A Geological Transect Across the Southwestern Peter Lake Domain, Saskatchewan

Transcription

1 A Geological Transect Across the Southwestern Peter Lake Domain, Saskatchewan Ralf O. Maxeiner and Rebecca Hunter 1 Maxeiner, R.O. and Hunter, R. (2002): A geological transect across the southwestern Peter Lake Domain, Saskatchewan; in Summary of Investigations 2002, Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep , CD-ROM, Paper A-3, 24p. Abstract The largely Archean Peter Lake Domain is wedged between the Wollaston Domain to the northwest and the Paleoproterozoic Wathaman Domain to the southeast, bounded in part by the Needle Falls Shear Zone and the Parker Lake Shear Zone, respectively. Its perceived high platinum group element potential and ambiguous geological history and setting prompted the Saskatchewan Geological Survey to initiate a detailed three-year mapping project. Historically, the domain has been subdivided into three main components: the Peter Lake Complex, its high-strain equivalents called the Parker Lake Gneisses, and a low-grade sedimentary succession, the Campbell River Group. In the first year of the project, a 40 km long and 10 to 15 km wide transect flanking Highway 905 was mapped between Courtenay Lake and the Wathaman River. The poorly exposed northern half of the map area comprises large intrusions of massive to weakly foliated syenogranite, part of which is fluoritebearing, and a dioritic to gabbroic suite. The southern half of the domain is better exposed and is underlain by massive to mylonitic, mafic to felsic plutonic rocks, including leucogabbroic to anorthositic, gabbroic, and dioritic suites, as well as younger granodioritic, monzonitic, and granitic intrusive suites. The Love Lake leucogabbro contains rare examples of well preserved primary igneous layering. Locally abundant fine-grained mafic xenoliths in the pluton have a tectonic foliation predating the fabric in the host. Several slivers of upper amphibolite facies migmatitic supracrustal rocks are between Peter Lake and the Wathaman River, as well as a 0.2 to 1.5 km outlier of lower amphibolite facies Campbell River Group quartzite and argillite containing well preserved primary sedimentary structures including crossbedding, and ball-and-pillow structures. The structural history included at least four ductile deformational events, two main regional metamorphic events, and late brittle faulting. Several outcrops contain disseminated iron sulphides, chalcopyrite, and rare azurite. Geochemical analyses of grab samples have not returned significant values of gold, copper, and/or platinum group elements. Keywords: anorthosite, Campbell River Group, copper, geochemistry, geochronology, Hearne Province, leucogabbro, Neoarchean, northern Saskatchewan, Parker Lake Gneisses, Peter Lake Complex, Peter Lake Domain, platinum group elements, Wathaman Batholith, Wollaston Domain. 1. Introduction According to Hulbert, (1989, p60-61), the Peter Lake Complex is the largest concentration of mafic rocks in Saskatchewan and, after the Duluth Complex, it is the second largest mafic intrusion complex in North America The immense size of this complex and the presence of significant PGE mineralization suggest that the Peter Lake Complex has substantial PGE potential. The Peter Lake Domain (Figure 1) is wedged between the Wollaston Domain to the northwest and the Paleoproterozoic Wathaman Domain to the southeast, bounded in part by the Needle Falls Shear Zone (Money, 1965; Stauffer and Lewry, 1993) and the Parker Lake Shear Zone (Ray, 1975; Lafrance and Varga, 1996), respectively. Its unusual lithological character and partly fault-bounded nature were reasons to give it separate domain status (Macdonald and Thomas, 1983; Saskatchewan Geological Survey, 1994), although many workers consider it to represent the southeastern margin of the largely Archean Hearne Province (e.g., Corrigan, 2001). Its perceived high platinum group element (PGE) potential and ambiguous geological history and setting prompted the Saskatchewan Geological Survey to initiate a detailed three-year mapping project. Selected areas or transects 1 Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2. Saskatchewan Geological Survey 1 Summary of Investigations 2002, Volume 2

2 have been chosen for detailed 1: scale framework mapping. In this first year of the project, a 40 km long and 10 to 15 km wide transect along Highway 905 was mapped between Courtenay Lake and the Wathaman River, stretching across the Peter Lake Domain and extending into the bounding Wollaston and Wathaman domains. Future work will involve transects along Reindeer Lake and through the central parts of the domain. Supporting geoscience will include geochemical, petrological, and geochronological studies to determine protoliths, tectonic settings, and age relationships of various rocks. This work will also include an evaluation of the mineral potential of the domain. Tyrell and Dowling (1896) were the first to report on the geology. The Spalding Lake sheet (part of NTS 64E-SW) was later mapped by Weeks (1941) for the Geological Survey of Canada and by Lewry et al. (1980) for the Saskatchewan Geological Survey. Other mapping in the larger Peter Lake Domain, mostly at scales of 1:63,360 (1 inch to the mile) and 1: , is summarized in Figure 2. The most recent of this has been carried out by the Geological Survey of Canada (Corrigan et al., 2000; Corrigan, 2001). 2. Regional Geological Framework Figure 1 - Main subdivisions of the Peter Lake Domain. The domain is largely Archean and comprises the Peter Lake Complex (Ray and Wanless, 1980), Swan River Complex (Stauffer et al., 1981; Corrigan, 2001), Parker Lake Gneisses (Ray, 1975), and Campbell River Group (Lewry, 1976; Lewry et al., 1980). The southwestern part of the domain is bounded by the Needle Falls and Parker Lake shear zones, however, these die out towards the northeast. On Reindeer Lake it is intruded along its southern flank by partly megacrystic granitoid plutons of the 1.86 Ga Wathaman Batholith (Corrigan et al., 2000; 2001; Corrigan, 2001). In the Cook Lake area, approximately 30 km to the northeast of Highway 905, the northern flank of the domain is unconformably overlain by feldspathic psammite, cobble conglomerate, or mafic volcanic rocks of the Paleoproterozoic Courtenay Lake Formation of the Wollaston Domain (Delaney et al., 1997; MacNeil et al., 1997). The Peter Lake Complex, which represents the largest component of the Peter Lake Domain, is a very heterogeneous, predominantly plutonic assemblage. It ranges in composition from ultramafic to felsic, and in structure from massive to mylonitic. It has been metamorphosed to upper amphibolite facies causing anatexis, yet locally has well preserved primary igneous layering. On Reindeer Lake, Corrigan (2001) identified minor units of mafic metavolcanic rocks, which he interpreted as the oldest component of the Peter Lake Complex. This is consistent with observations by Lewry et al. (1980), who Saskatchewan Geological Survey 2 Summary of Investigations 2002, Volume 2

