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Revealing the Earth’s mantle fromthe tallest mountains using theJinping Neutrino ExperimentOndřej Šrámek1, Bedřich Roskovec2, Scott A. Wipperfurth3, Yufei Xi4 & William F. McDonough3

accepte : 18 u ust 016
Pu is e : 0eptem er 016

The Earth’s engine is driven by unknown proportions of primordial energy and heat produced
in radioactive decay. Unfortunately, competing models of Earth’s composition reveal an orderof magnitude uncertainty in the amount of radiogenic power driving mantle dynamics. Recentmeasurements of the Earth’s flux of geoneutrinos, electron antineutrinos from terrestrial naturalradioactivity, reveal the amount of uranium and thorium in the Earth and set limits on the residual
proportion of primordial energy. Comparison of the flux measured at large underground neutrino
experiments with geologically informed predictions of geoneutrino emission from the crust provide
the critical test needed to define the mantle’s radiogenic power. Measurement at an oceanic location,
distant from nuclear reactors and continental crust, would best reveal the mantle flux, however, nosuch experiment is anticipated. We predict the geoneutrino flux at the site of the Jinping Neutrino
Experiment (Sichuan, China). Within 8 years, the combination of existing data and measurementsfrom soon to come experiments, including Jinping, will exclude end-member models at the 1σ level,
define the mantle’s radiogenic contribution to the surface heat loss, set limits on the composition of
the silicate Earth, and provide significant parameter bounds for models defining the mode of mantle
convection.
Recent cosmochemical observations have produced a range of compositional models for the silicate Earth andits prediction for the amount of radiogenic power in the Earth1–5. Likewise, new insights on the thermal andelectrical conductivity of the Earth’s core6–11 have greatly revised our understanding of the core–mantle boundary heat flux, which in turn has significant implications on the nature of the Earth’s surface heat flux. Thesefindings permit a broad range of estimates of the radiogenic power available in the silicate Earth. Of the 46 TWof heat output from the Earth’s interior12,13, anywhere between ~10 TW and ~30 TW are attributed to the decayof long-lived radionuclides (i.e., 40K, 232Th, and 238U) within existing compositional models14. The continental
lithosphere accounts for 8 TW15 leaving negligible (2 TW; i.e., 10 TW–8 TW) to significant (22 TW) amounts ofradiogenic power contributing to mantle dynamics16–20. The complex and inaccessible deep Earth system, wheremantle dynamics is coupled to processes in the metallic core, has so far resisted efforts to better constrain the K,
Th, U abundance in the Earth.
Compositional models of the Earth have been categorized into three groups based on the available radiogenic
power21,22: low-Q models (10–15 TW), medium-Q models (17–22 TW), and high-Q models (>25 TW). Low-Q
models assume a low K, Th, and U concentration in the material that formed the Earth (the enstatite chondrite
model and the non-chondritic model) or invoke an impact-induced loss of early differentiated crust enriched inheat-producing elements (the collisional erosion model). Medium-Q models estimate the silicate Earth composition using elemental fractionation patterns between melt (basalt) and melt residue (peridotite) while constraining
the ratios of refractory lithophile elements to abundances in C1 chondritic meteorites. High-Q estimates are
the high end-member of physical models which rely on simple relationship between the heat output from theconvecting mantle and the vigor of convection, described as a balance between thermal buoyancy driving thedynamics and thermal and momentum diffusion hindering the flow.
1Department of eop sics acu t of at ematics ansics
ar es ni ersit in ra ueoe o i c
180 00 ra a 8 ec epu ic. Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics,
ar es ni ersit in ra ueoe o i c
180 00 ra a 8 ec epu ic. 3Department of Geology, University
4of ar ano e e ar
D 0 4
nite tates. Institute of Hydrogeology and Environmental Geology,
inese ca em of eo o ica ciences
i ia uanina. orrespon ence an re uests for materia s s ou
e a resse to O. . emai : on re .srame
mai .com

Revealing the Earth’s mantle
from the tallest mountains using
the Jinping Neutrino Experiment1

Scientific RepoRts | 6:33034 | DOI: 10.1038/srep33034

doi:10.1038/srep33034

Ondřej Šrámek1, Bedřich Roskovec2, Scott A. Wipperfurth3, Yufei Xi4,William F. McDonough3
1 Department of Geophysics, Charles University, Prague, Czech Republic
2 Institute of Particle and Nuclear Physics, Charles University, Prague, Czech Republic
3 Department of Geology, University of Maryland, College Park, USA
4 Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang, China

Presented at International Workshop: Neutrino Research and Thermal Evolution of the Earth, Tohoku University, 26 Oct 2016

Crustalthickness

KamLAND&Borexino
have measured
geoneutrino flux

(CRUST1.0)

2Current geoneutrino measurements
20052011

2013

Borexino

90

2016
preliminary

80

Watanabe’s
talk yesterday

2010

2013

2015

100
9080707060605050404030302020

10

1 TNU (“Terrestrial Neutrino Unit”) =1 IBD event over a year-long fully eﬃcient exposure of 1032 protons

0100Compare to predictions from Earth models
to constrain abundance of Th, U in the Earth
3TNUTNU

100

KamLAND

How much radiogenic power in this planet?
CrustMantle
Core•

How much of the 46±3 TW of power coming out of the Earth is due toradioactivity?

