Marjolaine Pascal Kevin Ansdell Irvine Annesley. Collaborators: Dan Jiricka, Tom Kotzer, Michel Cuney and Marie-Christine Boiron

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1 An overview of the petrography, geochemistry, Raman, and fluid inclusion analysis of variably graphitic and graphite-depleted pelitic schist in the Dufferin Lake Zone Marjolaine Pascal Kevin Ansdell Irvine Annesley SGS Open House December 2013 Collaborators: Dan Jiricka, Tom Kotzer, Michel Cuney and Marie-Christine Boiron

2 Outline Geological Setting of the Dufferin Lake Zone Rock Units Objectives Petrography Raman analysis Geochemistry Fluid Inclusions study Summary and Conclusions

3 Regional Geological Setting Jefferson et al., 2007

4 Local Geological Setting The Athabasca Basin: relatively undeformed late Paleoproterozoic clastic sequence (the Athabasca Group), dominated by oxidized (hematitic) quartz arenite Dufferin Fault 250 m UC off-set Taltson Domain Centennial Zone Virgin River Shear Zone area Dufferin Lake Zone (DLZ) Mudjatik Domain Archean and early Paleoproterozic basement rocks: deformed metamorphic rocks Felsic gneisses are the dominant rock type in the Mudjatik Domain The Virgin River Shear Zone is cored by the Virgin Schist Group in the DLZ area Pelitic and variably graphitic metasedimentary rocks of the Virgin Schist Group have been metamorphosed to upper greenschist to amphibolite grade The post-athabasca Dufferin Lake thrust fault is a dominant structural element

5 Rock units Red/Green Zone: hematitic and chloritic Pelitic Schist Bleached Zone: Phyllite non-graphitic, foliated, clay alteration Variably graphitic Pelitic Schist Unconformity: friable, bleached and clay alteration

6 Objectives To examine the processes that may have led to the consumption of graphite in the basement rocks underlying uranium mineralization To provide some information on the similarities and differences between the variably graphitic rocks and the ones depleted in graphite

7 Porphyroblastic to granoblastic, variably mylonitic Strong ductile deformation quartz, chlorite, muscovite, CM/graphite define the foliation relict garnet and staurolite porphyroblasts C-S structure and rotated porphyroblasts A Petrography Low C content -B B High C content -A

8 Three carbon species: highly crystalline graphite (Gr) semi-graphite (or hydrothermal graphite) (HGr) carbonaceous matter (CM) Concentrated along the foliation, within shear zones and along younger brittle fault zones A B High C content Medium C content A -A -B

9 Red Green Zone: Alteration assemblage: clay minerals chlorite hematite microscopic graphite in the lower part of the RGZ carbonaceous matter Several quartz generations overprint the original fabric Porphyroblasts are replaced No carbon where hematite and quartz overprinted Upper part more hematitic (Red Zone) Lower part more chloritic (Green Zone) Bleached Zone: Clay minerals, dravite A B A -B -A

10 Raman spectra and carbon species Well-crystallised carbon = Gr First-order region 1580 (G) Second-order region 2700 (S1) 1350 (D1) 2900 (S2) Annesley et al Semi-graphite 1620 (D2) CM Jehlicka et al Low-crystallised carbon = CM (Beyssac et al., 2002)

11 The different Raman spectra within the graphitic pelitic schist G First-order region Counts D1 D S1 Second-order region / cm-1 Raman shift / cm Counts S2 0 Raman shift / cm Raman shift / cm-1

12 Different Raman spectra of carbon species in the different zones First-order region D1 D3 G SW SW SW SW Upper RGZ Upper RGZ S1 Second-order region S2 Lower RGZ Lower RGZ Graphitic Pelitic Schist Raman shift / cm Raman shift / cm-1

13 First-order region G S1 Second order region S2 D Raman shift / cm-1 / Raman shift / cm -1 Raman shift / cm-1 B Medium C content -B Region 1: HGr-Gr Region 2: HGr-CM 2 1

14 4000 First-order region G 1583 X 3000 Counts 2000 D Sample from the upper RGZ D S1 Second-order region Raman shift / cm -1 Raman shift / cm-1 Counts S2 A -A Raman shift / cm -1 Raman shift / cm-1

