New Understanding and mineral endowment of the Archaean ... · endowment of the Archaean, Palaeoproterozoic and Palaeogene of ... Ccp, Pn; up to 20%, ... Nugget-effects may be causing

G E O L O G I C A L S U R V E Y O F D E N M A R K A N D G R E E N L A N D

New Understanding and mineral endowment of the Archaean,

Palaeoproterozoic andPalaeogene of

South-East GreenlandBo M. Stensgaard & Jochen Kolb

Department of Petrology and Economic GeologyGeological Survey of Denmark and Greenland (GEUS)

with acknowledgement and contributions from members of the SEGMENT 2009-2015 project

Greenland Day Perth, Dec. 9th, 2015


Where are we?

• Tasiilaq; fully serviced Atlantic harbor• Daily (summer) flights to Iceland• Northern area; many smaller

settlements• Southern area; remote

• Mountainous, long valleys, deep fjord systems – no infrastructure

• Possibilities for hydropower solutions• Large sources of fresh water• No conservation areas, national

parks or private land owners

• South-East Greenland; access point to East Greenland

• Situated close to Iceland - between North American and European markets

• Well-connected with Iceland


3.400 million years of geology - what constitute South-East Greenland?

• Two Archaean cratons• Multiple deformation and metamorphic

orogenic events• Large Archaean mafic to alkaline

intrusive suite• Palaeoproterozoic collisional orogen • Large magmatic arc intrusives• Belts of Palaeoproterozoic

metasedimentary and metavolcanic rocks

• Large post-orogenic intrusive complexes

• Palaeogene break-up of the North Atlantic – recent intrusions and volcanic rocks

RAECraton

NAC


• Central located in a collage of cratons and orogens

• North Atlantic Craton• Nagssugtoqidian

Orogen• Ketilidian Orogen

Cratons and orogens

Global distributions of the cratons (crust >2.5 Ga old); modified after Bleeker (2003)


The basement – “the beating hearth of the Archaean“

Thrym Complex:• Dominated by poly-phase; migmatitic,

banded; basement fragments• Age: > 2850 Ma – 3450 Ma(?)

• up to 1 km wide and several 10s of km extending belts of paragneiss and mafic--ultramafic rocks

• Paragneiss: 750-800°C; < 7.5-9 kbar• Mafic granulite: ~ 800°C; 5-8 kbar ±

peridotite/pyroxenite• Partial melt at peak granulite facies:

HFSE depleted• Infiltrated by melts

• Mid- to deep Archaean crust• Products of crustal melting and major

thermal events

Model for the formation of the basement rocks of theNorth Atlantic Craton to the Skjoldungen OrogenyBagas et al. 2012.


Pyroxenite

Lommen‐Jættefjord Ni‐CuOrthomagmatic Ni‐Cu mineralisation in ultramafic rocks

Mineral endowment:

Mafic and ultramafic layers locally contains pods and layers of Ni- Cu sulphide mineralisation• Interstitial to net-textured sulphides – Po, Ccp, Pn;

up to 20%, or as disseminated sulphides• 1-2 m thick layers, several km along strike.• Up to 0.5% Ni, 0.25% Cu;

Pt 24 ppb, Pd 162, Cr 0.5%

• Tonnage to small; discontinuous – still potential

Ni-Cu mineralised zonesPeridotite

Mafic-ultramafic Ni-Cu mineralised bands (ountlined in green) at Kangerdlikajik Fjord. Cliff-wall 600 m

Ow

en 2

012 R

enni

ch20

12

Owen 2012, Rennich 2012, Kolb et al. 2012, Bagas et al. (submitted)


0

10

20

30

20erosion level

Deep-seated muscles of the Archean – multiple deformation events

Thrym Complex – Archaean South-East Greenland

• Regional compression until 2.7 Ga• Timmiarmiut Orogeny; 3.45 Ga grains

• Regional extension 2.7-2.66 Ga• Skjoldungen Orogeny;

collision/subduction• Penetrative foliation and metamorphism

• Regional transtension• Singertat stage

• Exhumation until 2.7 Ga• Ketilidian Orogen & Gardar rifting• Opening of the North Atlantic

–Brittle deformation, mafic dykes

Imag

es fr

om “T

he E

ssen

tial E

arth

”(Jo

rdan

& G

rotz

inge

r, 20

08).