3 Figure 2 - Summary of previous mapping in the Peter Lake Domain. described remnants of layered pyroclastic or volcaniclastic rocks in the dioritic to gabbroic units of the Peter Lake Complex. Figure 3 and Table 1 summarize historical geochronological data for the Peter Lake Domain. Major felsic plutonism in the Peter Lake Complex is constrained to 2580 to 2560 Ma (Ray and Wanless, 1980; Bickford et al., 1986; Annesley et al., 1992; Rayner et al., in review). The Lueaza River granitoid rocks (i.e., map unit 4 of Stauffer et al., 1981) represent a large component of the Peter Lake Complex on Reindeer Lake (Corrigan et al., 2000). They are composed of migmatized plutonic and sedimentary rocks, as well as non-migmatized strongly foliated and recrystallized granitoid rocks and minor supracrustal rocks. A sample of pink granitic gneiss intruding older grey gneiss from the Lueaza River granitoids on northwestern Reindeer Lake yielded rather complex results (Bickford et al., 2002; Rayner et al., in review). It provided U-Pb zircon age of 2629 ±10 Ma, which is the oldest age for the domain to date. The sample also has evidence for a second generation of zircon growth between 2590 to 2560 Ma, as well as a lower intercept age of 1800 Ma. Corrigan (2001) identified the Swan River Complex, originally named Swan River gabbro by Stauffer et al. (1981), as a separate suite that intruded the Peter Lake Complex (Corrigan et al., 2000). It also includes alkaline intrusives such as the Patterson Island Pluton (MacDougall, 1987). The complex is characterized by layered mafic, ultramafic and intermediate rocks including pyroxenite, olivine gabbro, leucogabbro, anorthosite, and diorite, all of which contain primary igneous minerals and have been only weakly metamorphosed to uppermost greenschist facies conditions. A 2562 ±4 Ma U-Pb zircon age (Corrigan et al., 2001) from the Swan River Complex on Reindeer Lake is the only age date for intermediate to mafic plutonism in the Peter Lake Domain. The Campbell River Group (Lewry, 1976; Lewry et al., 1980; MacDougall, 1987) forms a narrow upper greenschist to lower amphibolite facies supracrustal belt that lies within a northeast-trending asymmetrical synform northwest of Spalding Lake. This low-grade succession includes slate, phyllite, sulphide-bearing argillite, quartz arenite, and Saskatchewan Geological Survey 3 Summary of Investigations 2002, Volume 2

4 Figure 3 - Summary of previous U-Pb geochronological results for the Peter Lake Domain. minor mafic volcanic rocks. Its inferred age is Archean, based on the presence of xenoliths that resemble Campbell River Group lithologies in neighbouring diorite of the Peter Lake Complex (Lewry et al., 1980; Macdonald and Thomas, 1983). A more detailed study of the Campbell River Group (MacDougall, 1987) distinguished additional units of banded calc-silicate quartzite, calc-pelite, anthophyllite amphibolite, calc-silicate amphibolite, and amphibolitic epiclastic rocks, along with several intrusive lamprophyres of mixed composition and a quartz diorite unit. A western extension of the Campbell River Group, comprising quartzite, black siltstone/argillite and pink arkose containing detrital grains of blue quartz, was noted by MacDougall (1988) along Highway 905. The Parker Lake Gneisses (Ray, 1975) are confined to the southwestern end of the domain, where they largely parallel the Needle Falls and Parker Lake shear zones. They are strongly foliated and sheared mafic to felsic rocks that are interpreted as sheared equivalents of the Peter Lake Complex (Lewry et al., 1980; Macdonald and Thomas, 1983). A mylonitic megacrystic quartz monzonite of the Parker Lake Gneisses provided a U-Pb zircon age of 2566 ±8 Ma (Rayner et al., in review), similar to the age of felsic plutonism for the Peter Lake Complex (Figure 3, Table 1). A quartz monzonite, collected southwest of Peter Lake in the centre of the domain, yielded a titanite age of 2529 ±4 Ma. The titanite is reported to be igneous looking (Annesley et al., 1992), but is here speculated to represent a late Archean high-grade metamorphic event. Saskatchewan Geological Survey 4 Summary of Investigations 2002, Volume 2

5 Table 1 - Summary of previous U-Pb geochronological results for the Peter Lake Domain. PLC, Peter Lake Complex; WB, Wathaman Batholith in the Peter Lake Domain; SRC, Swan River Complex; CLF, Courtenay Lake Formation; and PLG, Parker Lake Gneisses. Lithology NTS UTM-E UTM-N Pink granitic gneiss, PLC southwest of Crane Island, Reindeer Lake Feaviour Peninsula granite, WB Feaviour Peninsula, Reindeer Lake Gabbro pegmatite, SRC southwest of Crane Island, Reindeer Lake Mylonitic quartzofeldspathic gneiss, CLF Wollaston Domain, Courtenay Lake Foliated syenogranite, PLC near Courtenay Lake microwave tower Weakly deformed granite, PLC Highway 905, near kilometre 120??? Quartz diorite, PLC Taylor Lake Pink granitic gneiss, PLC southwest of Crane Island, Reindeer Lake Swan River gabbro, SRC McLean Bay, Reindeer Lake Quartz monzonite, PLC Highway 905, near kilometre 120 Mylonitic megacrystic granodiorite, PLG Highway 905, near kilometre Pink granitoid gneiss, PLC southwest of Crane Island, Reindeer Lake Fine-grained foliated gneiss, PLC Combe Lake Grey megacrystic gneiss, PLC southwest of Crane Island, Reindeer Lake Pink granitic gneiss, PLC southwest of Crane Island, Reindeer Lake U-P age (Ma) zircon U-P age (Ma) other Reference 64E ±5 Bickford et al. (1986) 64E /-2 Corrigan et al. (2001) 64E ±27 Bickford et al. (1987) 64E ± ±40 (garnet) Annesley et al. (1992) 64E / ±15 (titanite) Annesley et al. (1992) 64E ± ± ±10 74H-1 Van Schmus et al. (1987) 2538 ±10 Ray and Wanless (1980) 64E ±22 Bickford et al. (1987) 64E ± lower intercept Corrigan et al. (2001) 64E ± ±4 (titanite) Annesley et al. (1992) 64E ±8 Rayner et al. (in review) 64E ± ±4 overgrowth Rayner et al. (in review) 64E ±5 Rayner et al. (in review) 64E ±19 Bickford et al. (1987) 64E ± ±4 overgrowth Rayner et al. (in review) Two ages from the northern margin of the domain, one from within and another from approximately 400 metres to the northwest of its boundary with the Wollaston Domain, provide age of /-8 Ma and 2076 ±3 Ma, respectively. The latter sample, a garnet-bearing mylonitic quartzofeldspathic gneiss that was interpreted as being intrusive in origin, yielded an age identical within error to the 2075 ±2 Ma quartz-feldspar porphyry of the Cook Lake area (Ansdell et al., 2000). The latter high-level intrusive into the Courtenay Lake Formation was thought to record the initiation of rifting along the southeastern edge of the Hearne craton. A feldspar megacrystic syenogranite from the southern margin of the Peter Lake Domain on Reindeer Lake yielded a U-Pb zircon age of /-2 and was interpreted to belong to the Wathaman Batholith suite (Corrigan et al., 2001). It provides clear evidence that the southern margin of the domain is intruded by the Wathaman Batholith. Titanite and lower intercept ages for the felsic granitoid rocks vary between 1830 and 1800 Ma, probably a result of the thermotectonic overprint produced by the Trans-Hudson Orogeny. Growth of titanite suggests that lower amphibolite facies conditions must have been reached during this event. However, Rayner et al. (in review) found no evidence of Paleoproterozoic zircon growth in their Peter Lake Domain samples, suggesting that metamorphic grades remained below upper amphibolite facies conditions. 3. Results From Field Work The transect was mapped by a five-person crew between the beginning of June and the end of August. Access was provided by Highway 905, and from there by traversing on foot, as well as utilizing canoes and inflatable boats. The northern 20 km of the transect, between Courtenay Lake and Peter Lake, is characterized by exceptionally poor bedrock exposure and extensive, almost continuous glacial and fluvioglacial deposits. Traversing is easy, as the forest is open and dominated by >30 year old pine trees. A forest fire that burned for a few days at the end of June destroyed over one thousand hectares of forest east and northeast of Combe Lake. The southern 20 km of the transect, between Peter Lake and the Wathaman River has a higher proportion of exposure, with moderate amounts of glacial and fluvioglacial overburden. Here, however, the forest was burnt in a huge fire in The deadfall and new growth made traversing on foot very difficult and slow. Saskatchewan Geological Survey 5 Summary of Investigations 2002, Volume 2

