Origin and Kinematic History of Highly Strained Gneisses in the Jan Lake East Area

Transcription

1 Origin and Kinematic History of Highly Strained Gneisses in the Jan Lake East Area Shi Rupan 1 and J.F. Lewry 1 Shi, R. and Lewry, J.F. (1991 ): Origin and kinematic history of highly strained gneisses in the Jan Lake East area; in Summary of Investigations 1991, Saskatchewan Geological Survey, Saskatchewan Energy Mines, Misc. Rep Previous work has defined a broad zone of heterogeneously highly strained to mylonitic orthogneisses and paragneisses enveloping and overlying the Sahli and MacMillan Point Archean basement inliers in the 'Pelican Window' of the Ha nson Lake Block (Lewry and Macdonald, 1988; Lewry et al., 1989; Lewry, 1990). The extent and degree of continuity, however, of this high-strain package along the eastern side of the Hanson Lake dome was poorly defined. This summer, the first author conducted 1 : scale remapping around the eastern part of Jan Lake (Figure 1), an area believed to include eastern extensions of the high-strain assemblage. All or parts of the area were previously mapped by Pyke (1966), Macdonald and MacQuarrie (1978), M acouarrie (1979) and Lewry et al. (1989). Work reported here will form the basis of an M.Sc. thesis, the main objectives of which are to: a) more clearly define the distribution and nature of ductile high-strain rocks formed dliring early deformation events in the region, b) document strain gradients across the high-strain gneisses and their less-strained protoliths, and establish sense of movement in the high-strain zone, and c) id entify the protoliths of the varied lithological components of the high-strain package, though fieldstructural, petrographic and geochemical investigations. 1. Rock Units a) Unit 1: Pelite Metatexite-diatexite Migmatitic gneisses derived from dominantly pelitic to psammopelitic sediments extend along the eastern shore of Jan Lake (Figure 1 ). They range from metatexites comprising dominant schistose to gneissose pelitic to psammopelitic paleosome with subordinate leucogranitic-pegmatitic neosome, to diatexites comprising 70 percent or more granitoid leucosome and plentiful ultramafic melanosomal 'restite', but retaining little or no clearly defined paleosome. Paleosome Components Metasedimentary paleosome mainly comprises quartz, plagioclase (quartz generally more abundant than plagioclase), subordinate K-feldspar and biotite content ranging from about 10 to 30 percent. Dominant pelitic gneisses typically contain garnet and sillimanite which are typically most abundant in the melanosome. Cordierite, although not obvious in hand specimen, is seen in thin section (Abbas-Hasanie and Lewry, this volume). Garnet crystals range from a few millimetres to several centimetres (locally to 7 cm) across. Generally, they form apparently slightly deformed porphyroblasts, although highly strained, pre- to syn-tectonic ovoidal garnet porphyroclasts with prominent recrystallization tails occur locally. Garnet generally forms less than 5 percent of the rock but locally ranges to 15 percent. Boudinaged garnet-rich (up to 40 percent} bands 0.5 to 2.0 m wide, parallel to the main foliation, occur in a few outcrops. Relict primary layering is locally well defined by mediumto fine-grained, mid- to dark-grey, relatively quartz-rich psammitic to psammopelitic metagreywacke beds, typically 3 to 10 cm but locally up to 1 m or more thick. Psammitic to psammopelitic members are also dominant locally. Psammitic layers typically contain only minor neosomal segregations, and are sparsely garnetiferous. Mafic amphibolite bands, comprising medium- to coarsegrained hornblende and plagioclase, ranging in thickness from centimetres to several metres, are typically boudinaged, locally rotated, and folded. These rocks are interpreted as mafic dykes rather than supracrustal layers (Lewry et al., 1989). Neosome components The pink leucogranitic to pegmatitic leucosome varies from discontinuous to semi-continuous 'lits' and lenses parallel to paleosome foliation ('stromatic' migmatites) to more irregular, partially discordant and highly folded masses enclosing subordinate paleosomal sch!ieren, and also forms isolated minor fold noses and irregular patches ranging from a few millimetres to over a metre across. Quartz, plagioclase and K-feldspar with minor biotite and, locally, cordierite and sillimanite are the main mineral components. Fabric relations between (1 ) Dcpartmcnl of Geology, University of Rq11na, Fl ogina. Saskatchewan. Saskatchewan Geological SuNey 169

