Designed by K. Michibayashi

Frontiers of sampling the mantle
by drilling to the Moho

Two IODP Proposals:- 805-MDP MoHole to Mantle (M2M: Umino et al., 2012)- 951-Full Hawaiian North Arch Crust (Umino et al., 2020)
Workshops:- Off Hawaii Drilling WS (Online, 2020 6-7)
- Kanazawa WS (2018.11)- Mohole Tokyo WS (2012.2)- Mantle Frontier WS (2010.10) Scientific Drilling (2011, v11)
- Kanazawa WS (2010, 6) & Scientific Drilling (2010, v10)
- INVEST WS & White Papers (2009.9)- Southampton WS report (2009.7)- Mission Moho WS (2006.9)

2022/8/8

Natsue Abe(Mantle Drilling Promotion Office, MarE3, JAMSTEC)
andSusumu Umino (Kanazawa Univ.)
on behalf of the M2M Proponents
Shuichi Kodaira, Tomoaki Morishita, Katsuyoshi Michibayashi, Damon A.H. Teagle, Benoît Ildefons,Peter B. Kelemen, Olivier Alard, Shoji Arai, Ryo Anma, Chris Ballentine, Gary Acton, Jeffrey C. Alt,Wolfgang Bach, Neil R. Banerjee, Juan Pablo Canales, Mathilde Cannat, Richard L. Carlso, Rosalind M.
Coggon, Laurence Coogan, Henry J.B. Dick, Toshiya Fujiwara, Yoshio Fukao, Jeffrey S. Gee, Kathryn
Gillis, Takeshi Hanyu, Alistair Harding, Yumiko Harigane, (Erik Hauri), Eric Hellebrand, Ikuo Katayama,Jeffrey A.
Karson, Hiroyuki Kimura, Jun-Ichi Kimura, Juergen Koepke, Hidenori Kumagai, C. Johan Lissenberg,
John Maclennan, Jinichiro Maeda, Christopher J. MacLeod, D. Jay Miller, Sumio Miyashita, Kentaro
Nakamura, James H. Natland, Toshio Nozaka, Mladen Nedimovic, Yasuhiko Ohara, Eiji Otani, PhilippePezard, Mark Rehkamper, Tetsuya Sakuyama, Takeshi Sato, Matthew O. Schrenk, Nobukazu Seama,Jonathan E. Snow, Eiichi Takazawa, Masako Tominaga, Takeshi Tsuji,Peter E. van Keken, Jessica M.
Warren, Douglas S. Wilson,Greg Moore, Steven D’Hondt, Laura Crispini, Brian Boston, Frieder Klein, Mikiya Yamashita, MichaelGarcia, Michelle Harris, Yuki Kusano, Yohey Suzuki, Elizabeth Trembath-Reichert, Yasuhiro Yamada,Fumio Inagaki and many WS participants

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe0Mohole Project“Mohole” = “Moho” + “Hole”

Mohorovičić (1857-1936) discovered the "moho” discontinuityin October 8, 1909 (P-wave arrivals)

Moho is the boundary between Earth’s crust and mantle and is ubiquitous.
It is the outermost boundary in Earth’s Interior but yet has been directly
investigated.

Thick continental crust (~ 30 km) > Thin oceanic crust (~ 6km)
Proposed original Mohole project in 1957

Photo: Fritz Goro
Harry Hess（1906-1969）
2022/8/8

Walter Munk(1917-2019 )TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

1Project “Mohole” 1957-1966
Drillship CUSS 1

Offshore Guadalupe Island
March-April 1961

Johna SteinbeckLife,
14 April 1961

Dynamic positioning~ 3500 m water depth
5 holes
Maximum penetration: 183 m,
Miocene sediments~ 14 m of basalt
f-.:'sÎi: i':¡- ,.::r:1 ,¡ìr,,;::,1:--..: ji; Cl:::: j.¡., -,,.:([L] acr-r pt rux rHE sr{ÍTË t*trJSE p*$}rrñrcT'CIfl ot 14 algp Ësr 'ffi I¡ETLEV I BROIs(r FßES¡ffiflT
i -. J,{oF scrÉ'{tËs E^s€G '4-'^-eêJ /4' HrTrstL:*T.HâYE ËETI^aA'€ll?
Fül-OUTflB FTT¡T Oã€P NüEfiTSf T}E TXPEF¡UdN¿m¡LL$€ tlr ffi$EcTloft I'ÎTE T]tE r¡*ar HfâsE of FRg\tEctHOIÐLE¡ TrË StrffiSS .tr !rüE',ÐRttÂfi$Ê."8l.lHnq$r Í,giltQo;,F, qfoF
ffir* qrå,oa¡.ßrPE I+$Ð ßE' T,rfr-=PqEry+.ï¡w of ,THE .

