New technologies provide transformative insights intoglobal geochemistry
Seem a K um ari
National P ostdoctoral Fellow
Centre for Earth Sciences
I ndian I nstitute of Science, Bangalore
International Symposium, Frontier of Understanding Earth's Interior and Dynamics
Hosted by Tohoku Forum for Creativity

24-Aug-22

International Symposium, TFC, Sendai

1Geoneutrino flux
Defines Radiogenic Power
Constrains Bulk Earth Composition
Why Geochemist should care???
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International Symposium, TFC, Sendai

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Major Questions

Current surface heat flux = 46 ± 3 TW
Earth’s radiogenic power

What drives the Earth’s dynamics

Interdisciplinary
approach

Mantle structures: whole VS layered convection
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International Symposium, TFC, Sendai3

Earth’s Thermal History
sets the Initial condition

Primordial Heat

• Planetary accretion• core formation

How much fuel isleft to drive theplate tectonics ??

Radiogenic Heat

• Short-lived isotopic decay,
26Al, 60Fe
• Decay of U, Th, and K
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throughout the Earth’s Evolution

International Symposium, TFC, Sendai

4Assumptions:

Mass fraction of Earth

Earth’s tau-age = 10 Myr

Time (million year)
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McDonough et al. (2020), G-cube

International Symposium, TFC, Sendai

5Particle physics endeavors in estimating the U, Th
β - decay process (e.g., U, Th, K, Re, Lu, Rb)

Antineutrino flux spectrum dΦ/dEν at position r from a given
radionuclide distributed with abundance A in the Earthup-quark

Inputs from geoscience:•chemical abundances A•

density ρInputs from nuclear/particle
physics:

down-quark

Electron anti-neutrino
Geoneutrino•decay rate D•

antineutrino intensity
spectrum dn/dEν,•

antineutrino survival
probability Pee

geoneutrino flux = global measure of present-day U and Th
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International Symposium, TFC, Sendai

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Global distribution of inland underground detectors
Red-detectors counting
geoneutrino
Purple- have counted
Blue- in thedevelopment and/orplanning stage
Bold blue- JUNO, in theconstruction phase.
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Geoneutrino emission and relative contribution
Total geoneutrino emission:

X

Stotal = Slithosphere + Smantle + Score
Slithosphere = SNear Field L + Sfar Field L
Stotal - Slithosphere = Smantle

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Relative Contributions

Araki et al. (2005), Nature24-Aug-22

Near-field crust ~50%Šrámek et al. (2005), Nature

International Symposium, TFC, Sendai

9KamLAND

𝟏𝟏𝟏𝟏. 𝟔𝟔+𝟓𝟓.𝟐𝟐−𝟒𝟒.𝟐𝟐 TW

8 TW

Total

𝟑𝟑𝟑𝟑. 𝟐𝟐+𝟏𝟏𝟏𝟏.𝟔𝟔−𝟏𝟏𝟏𝟏.𝟕𝟕 TW

Mantle30 TW

Borexino

KamLAND ≠ Borexino

1 kt liquid Scintillator

0.3 kt liquid Scintillator

Why this discrepancy??

24-Aug-22

International Symposium, TFC, Sendai

10Geologic model: Borexino
Agostini et al. (2020, Phy. Rev. D.)

HPE-poor, carbonate-rich;no igneous component
Sammon & McDonough (2022, EPSL)

rich in potassic magmatism

Sammon and McDonough (2022); EPSL
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International Symposium, TFC, Sendai

11Local crust (<500 km) contributes~50% of the total signal, andmostly the upper crust

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International Symposium, TFC, Sendai

12Agostini’20 -vs- GenericSammon and McDonough (2022, EPSL)

Hi-resolution crustal model is essential
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Geologic Model: KamLAND
Surface Sediments:
average upper
continental crust,
Rudnick and Gao(2014)
Deep crustal model:
Sammon andMcDonough (2021)