2 ' 103 so' Figure 1 - Geological sketch map of the eastern Jan Lake area. Unit 1, pelite metatexitediatexite; Unit 2, megac,ystic biotite tona/ite; Unit 3, non-megacrystic tonalitegranodiorite; Unit 4a, less strained homblende-biotite granodiorite complex; Unit 4b, moderately to highly strained porphyroclastic granodioritic gneisses; Unit 4c, protomy/onitic-mylonitic porphyroclastic, 'beaded' gneisses; Unit 5, Jan Lake granite. Megacrystic biotite leucotonalitegranodiorite occurs on many islands in the main basin of Jan Lake, and is intercalated with pelite diatexites along the eastern shore of Jan Lake and on islands of western Doupe Bay. The main rock types are all light grey to greywhite in fresh and weathered surfaces but vary from mediumleucosomal lits, foliation and early minor folds indicate multiphase leucosome development or, more likely, continuous leucosome generation thrnughout early deformational events. Very early leucosome layers parallel the main foliation and are commonly isoclinally folded, ribboned and disrupted. Later leucosome components are variably concordant and discordant to the main foliation and are either apparently undeformed or are folded only by late minor folds. Commonly, the leucosome bodies are prominently bordered by biotite-rich, garnet- or garnet-sillimanite-bearing melanosomal selvages up to several centimetres thick. Elsewhere, particularly in the diatexites, the melanosome forms plentiful lensoid to irregular patches external to or within the leucosome. Fabric The anatectic metasediments are strongly foliated, gneissic and schistose, and locally intensely laminated. Foliation is accentuated by highly elongate quartz and quartz-feldspar lenses which probably represent disrupted early neosome lits. Pre- and early synkinematic lithological elements, such as primary psammitic-psammopelitic layers, mafic dykes and early neosome, are completely transposed into the main foliation, disrupted, boudinaged, folded and rotated. Strongly laminated variants generally contain a variable amount of ovoidal to rounded white plagioc!ase and/or pink K feldspar porphyroclasts and smaller 'beads', generally from a few millimetres to about 2 cm across, but locally up to 5 cm. Some units, typified by a very biotite-rich matrix enclosing abundant ovoidal to rounded plagioclase porphyroclasts, resemble the biotite-rich porphyroclastic gneisses of the Church Lake area (Lewry, 1990) which were interpreted as 'mylonitic' derivatives of pelite diatexite. b) Unit 2: Megacrystic Biotite Leucotonalite-granodiorite coarse to very fine grained. White plagioclase, quartz (feldspar generally more abundant than quartz), variable amounts of biotite, ranging from less than 5 percent up to 15 percent locally, and local minor garnet are the mineral components. K-feldspar generally seems to be a subordinate constituent. The unit commonly incorporates up to 20 percent or more pink granitic neosome, typically as transposed and strongly foliated layers and thin laminae concordant to kinematic foliation. Strain effects are extremely variable, both regionally and at outcrop scale. The least strained variants are relatively homogeneous, weakly foliated rocks which typically contain up to 10 percent subidioblastic white plagioclase megacrysts. The only other inhomogeneity in such rocks is variably deformed neosoma1 granitic 170 Summary of Investigations 1991

3 material. Small ductile high-strain zones parallel to otherwise generally weak foliation are common. More highly strained types are medium to fine grained, intensely foliated and laminated, and locally include isolated, ovoidal to rounded plagioclase and/or K-feldspar porphyroclasts about 0.5 to 1.5 cm across. In some places, they also contain rotated mafic boudins. ln many places these rocks contain pinkish-grey, medium-grained, quartzofeldspathic layers with sparse, ovoidal K-feldspar porphyroclasts about 1 cm across as well as large and highly ribboned quartz lenses and small disrupted pegmatite sheets. Such layers are generally parallel or slight ly oblique to the main foliation and are interpreted as highly strained intrusive or neosomaj felsic sheets rather than primary layers. At one locality, a petite diatexite block 1.5 m across, occurring within moderately, hightystrained, biotite tonalitic gneiss appears to be a xenolith. On the basis of mineral content, lithological homogeneity, evident strain gradation between coarsegrained megacrystic variants and finer-grained types, a xenolithic inclusion, and lack of layering other than that resulting from transposition of neosome components, H1is unit is thought to be derived from plutonic protoliths. c) Unit 3: Non-megacrystic Tonalite to Granodiorite Non-megacrystic tonalite to granodiorite, exposed mainly on Busteed Island and small islands to the north and south, formerly identified as possible psammitic-psammopelitic metasediments by Macdonald and Macquarrie (1978), was