6 Several southwest-trending eskers transect the map sheet. The biggest intersects the south-central part of Peter Lake, another is north of Findlay Lake, and a third is half way between Warner and Robson lakes. Most glacial striations and chatter marks are oriented between 218º and 222º. An older set of glacial striae at 170º to 190º was observed in several locations. a) Peter Lake Domain The area can also be geologically subdivided into northern and southern components. The poorly exposed northern part is dominated by coarse-grained, massive to weakly foliated syenogranite and leucocratic syenogranite, with minor diorite, gabbro, and late mafic dykes (Figure 4). The preliminary 1: scale map of the southern part of the transect displays a complex plutonic terrain characterized by highly flattened units of quartz diorite to gabbro, monzonite to granite, minor migmatitic supracrustal screens, and an outlier of the low-grade Campbell River Group (Figure 4). There is no obvious change in rock types, proportion of rock types, or degree of deformation between Peter Lake and the Wathaman River, although the strain generally increases from north to south. Belts of intense deformation and mylonitization were also observed just south of Peter Lake. All plutons are highly flattened at map scale. Strain is heterogeneous and generally restricted to the marginal zones of the plutons, so that large bodies may appear unstrained and massive internally, but have mylonitized margins. The margins are also commonly characterized by complex intrusive relationships, which were transposed during shearing leading to layered or gneissic outcrop appearances. Due to the scale of mapping, however, we were able to distinguish individual rock types or combine outcrops of multiple lithologies into distinct units. Therefore, the previously used distinction between rocks of the Peter Lake Complex and Parker Lake Gneisses (Ray, 1975; Lewry et al. 1980) was revised. Most intrusive rocks described below form part of the Peter Lake Complex. All rock names for intrusive rocks follow Streckeisen s (1976) recommendations on the classification of plutonic rocks. Mineral percentages were estimated in the field and assigned sample names and were later verified with the help of a petrographic microscope. Classification of clastic sedimentary rocks follows the recommendations of Maxeiner et al. (1999). The prefix meta- is not used, as all of the rocks have been metamorphosed at greenschist to amphibolite facies. Only selected units and important observations and relationships are described in detail in this paper. For comprehensive and systematic descriptions of all units, the reader is referred to the legends of the accompanying maps. Love Lake Leucogabbro One of the largest mafic intrusions between Peter Lake and Love Lake is the Love Lake Leucogabbro 2. This ovoid pluton was mapped over an area of about 5 km by 10 km, but based on aeromagnetic data and previous mapping it extends further east for at least an additional 10 km. On the basis of published descriptions, Love Lake Leucogabbro appears similar to the 2.56 Ga Swan River Complex on Reindeer Lake (Corrigan et al., 2000). The Swan River Complex, however, intrudes the surrounding granitoid rocks, whereas the Love Lake Leucogabbro appears to predate surrounding granitic rocks in the Peter Lake area. The pluton comprises many different phases, but is dominated by leucogabbro. Minor components include pyroxenite, melagabbro, gabbro, gabbronorite, olivine gabbro, anorthosite, and diorite, as well as microgabbro and microdiorite. The main leucogabbroic phase of the pluton is medium grained, weathers a characteristic light bluish grey and is dark grey on fresh surface. It comprises plagioclase, amphibole, relict clinopyroxene, biotite, magnetite, pyrite, and hematite. Mafic mineral content generally varies between 15 and 25%, with magnetite typically accounting for at least 5% of that. The bluish weathering colour is due to the Ca-rich nature of the plagioclase (labradorite). Amphibole occurs both as relict igneous grains and as secondary metamorphic minerals replacing clinopyroxene and primary hornblende. Magnetite is commonly hematized and pyrite is ubiquitous, but rarely exceeds 1%. Primary igneous layering (Figure 5) was observed at only one locality, close to the northern margin of the pluton (UTM-E: ; UTM-N: ), where layers of anorthosite and gabbro alternate at 1 to 5 cm intervals. At several places, the gabbro contains abundant inclusions, which vary in diameter from decimetre to metre scale, in shape from angular to rounded, and in composition from mafic to ultramafic (Figure 6). Most of the inclusions are fine grained, locally feldspar porphyritic and some are possibly amygdaloidal. They have sharp contacts and some 2 Informal names appear in italics where first mentioned; the italics are subsequently dropped. 3 All UTM coordinates in this paper are given in NAD83. Saskatchewan Geological Survey 6 Summary of Investigations 2002, Volume 2

7 Figure 4 - Simplified geological map for the Peter Lake transect; references U-Pb age date locations can be found in Table 1; numbered locations refer to mineral occurrences described in text. Saskatchewan Geological Survey 7 Summary of Investigations 2002, Volume 2

8 are fractured and invaded by the leucogabbroic host. Some of the more ultramafic inclusions are rounded and display reaction rims, possibly indicating that they have been within the melt for a longer period of time (Figure 7). Based on these observations, the inclusions are interpreted as xenoliths rather than autoliths. One of the gabbroic units near the southern margin of the pluton contains primary orthopyroxene, clinopyroxene, and minor biotite and can be properly classified as a gabbronorite. Most of the orthopyroxene grains are rimmed by cummingtonite, as a result of subsequent amphibolite facies metamorphism. To the north, the Love Lake Leucogabbro is intruded by a large syenogranite pluton named the Robinson Lake Monzogranite (Ray, 1980). Along Highway 905, the Love Lake Leucogabbro is in contact to the north with fine-grained porphyritic volcanic or subvolcanic mafic rocks (unit Mv), which it probably intruded. Deformation is generally very weak. Most exposures of the leucogabbro are massive, but a weak flattening fabric defined by the alignment of mafic minerals locally trends east-west, parallel to the main regional foliation. Igneous layering, observed at one locality, also trends parallel to the main foliation. Some of the fine-grained mafic xenoliths appear to have a tectonic fabric, which predated emplacement of the pluton (Figure 6). Eastward towards the Johnson River, the pluton is cut by a pink leucogranite sheet, which has a northerly to northeasterly trend and foliation. Small shear zones within the Love Lake Leucogabbro also have northeasterly strike. Figure 5 - Primary igneous layering in the Love Lake Leucogabbro; alternating layers of anorthosite (white) and gabbro (dark grey); UTM-E: , UTM-N: Warner Lake Gabbroic Suite Several highly flattened composite intrusions varying in composition from pyroxenite to diorite are exposed between the Love Lake Leucogabbro and the Parker Lake Shear Zone. There are at least five separate dioritic to gabbroic belts, which are 200 to 400 m thick and continuous for more than 10 km along strike. These, and the Love Lake Leucogabbro, may have originally all been part of the same intrusive complex, which was later invaded by granitoid magmas and subsequently deformed. Figure 6 - Angular to subangular inclusions in leucogabbro of the Love Lake Leucogabbro; note the differing composition, texture, and foliations in these xenoliths; UTM-E: ; UTM-N: These intrusions are dominated by fine- to mediumgrained salt and pepper diorite, which is massive to strongly foliated and locally mylonitic. Main constituents are plagioclase, hornblende, biotite, epidote, and magnetite, with minor quartz, titanite, sulphides, and carbonate. The mafic mineral content varies between 20 and 35%. The gabbroic rocks are similar to the diorite, but typically have a mafic mineral content of around 50%. In contrast to the Love Lake Leucogabbro, plagioclase in these intermediate to mafic rocks is generally white weathering likely due to a low An-content (oligoclase and andesine). The magnetite content of the diorite and gabbro is highly variable. Locally, they contain up to 5% magnetite and have magnetic susceptibilities similar to Figure 7 - Round ultramafic xenolith displaying a reaction rim at contact with the host leucogabbro; Love Lake Leucogabbro; UTM-E: ; UTM-N: Saskatchewan Geological Survey 8 Summary of Investigations 2002, Volume 2

