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Robert Linnen, Department of Earth Sciences, University of Western Ontario
Metallogeny of Lithium Pegmatites
Acknowledgements: Laurisha Bynoe, Paul Kremer, Marieke Van LichterveldeDon Burt, Don Davis, Carey Galeschuk, David London, Gary Pearse, David Trueman
TANCO Tantalum Mining Corporation of Canada, Ltd.
Structure of the Talk
Review of Pegmatite Types and Classification Structural Controls of Pegmatite Emplacement
(focus on Tanco and Whabouchi) Exploration for Pegmatites, Traditional and
Novel Techniques
Pegmatite Classification
after Cerny (1991) in Simmons and Weber (2008)
Greenbushes, Quebec Lithium
Tanco (squi), Big Whopper
Wodgina
Whabouchi, Mt. Cassiterite, Kings Mtn
petalite – LiAlSi4O10
spodumene – LiAlSi2O6
squi: spod-qtz intergrowthPet = Spod + 2 Qtz
Spodumene Indicates Higher Pressure or Undercooling
from Linnen et al. (2012) after London (2005)
Multiple Commodities versus Single Commodities
Greenbushes PegmatiteCentral Lode Stage 1 at 11150 mNfrom Freeman and Donaldson (2004)
Long Section of the Tanco pegmatite
Černý et al., 1996
Lithium Pegmatites Have Extreme CompositionsWhat Processes Control this?
Granite pegmatites have granite compositions and are controlled by magmatic processes
London (2008)
London (2008) after Stewart (1978)
1.85% Li2O at eutectic
An Anatectic Origin?
Extreme Fractional Crystallization
from Breaks et al. (2005)
PeraluminousSedimentary sourceLi-Rb-Cs-F in micasBe in cordierite, muscoviteTa-Nb-Sn in Ti minerals
Separation Rapids Plutonfrom Breaks et al. (2005)
Extreme Fractional Crystallization
from Breaks et al. (2005)
Located at Margins of Major Subprovinces
also located at the boundary between major tectonic Sub-Provinces
Whabouchi Pegmatite
Houle (2003)
Greenbushes pegmatite Western Australia
Pegmatite-Shear Association
after Partington (1990)
after Duguet (2007)
Bernic Lake Pegmatite Group
• Tanco pegmatite
– Tabular, shallowly-dipping
– Hosted in prominent fracture set
– Rheologically competent lithologies
• Oompa Loompa
– Folded and/or boudinaged
– Hosted in highly deformed metavolcanics/volcaniclastics
Fracture-hosted, tabular
pegmatite, Tanco mine
Folded pegmatite, Bernic Lake
Pegmatite Emplacement Styles
from Kramer (2009)
Tanco2640 ± 7 Ma
Oompa Loompa2647 ± 2 Ma
• Doubly-dipping body
• Hosted in metagabbro
• Occurs in conjugate fracture set
Fracture-hosted tabular pegmatite at Tanco
Conjugate fracture set in gabbro at Tanco
From Stilling, 1995
From Kremer, 2009
From Kremer, 2009
Tanco Pegmatite
from Kramer (2009)
Model for the Emplacement of the Tanco Pegmatite
from Kremer (2009)
WhabouchiPegmatite
from Nemaska 2009 NI 43-101 report
(after Hocq, 1994)
Measured and Indicated Resource
of 27.99 Mt of 1.57% Li2O
(0.43 % Li2O cutoff)Nemaska Lithium
Inc. (2016)
WhabouchiGeology
from Bynoe (2014)
Granite monazite 2649 ±10 MaGranite zircon age
2704 ±8.6 Ma
Whabouchi zircon age 2577 ±13 Ma
Pegmatite zircon age 2594 ±11 Ma
Pegmatite monaziteage 2621 ±9.5 Ma
Pegmatite zircon 2530 ±14 monazite 2578 ±14 Ma
Pegmatite monazite 2584 ±7 to 2579 ±8 Ma
from Bynoe (2014) and unpublished data
Metabasites at Whabouchi
Distal to the pegmatite Turbulent shear zone with smeared leucocratic component
from Bynoe (2014)
Structural Analysis
Crosscutting relationship between the pegmatite and host rocks showing evidence of dextral sense of shear
Crosscutting relationship between the pegmatite and host rocks showing emplacement of the Li pegmatite after the onset of deformation
from Bynoe (2014)
Metabasite interpreted to be the preferred host and
shearing controlled pegmatite emplacement
from Bynoe (2014)
Whabouchi Pegmatite Emplacement
London (2008), after Cerny (1990)
Emplacement in Pegmatite Fields
London (2008), after Cerny (1990)
from Černý (1989)
Emplacement in Pegmatite Fields
Exploration - Prospecting
Whabouchi Pegmatite
Lithogeochemistry
from Fetherston, 2004
Lithogeochemistryat Whabouchi
from Bynoe (2014)
Recent Drilling
Nemaska press release (2016)
from Morgan & London (1987)
Most Indicator
Mineral Studies Have
Concentrated on
Pegmatite Minerals
Wallrock Minerals
Have Received Much
Less Attention
Rb in Biotite Around Tanco
from Galeschuk and Vanstone (2005)
Indicator Mineral Study of the Dibs Pegmatite
The Dibs pegmatite is completely buried, at a depth of ~ 70m
Found by lithogeochemistry, but Tanco had many false positives from lithogeochemistry
Lithogeochemistry from Drill Holes(Classic elements)
- Mobility of Li>Rb>Cs, similar to previous studies
- Note enrichment at the bottom
- Top of whole ~ 30 ppm Li (2x threshold), ~15 ppm Rb
& 5 ppm Cs (both values near threshold)
Cs anomaly
Linnen et al (2009)
Metabasite Mineral Chemistry
Linnen et al (2009)
Fracture Geochemistry
Late syn-kinematic
Amphibole±Plag±ZoisiteChlorite-Carbonate-Titanite
±Zoisite ±Amphibole
Late syn- to post-kinematic
Linnen et al (2009)
Chlorite
Note scale for Li, 100’s of ppm distal to pegmatite
Linnen et al (2009)
Summary of Li data (distal to pegmatite - 60m)
Whole-rock: 30 ppm Li
Fracture chlorite: 200 to 400 ppm Li
-Fracture chlorite may explain false-positive lithogeochemical anomalies- By contrast fracture chlorite shows promise as an exploration tool
Thank you