Abiogenic Hydrocarbons Produced Under Upper Mantle Conditions Alex Goncharov_Hydrocarbons

7/30/2019 Abiogenic Hydrocarbons Produced Under Upper Mantle Conditions Alex Goncharov_Hydrocarbons

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Abiogenic hydrocarbons produced underupper mantle conditions

Alexander Goncharov

Geophysical Laboratory, Carnegie Institution of Washington, USA


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Anton Kolesnikov

1,2

Raja S. Chellappa1

Maddury Somayazulu1

Subramanian Natarajan1

Russell J. Hemley1

Vladimir Kutcherov3

Participants:

1 Geophysical Laboratory, Carnegie Institution of Washington, USA2Lomonosov Moscow State Academy of Fine Chemical Technology, Russia3Royal Institute of Technology, Stockholm, Sweden


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Deep abiotic organics

Oil Company View

Russian-Ukrainian School


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HC

HH

HH

C

HH

H H+ +C

H

H

H

H

H

H

H

T, p

Kenney, Kutcherov et al. (2002), KONAK chamber3-5 GPa, 1200-1500K

Scott et al. (2004), DAC, 5-11 GPa, 773-1773K

3 2 3 4 4CaCO +12FeO+H O CaO+4Fe O +CH

3 2 2 3 4 n 2n+2nCaCO +(9n+3)FeO+(2n+1)H O nCa(OH) +(3n+1)FeO +C H

Synthesis of hydrocarbons

Realistic Earths minerals? Heavier hydrocarbons synthesis? Oxidizing conditions?

Methane polymerization

Is this viable for:


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Probe (Raman spectroscopy & X-ray diffraction)

Laser

Heating

Gasket

Sample

Coupler

Diamond

Anvils

a b

Ruby

Laser heating in the diamond anvil cell

MicrophotographSketch

In situmeasurements at high temperature

Mapping of quenched samples

Methane in Re gasket

with Ir coupler


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Sample preparations: minerals

Carbonate in 1:8 molar ratio ground andmixed in diamonite mortar/pestle

Ir coupler or compacted powder Loaded with H2O

Adequate care with all aspects ofcleaning

Reaction Zone

Before:

After:

Fayalite (Fe1.92Mn0.08SiO4): Rockport

Olivine (Mg1.8Fe0.2SiO4): San Carlos

Mineral Assemblages: Peridodite & Basalt


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Methanogenesis from minerals




Methane formation at relatively low temperatures; suggested pathway:

6 Fe2SiO4 + CaCO3 + 2 H2O = 4 Fe3O4 + CH4 + 6 SiO2+ CaO

Hydrous phases were not observed

(SiO4)(CO3)

Ice VII

CH4

starting sample

after LaserHeating

Fe3O4

(SiO2)

(Fe0.96Mn0.04)2SiO4:CaCO3 8:1 molar ratio

< 800 K X3

5-6 GPa, < 800 K


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(SiO4)

(CO3)IceVII

CH4

starting sample

After Laser

Heating Fe3O4?

(Mg0.90Fe0.10)2SiO4:CaCO3 8:1 molar ratio

X3

5.6 GPa

l = 0.3757

2

After leaserheat at 5.6GPa

Olivine +hydrousMg2SiO4phases

Methane formation at T > 2000 K, 5-6 GPa

Hydrous phase formation


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(SiO4)

(CO3)IceVII

(OH)

as-loadedsample

ResistiveHeating

Laser HeatingPeridodite : CaCO3 10:1 weight ratio

No methane formation at T > 1500 K, 5-6 GPa

Hydrous phase formation


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Carbonate reduction to CH4 observed even with Mg-rich mantle minerals

Further XRD characterization of reaction products and thermochemicalcalculations are needed.

Diamond reactivity (found in control experiments) need to be better addressed

Explore polymerization to higher hydrocarbons.