re-interpreted as highly-strained plutonic rocks, at least in part, by Lewry et al. (1989). Generally, their paleosome is uniformly medium to fine grained, incorporating a variable proportion of continuous to discontinuous, coarser-grained leucosomal quartzofeldspathic layers, patches and lenses. These are commonly bordered by biotite-rich melanosomal selvages, suggesting that the leucosome represents in situ anatexis, at least in part. The neosome locally contains small dispersed garnets or garnet aggregates. As in unit 2, these rocks are heterogeneously strained. Locally, for example at the north end of Busteed Island, relict, weakly foliated and homogeneous mediumgrained tonalite-granodiorite with plutonic fabrics is preserved. Commonly observed strain gradation suggests that more strongly foliated, medium- to finegrained variants are derived from similar plutonic protoliths via progressive ductile high-strain, dynamic recrystallization, and accompanying shredding and transposition of neosome. Quartz in the latter is intensely ribboned and large feldspars locally form ovoidal to rounded porphyroclasts averaging 0.2 to 0.5 cm across, some with well-developed tail complexes. In places, the fine-grained matrix includes sparse small, white to pink, rounded feldspar beads which may represent comminuted primary igneous crystals or derive from disruption of neosomal veins. Outcrop areas affected by heterogeneous intermediate strain commonly show narrow ductile mylonite zones subparallel to foliation in less strained parts of the outcrop. Strain gradients are clearly seen across the mar- gins of these zones. In some localities, as for example in a few outcrops examined outside the main map area along the southwest shore of Mirond Lake, lensoid 'tectonic fish' of coarser-grained tonalite are preserved in generally fine-grained, intensely laminate-foliated quartzofeldspathic gneisses. Foliation in the more highly strained components is locally defined by extreme quartz ribboning and more generally by development of a fine tectonic lamination. Minor high-strain zones, some displaying clear C-S fabrics, are also locally developed along the contacts between neosomal pegmatite sheets and tonalitic host rocks. These are generally subparallel to the main foliation but may represent a tater phase of deformation. locally, unit 3 rocks enclose blocks of medium- to finegrained, garnetiferous hornblende gneiss with welldeveloped mafic to felsic layering. These blocks are interpreted as metavolcanic xenoliths. Isolated to semicontinuous inclusions of uniform, medium- to coarsegrained L-tectonite amphibolite are interpreted as boudinaged and disrupted mafic dykes. Subunit 3a Subunit 3a, occurring mainly on Busteed Island and small islands to the north, is the dominant rock type. Jt is medium to fine grained, light grey to pale buff on weathered surfaces and pinkish grey or pink on fresh surface. The paleosome groundmass mainly comprises white and pink feldspar (55 to 60 percent), quartz (20 to 40 percent) and biotite (5 to 10 percent). Discrete white to pink neosomal quartzofeldspathic bands, ranging from a few millimetres up to 3 or 4 cm thick, generally form 10 to 15 percent of the rock but locally up to 40 percent. This subunit is generally thought to be derived from plutonic protoliths. Subunit 3b Subunit 3b, mainly occurring on the islands south of Busteed Island and in the east bay of Jan lake, has a high proportion of pink granitoid neosome, in continuous to semicontinuous layers, elongate lenses, irregular patches and ill-defined 'sweats', typically forming 30 to 50 percent but locally up to 80 percent of outcrop areas. The intervening medium- to fine-grained quartzofeldspathic host rock contains up to 40 percent biotite and may be either highly modified melanocratic paleosome or restitic melanosome. In places, particularly biotite-rich sch lieren tend to be concentrated along the margins of leucosome masses. Tight to isoclinal intrafolial minor folding of the neosome is common. Unlike the pelite diatexites of unit 1, this subunit contains little or no garnet or sillimanite; nonetheless, the high biotite content suggests that this subunit may derive from a metasedimentary protolith. Subunit 3c Subunit 3c, occurring mainly on Busteed Island, typically has a well developed gneissic foliation and mineral lineation defined by individual crystal alignment, multicrystal quartz ribbons and multicrystal monomineralic aggregates of feldspar and biotite, suggestive of an Saskatchewan Geological Survey 171

