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GSA 2009 - Austman et al - Fraser Lakes Zone B Granitic pegmatite and leucogranite-hosted uranium mineralization


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Poster presented at GSA 2009 Annual meeting about my research on the Fraser Lakes granitic pegmatite-hosted uranium mineralization.

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GSA 2009 - Austman et al - Fraser Lakes Zone B Granitic pegmatite and leucogranite-hosted uranium mineralization

  1. 1. GRANITIC PEGMATITE- AND LEUCOGRANITE-HOSTED URANIUM MINERALIZATION ADJACENT TO THE  WYL-09-50 Examination of several thin sections from drill hole WYL-09-50 indicated that the mineralized pegmatites and leucogranites contain varying amounts of quartz, feldspar, biotite, +/- garnet, +/- muscovite, +/- magnetite, +/- ilmenite, +/- pyrite, +/- titanite, +/- zircon, +/- ATHABASCA BASIN, SASKATCHEWAN, CANADA: A DIFFERENT TARGET FOR URANIUM EXPLORATION  allanite, +/- apatite, +/- monazite, +/- fluorite, +/-sphalerite, +/-molybdenite, +/- uraninite, +/- thorite, +/- uranothorite (Fig. 18 –26) Textures associated with the mineralization include pleochroic halos around radioactive inclusions and radiation cracks radiating from 1 1 2 the radioactive minerals into the surrounding crystals (Fig. 20, 23, 24). AUSTMAN, Christine L. , ANSDELL, Kevin M. , and ANNESLEY, Irvine R. (1) Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E2 (E-mail:; (2) JNR Resources Inc., Saskatoon, SK, Canada S7K 0G6 Abstract Fraser Lakes Zone B The richest uranium deposits in the world are unconformity-type deposits of the Proterozoic Athabasca Basin, Saskatchewan, Canada.  Examination of the drill core, combined with down hole gamma logs and geochemical analysis indicated the presence of elevated radioactivity due to However, about 55 km east of the Key Lake uranium mine, uraniferous granitic pegmatites and leucogranites intrude into a shear zone uranium and thorium mineralization in pegmatites, leucogranites and migmatitic leucosomes (Fig. 5, 6, 7, pegmatites are the red unit) at the contact between deformed Paleoproterozoic Wollaston Group metasedimentary rocks and Archean orthogneisses. The uranium  Up to 0.453 % U3O8 on surface (500 m x 1500 m area) and up to 0.183% U3O8 over 1.0 m in drill core (WYL-09-50) mineralization is directly related to these igneous rocks, and the aim of this project is to determine whether these represent a distinct  The deposit is cross-cut by an E-W dextral ductile-brittle structure and several later NNW– and NNE-trending brittle faults (Annesley et al., 2009), with Fig. 18 + 19 Granitic pegmatite (~ 191.6 m) with abundant zoned zircons (with Fig. 20 (PPL) + 21 (Reflected light) Finely disseminated uraninite grains in an altered target for uranium exploration in Saskatchewan or if the mineralization is related somehow to unconformity-type uranium deposits. the pegmatite emplacement being controlled by the NE-plunging antiformal fold nose primary cores and metamict rims), apatite, and monazite in a cluster of biotite. allanite with pleochroic halo. Granitic pegmatite at ~ 232.9 m.  Multiple generations of pegmatites with variable mineralogy, some containing uranium mineralization with others barren (Fig. 8, 9, 10, 11, 12) The magmatic-hosted deposits (Fraser Lakes Zones A and B) are in NE-plunging regional fold noses adjacent to a 5 km long folded EM  Zonation of the pegmatites is common due to igneous assimilation fractional crystallization (AFC) processes (Fig. 8, 10, 11)  The presence of epidote, hematite, fluorite, calcite, and chlorite alteration associated with weak to locally strong brittle fracturing conductor (i.e. graphitic pelitic gneisses). The more prospective Zone B sits within an antiformal fold nose, from which several drill  Several features indicative of partial melting are also found in the drill core, including diatexitic migmatites and boudined felsic melt pods (Fig. 9, 13, (Fig. 23 - 26) indicates the likelihood of post-crystallization hydrothermal fluid flow through the rocks. holes have intersected multiple intervals of uranium and/or thorium mineralization (up to 0.183% U3O8 over 1.0 m in drill core). The 14) zones are cross-cut by a number of E-W-, NNE-, and NNW-trending structures. Associated with the uranium are thorium and LREE  U– and Th– mineralization is accompanied by LREE enrichment and elevated amounts of pathfinder elements including Co, Cu, Mo, Ni, Pb, V, and Zn mineralization with elevated amounts of pathfinder elements including Co, Cu, Mo, Ni, Pb, V, and Zn. (see Fig. 15—17) Drill core observations revealed the existence of multiple generations of granitic pegmatites, including mineralized (generally subcordant to gneissosity, and believed to be syndeformational) and