Conclusions


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Raman Shift (cm-1)

2800 3200

RamanIntensity(arb.

units)

500 900 1400 1800 4000 4400

300 K

900 K

1500 K

C2H

6 C (graphite) H2

H2

C3H8

Raman Shift (cm-1)

1000 2000 3000 4000

RamanIntensity(arb.units)

(CH4)n(H2)m

H2

CH4

CH4

C (graphite)

x10

Position 1

Position 2

Position 3

Position 3

Diamond anvils(b)

(a)

CH4

CH4

400 900

H2

H2

C2H

6

Positions:

3 2 1

50 m

(c)

Raman shift (cm-1)

500 1000 1500

CH4-Ir-Re

3.83 GPa

CH4-Fe

3O

4-Re

2.19 GPa

C2H

6-Ir-Re

5.00 GPa

CH4

-Ir-W

6.64 GPa

C2H6

C

CH4

C3H8

C4H10

CH4-Au-B

4.04 GPa

H2

C2H6

C3H8

Methane and ethane reactivity: in situRaman diagnostics

CH4 C2-C4 alkanes +H2

CH4 C +H2

Ethane:

3C2H6 2C3H8+ H2C2H6 + H2 2CH4

Methane:

Gasket: Re, W, Au (liner)

Coupler: Ir, B, Fe3O4

To check reactionreversibility

Thermal insulation:Al2O3 (in selected exp.)

Temperature:

Position: Gasket/Coupler:


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Laser heating products: magnetite in methane

TwoTheta (degree)

8 10 12 14 16 18 20

Inte

nsity

(arb.units)

Diffraction pattern

GraphiteIce VII

bcc Fe

Diamond

Alumina

Methane

X-ray diffraction of the quenched products inoxidized conditions with Fe3O4 coupler

Fe

Diamond

Methane

Single-crystal diffraction

Single crystal Fe3O4

Fe3O4+2CH4 3Fe+2C+4H2O


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Temperature (K)

1000 1200 1400 1600

-8

-6

-4

-2

logfO2[F

MQ]

Pressure (GPa)

0 2 4 6

Temperature(K)

500

1000

1500

2000

Oce

anicge

othe

rm

CH4melting

0 65 127 188Depth (km)

Hydrocarbonformation

Shiel

dgeothe

rm2.19 GPa

South AfricaYakutiaSlave

DAC with IM buffer

a b

P-T-fO2 conditions in the DAC experiments and in the upper mantle


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Methane above 2 GPa and 1000-1500 K partially reacts andforms saturated hydrocarbons (C2-C4 alkanes: ethane,

propane, butane), molecular hydrogen and graphite.

The reaction does not require catalysts and proceed inoxidized conditions.

Formation of methane in similar experiments on ethanesuggests reversibility of hydrocarbon formation.

The experimental P-T-fO2 conditions of methane derivedhydrocarbon synthesis are appropriate for the Earthsmantle, creating the possibility of the abiogenic synthesis of

petroleum components in of the Earths upper mantle.

Conclusions


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Lupke et al., 2003

Probe

Pump

Time resolution (determined bythe laser pulse width 10s fs)

is comparable with bondbreak/creation time.

Outlook: Chemical Reactivity of Deep Earths CarbonBearing Phases using Optical spectroscopy at high P-T

Wavelength (nm)

600 650

Intensity(arb.units)

Radiative temperature10,000 K

125 GPa

silicate perovskite

2350 2400 2450 2500

1590 K

1840 K

2500 K

114 GPa

1050 K

300 K

(c)

fluid

'

fluid

Raman Shift (cm-1

)

N2

Pulsed laserheating in DAC

Pulsed Raman probe

Future scientific directions: shorter time-scale to study chemical kinetics & dynamics

to make data comparable to molecular dynamic simulations

Future technical developments of the laser heated DAC:1. Pulsed laser heating2. CARS & broadband fs spectroscopy in the DAC

3. Pump-probe spectroscopy- fs time scale


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AcknowledgementsMinerals:

Shell Inc.

CDAC

Prof. Dimitri Sverjensky (JHU)

Dr. Dionysis Foustoukos (GL)

Dr. Anurag Sharma (GL)

Smithsonian Institution

Methane: K. Litasov Y. Fei J. C. Crowhurst, M. Somayazulu, V. Struzhkin, R. Cohen,

D. Foustoukos, J. Montoya, T. Strobel S. Sinogeikin

Support:

A. K.: support of INTAS through YSF Ref. Nr. 06-1000014-6546.V. K.: support from INTAS Ref. Nr. 06-1000013-8750.A. G.: NSF-EAR, CDAC

Abiogenic Hydrocarbons Produced Under Upper Mantle Conditions Alex Goncharov_Hydrocarbons

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