4 originally coarse grain-size. Generally, they contain about 10 to 20 percent biotite (intermediate to that in subunits 3a and 3b), 50 to 60 percent feldspar and about 30 percent quartz. Semicontinuous pink quartzofeldspathic neosome layers averaging 1 to 3 cm in thickness lie parallel to the main foliation. In places, the rocks have a strong tectonic lamination accompanied by prominent quartz ribboning and small isolated rounded feldspar porphyroclasts 0.2 to 0.4 cm across. Large pink feldspar porphyroclasts are dynamically recrystallised into medium- to fine-grained crystal aggregates. We interpret this subunit to be derived from a relatively coarse-grained granitic-granodioritic plutonic proto!ith. As in Unit 2, this subunit locally has grey, medium- to fine-grained, quartzofeldspathic layers ranging from 1.5 to 15 cm thick, parallel or subparallel to foliation and containing prominent large, quartz ribbons and small, sparse ovoidal feldspar porphyroclasts. The grey layers are locally bordered or injected by small undeformed pegmatite sheets. On the basis of field relations, they are interpreted as syn-tectonic felsic dykes, injected along small shear zones, with late pegmatite sheets injected along the contact zones. d) Unit 4: Variably Strained Hornblende-Biotite Granodiorite Variably strained hornblende-biotite granodiorite underlies most of the area around and to the north and east of Doupe Bay. This unit is broadly granodioritic in composition, mid- to light-grey, and weakly to intensely foliated. Hornblende and biotite occur in variable amounts. At outcrop scale, much of the unit, particularly the more highly strained variants, incorporates relatively coarser and apparently less deformed lenses and irregular patches of granodioritic neosome. The neosome is characterized by prominent hornblende blastesis and is locally dominant. Boundaries between neosomal lenses and more strongly foliated finer grained paleosome are usually ill-defined and gradational. Locally, the neosomat zones include irregular to lensoid, coarsegrained ultramafic hornblende aggregates with sharp to diffuse boundaries; these are mostly interpreted as melanosomal segregations but some may represent disrupted mafic inclusions. Ovoidal to rounded plagioclase feldspar porphyroclasts and small 'beads', typically ranging in size from 0.1 to 1.2 cm across, are a prominent feature of the paleosome. The granodiorite complex displays a clear, albeit irregular increase in ductile strain from east to west across the Doupe Bay area, from unequivocally plutonic, weakly to moderately foliated granodiorite through increasingly highly strained and finer-grained granodioritic gneisses, to generally fine-grained protomylonitic and mylonitic gneisses. Boundaries between these strain states are irregularly gradational, heterogeneous and apparently anastomosing. Increase in strain is defined by: a) general decrease in grain size, b) more prominent ribboning of quartz grains, until advanced stages of strain where they disappear into the groundmass, c) increasing 'beading' of groundmass plagioclase grains, d) eventual replacement of a well-foliated gneissic groundmass by a less clearly foliated medium- to fine-grained dynamic recrystallization matrix, e) progressive elongation, disruption and rotation of white quartzofeldspathic neosomal layers and pink pegmatite sheets, and f) progressive isolation and rounding of large K-feldspar porphyroclasts which either originated as discrete porphyroblasts or derive from disruption of thin pegmatite neosome layers. On the basis of systematic variation in such strain indicators, the complex is divided into three subunits. Subunit 4a Subunit 4a comprises weakly to moderately strained, coarse- to medium-grained hornblende-biotite granodiorite with variable amounts of plagioclase megacrysts which locally display tight intrafolial folds defined by early neosomal quartzofeldspathic layers. Neosomal leucogranodiorite layers and patches are also locally deformed together with the main foliation by a later generation of open to tight minor folds. Weak quartz ribboning and weakly elongated to rounded plagioclase megacrysts are seen locally. Subunit 4b Subunit 4b includes moderately highly strained to protomylonitic, porphyroclastic granodioritic gneisses which constitute a markedly heterogeneous ductile strain transition between subunits 4a and 4c. In general, these rocks are medium grained and strongly foliated, with a variable percentage of ovoidal to rounded plagioclase porphyoclasts, 'beaded' groundmass plagioclase, and large ovoidal to rounded K-feldspar porphyroclasts, locally with medium- to fine-grained dynamic recrystallization tail complexes. Some semi-isolated large plagioclase and K-feldspar porphyroclasts are wrapped about by large intensely ribboned quartz subdomains and are probably derived from shredded neosomaj pegmatite veins. Subunit 4c Subunit 4c comprises protomylonitic to mylonitic 'beaded grey