granodiorite-greenstone region,the Glennie Lake domain (Lewry, in press), to the

west from a predominantly supracrustal belt to the east, whereas the Hanson Lake

extension of the Tabbernor fault south of Sandy Narrows merely offsets rock units

of broadly similar type.

2. Re-examination of shoreline exposures in arkosic metapsammit es lying just

east of the Tabbernor fault on Ourom and Manawan Lakes has revealed an abundance

of sedimentary s lump structures . The general dip is steep with younging to the

east and the bedding is in places picked out in magnet ite. Epidotic "balls ",

presumably derived from calcareous concretions or layers, are common . Palinspastic

estimation of slump directions in three cases indicates a paleoslope facing to the

southeast quadrant.

3. The Ourom meta-arkoses in the Manawan Lake area pass rapidly eas t into

gneissic granodiorites. Re - examination supports Kirkland's (1957) tentative view

that these are metamorphic equivalents of the metapsammites. By extending the

compilation farther east, using the cri teria of aeromagnetic "signature", applying

minor re-interpretations to the structure and extrapolating into areas of higher

metamorphic grade,a tentative general stratigraphy is being derived for the supra­

crustal rocks eas t of the Tabbernor fault. A thick sequence of meta-arkoses

(locally with conglomerates and mafic hornblendic layers as well as thin pelitic

horizons) close to the fault gives way in the east to more pelitic assemblages of

"Kisseynew" type . A me ta-volcanic unit outcropping along the Tabbernor fault may

be part of the psammite sequence and lamprophyre dykes occur here and in the

granitic terrain west of the fault (Kirkland, 1956).

4. A belt of high aeromagnetic values traces south from Sandy Narrows to just

east of Sarginson Lake over the outcrop of mixed gneissic granodiorites and

biotite-hornblende gneisses. High aeromagnetic values are in places associated

with quartz-monzonit es (as west of Bustead Island; Pyke, 1966) and also occur ove1

the felsic gneisses which approximately encircle the Sahli granite (Macdonald,

1974). Magnetite has been identified as the source of the high aeromagnetic

values in some of these examples. It is proposed that these rocks belong to one

general stratigraphic unit, broadly correlative to the Ourom meta-arkoses.

5. The Hanson Lake volcanics, date d as late Archean (Coleman, 1970) have been

correlated with the Tulabi Lake rocks and the Northern Lights Group in the Limestone­

Tulabi Lakes area (Macdonald and Pose hn, this volume). It is here suggested that

the Ourom meta-arkose together with the correlatives described in section (4) above,

are a yo unger stratigraphic assemblage, possibly Aphebian. Strong lateral variation

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is apparent in the sedimentary faciesof this assemblage, with coarser psammites

giving way to pelitic and semipeliti.c assemblages of "Kiss eynew type" to the east.

This, coupled with evidence of slumping, indicates the proximity of a tectonically

active margin to the basin along the line of the main Tabbernor-Sarginson fault

lineame nt. It is e nvisaged that ear ly movement on this fault marked the edge of a

fault-bounded basin, aulacogen or rift. In addition to the left-lateral movement on

this fault noted by previous authors, downthrow to the east is therefore also

indicated. Translation in both senses appears to diminish rapidly along the

Tabbernor fault north of Ourom Lake. The volcanic and hypabyssal events described

in section (3) above presumably took place in connection with the formation of the

rift.

6 . It has already been pointed out that the Tabbernor fault zone is also a fold

belt (Macdonald, 1975). The change from psammites to greywacke-pelite (Kisseynew)

facies across this narrow belt towards the east also coincides with a steep meta­

morphic gradient ( e .g. Kirkland, op. cit.; Macdonald, op . cit .; Sibbald, in press)

to upper amphibolite/granulite facies a nd a chan ge from uoright folds to those

overturned to the west. The Tabbernor " fold belt " appears to be a feature produced

by the interaction of rocks of the Kisseynew domain (thrusting from the eas t and

southeast) with the granite-greenstone (Glennie Lake) domain west of the Tabbernor

fault. Samples were co llected this summer by Dr. K. Bell from granites west of the

Tabbernor fault for radiometric age determination, to see if older material is

present in the Glennie Lake domain.