Collisional orogenKolb et al. 2012


A rarity of the Archaean – Skjoldungen alkaline-mafic province (SAP)• Archaean (2750-2660 Ma) alkaline-mafic

province (rare worldwide)• Outcrops along 80 x 30 km NW-SE trending belt• Ultramafic – mafic – felsic intrusions

- Pyroxenites, hornblendites,- Hbl norites, gabbronorites, diorites,- Monzonites, syenites, granites- Late nephelinitic & carbonatite rocks

• Geochemical subduction affinity• Syn- to post-tectonic intrusions

• Subduction-modified primitive mantle source – metasomatised mantle melting

• Derived magmas involving primitive mantle

Skjoldungen intrusives

Kokfelt et al. (in press)


Skjoldungen alkaline-mafic province (SAP)

• Young pulse; around 2695 Ma gabbro, gabbronorite, diorite, nephelinitic and carbonatite rocks

• Middle pulse; around 2713 Ma granite, diorite, syenite

• Old pulse; around 2744 Ma syenite, syenitic gneiss

• Last 2631 Ma; pegmatitesThree magmatic pulses:

Syenite with variably dissolvedmafic xenoliths

Granite-syenite at Sfinksen

Layered gabbro complex at Vend Om

Carbonatitic‐nephelinitic sheet2.6 Ga Singertât Complex

Kok

felt

et a

l. (in

pre

ss),

Næ

raa

et a

l. (in

pre

b.)


Magnetite-rich band withinthe layered gabbro sequence:Up to 1.5m thick over ca 50 m lateral distance, thinning out

Magnetite-rich band, locally with sulphides

Vend Om Gabbro Concordant magnetite‐rich band in Layered Series

Mineral endowment:

Marupgaard 2015, Kolb et al. 2015, Kokfelt et al. (in press)


Dropstone structure. Leuco-gabbro xenolith depressing layer in Vend Om Gabbro

Layered Series – bifurcating layer(similar to the famous Dwars River

location, Bushveld) at Vend Om

Magnetite-rich bands in layered mafic Intrusions• Several magnetite-rich layers; massive to disseminated

discovered in three layered gabbroic and dioritic intrusions.

• V-Ti-Fe potential; up to 1.7 wt% V2O5

However;• Grades not high• Small tonnage, tectonized• No PGE, Au encountered

– still possibilities Hermods Vig Diorite

Vend Om Gabbro

Iglermiut Gabbro

V‐Ti‐Fe potential in layered intrusions

Rhythmical modal layering in Vend Om

Mineral endowment:


W‐MoQuartz‐wolframite‐molybdenite vein & scheelite in amphibolite

Mineral endowment:

• Quartz-wolframite-molybdenite vein• C. 30 cm wide, subvertical – hosted in mafic granulite• 1.6% W; 263 ppm Mo• Re-Os dating: 2749±11 Ma – old SAP pulse;

monzogranite and Skirner Bjerge Syenite

• Scheelite in amphibolite• Up to 0.55% W• Believed to be contemporaneous with the dated vein

Ros

a &

Ulri

ch 2

013









RAECraton

NAC


• Palaeoproterozoic collisional orogen between the Rae and the North Atlantic craton

• Archaean orthogneisses deformed during the collision; basement ~3075-2650 Ma

• Subdivided from north to south into the: Schweizerland Terrane; thrusted on top of terrane

to the south, granulite facies, mainly 2860-2730 Ma orthogneiss Kuummiut Terrane; 1867±28 Ma eclogite facies;

1820 Ma decompression to amphibolite facies; migmatitic orthogneiss (ages between) 3035-2630 Ma) with doubly folded supracrustal belts –paragneiss, graphitic schist, marble, quartzite and lesser amphibolites and ultramafic rocks. Ammassalik Intrusive Complex (AIC); 1885 Ma,

magmatic arc related complex Isortoq Terrane; amphibolites, ultramafic –

Archaean orthogneiss and 1937±7 Ma banded orthogneiss.

