A geoneutrino “telescope” to view the inaccessibly
deep interior of the Earth:Ushering in a new era of multi-messenger geophysics
Inspired by multi-messenger astrophysics:
expensive detectors for photons, cosmic rays,
neutrinos, and gravity waves.

Seismology

Mich Tech

Ed Garnero

Geoneutrinos

Geochemistry

Matt Jackson
UC Santa Barbara
A. Stracke

A Dynamic Earth with a virtuallyinaccessible interior: A deep frontier!

Accessing the Earth’s
deep interior?

2012, Chikyū

The Soviet “Kola”
drill holeà1970-1992
à12.3 km deepàNowhere near mantle depths

The Earth’s mantle is a virtually inaccessible domain:
Sampled by intraplate “hotspot” volcanoes

French and Romanowicz (2015)

Hofmann, 1997

entrainment

Time step 1

80

Time step 2

Time step 3

Staudigel & Koppers (2015)

AtollSeamount

Large Low Shear Wave Velocity Provinces (LLSVPs) are largest
seismically-constrained features visible in the deep mantle

Fringingreef

The “mantle zoo”: origin of the species?
Wilson,1989

subduction
Workman et al. (2004)

Hofmann (1997)~20 km3/year oceanic crust & ~1 km3/year continent subducted
Hofmann, Nature,1997

Origin of thespecies?
Hofmann &White (EPSL,1982): HIMU
from ancient
subducted
oceanic crust

FOZO

Willbold and Stracke, 2006

White &Hofmann(Nature, 1982):
EM-1 & EM-2
from ancient
subducted
continentalcrustLavas as probesof the Earth’s deep interior
The observation that the mantle is heterogeneous leads tosome key questions in the study of the deep Earth:
1. How did the mantle become
heterogeneous? Subduction?
2. What are the bulk compositionsof geochemical reservoirs in the mantle?
3. When did various geochemicalreservoirs form in the chaotically-convecting
mantle? 4.56 Ga? 2.5 Ga? 0.65 Ga?
4. Where are the different geochemical
domains located in the mantle?

Brandenburg et al. (EPSL 2008)

Origin of EM2: Tracing continental
crust cycling through the mantle
Samoa (2005)
MORB = mid-ocean ridge basalt
OIB = ocean island (hotspot) basalt

tedpleDe

Chondrite
Sigsbee (1880)

EnrichedUpper
Continental
Crust
Jackson et al. (2007)

Many mantle “species” resulting from recycling
oceanic and continental crust… But where are they?
• The analogy of the zookeepers

Geochemical “zookeepers” know which “animals” are in the mantle zoo, butthey don’t know where the cages are.

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?

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Geoneutrino “zookeepers” wanted! What if the “animals” had highgeoneutrino luminosity? Then we could tell where the different animals are!

Ed Garnero

Seismological “zookeepers” know where the “cages” are, but they don’tknow which animals are in the cages!

Where is EM? Where is HIMU?
A multi-messenger geophysical approach is needed:
Constraints from seismology and geochemistry are insufficient.
Addition of geoneutrinos will revolutionize deep Earth science!
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?

?

French & Romanowicz, 2015

Two messengers: Connecting hotspot geochemistry with theseismic Large Low Shear Wave Velocity Provinces (LLSVPs)
Geochemical DUPAL
anomaly

Geochemical DUPAL vs seismic
low velocity anomalies

Hart, Nature, 1984

DEPLETEDENRICHED

LOW seismic V

LOW seismic V

DEPLETED
Castillo, Nature, 1988

DUPAL = Dupré+Allègre

LLSVP = Large Low Shear-wave Velocity Province

Over the past 30+ years,
global seismic velocity models andgeochemical databases have improved dramatically.

Comparing geochemistryand seismology: lava withlowest 143Nd/144Nd shownfor 46 oceanic hotspots.

Jackson et al. (2021)

Continental crust

More continental crust

DupaldomainContinental 143Nd/144Nd
associated with southern
regions of LLSVPs.

