Austman - Departmental Seminar - Fraser Lakes Zone B Mineralization
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Departmental seminar that I gave on my research on the Fraser Lakes Zone B U-Th-REE mineralization.
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Austman - Departmental Seminar - Fraser Lakes Zone B Mineralization
- 1. Fraser Lakes Zone BPegmatite-hosted U-Th-REE mineralization: Geology, geochemistry, and origin Christine Austman Department of Geological Sciences University of Saskatchewan
- 5. Granitic Pegmatite Mineralogy and Geochemistry
- 6. Alteration and Remobilization of U-Th-Pb-REE
- 9. Similarities to other uranium deposits
- 12. Unresolved issues still exist in understanding uranium source, fluid flow, and the nature of the reductant involved in the formation of unconformity- related (U/C) uranium deposits Determine if uraniferous pegmatites are related to high-grade unconformity-related uranium deposits of the Athabasca Basin (U protore?) Determine whether granitic pegmatites represent a distinct target for uranium exploration in Saskatchewan Purpose of this study
- 14. Paleoproterozoic Wollaston Group metasedimentary rocks
- 15. Hudsoniangranites, amphibolites, leucogranites, migmatites, and granitic pegmatitesRegional Geology
- 17. Two mineralized zones: A and B
- 18. Zone A is in a NNE-plunging synformal and Zone B is in an NNE-plunging antiformal fold nose
- 19. 5 km section of a complexly folded electromagnetic (EM) conductor (i.e. graphitic pelitic gneisses) is adjacent to Zones A and BWollaston Group metasedimentary gneisses Wollaston Group metasedimentary gneisses Johnson River Granite Inlier Fraser Lakes Granite Inlier Fraser Lakes Zone B Needle Falls Shear Zone Wathaman Batholith Fraser Lakes Zone A After Ray, 1979
- 21. Zone B mineralization outcrops at surface on the eastern edge of the swamp
- 24. Overall coarse grained to pegmatitic
- 25. Variable size (cm to several m scale)
- 26. Complexly zoned (igneous AFC processes)
- 27. Multiple generations of granitic pegmatites
- 29. Uraninite (Urn)
- 30. Uranothorite – Thorite (Uth)
- 31. Monazite (Mz)
- 32. Allanite (Aln)
- 34. Feldspar (Fsp)
- 35. Biotite (Bt)
- 36. Magnetite (Mgt)
- 37. Ilmenite (Ilm)
- 38. Pyrite (Py)
- 39. Fluorite (Fl)
- 40. Sphalerite
- 41. Molybdenite
- 42. Apatite (Ap)
- 43. Titanite
- 44. Rutile
- 45. Garnet
- 46. Chalcopyrite
- 47. Pyrrhotite
- 48. Graphite
- 53. Epidote (Ep)
- 54. Sericite (Ser)
- 55. Hematite (Hem)
- 57. Chlorite (Chl)
- 58. Hematite (Hem)
- 59. Clay minerals
- 60. Sausserite
- 61. Carbonate(Cal)
- 63. Radiogenically produced galena inclusions in U-Th-REE minerals
- 64. Uraninite and secondary uranium minerals in fractures with galena and pyrite
- 65. Monazite -commonly altered to hematite, chlorite, and clayAlteration of U-Th-REE phases and remobilization of U, Th, Pb
- 66. Major element geochemistry Legend
- 67. Samples range from strongly peraluminous (off the chart) to slightly metaluminous S-type granitoids Alumina saturation index
- 68. Two major compositional subdivisions of pegmatites; correspond to mineralogical subdivisions U- plus Th-rich Th- and LREE-rich Trace element geochemistry
- 69. Garnet Biotite Cordierite Sillimanite Spinel K-feldspar Quartz Plagioclase Rutile Myrmekite NO prograde muscovite Metamorphic Mineral Assemblages – Pelitic gneisses Upper amphibolite to lower granulite facies metamorphism
- 70. Clinopyroxene Orthopyroxene Hornblende Biotite Spinel Myrmekite Quartz K-feldspar Plagioclase Metamorphic Mineral Assemblages –Orthogneisses Upper amphibolite to lower granulite facies metamorphism
- 71. Pegmatites – Partial melting at depth vs. in situ melting ? Migmatitesassociated with the granitic pegmatites Leucosomes tend to be boudinaged Locally small pegmatitic veins of leucosome