9 those of the Love Lake Leucogabbro (i.e., 30 to 100x 10-3 SI); more typically they have magnetic susceptibilities of between 0.5 and 1 (x10-3 SI). The Warner Lake gabbroic suite is more deformed than the Love Lake Leucogabbro. The units are generally strongly flattened, most minerals are recrystallized, and primary textures are rarely preserved. Xenoliths of finegrained amphibolite and psammitic rocks are locally abundant. One of several examples of primary igneous layering is exposed at kilometre 118 on the eastern side of Highway 905 (UTM-E: ; UTM-N: ). Layering is on a scale of 1 to 5 cm and alternates between thinner anorthositic to dioritic and thicker gabbroic layers (Figure 8). In another part of the same outcrop, the gabbro is cut by late anorthositic veins (Figure 9). Most of the ultramafic rocks are highly recrystallized and largely amphibolitized. Some relict igneous minerals have been locally preserved; varieties of ultramafic rocks include olivine websterite and clinopyroxenite. Figure 8 - Primary igneous layering (262/85) in a gabbroic unit that transects Highway 905 at kilometre 118; UTM-E: ; UTM-N: Combe Lake Dioritic Suite Homogeneous, massive to weakly foliated dioritic to gabbroic intrusions occur in an 8 km long and 2 km wide belt that stretches along the Johnson River and through the central part of Combe Lake. They are typically medium grained, black and white weathering, yellowish to brownish grey on fresh surface, and friable due to sericitized plagioclase. Sodic plagioclase and hornblende dominate; minor constituents include epidote, titanite, biotite, and opaque minerals. Locally, there are gabbroic to dioritic pegmatite phases. The magnetic susceptibility is significantly lower than in the Love Lake Leucogabbro, typically varying between 0.3 and 0.7 (x10-3 SI). Locally, the gabbroic rocks grade into amphibolitized pyroxenite. No relict pyroxene or olivine were observed. Intrusive relationships between the dioritic and gabbroic phases are generally obscured, but in several outcrops they appear gradational into one another. No primary features were observed. The Combe Lake dioritic suite is cut by leucogranite sheets. Near the southern boundary, are two generations of mafic dykes, a feldspar and hornblende porphyritic set and a later aphanitic set. Both predate the main deformational event and are transposed. Some of these dykes have very high magnetic susceptibilities (e.g., 40x10-3 SI). Gneissic Quartz Diorite and Granodiorite Figure 9 - Intrusion breccia with late-stage anorthositic veins cutting massive homogeneous gabbro; eastern side of Highway 905 at kilometre 118; UTM-E: ; UTM-N: North of the Wathaman River is an approximately 3 km wide belt of intensely foliated and in part mylonitized orthogneisses. Outcrops in this belt generally contain multiple transposed rock types, including diorite, quartz diorite, granodiorite, and rare gabbro. There are also some fine-grained dark grey amphibolitic to biotitic components that may be of supracrustal origin. At the current scale of mapping, these orthogneisses were treated as a composite unit. They are the only rocks that appear similar to the Parker Lake Gneisses (Ray, 1975). Saskatchewan Geological Survey 9 Summary of Investigations 2002, Volume 2

10 Most of the rocks within this belt are heterogeneous and strongly variable in colour, grain size, composition, and texture. Layering is on a centimetre to decimetre scale, and locally folded. White to light pink feldspar porphyroclasts, between 0.5 and 1 cm in diameter, are common; locally there are hornblende porphyroblasts (Figures 10 and 11). Inclusions are also relatively common and some have a foliation which is oblique to the gneissosity (Figure 12), which led Ray (1980) to propose early deformation predating movement of the Parker Lake Shear Zone. Lewry et al. (1980), however, were unable to find conclusive evidence for deformation predating the shear zone, and interpreted the inclusions as tectonic fish that represent early stages of progressive strain rather than an earlier fabric. Partly porphyroclastic granodiorite generally intrude the dioritic to quartz dioritic phases within this orthogneiss belt, but are also strongly foliated to mylonitic. One such intrusion, the Warner Creek granodiorite, exposed at kilometre 108 on Highway 905, yielded a U- Pb zircon age of 2566 ±8 Ma (Rayner et al., in review; Table 1). Figure 10 - Feldspar porphyroclastic granodiorite gneiss overgrown by hornblende blasts; UTM-E: ; UTM-N: Many outcrops in this belt also contain massive to mylonitic monzonitic to quartz-monzonitic rocks, which are partly megacrystic (Figure 11). These rocks are probably related to the 1.86 Ga Wathaman Batholith, but some of these megacrystic rocks could also be Archean. Monzonitic Intrusive Suite A suite of monzonite, quartz monzonite, and monzodiorite intrudes the Warner Lake gabbroic suite and the gneissic quartz diorite to granodiorite suite. One of the main intrusions is on the eastern shore of Warner Lake. The suite is dominated by monzonitic rocks, but locally grades into quartz-monzonite with up to 10% quartz. Gradation into more syenitic and monzodioritic varieties is common. Generally the rocks are pink to grey, coarse-grained, massive to mylonitic, and commonly megacrystic. The mafic mineral content varies between 10 to 20%, and is dominated by biotite with minor amounts of epidote, hornblende, and titanite. Distinct units of megacrystic quartz monzonite are generally characterized by 10 to 15% quartz. Pink K-feldspar megacrysts up to 3 cm long compose up to 30% of the rock and generally define a tectonic foliation (Figures 13 and 14). Figure 11 - A K-feldspar megacrystic quartz monzonite (related to Wathaman Batholith?) cutting a gabbro; UTM-E: ; UTM-N: Most of the supracrustal remnants (see below) of the Peter Lake Domain are associated with and intruded by this monzonitic suite. The suite is post-dated by pink to brick-red granites (Figure 13), as well minor mafic dykes. Granitic Rocks Leucogranitic and syenogranitic plutons, in part megacrystic, underlie most of the area between Peter Figure 12 - Feldspar porphyroclastic quartz-diorite gneiss with a foliated xenolith; foliation in xenolith represents early fabric development during progressive strain ( tectonic fish ), rather that a pre-existing fabric; UTM-E: ; UTM-N: Saskatchewan Geological Survey 10 Summary of Investigations 2002, Volume 2