24-Aug-22

International Symposium, TFC, Sendai

14+𝟑𝟑.𝟔𝟔
Mantle Geoneutrino Flux : 𝟗𝟗. 𝟐𝟐+𝟓𝟓.𝟐𝟐−𝟔𝟔.𝟓𝟓 TNU or 𝟏𝟏𝟎𝟎. 𝟐𝟐−𝟒𝟒.𝟓𝟓 TW

U = 12.8 ppb, Th = 48.8 ppb

Assume, (K/U)BSE = 13800 ± 1300,Total mantle radiogenic power: 𝟏𝟏𝟐𝟐. 𝟔𝟔+𝟒𝟒.𝟔𝟔−𝟓𝟓.𝟕𝟕 TW

Lithosphere + mantle: 𝟐𝟐𝟐𝟐. 𝟏𝟏+𝟕𝟕.𝟏𝟏−𝟖𝟖.𝟗𝟗 TW from U, Th, and K

Total radiogenic power (U + Th): 𝟏𝟏𝟏𝟏. 𝟑𝟑+𝟓𝟓.𝟖𝟖−𝟕𝟕.𝟐𝟐 TW

U = 20.5 ppb, Th = 77.3 ppb~ peridotite (MS95), U = 20.3 ppb, Th = 79.5 ppb

Silicate Earth = 2.7 × CI carbonaceous chondrites

24-Aug-22International Symposium, TFC, Sendai

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Implication of understanding Bulk Earth Composition
Nature of accretion ofmaterial in inner nebula+ other planets formation

astronomical model ofplanet formation
Understanding of our solar
system’s planets(discovering life elsewhere)
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International Symposium, TFC, Sendai

16Compositional model of Earth
Earth: atom%

50405030

2020

101000Mg

SiFeAlSCaNi

One out of every two atoms inEarth is oxygen
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93%
Earth’smass

4030

O

Earth: weight%

6% Earth’smassOMg

SiFeAlSCa8 elements describe 99%
Earth’s massInternational Symposium, TFC, Sendai

NiU, Th17

Compositional model of EarthMineralogy

Earth: seismically defined

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International Symposium, TFC, Sendai

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Compositional model of EarthMineralogy

Seismic wave discontinuities arecoincident with major phase changes

Which one is right?

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International Symposium, TFC, Sendai

19ModelRadiogenic
Power (TW)UBSE (in ppb)
Enrichment
factor relative toCI Chondrites

24-Aug-22

Compositional model of Earth
Earth’s model -vs- Geoneutrino
Low Q
Med Q High Q(Javoy et al., (McD&S, (T&S,2010)
1995) 2014)
102030
111.5

20

2.7

30

3.9

𝝂𝝂� 𝒆𝒆 Flux
20.1
20.5
2.7

Two independent method, same conclusion
International Symposium, TFC, Sendai

20Compositional model of Earth
Mantle heterogeneity

Kellogg et al. (1999); Science
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Presence of geochemicallyheterogenous domains

International Symposium, TFC, Sendai

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Mantle heterogeneity

Feng et al (2021, Nat. Comm.)

Subducting plate stagnates
at variable depths

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Mantle heterogeneity

Bull et al (2009); EPSLCan we detect such variation ingeoneutrino flux??
24-Aug-22Šrámek et al. (2013); EPSL

Mantle geoneutrino prediction (excludingcrustal signals)
International Symposium, TFC, Sendai

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Mantle heterogeneity
Assumptions:Geochemical BSE and A&McD
depleted mantle abundances
Seismic tomographic model
S20RTS (Ritsema et al., 1999)
Enriched mantle

VS anomaly less than -0.25%
relative to PREM
Deeper than 1500 km

Can we detect such variation ingeoneutrino flux??
24-Aug-22Šrámek et al. (2013); EPSL

Mantle geoneutrino prediction (excludingcrustal signals)
International Symposium, TFC, Sendai

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Necessity of Ocean Bottom Detector (OBD)
Detector gets a “mostly-mantle“ signal

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International Symposium, TFC, Sendai25

Geoneutrino flux Defines Radiogenic Power : Proper geological assessment
 Constrains Bulk Earth Composition : Independent of Earth’sstructure

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ANEKĀNTAVĀDA

Sanskrit: “non-one-sidedness” or “many-sidedness”

Truth depends on one’s point ofview

No single point of view comprises
the complete truth

These views are not wrong, merelyincomplete.
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