7. Several of the greenstone septa in the Glennie Lake domain were visited.

Primary volcanic features can be found, as for example in the Keg Lake area (graded

bomb beds, mafic carbonate-ruff sequences) and on Sadler Lake (carbonate-·mafic

tuffs, pillow structures).

8. Granitoids in the Glenni e Lake domain have a strong, north dipping, foliation

in a strip from west of Frog Portage, Trade Lake southeast to Lindstrom Lake. Some

of these rocks were original mapped as psammitic gneisses, but their granitic origin

is demonstrated in fabrics preserved in phacoidal structures on Lindstrom Lake.

From Trade Lake southwards, the batholithi c bodies in the Glennie Lake domain tend

to be elongate NW-SE and NE and NNE dips are common. Overturning of the batholiths

and intervening greenstone septa to the SW or SSW, with compression in the same

direction, is indicated for the southern part of the domain. The refoliation in the

Trade Lake-Lindstrom Lake area appears to be related to this.

9. Movements on the Tabbernor faults progressed from ductile-mylonitic to brittle

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late faulting. These late brittle fractures are almost wholly obscurred under

muskeg or lake, but are revealed in topographic lineaments . At the southern

Shield margin, the Tabbernor fault zone is a complex splay of brittle faults. Many

of these continue south into the Ordovician Limestones as very strong join ts .

Inspection of air photos indicates that these approximately north- south fault/joi n t

lineaments extend as far south as the Saskatchewan River, south of latitude 54°N ,

across the full width of the Ordovician sub-crop. Similar lineaments are also

indicated by the aeromagnetic map .

References

Budding , A.J. and Kirkland, S . J .T. (1956) : The Geology of the Reindeer River Area; Sask. Dept. Mineral Resources , Rept . No . 22 .

Byers, A. R. (1957): The Geology and Mineral Deposits of the Hanson Lake Area, Saskatchewan, Sask. Dept. Mineral Resources, Rept. No . 30 .

Coleman, L.C. (1970): Rb/Sr isochrons for some Precambrian rocks in the Hanson Lake area, Saskatchewan; Canadian Journ . Earth Sci . , Vol . 7, 338-345 .

Coleman, L . C.; Gaskarth, J.W.; Smith, J . R. (1970) : Geology and Geochemistry of t he Hanson Lake area, Sask . Research Council , r.eology Division Rept . No . 10 .

Kirkland, S.J.T. (1957): The Geology of the Manawan Lake area (North Half) , Sask . Dept. Mineral Resources Rept . No . 27 .

(1976): The Geology of the Manawan Lake area (South Half), Sask . Dept. Mineral Resources Rept. No . 175.

Lewry, J.F. (in press): The Geology of the Glennie Lake area , Saskatchewan , Sask . Dept . Mineral Resources, Rept . No. 143 .

Macdonald, R. (1974) : Pelican Narrows (West) area, in Annual Summary of Field Investigations by the Saskatchewan Geological Survey 19 74 , Sask . Dept . Mineral Resources.

(1975): Compilation Geology, Pelican Narrows (63M) and Amisk Lake (63L) areas, in Summary of Investigations 1975 by Saskatchewan Geological Survey, Dept. Mineral Resources.

Padgham, W.A. (1968) : The Geology of the Deschambault Lake Dis t rict, Saskatchewan, Sask . Dept. Mineral Resources, Rept . No . 114 .

Pearson, D. (1972) : Geological Map of Saskatchewan (Precambrian area) , Dept. Mineral Resources and Saskatchewan Research Council .

Pyke, M.W. (1966): The Geology of the Pelican Narrows and Birch Po r tage Areas , Saskatchewan, Sask . Dept . Mineral Resources, Rep t. No . 93 .

Sibbald, T. I . I. (in press): The Geology of the Sandy Narrows (East) area, Sask . Dept . Mineral Resources, Rept . No. 170 .