2011 SOPAC Meeting Fiji Petersen

8/6/2019 2011 SOPAC Meeting Fiji Petersen

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Modern SeafloorMassive Sulfide

Deposits

S. Petersen

Seafloor Massive Sulfides (SMS)Seafloor Massive Sulfides (SMS)

Global characteristics, distribution,Global characteristics, distribution,and regional Pacific potentialand regional Pacific potential

Sven PetersenSven Petersen

(IFM-GEOMAR)(IFM-GEOMAR)

SPC-EU EDFDeep Sea Minerals Workshop,

Nadi, Fiji, 06.-08. June 2011


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Deposits

S. Petersen

influx of cold seawater (recharge)

H2O = H+ + OH-

Mg2+ + OH- = Mg(OH)2precipitation

excess H+ pH drop to ~ 4-5heating of seawater to > 400C

leaching of Cu, Zn, Fe, Au, S etc. from

the surrounding rockformation of hydrothermal precipitates

due to mixing of hot fluid with seawater

150C

375C

Reaction Zone

Gabbro

DikeSection

Extrusives

Magma

Recharge

Discharge

>30% water


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S. PetersenHydrothermal sites in theSouth Atlantic


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distribution of seafloor hydrothermal systems in the world ocean

Where do they form ?

latest discoveries:Cayman TroughWallis & FutunaNorthern MatasPiterskoe


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distribution of seafloor hydrothermal systems in the world ocean

Russian exploration claim area

Chinese exploration claim area

Manafe & DFI

mining liscence

Nautilusmining liscence

massive sulfides as aresource ?


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Examples are known in very different tectonicExamples are known in very different tectonicsettingssettings::

mid-ocean ridges(superfast, fast, intermediate, slow, ultraslow spreading centers)

off-axis volcanoes

intracontinental rifts & rifted margins

intraoceanic back-arc basins

intracontinental back-arc basinsvolcanic island arcs

(Hannington et al., 2005)

Basic Facts


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other factors: water depth, distance to land, EEZ ?


how many ?

grade ?

tonnage?


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S

ource:SOE

ST(Hawaii)

>80 % look like this !

NOAA


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at fast-spreading ridgesat fast-spreading ridges

short lived hydrothermal activityshort lived hydrothermal activity

cyclic volcanic and hydrothermal activitycyclic volcanic and hydrothermal activity

quick burial by extrusivesquick burial by extrusives

90% of the metals lost to the plume90% of the metals lost to the plume

massive sulfides atmid-ocean ridges


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1 cm

pyrite - chalcopyrite - sphalerite

1 cmisocubanite -

pyrrhotite - wurtzite

average geochemistry of MORB-

hosted massive sulfides

mainly pyrite with5 % Cu9 % Zn

0.3 ppm Au

(strong bias due to sampling of chimneys)



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S. Petersen

systems at slow-spreadingsystems at slow-spreadingridges tend to be larger !ridges tend to be larger !

commonly located off-axiscommonly located off-axis

deep penetrating faults allowdeep penetrating faults allowlong-lasting fluid flowlong-lasting fluid flow

some sites associated withsome sites associated with

mantle rocksmantle rocks


ne


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N

0 5 10 km

1520'

Nfrac

turezo

ne

basaltic lava floor

mantle rocks

Logatchev

Logatchev hydrothermal field2 hydrothermally active fields

largest field 800x300 m


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Logatchev hydrothermal field

1 cm

64ROV-11D

hosted in mantle rockswater depth 3000mvery high Cu and Au grades !

23 % Cu

4 % Zn

11 ppm Au

Is it possible to utilize this ?

atth

esurf

ace


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-u rich chimneyu rich chimney

wasteaste



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Deposits

S. Petersenmassive sulfides inback arc basins

Hydrothermal sites in

Papua New Guinea


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S. Petersen

PacManus samples

10.3 % Cu

22.6 % Zn

0.5 % Pb

205 ppm Ag

14 ppm Au

PACMANUS hydrothermal field

host rocks: volcanic suite from basalt to rhyolithewater depth: 1650m

Yeats (CSIRO)

atth

esurf

ace


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58-GTVA

altered dacitealtered dacite


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exploring companies: exploring countries:Nautilus South KoreaBluewater, and others Russia China

(France/Germany)

PacManus

20102010

Susu Knolls

=1. mine site ?