rrf*,,#-,,ï,æ¡-ttç'rot

i+FffiP.-irtÌis

í*.,.rË_ffigF,ms.;

MSH,F'"ßN*,.,[J.,-M.QN

The first sampling of oceanic basaltic crust achievedby the Cuss 1 team received a personal letter ofcongratulations from President Kennedy.
2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe2..

Project “Mohole” 1957-1966
Offshore Guadalupe Island
March-April 1961

CUSS 1

Johna Steinbeck
Life,
14 April 1961

Dynamic positioning~ 3500 m water depth
5 holes
Maximum penetration: 183 m,
Miocene sediments~ 14 m of basalt

1966, the U.S. Congress issued a formal cease and desist order.

This frontier has been a symbolic goal for many geoscientists
over decades but was beyond the reach of available
technology at the time.
40 years later…, D/V Chikyu was built and would become feasible.
2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe3

The Upper mantle anisotropy

Peridotite mantle

Two rock types have Vp > 8.0km/s and density ~ 3.2g/cm3
Peridotite：
Ultrabasic rock（SiO2<45wt%）
Olivine dominant (＞40％)
with possible strong
anisotropy

orEclogite (Gt＋Cpx）:
Basic rock (SiO2
45~53wt%；basalticcomponent）
Garnet dominant withisotropic

Photo by @tatsukix

Evidence of the peridotitic upper mantle:
Hess (1964; Nature) found the upper most mantle has a strong anisotropy of the seismic
velocity. It was observed during the site survey at two Mohole site (Hawaii and Baja
California).

After this, Ringwood & Green (1966) demonstrated by high-P experiment thatthe oceanic Moho is much shallower than the pressure of the phase transition
between Gabbro/Eclogite, which is deeper than 36km.
Now we believe the upper mantle is composed of peridotite.
It is the result of the Mohole study at the beginning.
4History of scientific ocean drilling
WSs to initiate IODP

1997 Tokyo

1999 Vancouver

Science Plans
IODP Phase II SP(2013-2023)

IODP Phase I SP(2003-2013)

2022/8/8

1961

Project Mohole1968

Deep Sea Drilling Project

1975

Japan joined DSDP

1983

Ocean Drilling Programwith 21 member countries

Cuss I(US Navy）
ProjectMohole
Glomar
Challenger(DSDP)

JOIDES
Resolution(ODP, USIODP)

1985

D/V JOIDES Resolution launched

2003

Integrated Ocean Drilling Program
D/V Chikyu
w/25 countries (IODP Phase I)(Japan, IODP)

2005

D/V Chikyu launched

2013

International Ocean Discovery
Program (IODP Phase II)

2024

Scientific Ocean Drilling (2050 Science Framework)

2050 Science Framework

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

MissionSpecificPlatform(ECORD, IODP)

5

Drill holes in oceanic crust (>100m, 1974-2018)
Michibayashi et al., Oceanography, 2019.

Hard rock ~ 3% of drill cores, 97% sediment2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe• Small amount of cores• No full crustal section
6

Mantle Drilling
D/V Chikyu

Proposed MoHole to Mantle (M2M) in 2012

IODP Proposal (805-MDP: Umino et al.)2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

7

MoHole To the Mantle (M2M)

IODP Proposal (805-MDP: Umino et al.)1.

4 main Science targets

Sample Return

2. Naturel of Moho

10 fundamental questions
3. Crust formation
4. Frontier and limits of life

Structure and compositionof convecting mantle,
obtaining in-situ mantle
sample2022/8/8

Geological meaning of
Moho and seismic
layers in the crust

Bulk composition, andmode(s) of accretion offast spread crust

TFC_Frontier of Understanding Earth’s Interior and Dynamics_Abe

Lithosphere aging, chemical
fluxes, and limits andcontrolling factors of life8

1 Sample Return

Obtain the first in-situ samples of Earth's mantle- Estimation Gap: basalt and mantle
Mantle composition is commonly estimated by basalt composition, which is
produced as a partial melt of the mantle peridotite. There is a large gap of
the concentration between basalt (MORB) and abyssal peridotite.
• Compositional and isotopic heterogeneity• Volatiles contents (CO2, H, …)Late veneer• Contribution to global carbon budget• Melt migration processes• Physical properties (rheology, seismic anisotropy, …)
Temperature and viscosity of mantle