- 72. Melt occasionally forms thin rims around minerals, and locally larger blobs Common near the contact between biotite and garnet and within K-feldspar Biotite frequently shows degradation due to partial melting Migmatites and melt-textures in the pelitic gneisses
- 74. Transported upwards along the structural discontinuity/contact between Archean and Wollaston Group (b)
- 75. Underwent igneous assimilation-fractional crystallization during transport and crystallization
- 76. Melts were concentrated in antiformal fold noses (c)
- 77. Peraluminous to weakly metaluminous chemistry agrees with the pegmatites forming due to partial melting of pelitic gneissesc b a
- 79. Structurally controlled: mineralization concentrated in antiformal fold noses
- 80. Concentrated in areas of highest metamorphic grade
- 81. Formed from melts generated by partial melting of metasedimentary gneissesModified from Ray, 1979 Extract Resources, 2009
- 83. Chlorite, clay, and hematite alteration with drusy quartz found in Zone B drill core is similar in appearance to that of basement-hosted unconformity uranium deposits~150 – 200 m Modified from Ray, 1979 Jefferson et al. 2007
- 85. Hosted by Hudsonian granitic pegmatites intruding at/near the contact between Wollaston Group metasediments and Archean orthogneisses
- 86. Granitic pegmatites formed by partial melting of metasedimentary rocks in the middle to lower crust followed by transport and assimilation-fractional crystallization
- 87. Regional metamorphism up to lower granulite facies
- 88. Granitic pegmatites experienced post-crystallization alteration and remobilization of U and Th
Notas del editor
- Indicate geology of u deposits from east Athabasca generally associated w/ Wollaston DomainFraser Lakes Zone B is also in the Wollaston DomainControversy – source rocks?
- Study to provide additional constraints on the origin of Athabasca unconformity-related U deposits as well as characterize the pegmatites as their own unique target for U mineralization
- Area Multiply deformed and metamorphosed about 1.8 Ga during the THOAthabasca Basin unconformably overlies the metamorphosed rocksTHO source of sediment for Athabasca BasinArea Square larger and brighter color!!! More contrast (Drk red)
- Refolded fold structure – polyphase folding – defined by lithological units and EM conductorSuperimposed ductile-brittle (E-W) and brittle structures (NNE and NNW)
- Point out E-W brittle fault
- NE, NNW brittle faults, E-W shearsApproximate locations of first 3 drill holes, all hit mineralization.
- Late tectonic to post tectonic pegmatitesUnmineralized pegmatites tend to be later, but not always the case
- Emphasize they are graniticComplex variable bt-rich to qtz-rich to k-sp rich; mineralization greatest within biotite rich quartz rich pegmatitesComplexly zoned because of AFC processesSubdivided into two groups U-enriched vs. Th + REEs
- Stack photos
- Stack Have arrows to pel gn, u rich peg, th rich pegm, non rad pegmatite. Two diagrm
- Shand diagram
- Log U vs. SiO2Log Th vs. SiO2Log La vs. P2O5Th vs. U
- Digress to talk about the host rocks to the granitic pegmatites since their metamorphic grade is importantNO prograde metamorphic muscovite
- Scale bar and Kretz symbols
- Melt Transfer zoneBottom part gt richMid crd + gtUpper crdGt in pegmatites – coming from deeper, gt-sill-crd host rock, middle to upper zone
- Basement relationships very similar, Similar to Rössing (one of the largest open pit U mines) and Rössing South, also similar occurrences in Grenville
- Top figure shows what it may have looked like when the Athabasca was overtop.Bottom figure shows the location of basement and sandstone hosted uranium deposits, alteration zones, etc.