15 High C content A Geochemistry A Medium C content B C B Low C content C

16 No distinct differences in major elements between the RGZ and the graphitic pelitic schist The samples from the bleached zone are enriched in TiO 2, Al 2 O 3, Na 2 O and K 2 O Na enrichment may result from the possible growth of fine-grained albite within the clay mineral assemblage High boron content (up to 13,100 ppm) due to high dravite content in the bleached zone

17 Fluid Inclusions study Sample descriptions Red/Green Zone (near the unconformity) below the mineralized area Brecciated Principally composed of hematite and chlorite Study on quartz boudins and quartz veinlets Moderately graphitic pelitic schist From a non-mineralized area Composed of rotated quartz boudins, sulfides along fractures, and quartz veinlets

18 Quartz Generations Q3 Q1: metamorphic quartz Q2a: quartz vein subparallel to the schistosity, it is pre- to syn-ductile deformation Q2b: similar to Q2a, but clearer quartz Q3: brittle quartz vein consisting of druzy, clear quartz, and carbonates Q4: late narrow quartz veinlets with carbonate, hematite, and pyrite Q4 Q2 Sample SW from the RGZ Only Q3 and/or Q4 could potentially be related to uranium mineralization Q2 Sample SW from the variably graphitic pelitic schist

19 Fluid Inclusion Types L+V 10% +halite Qtz (Q2) V % Qtz (Q2/Q3) L+V 10% Graphitic pelitic schist Red/green zone monophase vapor two-phase (L+V) three-phase (L+V+Halite)

20 Microthermometry Summary Basement Rocks Mineralized area Fluid Inclusion Type Fluid Inclusion size (μm) Fluid Inclusion chronology Range ( C) Two-phase (L+V) <Tmice< <Th< Red/ green zone In Three-phase (L+V+Halite) secondary <TmH< <Th< <%NaCl< 34.1 Monophase vapor TH Graphitic pelitic schist Out Monophase Vapor secondary <TH< -74.1

21 Temperature of homogenization (Th) versus temperature of melting ice and temperature of halite dissolution (Tm), with the area for Na-Ca-Mg brine and Na- Ca-Mg-Li brine. Data fields (after Derome et al. 2005)

22 Microthermometry Summary Basement Rocks Mineralized area Fluid Inclusion Type Fluid Inclusion size (μm) Fluid Inclusion chronology Range ( C) Two-phase (L+V) <Tmice< <Th< Red/ green zone In Three-phase (L+V+Halite) secondary <TmH< <Th< <%NaCl< 34.1 Monophase vapor TH Less altered rocks Out Monophase Vapor secondary <TH< -74.1

23 Raman Analysis: Results RGZ Graphitic pelitic schist CH 4 In graphitic pelitic schist 0 <CO2 (%wt)< <CH4 (%wt)< <N2 (%wt)< <Th ( C)< In graphitic pelitic schist 0 <CO2 (%wt)< <CH4 (%wt)< <N2 (%wt)< <Th ( C)< N 2 CO 2 In RGZ CO2 (%wt) = <CH4 (%wt)< <N2 (%wt)< 85.3 Th ( C) =

24 Summary and Conclusions Bleached Zone Red Zone RGZ Green Zone Variably graphitic pelitic Schist No carbon species observed Most highly altered with enrichments in Al, Ti, Na, K, B, and U Variable loss of graphite (+ sulfide) confirmed macroscopically, petrographically, and geochemically Carbon species present, but in very low quantity Mainly amorphous carbon Similar major element composition with the graphitic pelitic schist Loss of C and S Quartz +/- hematite overprint the original fabric, and may be linked to the loss of graphite Evidence for 2 brines: The regional basinal fluid (Na-Ca-Mg brine) An evolved brine possibly related to U mineralization (Na- Ca-Mg-Li brine) Different kinds of mainly well-ordered carbon species Monophase vapor FI Could be generated by the breakdown of graphite to CH 4 and associated feldspars/micas to NH 4 and N 2 Three possible reductants for uranium mineralization

25 Thank you! Questions? Dufferin Lake