13.07.13 snowball or slushball earth glaciation 2.4ga? resolving … · 2013. 7. 18. · 13.07.13!...
TRANSCRIPT
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Snowballearth.org
Ilya Bindeman, University of Oregon
Collaborators: A.K. Schmitt (UCLA), D.A.D. Evans (Yale), N.S. Serebryakov (Moscow), A. Bekker (Manitoba)
Thanks to: P. Hoffman ( U Victoria), Guan B, J Eiler (Caltech) J Vazquez (USGS) NSF grant EAR 108786
Snowball or Slushball Earth Glaciation 2.4Ga? Resolving microanalytical evidence in subglacially hydrothermally-altered (down to -27.3‰ δ18O) rocks and coeval supergene materials
Snowballearth.org
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Valley et al., 2005
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The world “record”: 2.45Ga, -27.3‰ δ18O metagabbro/gneisses from Karelia, Russia���
δD= -235‰
Global Distribution of water isotopes www.waterisotopes.org
Karelian values
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Comparison with Modern climates
... Greenland-like, -20°C to -35°C
-25‰ and below
Low-δ18O rocks and magmas track cold climates
-25
-15
-5
5 Rock
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Belomorian Belt
A!
In 2.4 Ga gabbro 2.6 Ga gneiss
The lowest isotope values:
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Ky-Grt-Bi Grt-Bi
Ruby-Grt-Bi
Grt-gabbro
-27.3‰
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“Old” isotope sampling map 2011
and 2012:
2011
2010 Red – low δ18O Yellow- normal
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Isotope Profiles in other localities:
Bindeman and Serebryakov, EPSL, 2011
Equilibrium within crystal clusters, δ18O heterogeneity on cm, m, 10 m scales
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Bull’s Eye patterns are very common in ore deposits (Taylor, 1973, 1974), in Skaergaard Intrusion (Taylor and Forester 1979)
Explanation: Rifting under ice
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Summary of field/geological observations
• 2.6 Ga Gneiss, 2.4 Ga mafic intrusions, 1.9 Ga metamorphism
• Depletions of δ18O and δD are in or near contacts with 2.4-2.45 Ga mafic intrusions
• These intrusions are related to rifting • Depletions of δ18O and δD form “bull’s eye” concentric
pattern, characteristic of modern hydrothermal systems • Depleted localities occur over 220 km
Bindeman et al. 2013 in press
Tectonic Story Zircon Story!
2.6Ga
2.4 Ga hydrothermal alteration
1.9Ga metamorphism
Low-δ18O matrix ca -27‰ Intact 2.6 Ga, +7‰ zircon
Low-δ18O matrix, 1.9Ga, -27‰ rims
Normal-δ18O matrix, zircon
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Methods
K a relia 17- O va ria tions
y = 0.5276x + 0.2033
R2 = 1.0000
-20
-15
-10
-5
0
5
10
-40 -30 -20 -10 0 10
1 0 0 0 * l n(1 + d 1 8 O /1 0 0 0 )
10
00
*ln
(1+
d1
7O
/1
00
0)
Karelian samples firmly belong to the “Equilubrium” terrestrial 18O/16O -17O/16O fractionation line
TFL
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Cometary Impact? No: Δ17O = 0‰
Analysis of individual minerals in crystal clusters
Bindeman et al 2010
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Isotope Mapping of a single corundum crystal
Fig. 5
Hydrogen Isotopes Insights - record low δD of -235‰
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2.4Ga Subglacial Rifting
Karelia in the Paleoproterozoic:
Bindeman Schmit Evans 2010
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Paleoprot. glacial
deposits
a"er assembly in the Nuna
supercon4nent
Figure from Young, 2004
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Using zircon to resolve the timing of δ18O depletion
• Perfect mineral to retain U-Pb age and δ18O values • Requires high T (ca>650°C) to recrystallize or exchange O • So it only records magmatic or metamorphic episodes • Untouched by hydrothermal alteration
Dating synglacial intrusions = Dating glaciations (and rise of atmospheric oxygen)
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Zircon Story: 2.6Ga rock
2.4 Ga hydrothermal alteration
1.9Ga metamorphism
Low-δ18O matrix ca -27‰ Intact 2.6 Ga, +7‰ zircon
Low-δ18O matrix 2.6 Ga, +8‰ zircon cores, 1.9Ga, -27‰ rims
Normal-δ18O matrix, zircon
rims K5
rims AB-3351
When did the δ18O depletion happen? Nuna Superia Supercontinents:
Rifti
ng, h
ydro
ther
mal
alte
ratio
n
Rifti
ng, h
ydro
ther
mal
alte
ratio
n
Glacials
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How did it happen?
Do Karelian rocks record Snowball or “Slushball Earth”?