gneisses' which constitute a relatively welldefined ductile high-strain zone. In the north, this zone lies between unit 1 petite diatexites and less strained subunits of the granodiorite complex. In the south, it lies entirely within unit 4. The subunit typically displays variable amounts of small discrete grey-white feldspar 'beads' in a medium- to fine-grained dynamic recrystallization matrix. In addition, highly disrupted neosomal pegmatite sheets and small to large ovoidaj to rounded plagioclase and K-feldspar porphyroclasts with or without tails also occur in places. Locally they are intensely laminated, with only sparse sporadic small feldspar 'beads'. Commonly, the high-strain fabric is obscured by extensive hornblende blastesis; the hornblende crystals are generally idioblastic, 0.4 to 1.5 cm in size and clearly post-date the high-strain fabric, a feature also noted in the ductile shear zone in the Tulabi Lake area (Lewry, 1990). 172 Summary of Investigations 1991

5 e) Unit 5: Jan Lake Granite and Pegmatite Late- to post-tectonic granites and pegmatites of the Jan Lake suite are dominant in the Doupe Bay area. Generally, they form medium- to very coarse-grained, massive to weakly foliated, cross-cutting to subcondordant sheets, dykes, apophyses and larger irregular intrusive bodies. Commonly, foliation in Jan Lake granite bodies is most prominent near contacts with older country rocks. Pegmatite sheets cut all other rocks in the area and commonly display small brittle to ductile shear zones, either at their contacts with surrounding rocks or in the middle of the sheets. Their emplacement was possibly controlled, in part, by late-stage brittle-ductile shear zones. An east-west-trending, uniform, coarse- to mediumgrained, biotite-rich granitic dyke cutting unit 3 rocks on Busteed Island is incl uded in unit 5 because of its generally weak foliation. Jan Lake granite and pegmatite are the dominant rock types in the Doupe Bay area, with rocks of unit 4 occurring mainly as highly subordinate, large and small xenol'1ths and rafts within them. However, in order to emphasize the structurally more important strain distribution in rocks of unit 4, the extent of the Jan Lake suite is not fully shown on the accompanying map. 2. Structure All rocks in the area other than those in unit 5 underwent polyphase ductile deformation. Many outcrops show complex minor fold interference patterns, defined mainly by leucosomal lits, mafic folia and prior foliation. a) Early Kinematic Fabrics Details of early structural sequence are best preserved in unit 1 pelite diatexites. Here, an S1 gneissic foliation, paralleled by primary layering, early neosomal lits and mafic folia, is locally distinguishable. In general, however, it is completely transposed into, and indistinguishable from a dominant regionally developed S2 foliation which is axial planar to tight to isoclinal and commonly isolated intrafolial F 2 minor folds defined by transposed primary layering and early leucosomal-me!anosomal laminae (Lewry et. al., 1989). Such folds are typified by highly attenuated to discontinuous limbs and thick, 'acute' hinge zones. Fold amplitudes range from a few centimetres to several tens of centimetres. Such intrafolial folds are less common in other rock units. In rare cases, minor intrafolial isoclines are defined by primary psammitic layers (So) para!le!ed by finely foliated and disrupted quartzofeldspathic leucosome layers (81) incorporating ovoidal feldspar porphyroclasts. These S1 fabric elements are deformed around the fold noses, where they are oblique to dominant S2 axial plane fabrics. Even more rarely, F2 folds are seen to refold earlier F1 intrafolial isoclines defined by primary lamination. In other rock units, no distinction between D1 and D2 planar fabrics and minor folds was established. The extreme regional and local ductile strain variation is clearly related to the D1/D2 progressive strain continuum, since mylonitic foliation documented in many rock units is clearly refolded by 03 and 04 folds. S1/S2 strain gradation from plutonic protoliths to essentially mylonitic and locally porphyroclastic quartzofeldspathic gneisses is well documented in units 2 and 3. Both local and broader regional gradation from relatively weakly foliated granodiorites to their protomylonitic and mylonitic derivatives in unit 4c is also well-defined. The main high-strain zone represented by unit 4c appears to be a northerly extension of a comparable ductile shear zone in granodioritic to tonalitic rocks identified by Lewry (1990) farther south, in the northeastern part of the Tulabi-Church Lakes area_ Its divergence from the pelite diatexite-granodiorite boundary suggests that it may represent a higher level splay rooting in