•How much radiogenic heating in the mantle to power thermal convection?

•Earth’s mantle has uniform composition, or is layered, or has complex structure?

•How much is the crust enriched in heat-producing elements relative to themantle? Local crust around detector?

•What is the composition of material from which Earth was built?

•Rate of cooling of the Earth, at present and over time?
4

Three more experiments
measuring geoneutrinos
to come5

SNO+(soon)

JUNO(2020)

Jinping(>2020)In this letter of intent, we propose the Jinping Neutrino Experiment (Jinping), a uniq
for low-energy neutrino physics, astrophysics and geophysics. The total detector
about 4 kiloton of liquid scintillator or water-based liquid scintillator, with a fid
kiloton for neutrino-electron scattering events and 3 kiloton for inverse-beta inteWith low radioactivity backgrounds, based on existing technology, and low cosmoge
backgrounds, based on depth and location, Jinping would have unprecedented sens
China JinPing Laboratory (CJPL) has a number of unparalleled features (Foverburden, lowest reactor neutrino background, dominant crustal geo-neutrino signronmental radioactivity, longest solar neutrino path through the Earth, etc. All of t
identify it as the world-best low-energy neutrino laboratory. Moreover, CJPL has itical advantages, including being within two hours of an airport, reachable on go
drive-in access for trucks, and with excellent supporting infrastructure. The first,the laboratory (CJPL I) is already inhttp://jinping.hep.tsinghua.edu.cn
operation, hosting dark matter experiment
3 being excalargephase(CJPLII)
isalreadyunderconstruction,with∼100,000m
Beacom et al. arXiv:1602.01733

Nuclear reactors

Total Muon Flux (cm-2s-1)

Jinping Neutrino Experiment−310WIPP
KamiokaGran_Sasso
Homestake
CJPL

10−410−5−610

SoudanBoulbyModaneSudbury

10−7
10−8−910−1010
Beacom et al. arXiv:1602.01733

10−11e 7: (Color online) World map with all currently running and being constructed nuclear powers and SNO, Gran Sasso, Kamland and Jinping laboratory locations marked.

Y. C. WU, Chinese Phys. C37, 086001 (2013).

nternational Atomic Energy Agency, http://www.iaea.org/ (2015).

6610810107
Reactor Neutrino Rate (cm-2s-1)
Beacom et al. arXiv:1602.01733

1. Geoneutrino flux prediction at Jinping
2. Prospects for combined analysis of all measurements
3. Studying lithosphere with geoneutrinos

7

We calculated geoneutrino flux prediction
at Jinping
φ … Antineutrino flux
X … Natural isotopic mole fraction
λ … Half-life
NA … Avogadro’s number
μ … Standard atomic massnν … Number of antineutrinos per decay⟨Pee⟩ … Average survival probability
A … Elemental abundanceρ … Mass densityr … position

Predicting geoneutrino flux from emitters (232Th, 238U)
distributed spatially with mass fractions A(r)in the Earth with mass density ρ(r)Previous geonu emission models:(non-exhaustive list)•
Krauss et al. 1984•
Kobayashi & Fukao, 1991•
Mantovani et al. 2004•
Enomoto 2005 (PhD)•
Enomoto et al. 2007•
Fiorentini et al. 2007•
Huang et al. 2013
•Usman et al. 20158

Geoneutrino emission model• Model of crustal geometry and material density from CRUST1.0 model (Laske et al.)• Material density in the mantle from PREM model (Dziewonski & Anderson 1981)• Assume negligible Th, U in the core
• Total amount of Th, U in Silicate Earth from estimate by Arevalo et al. 2009, 20±4 TW radiogenic power)

1º lat × 1º lon crustal tiles

CRUST

1.0Crust

upper sediments

depthMantle

Core

Vertical structure of a crustal tile

middle sediments
lower sediments
upper crust

PREM

middle crust
lower crust

Oceanic
reference Earth radius 6371 km

Sediments (layers 3–5)
Upper Cont. Crust (layer 6): Rudnick & Gao 2014
Middle Cont. Crust (layer 7): Rudnick & Gao 2014