11 Lake and Courtenay Lake, and also occur as late intrusive sheets and dikes in the area between Peter Lake and the Wathaman River (in part indicated by cross-hatching on the map in the accompanying map package). Large plutons of coarse- to very coarse-grained syenogranite were delineated on northern Peter Lake, northern Combe Lake, northwestern Vollman Lake, and immediately south of the Love Lake Leucogabbro. Most of these bodies contain biotite and epidote, with only minor amounts of hornblende in a few outcrops. Some textural variations exist. Figure 13 - Foliated megacrystic monzonite cut by brick-red granite; UTM-E: ; UTM-N: Figure 14 - Close-up of typical non-megacrystic monzonite; UTM-E: ; UTM-N: The Vollman Lake syenogranite is coarse to very coarse grained and locally megacrystic, with up to 2 cm long pink microcline crystals. It typically contains 25 to 30% coarse interstitial quartz, and up to 10% mafic minerals comprising biotite, chlorite, and magnetite. One outcrop contains minor amounts of purple fluorite, largely located on late fractures. The granite is generally well foliated and because of its megacrystic nature has a distinct augen texture. It is intruded by mafic dykes, and by late granitic pegmatite sheets, which are in part transposed and sheared. The western margin of the granite is cut by northeast-trending shear zones, which are likely related to the Needle Falls Shear Zone. The coarse- to very coarse-grained syenogranite underlying large parts of northern Combe Lake is characterized by 30 % quartz, and up to 15% mafic minerals. In contrast to the Vollman Lake syenogranite, it contains hornblende as well as biotite, is generally less deformed, and equigranular. Another distinctive feature of this body, which was observed on many outcrops, is its seriate texture with gradational grain size variation from medium (1 to 2 mm) to very coarse (up to 2 cm). A geochronology sample of a fine-grained foliated gneiss from Combe Lake appears to have been collected within the confines of this intrusion and yielded a U-Pb zircon age of 2580 Ma ±5 Ma (Rayner et al., in review; Table 1; Figure 4). The syenogranite underlying most of Peter Lake is tentatively correlated with Ray s (1980) Robinson Lake monzogranite. It is pink to brick red, coarse grained, homogeneous, and massive to weakly foliated. It contains up to 10% biotite and minor amounts of magnetite. Local mylonite zones cause the development of an augen texture. The granite immediately south of the Love Lake Leucogabbro was dated by Annesley et al. (1992) and yielded a U- Pb zircon age of 2566 Ma ±2 Ma and a titanite age of 2529 Ma ±4 Ma. Emplacement of leucogranite was one of the last intrusive events. South of Warner Lake, a medium-grained leucogranite cuts megacrystic quartz monzonite as well as monzodioritic to dioritic gneisses. On Combe Lake, several sheets of leucogranite cut the Combe Lake dioritic suite. The Love Lake Leucogabbro is also intruded by several leucogranite sheets, one of which is north trending and in part aplitic. Leucocratic Fluorite-bearing Syenogranite A leucocratic syenogranite, between Courtenay Lake and Vollman Lake at the northern end of the map area, is locally fluorite bearing and possibly of a peculiar age. Its northwestern margin is highly strained and cut by an extension of the Needle Falls Shear Zone, which obscures the relationship between the Peter Lake and Wollaston domains. A foliated syenogranite collected within the confines of this unit (outcrop was not observed by the present authors) yielded a U-Pb zircon age of /-8 Ma and a titanite age of 1809 ±15 Ma (Annesley et al., 1992). Although the precision of the zircon age is poor, it is similar to two other ages, which were obtained only a few kilometres to the north within the Wollaston Domain. Therefore, the age is considered broadly accurate and the Saskatchewan Geological Survey 11 Summary of Investigations 2002, Volume 2

12 pluton may represent the intrusive root to rift-related quartz-feldspar porphyries in the Courtenay Lake Formation of the Wollaston Domain (Delaney et al., 1997; Ansdell et al., 2000). Campbell River Group A 1.5 km long and 200 m thick north-dipping monoclinal sequence of quartzitic to argillaceous sedimentary rocks, which lies between quartz monzonite bodies of the Peter Lake Complex, is correlated with the Campbell River Group. The unit is exposed at kilometre 111 on Highway 905, in a low-lying area between two muskegs. A series of large outcrops provides good exposures for several hundred metres to the west of the highway. Further west, outcrops are fewer, and generally bound to topographically higher areas, which are interspersed with numerous areas of felsenmeer and block fields in the low-lying regions. One hundred metres to the east of the highway, the Campbell River Group is covered by muskeg and glacial deposits. As part of a B.Sc. investigation undertaken by Rebecca Hunter, a 100 by 150 m large outcrop alongside the highway was chosen for detailed mapping and several stratigraphic sections were completed. Two additional sections were completed from outcrops approximately 1.0 and 1.4 km west of the highway. Based on these sections and the detailed map, four units were defined (Figure 15). All units show consistent stratigraphic top indicators to the north and an overall fining-upward succession. Unit 1 consists primarily of a very fine-grained, ripplelaminated feldspathic arenite, with minor cross-bedded lenses of coarse- to very coarse-grained quartz arenite and alternating 1 to 10 cm thick argillaceous beds. Blue quartz grains, up to 5 mm in diameter are common in the Figure 15 - Schematic cross-section through the Campbell River Group near quartz arenite beds (Figure 16). Highway 905. Measurements from 20 rippled foresets (Figure 17) in Unit 1, yielded a unimodal east-southeast-trending (Figure 18) paleocurrents direction. Unit 2 consists of coarse- to very coarse-grained quartz arenite with a few wavy, irregular argillite beds, between 1 and 5 cm thick. Bedding within this unit is disturbed due to soft sediment deformation between the quartz arenite and argillaceous layers. Unit 3 is an argillite with distinct 3 to 25 cm thick crossbedded quartz arenite lenses, displaying scoured bases. Also present are 1 to 3 mm, wavy laminated quartz arenite layers showing truncated surfaces, which confirm a way-up direction to the northwest. The unit is further characterized by soft-sediment deformation in the form of load casts, and ball-and-pillow structures. Figure 16 - Pebbly layer in quartz arenite of Unit 1 with brown, grey, and blue quartz pebbles up to 5 mm in diameter; UTM-E: ; UTM-N: The top of the exposed succession (Unit 4) is mainly an argillaceous unit with minor coarse-grained quartz arenite beds ranging from 2 to 5 cm thick. Unit 4 lacks Saskatchewan Geological Survey 12 Summary of Investigations 2002, Volume 2

13 Figure 17 - Rippled foresets in quartz arenite beds of Unit 1; stratigraphic top towards top of photo; UTM-E: ; UTM-N: the cross-bedded and laminated quartz arenite beds that are characteristic of Unit 3. In felsenmeer southwest of the large highway outcrop, angular blocks (20 to 80 cm in diameter) of pebbly feldspathic wacke with flattened pebbles of quartz and feldspar (2 to 10 mm in diameter) were observed, along with coarse- to very coarse-grained feldspathic arenite to subarenite. The latter are similar to the sub-arenite of Unit 1. The pebbly feldspathic wacke, though not observed in outcrop, may represent a coarse basal unit stratigraphically underlying Unit 1. The stratigraphic sections of the Campbell River Group quartzite (Figure 15) reveal a fining upward sequence beginning with a pebbly, possibly channeled base, overlain by rippled beds with east-southeast-directed paleocurrents and ending with primarily argillaceous beds exhibiting load casts and ball-and-pillow structures. This depositional sequence may be consistent with a prodeltaic depositional environment, an interpretation that is strengthened by recognizing that, in the east, the group comprises a primarily fine-grained and euxinic sedimentary sequence, including argillite, pelite and sulphidic mudstone (MacDougall, 1987). This suggests lower sedimentation rates and anoxic, deep-water conditions. Contacts between the Campbell River Group and surrounding quartz monzonite bodies of the Peter Lake Complex are not exposed. Close inspection of the plutonic rocks provided no evidence of Campbell River Group xenoliths, although MacDougall (1987) and Lewry et al. (1980) speculate on the presence of such xenoliths. Also, no intrusive rocks were observed on any of the Campbell River Group outcrops; based on our observations an intrusive relationship therefore seems unlikely. A faulted contact is suggested by high-strain gradients from massive to mylonitic in the adjacent quartz monzonite bodies. Although we prefer an allochthonous origin for the Campbell River Group, other models may have to be entertained as more geochronological data become available. Also, an assessment of metamorphic conditions within the group compared to those of the surrounding rocks is needed. Other Supracrustal Rocks Figure 18 - Paleocurrent data for Unit 1 of the Campbell River Group. Xenoliths of supracrustal rocks occur in some of the intrusions, particularly the Love Lake Leucogabbro, and also as isolated outcrops and small dismembered units, particularly between Love Lake and Warner Lake. In contrast to the Campbell River Group, all have been metamorphosed at upper amphibolite facies conditions. They comprise, in order of decreasing abundance, migmatitic pelite to psammite, amphibolite derived from mafic volcanic rocks, felsic volcanic rocks, quartzite, iron formation, and polymictic conglomerate. Saskatchewan Geological Survey 13 Summary of Investigations 2002, Volume 2