Need samples &measurement- Estimation Gap: whole earth

Up to 0.7 wt% (carbon) and 0.02 wt% (H2O) on the earth’s surface
vs. av. 3.2 wt% (carbon) and 2 wt% (water) in whole Earth estimated from C1 chondorite

How much CO2 in the lithospheric oceanic mantle ? (10 ppm > ~1020 tons for 10km)
2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

92. Geological nature of Moho?
6 km thick ubiquitous oceanic crust = 10 km – 4km water depth

Andrija Mohorovičić

Seismic imaging ofPacific lithosphere
Global map of Moho depth (from GOCE data, 2012)• Is the Moho the interface between :- magmatic crust & residual mantle ?
- magmatic rocks of different compositions ?
- serpentinized mantle & fresh mantle ?
- mantle + magmatic intrusions & mantle ?
2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

102. Geological nature of Moho?

Borehole seismometer

Fujie et al. (2020)Geology
Shinohara et al. (2008)PEPI

Need samples to test the hypothesis

2. Geological nature of Moho?
What is the upper/ lower crust boundary?

Layer 2 Pillow lava(basalt)?
Layer 3 SheetedDike(basalt)

1256D

Gabbro504B 2111mbsf

Peridotite

504B- Gabbro/Layer2 <= Hole 1256D- Sheeted /Layer 3 <= Hole 504B.

A seismic boundary
Lithological boundary
2022/8/4

MantleAOGS2022_IG14A0009_AbeMoho

1256D 1500mbsf

3. Formation of the oceanic crust , the mode of accretion
Ocean ridge
Convergent
plate margin

MOR

Continental
intraplate
Oceanic
intraplate

Magma production rate (km3/yr)(Degree 12 Spherical Harmonic) after Pollack et al. (1993)

Extrusive

Intrusive

Total

Producingrate (%)

MOR

3182160-80

Japan, Chile etc

Subduction

0.4-0.6

2.5-8.0

2.9-8.6

8.6-33Yellowstone,
Kilimanjaro etc

Intraplate(continent)

0.03-0.1

0.1-1.5

0.13-1.6

0.4-6.2

Intraplate(ocean)0.3-0.4

1.5-2.0

1.8-2.4

5.4-9.3

Total

3.7-4.1

22.1-29.5

25.8-33.6

Hawaii, Canary, Azores,
Tahiti Islands etc

Magma production rate in Cenozoic: Data from McBurny (1993)
2022/8/8

TFC_Frontier of Understanding Earth’s Interior and Dynamics_Abe

133．Formation of the oceanic crust- A reference site of the continuous deep hole into the mantle layer- Mid ocean ridge : the biggest heat radiator from the earth interior- The pattern of the hydrothermal circulation in deep is controlled by formation processes of the oceanic crust- Bulk crust composition

Two endmember models of crust accretion

Gabbro-Glacier

Henstock et al., 1993,
Phipps-Morgan and Chen, 1993,
Quick and Denlinger, 1993

Sheeted Sills

Boudier et al., 1996
Kelemen et al., 1997
MacLeod and Yaouancq, 2000
Layer2
Layer3

Magmachamber
Moho

and the outermost

Moho is the only boundary to reach, observe and describe in-situ melt migration system.
2022/8/8

TFC_Frontier of Understanding Earth’s Interior and Dynamics_Abe

144. Limits and controlling factors of life
Hydrological-Geochemical-Microbiological Feedbacks

MoMARDREAM Cruise, 2008

Reaction front of lithosphere - seawater• What processes control exchanges ?
• Impact on global bio-geochemical
cycles ?
• Limits (and controlling factors) of
deep biosphere ?

M2M proposal (Umino et al., 2012)
2022/8/8

TFC_Frontier of Understanding Earth’s Interior and Dynamics_Abe

Ludwig et al. (2006) GCA
15

Where?