Oceanic Sediments (layers 3–5): Plank 2014
Oceanic Crust (layers 6–8): White & Klein 2014

Lower Cont. Crust (layer 8): Rudnick & Gao 2014
Continental Lithospheric Mantle
Huang et al. 2013

175 km depth

Depleted Mantle: Arevalo & McDonough 2010
radius 4202 km

Enriched Mantle: Th, U abundance from mass balanceradius 3480 km

9Oceanic CrustContinental CrustContinental

Mass fractions of Th and U

Geoneutrino emission model
Treatment of uncertainties• 1σ uncertainties on Th, U concentrations adopted from composition estimates
Oceanic
reference Earth radius 6371 km

Sediments (layers 3–5)
Upper Cont. Crust (layer 6): Rudnick & Gao 2014
Middle Cont. Crust (layer 7): Rudnick & Gao 2014

Oceanic Sediments (layers 3–5): Plank 2014
Oceanic Crust (layers 6–8): White & Klein 2014

Lower Cont. Crust (layer 8): Rudnick & Gao 2014
Continental Lithospheric Mantle
Huang et al. 2013

175 km depth

Depleted Mantle: Arevalo & McDonough 2010

Monte Carlo approachradius 4202 km

Enriched Mantle: Th, U abundance from mass balanceradius 3480 km• Fluctuate abundances in each chemical reservoir according to the assumed
distribution (normal, log-normal)• Assume U and Th abundances are fully correlated within a layer• Assume compositional estimates in different reservoirs are independent• As we throw dice, may run into problem:

More Th and/or U needed to fill Crust + CLM + DM
than what is available in Silicate Earthi.e., negative concentration in EM where EM = BSE − (Crust + CLM + DM)
10

Oceanic CrustContinental
Continental Crust• Uncertainty in crustal structure not includedFilling the Silicate Earth with Th & U

Th abundance in DM

Without loop
With loop

Calculate masses of reservoirs

Generate fluctuated abundances for Silicate Earthand layers of LithosphereTh abundance in EM

Generate fluctuated abundances in Depleted Mantle
Calculate abundances in Enriched Mantle
Is Enriched Mantle enriched? AEM(U,Th) ≧ ADM(U,Th)?
NoYes

Correlation DM–BSE for Th

The loop eliminates
unphysical values

Calculate geoneutrino flux.
11

Without loop

With loop

Geoneutrino flux prediction at Jinping
28.15°N, 101.71°E, 2400 m depth

82% Crust
86% Crust + CLM

14% Mantle
22% U78% U

Total TNU

~ Uncertainty of crustal structure – results using different crustal models
CRUST1.0

CRUST2.0

LITHO1.0

47.7 ± 7.2 TNU

42.9 ± 6.4 TNU

51.0 ± 7.6 TNU

12Geoneutrino flux prediction
at 5 detectors
Near-field crust + CLM
Far-field crust + CLM
Mantle
54%

49%

48%

49%

54%

22%
24%

30%

32%

33%

21%

20%

18%

1332%

14%

Geoneutrino flux prediction
at 5 detectors

Total flux

Rad. heat
TW

KamLAND
TNU

JUNO
TNU

Borexino
TNU

SNO+TNU

Jinping
TNU

20.4

34.8 +4.2−4.0

38.9 +4.8−4.5

41.4 +5.1−4.8

44.2 +5.3−5.1

58.5 +7.4−7.2

8.3 +2.5−2.7

8.2 +2.5−2.7

8.2 +2.5−2.7

8.2 +2.5−2.7

8.1 +2.5−2.7

Mantle(DM + EM)
Lithosphere(Crust + CLM)

8.2

26.5 +4.3−3.9

30.6 +4.9−4.5

33.2 +5.3−4.9

36.0 +5.6−5.2

50.4 +7.8−7.6

Crust

7.4

24.2 ± 3.5

28.1 ± 4.1

30.6 ± 4.5

33.3 ± 4.8

47.7 ± 7.2

CrustHuang et al. 2013

6.8

20.6 +4.0−3.5

29.0 +6.0−5.034.0 +6.3−5.7

Crust
Huang et al. 2014
Crust
Strati et al. 201530.7 +6.0−4.2
28.2 +5.2−4.5

Comparison to previous studies

14

Local flux at Jinping
tile-by-tile of CRUST1.0XX
YY%

TNU flux from Lithosphere% contribution to total Litho.

23% of signal from
“Jinping” tile
54% of signal from“near-field lithosphere”(6º lon × 4º lat region)

15

Studies of near-field lithosphere…

Local geonu flux

around KamLAND(Enomoto et al. 2007)

60ltang

to90

inp50

Ji

heresplitho

45
40O,

NJU +,dan SNOlm ,Ka xinota etal BoroT

353025100807060504020301510ntlema

50% of Jinping signal

55

Geoneutrino signal in TNU

around SNO+ (Huang et al. 2014, Strati et al.)