14 One unit of psammopelitic to pelitic migmatite is about 200 m thick and extends for about 2 km along strike, and is transected by Highway 905 just north of kilometre 118. It is enclosed by dioritic to gabbroic rocks of the Warner Lake gabbroic suite. Up to 50% of the unit is composed of a tonalitic leucosome that locally has plagioclase porphyroblasts. Layering, caused by the transposition of locally generated medium- to coarse-grained tonalitic leucosome, biotite-rich melanosome, and a fine- to medium-grained biotite-rich paleosome, is generally complexly folded and injected by younger leucosome (Figure 19). Minor garnet and/or cordierite is locally present. Quartz veining is prevalent on some of the outcrops, but certain quartz-rich layers may be sedimentary in origin. Up to 20% of the unit is made up of fine-grained amphibolite. These are generally internally homogeneous, but display agmatitic textures (Figure 20) due to injection by tonalitic leucosome generated in the neighbouring pelitic migmatite. The amphibolite derives either from intermediate to mafic volcanic rocks or from dykes, and predates the migmatization. Along strike, this mixed unit of pelitic migmatite and amphibolite passes into leucotonalitic diatexite, which is generally white weathering, medium- to coarse-grained and composed of plagioclase, quartz, and biotite. Migmatitic sedimentary rocks are also exposed approximately 6 km southeast of those previously described. One 20 by 20 m heterogeneous outcrop comprises a complexly folded succession of fine-grained migmatitic psammite, calcic psammopelite, impure quartzite, intermediate volcaniclastic rocks, and minor silicate-facies iron formation. Biotite, garnet, and hornblende are the main aluminium silicate minerals. The silicate-facies iron formation is thinly laminated, with alternating layers of chert, magnetite, and quartzofeldspathic rock, as well as garnet-quartz pods up to 10 cm in diameter and containing up to 50% garnet. Partial melting has produced a hornblende-plagioclase-rich leucosome in the intermediate rocks and a plagioclase-quartz-garnetbearing leucosome in the psammitic to psammopelitic rocks. Subsequently, these were intruded by sheets and dykes of diorite and granodiorite. One isolated outcrop of polymictic pebble conglomerate and psammite lies along strike with some of the migmatitic psammopelite units. It is located approximately 2 km northeast of Highway 905 and is about 10 by 2 m in maximum dimensions. Layering is parallel to the main foliation. At the structural base of the succession, a several metre thick layer of polymictic conglomerate is exposed. It is composed of generally 1 to 2 cm long, highly flattened pebbles of light grey felsic volcanic rocks, minor fine-grained black mafic rocks, and pink feldspar, set in a fine-grained psammitic matrix. Rarely, clasts reach 10 cm in length and one of these is internally folded. Structurally and possibly stratigraphically overlying the conglomerate are grey- to buff-weathering, fine- to very fine-grained strongly foliated quartzofeldspathic rocks of possible psammitic derivation. A fine-grained plagioclase-phyric mafic rock (Figure 21) occurs immediately north of the Love Lake Leucogabbro, and is interpreted as volcanic in origin; xenoliths of this unit can also be seen within the Love Lake leucogabbro. Several other units of fine-grained amphibolite occur throughout the area, but are texturally nondescript. Some may derive from intermediate to mafic volcanic rocks; others may represent sheared equivalents of dykes or may have dioritic to gabbroic protoliths. Two outcrops of fine-grained felsic rocks, interpreted as volcanic in origin are exposed in the Peter Lake area; one in Delorme Bay, and the other between Peter Lake Figure 19 - Migmatitic psammopelite and amphibolite; in situ melting, but also later injection of leucosome; UTM-E: ; UTM-N: Figure 20 - In situ melting of pelite (below pencil) produces leucosome; derived melt leucosome gets injected into amphibolite (above pencil), producing agmatitic texture; outcrop on Highway 905; UTM-E: ; UTM-N: Saskatchewan Geological Survey 14 Summary of Investigations 2002, Volume 2

15 Figure 21 - Plagioclase-phyric mafic rock of presumed volcanic origin; outcrop along Highway 905; UTM-E: ; UTM-N: and the Wathaman River, roughly on strike with, and 2 km to the northeast of, the Campbell River Group outcrops. The Delorme Bay lakeshore outcrop is about 8 by 8 m in maximum dimensions and is characterized by a layered and foliated succession containing dacitic tuff breccia, laminated volcaniclastic rock, feldsparporphyritic dacite, and aphanitic rhyodacite. All are light grey to beige weathering, and have a very finegrained felsic matrix containing about 5% biotite, as well as minor amounts of muscovite and epidote. Isolated zones on the outcrop contain up to 5% garnet, likely an affect of alteration. Layering is on a scale of 50 cm and on a centimetre scale in the laminated volcaniclastic interval. One example of cross-bedding in this interval suggests a reworked, rather than primary, volcanic origin. The tuff breccia may be of pyroclastic origin and the feldspar-porphyritic component likely has a subvolcanic precursor. The depositional environment suggested by this succession is shallow water, proximal to a felsic volcanic centre. The second outcrop, about 20 by 20 m in diameter, comprises medium-grey to light pinkish grey, very fine-grained dacitic and rhyolitic rocks. These rocks contain 20 to 30% quartz, up to 15% (dacite) to 40% (rhyolite) K-feldspar, plagioclase, and minor amounts of biotite, muscovite, and opaque minerals. No primary features are preserved. Several isolated examples of fine-grained pink quartzofeldspathic gneisses predating emplacement of quartz monzonitic and monzonitic intrusions are exposed between Warner Lake and the Wathaman River. These gneisses are of presumed supracrustal origin. b) Wollaston Domain and Needle Falls Shear Zone A small 1 km 2 area of the Wollaston Domain east of Courtenay Lake was mapped to better understand the contact relationship between the Wollaston and Peter Lake domains. This area was previously mapped by Scott (1970) at 1:10 000, Coombe (1994), and more recently by Delaney et al. (1997), who produced a series of schematic crosssections. Our mapping identified the following components of the Courtenay Lake Formation (Scott, 1970; Delaney et al., 1997): cross-bedded feldspathic psammite, intraformational polymictic boulder conglomerate, fine-grained garnetiferous feldspar-porphyritic dacite, highly magnetic mixed amphibolite (in part amygdaloidal or pillowed, but largely of ambiguous origin), and minor impure partly garnetiferous quartzite. Bedding dips and faces generally to the northwest, but as the Peter Lake Domain is approached, folding results in east-dipping bedding planes. Schistosity defined by biotite and muscovite dips consistently to the east, irrespective of the fold limb and therefore must post-date this folding event. The schistosity steepens to subvertical within mylonite zones as the Needle Falls Shear Zone is approached. The highly strained contact between the Wollaston and Peter Lake domains in the Courtenay Lake area likely represents a northeastward continuation of the Needle Falls Shear Zone. The eastern extent of the Wollaston Domain includes sheared varieties of feldspathic psammite (muscovite-biotite gneiss), impure quartzite, and microdiorite. The western extent of the Peter Lake Domain is marked by a pink, fine-grained, homogeneous, mylonitic leucogranite containing biotite and minor muscovite. It grades easterly into a relatively homogeneous, pink, medium-grained equigranular, leucocratic, biotite syenogranite. Further northeast, in the Cook Lake area, MacNeil et al. (1997) recognized an unconformity between the Courtenay Lake Formation and rocks of the Peter Lake Domain including leucogranite and variably granitized quartzofeldspathic paragneiss. c) Wathaman Batholith and Parker Lake Shear Zone The Wathaman Batholith is on the southeast side of the Peter Lake Domain and is overprinted by the Parker Lake Shear Zone. The batholith is here represented by protomylonitic to ultramylonitic megacrystic quartz monzonite. Tectonic layering is on a scale of 10 to 50 cm and is defined by the degree of megacryst preservation, with protomylonitic layers containing more than 50% relict megacrysts and ultramylonitic layers containing less than 10% megacrysts. There are both gradational with sharp contacts between layers. Some of the layers are fine-grained Saskatchewan Geological Survey 15 Summary of Investigations 2002, Volume 2