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NOAA

massive sulfides atisland arc volcanoes


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mid-ocean ridges island/back arcsbasalt exposed mantle interm. - felsic

Fe, Cu, Zn Cu, Fe Cu, Zn, Pb, Ba

Co Au, Co, Ni, Sn As, Hg, Sb, Au, Ag~1 ppmAu 3-10 ppmAu 530 ppm Au!

deep water deep water shallow water

source: geochemical differences in the rocks themselves+ additional factors (magmatic input, biology, zone refining, ... )



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high grade (CuAuZn) or large deposits


TAG

Middle Valley

Manus

Suiyo

KrasnovSemyenov

Kairei

13N, EPR

Atlantis II

Logatchev


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Will these deposits by of commercial interest ?



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Uchaly + Novo Uchaly (>220 Mio t)

compared to those on land ?

Gay (>380 Mio t)



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NOAA

Kelley et al., 2001

(C

)Nationa

lGeograph

ic1

992

MARUM



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typical EPR chimneys 0.x Mio t

Atlantis II Deep (Red Sea) 94 Mio t drilledore mud from brine pool

Middle Valley (JFR) 8-10 Mio t drilledlarge sulfide lenses in sediments (Fe dominated)

13N Seamount (EPR) 5-10 Mio t ?

Krasnov, Semyenov ~ 15 Mio t ?large pyrite mounds (Fe dominated)

TAG (MAR) 4 Mio t drilled(low grade in interior)

Suzu Knolls; Manus Basin >2 Mio t drilled(indicated + inferred)


M d S fl


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high grade or large deposits

XX

XFe-only

Xtoo small

X

too deep ?

size ?

X

too deep ?low grade ?

X

too small

size ?

TAG

Middle Valley

Manus

Suiyo

KrasnovSemyenov

Kairei

13N, EPR

Atlantis II

Logatchev


M d S fl


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S. Petersen

Mining seafloor massiveMining seafloor massivesulfides needs:sulfides needs:

2 mio tonnes of ore /year

(~ 200x200x20m)life-time of 10 years(= 20 mio t of ore !)(may be contained in several orebodies !)

Currently not known !

Will mining of seafloor massive sulfides replace land mining?Will mining of seafloor massive sulfides replace land mining?


M d S fl


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worldwide VMS Districts (>> 6 billion tonnes)

GSC


50 % in only 50 deposits of >50 mio t

M d S fl


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a snapshotin time

At most the modern oceans contain only 175 million years worth of metal !Current exploration is considering only young crust !One giant deposit every 200 mio years !

Why is the geologic record so well endowed?


M d S fl


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Most seafloor sites:Most seafloor sites:

are too small

are of low grade

occur too deep

are too far from land

occur in the Area (politics)

or are active and too hot

but: mining of few sites might beeconomically feasible


Modern Seafloor


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S. Petersenregional Pacific potential

Modern Seafloor


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Deposits

S. Petersenregional Pacific potential

Modern Seafloor


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Opportunities:

There is still a large potential for newdiscoveries using regional surveys!

regional Pacific potential

Modern Seafloor


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Back-arc spreading centers still have large potential todiscover new sites ! By far most of those will be small.

Intra-plate volcanoes are underexplored but have limitedpotential for sulfide deposits.

Island-arc volcanoes have large potential, but frequent

eruptions and shallow water depth may limit sulfidepotential near the seafloor.

Where are the large deposits

in the Pacific region ?

regional Pacific potential

Modern Seafloor


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S. Petersen

Current research and exploration ismainly related to active deposits at ornear spreading axis.

many deposits are buried underneathsediments or lava.

Systematic surveys for hidden depositsare lacking.

Regional geological and geophysicalexploration using towed systems orAUVs is necessary to define resource

potential.

seafloor hydrothermal systemsseafloor hydrothermal systems

Challenges

Modern Seafloor IFM GEOMAR


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6000m depth rating, 4Kn max. speed24 h station timeturbidity sensor (ECO), Eh-sensor (NIST

Japan), CTD, 120/410 kHz side-scansonar (Edgetech), ADCP

3 konfigurations200/400 kHz multibeam (RESON 7125D)or sub-bottom profileror b/w digital camera + flash

underwater navigation:transponder (LBL, USBL)inertial navigation (Kearfott)

IFM-GEOMARsAUV ABYSS

Modern Seafloor


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central part= 65 km !

Reson Seabat 7125400 kHz

AUV-basedbathymetry

Modern Seafloor


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S. PetersenAUV-basedbathymetry

Modern Seafloor


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S. Petersen


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2011 SOPAC Meeting Fiji Petersen

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