Geochronologic Studies in the La Ronge and Glennie Domains 1

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1 Geochronologic Studies in the La Ronge and Glennie Domains 1 T.K. Kyser2, M. Fayek2, and T.1.1. Sibbald Kyser, T.K., Fayek, M., and Sibbald, T.1.1. (1992): Geochronologic studies in the la Range and Glennie domains; in Summary of Investigations 1992, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep This paper presents the results of new and Pb-Pb studies of zircons from a diversity of rock types in the La Ronge and Glennie domains. Previously published U Pb ages of volcanic and intrusive rocks from these domains are summarized as are Ar-Ar ages of minerals associated with gold mineralization in the La Range Domain. Zircons from the following samples of rocks from the La Ronge Domain were selected for and Pb-Pb analysis (Table 1 ): the granitic phase of the Little Deer Lake composite pluton, which hosts the Contact Lake lode gold deposit; a rhyolite from the nearby Pap Preview area; a meta-arkose hosting the Greywacke gold showing; and the diorite phase of the Kruger Lake Pluton associated with the Bay Zone gold showing. In the Glennie Domain, zircons from a quartz-feldspar porphyry, one of the rocks hosting mineralization at the Seabee gold deposit in the Glennie Domain, were also analyzed (Table 2). The techniques used for determining the age of the zircons were Pb-evaporation, for single zircons described by Ansdell and Kyser (1991, in prep. a) and, described by Krogh (197, 1982). The Pb-Pb technique is a simple and relatively fast method of analyzing the age of a single zircon. Laboratories that use the technique also measure Pb-Pb ages, but these are usually younger than the concordia ages of the zircons. However, the Pb-Pb ages obtained from digestion of zircons are rarely as reliable as the Pb-Pb ages obtained from the evaporation technique because the former contains Pb from extraneous sources that are difficult to remove. Ages obtained from the analysis of single zircons using the Pb-evaporation technique are similar to those obtained from either precise single zircon dissolution techniques or from more conventional dissolution techniques including fractions of different zircons (Table ). 1. La Range Domain The Little Deer Lake Pluton, which is crosscut by the structures that host the Contact Lake gold deposit, yields a Pb-Pb age of 187 ± Ma. This is among the youngest intrusives in the La Ronge Domain, along with the Waddy Lake stock and the Numabin Bay tonalite (Table 1 ). The Star Lake Pluton and Island Lake Pluton, which respectively host the structurally-controlled Star Lake and Jasper lode gold deposits, yield and Pb Pb zircon ages of ca. 18 Ma {Bickford et al., 1986). The Kruger Lake Pluton, which hosts the Bay Zone gold showing, is among the oldest of the intrusions in the La Ronge Domain, with a Pb-Pb age of 1867 ±7 Ma (Table 1). Thus, structurally-controlled lode gold deposits in the La Range Domain are hosted by plutons that have ages spanning the entire range of intrusive events, from 184 to 1867 Ma. The Pap-Preview rhyolite yielded an imprecise age of 18 ± Ma (Table 1). The zircons from this unit were euhedral but very small (i.e. <20 µm). The large uncertainty associated with the age may be due to the presence of inherited zircons because one fraction of zircons, that was not used to determine the age, yielded an aberrantly old age. The rhyolite appears to be significantly younger than falsie volcanics of the Central Metavolcanic Belt, although there is large uncertainty in the determination (Table 1 ). The indicated age is ca. 10 Ma younger than the age of 184 ±2 Ma (Heaman, per. comm., 1992) determined for the North