16 quartz monzonite to leucogranite, without any apparent relict feldspar megacrysts, but with highly ribboned quartz. In such cases, the sharp contact with neighbouring megacrystic quartz monzonite cannot simply be explained by variable strain, but rather has to reflect a primary compositional variation (e.g., transposed dykes). A weak subhorizontal stretching lineation is seen on some of the outcrops. Extensional shear bands and winged porphyroclasts indicate a dextral sense of shear, consistent with previous interpretations (Lafrance and Varga, 1996). Late brittle deformation has resulted in widespread cataclasis, which can be observed on many of the outcrops lying in the Parker Lake Shear Zone. 4. Economic Geology and Geochemistry Table 2 contains new whole-rock geochemical data. No interpretation is provided at this time. Tables 3 and 4 show analyses of grab samples to test for the presence of gold, copper, and PGEs. One previously recognized copper showing on Combe Lake (SMDI 545) was examined, and a new occurrence was discovered during the summer (see below). Slightly elevated PGE concentrations were encountered in several of the analyzed samples of maficultramafic rocks (Table 4); interestingly, one (sample RM ) is located along strike of the newly discovered copper occurrence. A preliminary general assessment of the western portion of the Peter Lake Domain suggests a potential for coppernickel and possibly PGE mineralization within the Warner Lake gabbroic suite. The Love Lake Leucogabbro lies along strike and likely hosts the Cu-Ni-PGE showing discovered by SMDC in 1982 (SIR assessment file 64E ), approximately 20 km east-northeast of Love Lake in the Korvin Lake area. A systematic geochemical survey of this pluton may detect additional prospective areas. The presence of primary igneous layering within the pluton, albeit sporadic, is encouraging. a) Disseminated Sulphide Occurrences Several new sulphide occurrences were discovered. Occurrence #1 is located approximately 3 km northeast of the Warner Lake gravel pit (Figure 4) and approximately 100 m north and within sight of a small unnamed lake (UTM- E: ; UTM-N: ; ±6 m). It is exposed in a small 1 m 2 outcrop of gabbroic to pyroxenitic rocks at the side of a small ridge. The rock is fairly heterogeneous and completely amphibolitized, with strongly varying mafic mineral content. Minor east-west-trending shear zones are present. Hand samples from this outcrop contain 5 to 10% disseminated sulphides, comprising predominantly pyrrhotite (5%), with minor amounts of chalcopyrite (1%), pyrite (1%), and azurite (trace). The magnetic susceptibility is fairly low (i.e., an average of 0.5x10-3 SI). An analysis of a grab sample (RM ) has slightly elevated concentrations of Au, Pt, Pd, Cu, and Ni (Tables 3 and 4). Nearby outcrops of gabbroic to pyroxenitic rocks only contain trace amounts of sulphides. Along the lakeshore, south and structurally below the gabbro, are felsic mylonites. These are likely related to a belt of granitic to granodioritic rocks, which post-date the gabbro and were later mylonitized. Two kilometres west of this occurrence, within the same belt of dioritic to gabbroic rocks, is a weakly mineralized gabbroic to ultramafic rock with up to 2% disseminated pyrite, pyrrhotite, and chalcopyrite. An analysis of a grab sample of gabbro has no enrichment of PGEs (Table 4). A clinopyroxenite (occurrence #2; Figure 4), which also forms part of the Warner Lake gabbroic suite, containing minor amounts of disseminated pyrite, magnetite and chalcopyrite was sampled on north Warner Lake (RM ) and gave slightly elevated PGE concentrations (Table 4) and strongly enriched Cr concentration (Table 2). Still in the same belt, quartz dioritic to gabbroic rocks on the western shore of Warner Lake, contain minor amounts of disseminated pyrite and chalcopyrite. These rocks have also been affected by shearing and silicification in the form of minor quartz veins. Millimetre-sized pyrite cubes are associated with these quartz veins and within mylonitic section. Two grab samples of these sheared rocks were analyzed (sample RM ) and revealed no significant concentrations of gold or copper (Table 3). A small outcrop of ultramafic actinolite schist (occurrence #3; Figure 4) forms part of a larger unit of ultramafic rocks in the hanging wall of the Campbell River Group. The ultramafic rocks are interpreted to be of intrusive origin. A sample of the actinolite schist (RH ) was analyzed and had elevated concentration of Au, Ag, and Cu (Tables 3 and 4). Saskatchewan Geological Survey 16 Summary of Investigations 2002, Volume 2

17 Table 2 (continued) - Whole-rock major and trace elements geochemical data for selected grab samples; analyses obtained from Activation Laboratories Ltd.; negative values equal not detected at that lower limit; abbreviations: sul, sulphide; py, pyrite; cpy, chalcopyrite; mt, magnetite; and ht, hematite; percentage given reflects total opaque mineral content. Sample ID RM RM RM RM RM RM RM RM RM RM RM Field description Intermediate Gabbro Sheared gabbro Quartzdiorite Leucogabbro Amphibolitized Actinolite schist Pyroxenite Leucogranite Quartz- Granite volcanic? clinopyroxenite Monzonite Wakefield Lake S Warner Lake S Peter Lake General area Highway 905 ~ kilometre 111 N of Gravel Pit Warner Lake Warner Lake Highway 905 ~ kilometre 124 Warner Lake Wathaman River SW Warner Lake UTM - E (NAD 83) UTM - N (NAD 83) (in wt %) SiO TiO Al2O Fe2O3 (tot) MnO MgO CaO Na2O K2O P2O L.O.I Total (in ppm) Cr , Ni Co Sc V Cu Pb Zn Bi Sn Rb Cs Ba 1, ,020 1, , Sr Tl Ga Ge Ta Nb Hf Zr Y Th U La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Saskatchewan Geological Survey 17 Summary of Investigations 2002, Volume 2

18 Table 2 (continued) - Whole-rock major and trace elements geochemical data for selected grab samples; analyses obtained from Activation Laboratories Ltd.; negative values equal not detected at that lower limit; abbreviations: sul, sulphide; py, pyrite; cpy, chalcopyrite; mt, magnetite; and ht, hematite; percentage given reflects total opaque mineral content. Sample ID RM RM RM RM RM RM RM RM RM RM RM Field description Gnt-bearing feldspathic psammite General area East Courtenay Lake Strongly fol. leucogranite w diss. pyrite East Courtenay Lake Leucogabbro w diss. pyrite plus magnetite Leucogabbro w diss. sulphides and magnetite Love Lake area South of 'Ziggy Lake' Diorite Fine-grained amphibolite Gabbro w 2% diss. py, po, cpy (SMDI 545) Love Lake area East of Love Lake Combe Lake Highway 905 ~ kilometre 117 Granodiorite Quartz-monzonite Granite Megacrystic monzonite Highway 905 ~ kilometre 114 Highway 905 ~ kilometre 121 Highway 905 ~ kilometre 113 UTM-E (NAD 83) UTM-N (NAD 83) (in wt %) SiO TiO Al2O Fe2O MnO MgO CaO Na2O K2O P2O L.O.I Total (in ppm) Cr Co Sc V Bi Sn Rb Cs Ba Sr , , Tl Ga Ge Ta Nb Hf Zr Y Th U La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Saskatchewan Geological Survey 18 Summary of Investigations 2002, Volume 2

