update from the mantle group · sclm beneath the superior craton geotherm: 41mw/m2 at ~2700 ma...
TRANSCRIPT
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METAL EARTH Advisory Board Meeting
Update from the Mantle Group
J. Czas, A. Vezinet
D.G. Pearson, S. Shirey
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Archean continental crust Adrien Vezinet – Part 2
The lithospheric mantleJanina Czas – Part 1
Outline
Unconventional approaches to the study of metal endowments
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The lithospheric mantleAge, composition and metal endowment
J. Czas, A. VezinetD.G. Pearson
Collaborators: S.B. Shirey, P. Waterton, D.J. Schulze,C. Veglio, C. Lawley (GSC)
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The Lithospheric Mantle
Why is it important to study the lithospheric mantle?
?
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The Lithospheric Mantle
Why is it important to study the lithospheric mantle?
Metal endowment derived from Earth’s mantle
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Where do our samples come from?
Cratonic lithospheric mantle
- 50 – 250 km
- 500 – 1300 oC
- Record geochemical conditions
at the time of eruption
window into the deep & past
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Where do our samples come from?
Cratonic lithospheric mantle
- 50 – 250 km
- 500 – 1300 oC
- Record geochemical conditions
at the time of eruption
window into the deep & past
![Page 8: Update from the Mantle Group · SCLM beneath the Superior Craton Geotherm: 41mW/m2 At ~2700 Ma (Hasterok and Chapman, 2011) Wawa websterites Kirkland Lake peridotites. Kirkland Lake](https://reader033.vdocument.in/reader033/viewer/2022060215/5f05d6a67e708231d414f6bc/html5/thumbnails/8.jpg)
Metals in the lithospheric mantle
Role of lithospheric mantle in metal endowment
Age of the lithospheric mantle
Timing and location of metals storage and transport
Key QuestionsKirkland Lake Peridotite
1 cm
Sulphide
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Superior Craton
WATWawa-AbitbiTerrain
Kirkland Lake (kimberlites 147 158 Ma)
Wawa(lamprophyres 2685 - 2744 Ma)
after Percival et al., 2012
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Superior Craton
Unique opportunity to study the lithosphere beneath major gold deposit
Kirkland Lake Kimberlites
Lawley et al. unpublished
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Superior Craton
Schaeffer and Lebedev, EPSL 2014
Midcontinent Rift
Perturbations in S-wave velocity model at 100km
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Superior Craton
WATWawa-AbitbiTerrain
Kirkland Lake (kimberlites 147 158 Ma)
Wawa(lamprophyres 2685 - 2744 Ma)
after Percival et al., 2012Midcontinent Rift
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Kirkland Lake Kimberlites
SCLM beneath the Superior Craton
Geotherm: 40mW/m2
At ~150 Ma(Hasterok and Chapman, 2011)
Wawa websterites
Kirkland Lake peridotites
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Kirkland Lake Kimberlites
SCLM beneath the Superior Craton
Geotherm: 41mW/m2
At ~2700 Ma(Hasterok and Chapman, 2011)
Wawa websterites
Kirkland Lake peridotites
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Kirkland Lake Kimberlites
SCLM beneath the Superior Craton
Wawa websterites
Kirkland Lake peridotites
Blocking Temperature
Conventional Isotopes
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The age of the lithospheric mantle
187Re
187Os
melt
Residual mantle
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The age of the lithospheric mantle
TRD = Minimum age (Re depletion)
Re/Os=0
187Re
187Os
Residual mantle
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Age of the Superior cratonic mantle
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Summary
Lithospheric mantle beneath Wawa & Kirkland Lake
Difference in age (data) and composition
Emerging picture
Olivine can host metal elements
Depth dependent metal concentration in lithosphere
Potential effects of large scale metasomatism
(Midcontinent Rift)