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+4‰
+6‰
-2‰
-11‰ ? Tiny amounts, Mixed with snowflakes
δ18O water, ‰
Jormangund Climate State (2011):��� Dorian Abbot (U Chicago)
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Modern
Hard-Snowball
Jormangund
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Slush-Ball vs Hard Snow Ball Earth climate models and implications
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18O/16O in Global Circulation Model of Slushball Earth δ18O, ‰
Jun-Eun Lee and Bindeman in prep.
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T a nd d18O vs la titude
-70
-60
-50
-40
-30
-20
-10
0
10
-25 -15 -5 5 15 25 35 45 55 65 75
La titude, degrees
T o
r d
18
O,
‰ S
MO
W
T' °Cd18O, precipi tation
Equa
tor
Over Ocean
Over continent
Karelian Position
Conclusions and what’s next? - Kareilan Gneiss record depletion during ~2.4 “Slushball Earth” or
Jurmangand episode (the first of the 3) to allow for effective vapor δ18O, δD distillation
- What is next? We are trying to find sedimentary rock that would
correspond in age to the Slushball Earth episode - Testing stability of the Slushball Earth model is required
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Supracrustal Materials that may record δ18Owater:
- Secondary Quartz – Amygdaloids - Glacial Rock flower - Pillow basalts - Shales
Comparison with Antarctica
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Why most depleted oxygen isotopes are found in mid- to ultrahigh-pressure metamorphic rocks? - Dabie Shan -Sulu (China) coesite-bearing eclogites, -10 to +2 ‰ (Rumble and Yui, 1998; Zheng et al. 2004-2010) 800-200 Ma 500 papers published on δ18O in Dabie Shan! - Kokchetav (Kazakhstan), coesite-bearing, down to -3.9‰ (Masago, Rumble et al 2003) 580-530 Ma Now Karelia -27‰! Mid grade kyanite-bearing gneisses 2.6-1.8 Ga
Bindeman et al., 2013 in press
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Fiordfelt +7.3, +12.2‰
Makbal +6.9‰
Kumdikul +6.6‰
Alpe Arami +3.9-5.4‰
Erzgebirge
Rodopi +11.3‰
+10.6‰
Sederonero +13.4‰
Oxygen isotopic values of diamond-bearing, exhumed UHP metamorphic rocks: Mostly high-δ18O
Sample collection of Larissa Dobrzhinetskaya, UC Riverside
How long does it take?
Snowballearth.org
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Dissolution in 200°C fresh water
Reed et al. Chiller Program
Modeling Chemical ���change to make ���
high-Al lithology
Fig. A Retrogression of oxygen isotopic values in a typical corundum bearing assemblage as a function of cooling and d ifferential closure using Fast Grain Boundary diffusion model of Eiler, Baumgartner, and Valley, (1993). Notice that even at slow cooling rate of 1 degree per million years corundum, garnet, hornblende, staurolite, and kyanite do not retrogress and preserve their original, peak metamorphic temperature of formation. Plagioclase, rutile, and biotite display retrogression of less than 0.7 permil. Sizes of minerals and their proportions are given in the table. At faster cooling rate even less retrogression is expected. Therefore, Isotope heterogeneity observed within hand specimen (see Table A1 and Bindeman et al. 2010, Fig. 2) cannot be explained by differential retrogression and must reflect source variability and interaction with external fluids.
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Extra Generic Snowballearth slides from Snowballearth.org
Pale
opro
tero
zoic
?
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Paleoproterozoic Glaciations
Hydrologic Cycle on Snowball Earth? None
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Vaalbara supercraton
Paleomag. (De Kock et al., 2009)
Meteorite Bore Member, Kungarra Fm (Pilbara) Makganyene Fm (Kaapvaal)
Paleoproterozoic glacial deposits original distribu4on in the
Superia supercraton
Hw
K
C Hn Ch
S
Figure a2er Ernst & Bleeker 2008
reassembled in Nuna
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Stratigraphic column of the Huronian Supergroup in Ontario, Canada (modified from Bekker et al., 2006: One OR Three Glaciations?
2.32Ga
2.4 Ga Karelia Glaciation
Glacial paleolatitudes
darker shade indicates more reliable paleomagnetic data
Paleoproterozoic units Meteorite Bore: 05° Makganyene: 11° Gowganda: 03° (?) Sariolian: 07-27°
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a b c
d e
Field relations between different rock types: a) original Chupa gneiss; b) St-Pl pseudomorphs over large crystal of Ky at Khitostrov; c) rock with large Crn; d) St-Pl pseudomorphs over large crystal of Ky at Khitostrov; d) Corundum-bearing rock (pen is pointing to Crn), impregnated by plagioclazite at Khitostrov; e) large crystals of garnet in chloritic rock inside amphibolite at Mt. Dyadina.