19 Table 3 - Analyses of gold and other elements for selected grab samples; analyses obtained from Activation Laboratories Ltd.; negative values equal not detected at that lower limit; abbreviations: na, not analyzed; other abbreviations as in Table 2. Sample ID Field description RM Quartz vein with pyrite in sheared gabbro RH Leucogabbro with sulphides RH Actinolite schist (#3 in Figure 4) RH Deformed quartz monzonite with 3% sulphides RM Quartz vein with pyrite in sheared leucodiorite RM Garnetiferous feldspathic psammite RM Strongly fol. leucogranite with disseminated pyrite RM Megacrystic qtz monzonite with diss py, po, cpy, mt RM Leucogabbro with diss. pyrite and magnetite RM Gabbro with disseminated sulphides (#1 in Figure 4) RM Foliated monzonite with disseminated pyrite RM Amphibolite with disseminated sulphides and magnetite RM Silicified gabbro with diss. pyrite (#4 in Figure 4) UTM-E (NAD 83) UTM-N (NAD 83) Mass g Au ppb Ag ppm na na As ppm Co ppm Cr ppm Cu ppm Mn ppm Mo ppm Ni ppm Pb ppm Sm ppm Sr ppm V ppm Y ppm Zn ppm Rb ppm na na Ba ppm na na Sb ppm na na Ta ppm na na Th ppm na na U ppm na na La ppm Ce ppm na na Nd ppm na na Eu ppm na na Tb ppm na na Lu ppm na na Sc ppm Yb ppm na na Fe % Na % Al % Ca % K % Mg % P % S % Ti % Saskatchewan Geological Survey 19 Summary of Investigations 2002, Volume 2

20 Table 4 - Au, PGE, and Cu-Ni-Zn analyses for selected intermediate to ultramafic rocks from the Peter Lake area; analyses obtained from Activation Laboratories Ltd.; negative values equal not detected at that lower limit; abbreviations as in Table 2. Sample ID Field description General area Location (NAD 83) Au Pt Pd Cu Ni Zn UTM-E UTM-N ppb ppb ppb ppm ppm ppm RM Actinolite schist Highway 905, kilometre (#3 in Figure 4) na na na RM Gabbro Wathaman River na na na RM Amphibolite (py: 1%) Highway 905, kilometre na na na RM Sheared gabbro (py>cpy: 1%) Warner Lake na na na RM Quartzdiorite (py: 1%) Warner Lake na na na RM Leucogabbro (mt>ht: 5%) Love Lake na na na RM Gabbro (po, py, cpy: 2%) North of Gravel Pit na na na RM Clinopyroxenite (py>mt>cpy: 2%) Warner Lake (#2 in Figure 4) na na na RM Melagabbro Love Lake na na na RM Actinolite schist (1% sul) Wathaman River na na na RM Pyroxenite (py: 2%) Warner Lake na na na RM Gabbro (py: 1%) Warner Lake na na na RM Diorite (py: 1%) Warner Lake na na na RM Leucogabbro (mt>py: 5%) South Peter Lake RM Leucogabbro (mt>py: 5%) South of Ziggy Lake na na na RM Leucogabbro (py + po: 2%) South of Ziggy Lake RM Gabbro (po>py>cpy: 5%) Northeast of gravel pit (#1 in Figure 4) na na na RM Diorite (py: 1%) Love Lake RM Amphibolite (py>po: 3%) North of Love Lake na na na RM Silicified gabbro (py 1%) North of Love Lake (#4 in Figure 4) na na na RM Gabbro (po, py, cpy: 2%) Combe Lake (SMDI 545) The best geochemical results this year were obtained from a sample of silicified, chloritized, and sheared gabbro of the Love Lake Leucogabbro (occurrence #4; Figure 4). A 40 by 40 m large outcrop of medium-grained, black and white-weathering, equigranular, homogeneous, massive to weakly foliated gabbro is cut by minor shear zones. The shear zones are characterized by chloritization, silicification, and up to 2% disseminated pyrite, magnetite and chalcopyrite. A grab sample of this sheared gabbro (RM ) returned 3.3 ppm Ag, over 100 ppb Au, and 1849 ppm Cu, but no elevated concentrations of PGEs (Tables 3 and 4). A copper occurrence (SMDI 545) in gabbroic rocks of the Combe Lake dioritic suite is exposed in a bay along the eastern shore of Combe Lake (Scott, 1970; Figure 4). It comprises disseminated chalcopyrite, pyrite, pyrrhotite, and malachite totalling about 2% sulphides. The sulphides are in part remobilized on late fractures. A grab sample (RM ) was analyzed and gave slightly elevated concentration of Cu and Ni (Table 4). 5. Thermotectonic History Only limited data are currently available to unravel the complex structural history of the area. As it is a predominantly plutonic domain, the rocks are generally not layered and therefore rarely folded at outcrop scale. Second-generation foliations are also scarce. Similarly, assessing the metamorphic grade was difficult, because of the preponderance of plutonic rocks. In addition, little geochronological data are available to provide an absolute framework for the different thermotectonic phases. Nevertheless, a preliminary general framework is presented in Figure 22. Early D1 deformation was likely Neoarchean in age based on a number of observations: 1) the Love Lake Leucogabbro, which is assumed to be contemporaneous with the 2.65 Ga Swan River Gabbro (Corrigan et al., 2001), contains deformed xenoliths of mafic volcanic rocks (Figure 6); 2) one clast in the lone outcrop of polymictic conglomerate observed to date, is internally folded; and 3) the monzonitic intrusion east of Warner Lake contains a small unit of isoclinally folded migmatitic psammopelite; the monzonite possibly post-dates migmatization and isoclinal folding of the psammite. Not all of these signs of early deformation are necessarily related to the same thermotectonic event. The main regional foliation, which affects the majority of units in the Peter Lake Domain, was formed during a second (D2) deformational event and resulted in the development of gneissic fabrics and alignment of planar mineral. A third regional deformational event (D3) is manifested in east-northeast-trending, upright, outcrop- to map-scale close to tight folds. F3 fold axes were rarely measured, but are likely subhorizontal based on an equal area projection of all measured S2 foliations (not shown). One such map-scale fold is preserved on north Warner Lake. The orientation of a third-generation schistosity (S3) relative to the S2 gneissic fabric, which is here exhibited by partly sheared granodioritic to dioritic rocks, suggests the presence of a map-scale antiform paralleling a bay on Saskatchewan Geological Survey 20 Summary of Investigations 2002, Volume 2

21 Figure 22 - Preliminary schematic illustration of the thermotectonic history of the western Peter Lake Domain. northwestern Warner Lake. The southern shore of the bay parallels the south-dipping s-limb, and the north shore parallels the north-dipping z-limb of a tight mapscale, slightly east-plunging F3-fold. Figure 23 shows an outcrop-scale third generation S-fold, related to this major structure. The fold deforms earlier F2 isoclinal folds and has an axial planar schistosity defined by biotite. Outcrops within the gneissic granodiorite to quartz diorite suite just north of the Parker Lake Shear Zone, also commonly display tight F3 folds and S3 schistosity oblique to the S2 gneissic fabric. At least one upper amphibolite facies metamorphic event, likely coinciding with D2, has affected large parts of the Peter Lake Domain, as well as sedimentary rocks along the northwestern margin of the Peter Lake Domain (MacNeil et al.,1997). The Love Lake Leucogabbro, Warner Lake gabbroic suite, and the migmatitic supracrustal rocks between Peter Lake and Figure 23 - F3 fold with axial planar biotite refolding earlier isoclinal fold; northwestern bay of Warner Lake; UTM-E: ; UTM-N: Saskatchewan Geological Survey 21 Summary of Investigations 2002, Volume 2