1st MoHole : fast-spread plate (Typical oceanic plate)• Majority of crust recycled into
mantle in past 200 Ma• ~20% of modern ridges~50% of present ocean floor~30% of Earth's surface• Relatively continuous and uniform
Data fromMüller et al.,2008

Fast-spreading (simple)• Most of subduction slabs are the fast-spreading
lithosphere

Slow-spreading (complex)

From M2M proposal

Schematic along-axis cross-sections of fast and slow spreading crust at the mid-ocean ridges.
2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

16

Where? (In the pacific)
Criteria to meet scientific objectives! Simple tectonic setting! Normal crust (~6.0 km thickness）! Clear Moho discontinuity (reflector)

Technical constraints•Water depth >~ 4000 ｍ•Total length < 12ｋｍ (<7 kmbsf)•Cool Moho temperature (<250°C)

A. Thermal model of the oceanic plate (Half-Space).
B. Actual measurement of the water depth vs crustl Age

Logistics and housekeeping- Near heliport- Close to main port
- Stable sea condition- Blue ocean or member
country’s EEZ

M2M proposal(after Carlson &Johnson, 1994)

Technological constraints: <~250°C in the mantle & ≤4000-4500 meters of water
2022/8/8

TFC_Frontier of Understanding Earth’s Interior and Dynamics_Abe

17Where?

The trade-off between water depth and temperature
Carlson & Johnson, 1994

Technological constraints: <~250°C in the mantle & ≤4000-4500 meters of water

3 site candidates

2022/8/8-Cocos Plate (Site 1256D)-

Off Baja California-

Off Hawaii

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

18

Half spreading rate(mm/yr)
Crustal Age (Ma)

Total penetration(km)
Inferred MohoT(°C)
Sediment
Thickness (m)Crustalthickness(km)Distance frommain port (km)ProsCocosPlate
110
15- 3.4 –5 - 5.5 ~1019 3.6> 250
250 300
55.5~600
Shallow water
depth andtotal length,
near deep hole
High-TBaja
Californi
a45 602030~610 11200 250
80 130~68001000
Moderate T

Few site survey
data, off-ridge
volcanism?

OffHawaii
40 45
75- 4.1 –~ 6.25
81 4.5>11~150~200~
6.25
~400
Low Moho-T,
close to main
port
Total depth,
near hotspot

4.3

Cons

Crustalthickness(km)Water Depth (km)Site Candidate

Conditions of the three candidates

Each site has Pros & Cons

19Feasibility studies

Plus, JAMSTEC conducted the feasibility study in 2021.
Eguchi&Sawada, (2022) Chikyu Monthly written in Japanese
2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

20Feasibility studies
Coring (sampling) strategy

BLADE Final report (2013)

2022/8/8

Casing strategy

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

Eguchi & Sawada (2022)

21

Sediment
Thickness (m)Crustalthickness(km)Distance frommain port (km)55.5~600~610 - 200 11 250
80 130~68001000

40 - 7545 81
4.1–4.5~
6.25>
11~150 ~200~6.25~400Project (date)

Inferred MohoT(°C)
250 300

On site (date)

Total penetration(km)~10 > 250

Cons

Crustalthickness(km)55.5High-T

Water Depth (km)

3.4–
3.6

202 - 289
250 - 337

Few site survey
data, off-ridge
volcanism?

Crustal Age (Ma)15110
19Pros4.3

Total depth,
near hotspot

OffHawaii
2030
Moderate TBaja
45 Californi
60a

Low Moho-T,
close tomain port

Half spreading
rate (mm/yr)

Cocos
Plate
Shallow water
depth andtotal length,
near deephole

Site Candidate

Conditions of the three candidatesEstimated number of days for drilling
After Eguchi & Sawada (2022)

208 – 327
244 – 363

221 - 341
248 - 368

22

Off Hawaii mid-aged crust drilling (IODP 951-Full; Umino et al. 2020)< 2500mbsf
Umino et al. (2021)Sci.Drill.
2022/8/8

Layer 2/3 (upper/lower crust) boundary
TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

23

“What good will it do to get a single sample of the mantle?...”“Perhaps it is true that we won't find out
as much about the earth’s interior
from one hole as we hope.
To those who raise that objection, I say,
If there is not a first hole,
there cannot be a second or a tenth ora hundredth hole.
Photo: Fritz Goro

2022/8/8

We must make a beginning.”--- Harry Hess, April 1958

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

24

Thank you!

2022/8/8

TFC_Frontier of Understanding Earth’s Interior and Dynamics_Abe252022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe262022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe

27

IODP Moho to Mantle proposal(805-MDP: Umino et al.2012) Proponents

2022/8/8

TFC_Frontier of Understanding Earthʼs Interior and Dynamics_Abe28