nonmineralized (discordant to gneissosity, and probably post– tectonic) varieties, with some of the pegmatites showing compositional zoning due to igneous AFC processes. While this is a magmatic-hosted U-Th deposit, the presence of clay alteration and structural features in Zone B drill core similar to that Fig. 22 Biotite-rich section of Fig. 23 Granitic pegmatite (215.8 m) Fig. 24 (PPL) + 25 (XPL) Granitic pegmatite (215.8 m) with Cal-Fl-Qtz Fig. 26 Granitic pegmatite (166.2 m) of basement-hosted unconformity uranium deposits (e.g. Millennium, P Patch, Eagle Point, and McArthur River Zone 2) raises the granitic pegmatite (216.5 m). containing zircon and allanite. veining and alteration of feldspar to Ep, Hem, Chl, Cal, and Musc. with alteration and fracturing. possibility that altered remobilized parts of the Fraser Lakes zones formed at the same time as unconformity-type mineralization in the Athabasca Basin. This project will integrate field observations and geological, geochemical, and geophysical datasets so to develop a metallogenetic model for the Fraser Lakes deposit, and clarify its relationship with the rich uranium deposits in the Athabasca Basin Comparisons to other types of Uranium Deposits (e.g. U protore).  Several unconformity-type uranium deposits in the Athabasca Basin contain peraluminous leucogranites and pegmatites in the basement rocks (Annesley et al., 2000a, 2000b, 2005, 2009; Annesley and Madore, 1999; Madore et al., 2000; Portella and Annesley, 2000) that have similarities to the pegmatites at the Fraser Lakes deposits, including host rocks, mineralogy, and presumed origin. Introduction  As well, drill core observations (Zone B) indicated the presence of chlorite and hematite alteration similar to that in basement-hosted The Fraser Lakes Zones A and B uranium deposits are located in JNR Resources Inc.’s unconformity deposits (Annesley et al., 2000), indicating that there was likely Athabasca hydrothermal fluid movement through the Way Lake Property in northern Saskatchewan, Canada, ~25 km southeast of the Fraser Lakes area, which may have led to remobilization of the uranium and thorium into an unconformity-type deposit. Athabasca Basin (location of the highest-grade uranium deposits in the world) and  The Fraser Lakes uranium-thorium-LREE deposits are also similar to some of the pegmatite-, vein– and skarn-hosted deposits found in 55 km east of the Key Lake U mine. the Grenville Province (Lentz, 1991), and are believed to have a similar origin (partial melting at deep to moderate crustal levels). The Way Lake Property is underlain by Paleoproterozoic Wollaston Group Conclusions metasedimentary rocks (including graphitic pelitic gneisses) and Archean orthogneisses that underwent complex deformation, intrusion, and metamorphism during the Trans-  Structurally controlled, basement-hosted U, Th, and LREE mineralization in Hudsonian-aged leucogranites and granitic pegmatites Hudson Orogen (~ 1.8 Ga). An approximately 65 km long electromagnetic (EM) that intrude Paleoproterozoic graphitic pelitic gneisses at the unconformity with Archean granitoids. conductor runs across the property, with the Fraser Lakes deposits hosted adjacent to a  Zone B has up to 0.183% U3O8 over 1.0 m in drill core, and up to 0.453% U3O8 in outcrop grab samples. 5 km section of the conductor (see Fig. 2 and 3) in NE-plunging synformal (Zone A) and  Pegmatites have similar mineralogy to migmatitic leucosomes in the core, indicating that the pegmatites may be the products of partial antiformal (Zone B) fold noses. The mineralization consists of uraniferous pegmatites Fig. 12 Granitic pegmatite (96.8 m) in WYL-09-41 with hematite crustal melts. Fig. 8 Drill core from WYL-09-50 showing fractionation from quartz-rich to staining, and up to 2100 cps. and leucogranites that intrude the highly deformed contact between the basal Wollaston  Post-crystallization alteration and fluid flow through the rocks raises the possibility of post-crystallization uranium remobilization feldspar-rich in the granitic pegmatite core (158.7 - 62.7m). Group metasedimentary rocks and the Archean granitoids. It is estimated that the Fig. 1 Location of JNR’s properties in northern  Fraser Lakes U-deposits are similar to several basement-hosted U-deposits in the Athabasca Basin, including the Eagle Point, McArthur Athabasca sandstone/basement unconformity was about 200-250 m above the presently Saskatchewan, including the Way Lake Property River Zone 2, Millennium, and P-Patch deposits, indicating a possible relationship between the pegmatite-hosted and unconformity- (modified from map on JNR Resources Inc. website) exposed outcrop (Annesley et al., 2009). type deposits.  