Lake 'felsite' within the Mclennan Group. This age relationship is apparently inconsistent as the Mclennan Group unconformably overlies the Pap-Preview rhyolite sequence of rocks, suggesting that the true age of the rhyolite is significantly younger, but still within error, or that the North Lake felsite is a sediment rather than a primary volcanic rock. In the latter case its contained zircons are detrital and are likely derived from plutons of Contact Lake age. The Greywacke gold showing is hosted by meta-arkosic rocks of the Maclean Lake Belt near their boundary with the Mclennan Group. Although zircons from this unit were sparse, four zircons of presumably detrital origin, yielded Pb-Pb ages ranging from 1827 to 1886 Ma. Maximum host rock age is constrained by the youngest zircon, that is, 1827 ±6 Ma. Volcanic and intrusive rocks in either the La Range or Glennie domains could have been the major source of the zircons in the meta-arkose (Table 1). In that the Mclennan Group overlies the Maclean Lake Belt rocks, the occurrence of ca. 180 Ma zircons in the latter provides a maximum age for the former lending weight to the suggestion that the zircons from the North Lake felsite are detrital. (1) Saskalchewan Project A 141 was funded in under the Canada-Saskatchewan Partnership Agreement on Mineral Development with additional funding from NSERC Operating and Equipment Grants to T.K. Kyser. (2) Department o f Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, S7N OWO. 10 Summary of Investigations 1992

2 Table 1- Summary of and 207 Pb/ 06 Pb ages from the La Ronge Domain. Sample Name Description Zircon Dating Method Age (Ma) Reference Little Deer Lake Pluton composite, calc-alkaline (central granitic phase hosting the Contact Lake gold deposit)* ( zircons) 187 ± Pap-Preview Rhyolite hosting the Pap-Sulphide gold showings 18 ± Greywacke metasediment hosting the Greywacke gold showing 1827 ±6** 1828 ±11** 1844 ±6** 1886 ±7** Kruger Lake Pluton diorite /monzodiorite hosting the Bay Zone gold showing ( zircons) 1867 ±7 Laroque Lake Rhyolite 1876 ± 2 McLennan Lake Rhyolite 1882 ±9 2 Island Lake Pluton zoned, calc-alkaline (central granitic phase hosting the Jasper gold deposit)* ( zircons) 18 ± ±8 Star Lake Pluton :i:oned, calc-alkaline (central granitic phase hosting the Star Lake gold deposit)* U Pb 1848 ±14 2 Brindson Lake Pluton quartz diorite to 1866 ±12 2 Waddy Lake Rhyolite 1880 ±7 2 Upper Waddy Lake Stock medium- to fine-grained hornblende granite 184 ±1 2 Kenwood Lake Pluton medium- to coarse-grained monzodiorite 18 ±9 2 Nistoassini-Nayelles Pluton medium- to coarse-grained granite 18 ±10 2 Contact Lake Pluton strongly foliated biotite granite 18 ±16 2 Macoun Lake Pluton 1849 ±10 2 Numabin Bay Tonalite strongly foliated mediumgrained 187 ±8 2 * parentheses indicate the phase which has been dated ** detrital zircons 1 = this study 2 = Bickford et al. (1986) = Hrdy et al. (1991) a) Age of Gold Mineralization in the La Ronge Domain Geologic and petrographic relations indicate that structurally-hosted lode gold deposits within intrusions are very late in the evolution of the La Range Domain. The gold was deposited concurrently with hydrous phases such as biotite (Star Lake area) or muscovite (Jasper and Contact Lake deposits) and sulphides such as galena and chalcopyrite. Ar-Ar spectra of muscovite, Saskatchewan Geological SuNey 11

