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2009 Saskatchewan Geological Survey Open House poster on the Fraser Lakes Zone B pegmatite-hosted U-Th-REE mineralization
2009 Saskatchewan Geological Survey Open House poster on the Fraser Lakes Zone B pegmatite-hosted U-Th-REE mineralization
THE FRASER LAKES URANIUM DEPOSITS: FIELD RELATIONSHIPS, PETROGRAPHY, 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, +/- AND GEOCHEMISTRY OF URANIFEROUS PEGMATITES AND ASSOCIATED ALTERATION 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 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: email@example.com); (2) JNR Resources Inc., Saskatoon, SK, Canada S7K 0G6 Abstract Fraser Lakes Zone BThe 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 uranium and thorium mineralization inHowever, about 55 km east of the Key Lake uranium mine, uraniferous granitic pegmatites and leucogranites intrude into a shear zone pegmatites, leucogranites and migmatitic leucosomes (Fig. 5, 6, 7, pegmatites are the red unit, with the gamma probe results in blue alongside the logs)at the contact between deformed Paleoproterozoic Wollaston Group metasedimentary rocks and Archean orthogneisses. The uranium Pegmatite emplacement is controlled by the NE-plunging antiformal fold, with the pegmatites being concentrated in the fold nose areamineralization is directly related to these igneous rocks, and the aim of this project is to determine whether these represent a distinct The deposit is also cross-cut by an E-W dextral ductile-brittle structure and a number of later NNW– and NNE-trending brittle faults (Annesley et al., 2009) 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 alteredtarget for uranium exploration in Saskatchewan or if the mineralization is related somehow to unconformity-type uranium deposits. Up to 0.453 % U3O8 was found in surface samples in a 500 m x 1500 m area and up to 0.183% U3O8 over 1.0 m in drill core (WYL-09-50) 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 fracturingconductor (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, 14) (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 U– and Th– mineralization is accompanied by LREE enrichment and elevated amounts of pathfinder elements including Co, Cu, Mo, Ni, Pb, V, and Zn (see Fig. 15—17)zones are cross-cut by a number of E-W-, NNE-, and NNW-trending structures. Associated with the uranium are thorium and LREE Chlorite and hematite alteration similar to that found in basement-hosted unconformity deposits is found in several drill holesmineralization with elevated amounts of pathfinder elements including Co, Cu, Mo, Ni, Pb, V, and Zn. Drill core observations revealed the existence of multiple generations of granitic pegmatites, including mineralized (generallysubcordant 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 theAthabasca Basin. This project will integrate field observations and geological, geochemical, and geophysical datasets so to develop ametallogenetic 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-hostedThe Fraser Lakes Zones A and B uranium deposits are located in JNR Resources Inc.’s unconformity deposits (Annesley et al., 2009), indicating that there was possibly Athabasca hydrothermal fluid movement through theWay Lake Property in northern Saskatchewan, Canada, ~25 km southeast of the Fraser Lakes area and remobilization of the uranium and thorium mineralization.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 uranium deposits55 km east of the Key Lake U mine. in 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 Groupmetasedimentary rocks (including graphitic pelitic gneisses) and Archean orthogneisses Conclusionsthat underwent complex deformation, intrusion, and metamorphism during the Trans- Structurally controlled, basement-hosted U, Th, and LREE mineralization in Hudsonian-aged leucogranites and granitic pegmatitesHudson 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 antiformal (Zone B) fold noses. The mineralization consists of uraniferous pegmatites Fig. 12 Granitic pegmatite (96.8 m) in WYL-09-41 with hematite Pegmatites have similar mineralogy to migmatitic leucosomes in the drill core, indicating that the pegmatites may be the products ofand leucogranites that intrude the highly deformed contact between the basal Wollaston Fig. 8 Drill core from WYL-09-50 showing fractionation from quartz-rich to staining, and up to 2100 cps. partial crustal melts.Group metasedimentary rocks and the Archean granitoids. It is estimated that the Fig. 1 Location of JNR’s properties in northern feldspar-rich in the granitic pegmatite core (158.7 - 62.7m). Post-crystallization alteration and fluid flow through the rocks raises the possibility of post-crystallization uranium remobilizationAthabasca sandstone/basement unconformity was about 200-250 m above the presently Saskatchewan, including the Way Lake Property Fraser Lakes U-deposits are similar to several basement-hosted U-deposits in the Athabasca Basin, including the Eagle Point, McArthurexposed outcrop (Annesley et al., 2009). (modified from map on JNR Resources Inc. website) River Zone 2, Millennium, and P-Patch deposits. The Fraser Lakes deposits also show similarities to pegmatite--hosted uranium deposits in the Grenville Province.The purpose of this M.Sc. study is to develop a metallogenetic model for the Fraser Lakes deposits, and clarify their 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.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, further whole-rock geochemical to igneous assimilation-fractional crystallization (AFC) granitic pegmatite shown in Fig. 10. analysis, Pb-isotope studies, REE-analysis, Cl-analysis, and U-Pb chemical age dating of the mineralization and the development of a melt pods and granitic pegmatites. processes. metallogenetic model and examination of 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, http://www.jnrresources.com/; e-mail: firstname.lastname@example.org 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 holeWYL-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 AcknowledgementsWhole 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 forCouncil 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.