The Fraser Lakes deposits also show similarities to pegmatite--hosted uranium deposits in the Grenville Province. The purpose of this M.Sc. study project is to develop a metallogenetic model for the Fraser Lakes deposits, and Fig. 10 Granitic pegmatite in WYL-09-40 (116.5 -127.9 m) Fig. 11 Quartz-rich (up to 80%) pegmatite (121.3 to 149 m)  The potential exists for finding basement-hosted unconformity-type mineralization in the Fraser Lakes area. clarify their relationship with the rich uranium deposits in the Athabasca Basin. Fig. 9 Drill core from WYL-09-524 (15.6—19.8 m) with boudinaged crustal showing fractionation from feldspar-rich to quartz-rich due further down in drill hole WYL-09-40 than the feldspar-rich  Future work will include: petrographic examination of other drill holes, electron microprobe work, whole-rock geochemical analysis, Pb to igneous assimilation-fractional crystallization (AFC) granitic pegmatite shown in Fig. 10. melt pods and granitic pegmatites. -isotope studies, REE-analysis, Cl-analysis, and U-Pb chemical age dating of the mineralization and the development of a metallogenetic processes. model and to examine the potential for future discoveries in the area. References Annesley, I., Cutford, C., Billard, D., Kusmirski, R., Wasyliuk, K., Bogdan, T., Sweet, K., and Ludwig, C. (2009) Fraser Lakes Zones A and B, Way Lake Project, Saskatchewan: Geological, geophysical, and geochemical characteristics of basement-hosted mineralization. Proceedings of the 24th International Applied Geochemistry Symposium (IAGS), Fredericton, NB. Conference Abstract Volume 1. p. 409-414. Annesley, I.R. & Madore, C. (1999) Leucogranites and pegmatites of the sub-Athabasca basement, Saskatchewan: U protore? Mineral Deposits: Processes to Processing (Stanley, C.J. et al., eds.), Balkema 1: 297-300. Annesley, I., Madore, C., Kusmirski, R., and Bonli, T. (2000) Uraninite-bearing granitic pegmatite, Moore Lakes, Saskatchewan: Petrology and U-Th-Pb chemical ages. In: Summary of Investigations 2000, Volume 2, Saskatchewan Geological Survey, Saskatchewan Energy and Mines, Miscellaneous Report 2000-4.2. p. 201-211. Annesley, I.R., Madore, C. and Portella, P., 2005, Geology and thermotectonic evolution of the western margin of the Trans-Hudson Orogen: evidence from the eastern sub-Athabasca basement, Saskatchewan, Canadian Journal of Earth Sciences, 42, 573-597. Kretz, R. (1983): Symbols for rock-forming minerals. American Mineralogist, 68, 277-279. Fig. 13 Boudinaged felsic melt pods with garnet JNR Resources Inc. (2009) —Home Page—Oct. 10, 2009, Saskatoon, 10/10/2009,; e-mail: cores in WYL-09-37 (188.1 to 192.6 m) Lentz, D. (1991). U-, Mo-, and REE-bearing pegmatites, skarns and veins of the Grenville Province, Ontario and Quebec. Can. Journal of Earth Sciences, 28, 1-12. Fig. 2 Topographic map showing the location of the Fraser Lakes Zones A and B Fig. 3 Total field aeromagnetic image and trace of the EM conductor in the Madore, C., Annesley, I. and Wheatley, K., (2000) Petrogenesis, age, and uranium fertility of peraluminous leucogranites and pegmatites of the McClean Lake / Sue and Key Lake / P-Patch deposit areas, deposits, the folded EM conductor, and drill hole collars. Fraser Lakes area, location of Fraser Lakes Zones A and B, and drill holes. Saskatchewan. GeoCanada 2000, Calgary, Alta., May 2000, Extended Abstract 1041. (Conference CD). Portella, P. and Annesley, I.R. (2000a) Paleoproterozoic tectonic evolution of the eastern sub-Athabasca basement, northern Saskatchewan: Integrated magnetic, gravity, and geological data. GeoCanada 2000, Calgary, Alta., May 2000, Extended Abstract 647. (Conference CD). Analytical Methods Portella, P. and Annesley, I.R. (2000b) Paleoproterozoic thermotectonic evolution of the eastern sub-Athabasca basement, northern Saskatchewan: Integrated geophysical and geological data. in Summary of Investigations 2000, Volume 2: Saskatchewan Geological Survey, Saskatchewan Energy and Mines, Miscellaneous Report 2000-4.2, 191-200. Drill core from the Fraser Lakes Zone B deposit was examined for this study, with several samples from drill hole WYL-09-50 taken for petrography. After drilling, each hole was probed using a gamma-ray probe to test for radioactivity. Fig. 14 Diatexitic migmatite with hematite Acknowledgements Whole rock geochemical analysis on selected samples from each drill hole was completed by the Saskatchewan Research alteration in WYL-09-42 (~ 88.5 m) The authors acknowledge the financial support of JNR Resources Inc., NSERC (Discovery Grant to Ansdell) and the University of Saskatchewan (Graduate Scholarship to Austman). Thanks to Blaine Novakovski for Council Geo-Analytical Laboratories in Saskatoon. preparing the thin sections, to Kimberly Bradley from JNR Resources Inc. for her assistance with petrography, and the Saskatchewan Research Council for the geochemical results.