3 Table 2 - Summary of and 207 Pbj20 6 Pb ages from the Glennie Domain. Sample Name Description Zircon Dating Method Age (Ma) Reference Parr Lake Rhyolite with quartz and feldspar phenocrysts 1881 ±6 Deschambault Narrows Tonalite tonalite 180 ±4 Wykes Lake Pluton 180 ±9 Eyahpaise Pluton tonalite 189 ± Stevens Lake Pluton granodio rite 186 ±7 Dirks Lake Gneiss biotite-hornblende-quartzfeldspar gneiss 182 ±12 Laonil Lake Intrusive quartz diorite 1889 ±9 Seabee Porphyry quartz-feldspar porphyritic lens ( zircons) 1877 ±10 Brownell Lake Pluton granite 181 ±7 6 Maynard Lake Intrusive feldspar porphyry 184 ±4 7 Maynard Lake Pluton g ranod iorite / 6 Gee Lake Rhyolite 1866 ± 7 Porky Lake Rhyolite 188 ±2 7 Carroll Lake Gneiss gneiss 189 ± 8 Wood Lake Batholith leucocratjc to mesocratic to tonalite 180 ±1 9 McGillivray Bay Gneiss dioritic gneiss 187 ±7 Drinking Lake Gneiss gneiss 1846 ± Mountain Lake Gneiss gneiss 189 ±10 Drope Lake Gneiss quartz diorite gneiss 180 ±1 Thomas Lake Gneiss quartz diorite gneiss 181 ±2 Lac La Ronge Gneiss gneiss 2482 ±1 lskwatikan Lake Gneiss gneiss 2464 ±28 1 = this study = Bickford et al. (1986) = Chiarenzelli (1989) 6 = Delaney et al. (1991) 7 = Heaman eta/. (1991) 8 = Van Schmus and Bickford (1984) 9 = Delaney et al. (1988) from the Jasper gold deposit, and biotite, from deposits within the Star lake Pluton, yield ages of 1719 Ma (Table 4). These ages are similar to the 1742 Ma Rb-Sr age obtained from coexisting tourmaline and feldspar gangue minerals from veins within the Star Lake area (Ibrahim and Kyser, 1991). These results indicate that structurally-controlled gold mineralization may have occurred up to 100 Ma after the youngest igneous events within the la Ronge Domain. Similar results were obtained for the relative age of intrusive events and lode gold mineralization in the Flin Flon Domain by Ansdell and Kyser (in prep. b) and Fedorowich et al. (1991). 12 Summary of Investigations 1992

4 2. The Glennie Domain The Glennie Domain comprises Early Proterozoic rocks spanning the spectrum of ages from ca. 180 to 1890 Ma (Table 2). The Seabee deposit is partly hosted by a quartz-feldspar porphyritic lens that yields zircon Pb-Pb ages of 1877 ±10 Ma. This is among the oldest intrusive bodies in the Glennie Domain. Petrographic relations indicate that the gold and associated minerals of the Seabee deposit are relatively undeformed and late and probably much younger than the maximum age constraint provided by the dating of the porphyry. Work is presently under way to determine the age of the gold mineralization more precisely. Table - Comparison of 207 Pb/ 06 Pb and ages of zircons. Sample Duluth Anorthosite. Minnesota Otto Stock granitoid, Kirkland Lake, Ont. Phantom Lake, Flin Flon Domain, Sask. Boot Lake monzodiorite, Flin Flon Domain, Sask. Island Lake Pluton, La Range Domain, Sask. References in parentheses 1 = this study 2 = Heaman et al., this volume = Bickford et al. (1986) 4 = Hrdy et al. (1991) 10 = Ansdell and Kyser (in prep. a) 11 = Corfu et al. (1989) 12 = Ansdell and Kyser (1991) 1 = J. Paces (pers. comm.) 207 Pbj2 6 Pb age (Ma) 1098 ±16 (10) 1108 ±12 (10) 267 ±4 (12) 268 ±4 (12) 1840 ±7 (12) 1842 ± 1 (12) 18 ±8 (4). Acknowledgments We would like to thank Karla Richard and Michele Innes for their diligence in picking the appropriate samples, and Dale Schultz for his input. We gratefully acknowledge April Vuletich for donating her time in obtaining some of the analytical results. 4. References Ansdell, K.M. and Kyser, T.K. (1991): Plutonism, deformation, and metamorphism in the Proterozoic Flin-Flon greenstone belt, Canada: Limits on timing provided by the single-zircon Pb-evaporation technique, Gear., v19, p age (Ma) 1099 ±1 (1) 1099 ±1 (1) 2680 ±1 (11) 188 ±2 (2) 188 ±2 (2) 18 ±22 () --,c"'h-=-e.,,m.,..1c-};h~~e:~t~:n~:~~~~~ ~nyd zircon during the Pb-evaporation technique; Submitted to American Mineralogist ,..,.,.