20
100

110100

1000

10000

Distance to emitter in km

around Borexino(Coltorti et al. 2011)

We need refined models of lithosphere around JUNO and Jinping
detector

Geo* reference model for China~500 km• Refined “voxelated” model of lithospherelithosphere16• To each voxel, assign material density,Vp and Vs seismic speeds, heat flux(at surface), chemical composition, …

Results from detectors combined
Current status
The night before
60

Fitting line of slope 1:
detectors see the same mantle

50

Measuredby physics:
Total geonu
KamLAND 2013
Borexino 2015
measurements

Total geonu in TNU

Borexino
40

KamLAND

Intercept is mantle signal

30
TW radiogenic
power in BSE

2030
1000102030

4050

20

Result:10Mantle = 6.0 ± 7.2 TNU
60

Lithospheric flux in TNU

Predicted from geology: Lithosphere
17Emission model

8–27 TW radiogenic
power in the EarthResults from detectors combinedCurrent status
6050

Measuredby physics:
Total geonu
KamLAND 2016
Borexino 2015
measurements

Total geonu in TNU

Borexino
40

KamLAND
30
TW radiogenicpower in BSE

2030
1000102030

40

50

20

Result:10Mantle = 8.8 ± 6.4 TNU
60

Lithospheric flux in TNU

Predicted from geology: Lithosphere
17Emission model(72% rel. uncertainty)

Results from detectors combined
Future prospect ~2025
Existing geoneutrino experiments are limited by low statistics,
continue to collect data.
What can we expect around 2025 with results from 5 experiments?

Meaured/expectedgeoν annual count rate
KamLAND

14Borexino

4.2

SNO+

20JUNO

400

Jinping

100•

KamLAND
Watanabe talk Jan-2015: expected to reach 11% uncertainty ofgeoneutrino measurement in 7 more years of data taking•Borexino
Extrapolating the statistics, we predict uncertainty of 13% after 6 additional years•

SNO+
We estimate measurement uncertainty at 9% after 6 years•JUNO
Han et al. 2016: 6% uncertainty after 5 years of live time•

Jinping
Beacom et al. arXiv:1602.01733: uncertainty of 4% after exposure of 3 kilotons over 5 years
18Results from detectors combined
Future prospect ~202570Jinping

60

Vertical axis
Simulated measurement:• Total flux from emission model• Uncertainty est. based on previous slide

SNO+
Borexino
JUNO
KamLAND

50Total geonu in TNU

Horizontal axis
Lithospheric flux from emission model

40

30
TW radiogenic
power in BSE

Mantle result:

20High−Q
10Medium−Q

30

High-Q: 17.7 ± 3.1 TNU

20Med-Q:

8.2 ± 2.9 TNU

10Low-Q:

1.8 ± 2.7 TNU

Low−Q
0010203040

Lithospheric flux in TNU

5060
19

Study lithosphere with geoneutrinos?
1 detector•We measure total geoneutrino flux.

•We “know” the lithospheric flux and resolve the mantle. (or vice versa)>1 detectors combined•Assuming they “see” the same mantle, we can test the lithospheric model.

~3000 km~3000 km
Mantle3100 km

Jinping

00
13km
JUNO

KamLAND

mk
0029

Core
R=1600 km

R=3200 km
20Seismically slow “red” regions in the deep mantle
3-D structure of enriched mantle?
Bull et al 2009, after Ritsema et al 1999

Geoneutrino flux from mantle with enriched “piles”
TNU
10.5
KamLAND
Borexino

Jinping

JUNO

SNO+

10.0
9.5
9.0
8.5

Total geoneutrino flux
mantle+ +lithosphere
CrustMantle

8.0TNU
55

Gran Sasso

Sudbury

50
45

Kamioka
Hawaii40
35Šrámek et al. 2013

30
25
20
15

21

Almost identical mantle signal(7.7 vs 7.8 vs 8.0 in TNU)Testing regionallithosphereG1,tot = Gmantle + G3,litho-far + G1,litho-regvv
G2,tot = Gmantle + G3,litho-far+ G2,litho-reg

G3,tot = Gmantle + G3,litho-far + G3,litho-reg

Measurement• Mantle: unknown, same for all• Far lithosphere: fixed• Regional lith.: Fit to geoν data•

3 measurements
4 unknowns
1 constraint … minimization of misfit
between a priori and tuned regional
model

Jinping

TNU

same fixed model
for all 3Tuning
the model

KamLAND
JUNO

22

KamLAND

JUNO

Jinping