Low 143Nd/144Nd in austral hotspots means continental
crust subduction focused in austral hemisphere

Gondwana

Jackson & Macdonald, 2021 (submitted)

Hypothesis: Gondwana assembly (ca. 650-300 Ma) from continental collisions
in southern hemisphere resulted in continental subduction into austral mantle.

Problem: During the Precambrian, continental assembly and subduction
occurred at all latitudes, so we might expect to see continental crust signaturesin hotspots at all latitudes.
Solution? A mechanism is needed in which deep continental crust subduction”turned on” when Gondwana started to assemble in the southern hemisphere.

First observed continental ultrahigh pressure at ~650 Ma:
Onset of deep slab breakoff and deep continental subduction?

Warm &Shallow(Brown et al., 2020)

Cold &Deep
Jackson & Macdonald (2021, submitted)

Two ingredients needed to explain Dupal formation:
Timing and latitude of continental crust subduction
But, what aboutcontinental crust
subducted from 300
Ma to the present?
It takes ~200 Ma forsubducted crust toreach the coremantle boundary,and then another 100
Ma for a plume toContinents focused in Southern Hemisphere from 650-300 Ma
rise.

Reconstruction based on Merdith et al. (Earth Sci. Rev., 2020).

Jackson & Macdonald (2021, submitted)

Geodynamic consequenceof continental crust in thesouthern hemispheremantle:More austral radiogenic
heating and, thus, more
austral plumes!

Workman et al., (G-cubed, 2004)

The radiogenic powerbalances:àRadiogenic power carried by
all mantle plumes is ≥2 TW.
à2 TW generated by a
subducted mass of continental
crust equivalent to ~1/3 of themass of modern continents.

Continental crust in the deep southern hemisphere mantle?
Multi-messenger geophysics—seismology, geochemistry,geoneutrinos—makes this a testable hypothesis.
àThe continental crust has nearly 2 orders of magnitude higher U & Th
concentrations than ambient mantle; continents host 1/3 of U & Th in the Earth.
àThe southern hemisphere regions of LLSVPs are host to continental crust,
perhaps 1/3 of mass of continental crust at the surface.
Hypothesis: The southern hemisphere regions of LLSVPs should have highgeoneutrino luminosities.

Šrámek et alMobile oceanic geoneutrino detector• Detector must be in an oceanic setting. If in continental setting,then geoneutrino signal from deeply subducted crust will beobscured by shallow crustal geoneutrinos.
• Detector should be mobile to be able to “map out” distributionof U and Th rich regions of mantle.

Acknowledgements••••••

Grad students and post docs in my lab: Rita Cabral, Ellie Price, Drew Reinhard, Mark Edwards, LoriWillhite, Olivia Anderson, Sunna Harðardóttir, Ruixia Bai, Ben Byerly, Gordana Garapic, Xiao Li Wang
Undergraduate students in my lab: Starla Toto, Allissa Drye, Keli McGuire, Gordon Williams, ScottPeimann, Cassidy Meehan, Alexandra Nicklin, Jonathan Pinko, Lori Willhite, Floyd Jaggy, AddisonSani, David Huckle, Jarod Payne, Stephanie Kukolich, Moira Poje, Caitlin Brown, Zuo Jin Ang, AustinSu, Jessica Stellman
Francis Macdonald
Jasper Konter (UH Manoa)
Thorsten Becker (UT Austin)
Bernhard Steinberger (GeoForschungsZen.Potsdam)Mark Jellinek (U. British Columbia)
James Farquhar (U. Maryland)

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Anthony Koppers (Oregon State U.)
Rich Walker (U. Maryland)Andi Mundl-Petermeier (Universität Wien)
Rick Carlson (DTM)
Janne Blichert-Toft (Lyon)
Estelle Rose-Koga and Ken Koga (Clermont-Ferrand)

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Raj Dasgupta (Rice)
Martin Whitehouse (NORDSIM, Stockholm)
Jabrane Labidi (IPGP)Mark Kendrick (University of Queensland)
Saemi Halldórsson (U. Iceland)
Fred Moynier (IPGP)••