(in prep. b): Mesothermal gold mineralization in a Proterozoic greenstone belt: Western Flin Flan Domain, Saskatchewan, Canada; Submitted to Economic Geology. Bickford, M.E., Van Schmus, W.R., Macdonald, R., Lewry, J.F., and Pearson, J.G. (1986): zircon geochronology project from the Trans-Hudson Orogen: Current sampling and recent results; in Summary of Investigations 1986, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 86-4, p Chiarenzelli, J.R. (1989): The Nistowiak and Guncoat gneisses: Implications for the tectonics of the Glennie and La Range Domains, northern Saskatchewan, Canada; unpubl. Ph.D. thesis, Univ. Kansas, 229p. Table 4 - Summary of 40 Ar/ 9 Ar ages from the Star Lake area, La Ronge Domain. Sample Name and Description Mineral Closure Spectra Age (Ma) Spectra Temperature Type Jasper Gold Deposit (a) vein muscovite 0 ±0* disturbed Star Lake Pluton (b) biotite from Rush Lake vein near vein-wall rock contact 00 ±0** plateau 1719 ± Star Lake Pluton (c) biotite from wall rock 00 ±0** near Rush Lake veinwall plateau 1719 ± rock contact Star Lake Pluton (d) biotite a few metres away from Rush Lake 00 ±0** plateau 1719 ± vein * Hanes (1991) ** Harrison et al. (198) Saskatchewan Geological SuNey 1

5 Corfu, F., Krogh, T.E., Kwok, Y.Y., and Jensen, LS. (1989): U Pb zircon geochronology in the southwestern Abitibi greenstone belt, Superior Province; Can. J. Earth Sci., v26, p Delaney, G.D., Carr, S.D., and Parrish, R.R. (1988}: Two zircon ages from eastern Glennie Lake Domain, Trans Hudson Orogen, Saskatchewan; in Radiogenic Age and Isotopic Studies, Report 2, Geel. Surv. Can., Misc. Pap , p1 8. Delaney, G.D., Heaman, L.M., Kama, S., Parrish, R.R., Slimmon, W.L., and Reilly, B.A. (1990): sphene/zircon geochronological investigations; in Summary of Investigations 1990, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 90-4, p4 7. Fedorowich J., Stauffer, M. R., and Kerri ch, R. ( 1991 ) : Stru C tural setting and fluid characteristics of the Proterozoic Tartan Lake gold deposit, Trans-Hudson Orogen, northern Manitoba; Econ. Geol., v86, p Hanes, T.A. (1991): K Ar and 40 Ar; 9 Ar geochronology: Methods and applications; in Heaman, L.H. and Ludden, J.N. (eds.), Short Course Handbook on Applications of Radiogenic Isotope Systems to problems in Geology, Mineral. Assoc. Can., v19, p27-7. Harrison, T.M., Duncan, I., and McDougall, I. (198): Diffusion of 40 Ar in biotite: Temperature, pressure, and compositional effects; Geochim. Cosmochim. Acta, 1149, p Heaman, L.M., Kame, S.L., Delaney, G.D., Harper, C.T., Reilly, 8.A., Slimmon, W.L., and Thomas, D.J. (1991): geochronological investigations in the Trans-Hudson Orogen, Saskatchewan: Preliminary results by the ROM Laboratory in ; in Summary of Investigations 1991, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 91-4, p74-7. Hrdy, F., Kyser, T.K., and Kusmirski, R.T. (1991): Mineral paragenesis, fluid characteristics, and radiogenic isotopic data from the Proterozoic Jasper gold zone, La Ronge Domain; in Summary of Investigations 1991, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 91-4, p Ibrahim, M.S. and Kyser, T.K. (1991): Fluid inclusion and isotope systematics of the high-temperature Proterozoic Star Lake lode gold deposit, northern Saskatchewan, Canada; Econ. Geel., 1186, p Krogh, T.E. (197}: A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations; Geochim. Cosmochim. Acta, v7, p (1982): Improved accuracy of zircon ages by the creation of more concordant systems using an air abrasion technique; Geochim. Cosmochim. Acta, v46, p Van Schmus, W.R. and Bickford, M.E. (1984): Preliminary U Pb age data from the Trans-Hudson Orogen in northern Saskatchewan; in Summary of Investigations 1984, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 84 4, p Summary of Investigations 1992

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