a more fundamental movement zone within the highly incompetent pelite diatexites. Although strain variation in the latter was not consistently identified; its lithological character and the evident presence of a high proportion of anatectic melt throughout D1 /02 deformation suggests that it is likely to have suffered even greater strain than the plutonic units. The most highly deformed components of units 1 to 4 all locally display evidence of a significant simple shear strain component, including prominent rotated (deltatype) tailed feldspar porphyroclasts, rotated mafic boudins and more isolated mafic inclusions, and local C S fabrics. Such shear-sense indicators observed on subhorizontal outcrop surfaces of unit 1 pelite diatexite overwhelmingly indicate dextral shear-sense, whereas indicators in subunits 4b and 4c mostly show sinistral shear-sense. Stretching 1ineation related to these indicators was only rarely identified and the three-dimensional significance of the variation in shear-sense is presently unclear. b) Late Fold Phases The S1 /82 ductile strain fabric, including mylonitic variants thereof, is widely refolded by open to tight f3 minor folds which are locally accompanied by an S3 axial plane fabric oblique to early foliation. A later f4 open fold set can also be differentiated locally. Most open to tight folds (Figure 2) are thought to be F3 structures. Their plunge variation is probably the result of both variation in prior attitude of S1 /82 foliation and broad F4 regional refolding. In the south, the minor folds generally plunge towards the south-southwest approximately coaxial with major f3 regional folds farther south (Lewry et al., 1989). Early foliation in the northern part of the area defines a major open fold with a statistical plunge of 40 toward 110. This orientation is discordant with the general northeasterly trend of f4 regional folds (Lewry et al., 1989) and the fold is interpreted as an f3 structure. 3. Metamorphism Coexisting garnet, sillimanite and K-feldspar, and general absence of muscovite in diatexitic pelites, high Saskatchewan Geological Survey 173

6 N 2) Most rocks in the area have undergone at least two phases of partial melting, four phases of fold deformation and variable simple shear deformation. Partial melting took place prior to 03 folding, and prior to and/or during high-strain simple shear deformation. 3) Most of the map area attained middle to upper (probably uppermost) amphibolite facies conditions during the 01 to D2 folding and essentially coeval ductile, high-shear-strain deformation References Lewry, J.F. (1990): Bedrock geology, Tulabi-Church Lakes area: derivation and significance of porphyroclastic gneisses in the Pelican Window; in Summary of Investigations 1990, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 90-4, p Lewry, J.F. and Macdonald, R. (1988): Observations on deformation in the Glennie Domain and Hanson Lake Block; in Summary of Investigations 1988, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 88-4, p Figure 2 Stereoplot of hingelines of post-d2 minor tight to open folds (34 points) percentage partial melting of both pelitic and plutonic protoliths and deformational relationships of neosomal components indicate that high grade (upper amphibolite facies) conditions were attained and probably maintained throughout the D1 to D2 events. Anatexis appears to have occurred both prior to and during development of the high-strain protomylonitic to mylonitic fabric in the orthogneiss units. 4. Preliminary Conclusions 1) Most or all of the rocks included in units 2, 3 and 4 in the eastern Jan Lake area are derived from plutonic protoliths, rather than from psammites and crystal tufts. Their present character is the result of heterogeneously high ductile strain related to early phases of regional deformation. Lewry, J.F., Macdonald, R. and Stauffer, M.R. (1989): The development of highly strained rocks in the Pelican Window during high-grade metamorphism and pervasive anatexis; in Summary of Investigations 1989, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 89-4, p Macdonald, R. and MacQuarrie, R.R. (1978): Geological re -investigation mapping, Jan Lake area (part of NTS area 63M); in Summary of Investigations 1978, Saskatchewan Geological Survey, Sask. Miner. Resour., Misc. Rep , p16-24 MacQuarrie, R.R. (1979): Geological re-investigations mapping, Birch Portage South (NTS area 63L-15S); in Summary of Investigations 1979, Saskatchewan Geological Survey, Sask. Miner. Resour., Misc. Rep , p Pyke, M.W. (1966): The geology of the Pelican Narrows and Birch Portage areas, Saskatchewan; Sask. Dep. Miner. Resour., Rep. 93, 68p. 174 Summary of Investigations 1991

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