• Large post-tectonic intrusive complexes; ~ 1665 to 1525 Ma, diorite, granodiorite, gabbro, granite

• Palaeogene intrusive suite including volcanicsand dolerite dyke

Schweizerland Terrane

Kuummiut Terrane

AIC

IsortoqTerrane

Thrym Complex

RAECraton

NACCraton

Nag

ssug

toqi

dian

Oro

gen

–S

outh

-Eas

t Gre

enla

nd

Palaeogene Intrusive Suite

?


• Niflheim thrust• Supracrustal units of the

Kuummuit Terrane


~

Niflheim Thrust; Archaean orthogneisses in amphibolite (footwall) and in granulite facies (hangingwall); 2733±5Ma and 2705±15Ma respectively.



Marble and graphitic schist from the air

Palaeoproterozoic graphitic schist, paragneiss and marble; 1 wide belt north of Heilheim Gletcher.


Complex history with nappe formation, large domes and synformal


Large scale isoclinal folding


GraphiteGraphite mineralisation in schist

Mineral endowment:

Ros

ing-

Scho

wet

al.

2015

.

Rosing-Schow et al. 2015

Supergene limonite alteration zone in central Auppaluttoq. The zone is approximately 300 m wide and surrounded by orthogneiss.

• Graphite within meta-pelite/-schist units within the supracrustal is widespread

• Within certain horizons and structural controlled zones these approach ore grade• Two areas have been studied in detail,

Auppaluttoq and two at Kangikajik(<30 wt.% graphitic carbon)

• Uninvestigated graphite occurrences are present in between

• Strong supergene alteration; loose limonite gravel, which contains graphite flakes as a main component. One area being 2.5 × 2.5 km.

• Flakes up to 6 mm; average of 3.33 mm ± 1.21 mm

• Most likely hydrothermaldeposited graphite


Gold[?]Mineral endowment:

1.1 ppm

20 ppmQz-vein

2 ppm

7.5 ppmAmphibolite

5.2 ppmAmphiibolite 14.7 ppm

2.5 ppm

10.6 ppmQtz w. pyrite

1.1 ppm

15.2 ppmQtz w. pyrite

11.1 ppmGraphite-

garnet-gneiss

40 km

Ujarassiorit results 1989-2013, Au above 50 ppb with indications of those above 1 ppm Au (both float and bedrock; locations uncertain)

Au>1ppm

• Former exploration results• Ujarassiorit results• SEGMENT Geochemistry 2010

• GEUS-MMR fieldwork

190 ppb Au in stream sediment geochemistry

MMR-GEUSStream SedimentGeochemistry 2010


Gold[?]Quartz‐veins with elevated gold; Ujarassiorit samples; [?]

Mineral endowment:

• Follow-up on Ujarassiorit by GEUS-MMR; 11 g/t Au at Auppaluttoq• confirmed occurrences of anomalous gold

(0.5 g/t) within quartz-veins • Other anomalous areas (floats) were

not confirmed.• More potential targets are present

• A GEUS-MMR targeting exercise is ongoing

• Gold seems to be hosted in quartz-vein systems within supracrustals; these are very weathered and appear as rusty-gossans.

• A gold potential is present; but more detailed field campaigns are wanted• e.g. detailed large rock and soil-sampling

program• investigations of weathering; leaching of

metals under Arctic conditions

The local Ujarassiorit 1st prize winner William Umerineq at the Auppaluttoq site where he samples 11 g/t Au. GEUS-MMR were not able to replicate this; but picked-up 0.5 g/t Au in quartz-veins from the site. Nugget-effects may be causing this and only limited work have been carried out on the site.

Poulsen et al. 2013



Anorthosite enclaves in migmatiticorthogneiss

Granite invaded orthogneiss


Large ultramafic lens, followed by granite and with amphibolitesequence in the background


RubyRuby‐sapphire in metasomatic alteration zones

Mineral endowment:

Metasomatic reaction band in ultramafic rock with concentric mineral zones; core zone consists of pure biotite, locally enveloping a black amphibole + purple ruby zone.

• Follow-up on Ujarassiorit winning ruby sample by GEUS-MMR revealed several ruby occurrences in the area• Same characteristics: ruby-sapphire

occurs where late-stage felsic pegmatitescrosscut and metasomatically interact with metamorphosed ultramafic rocks.

• Progressive metasomatic replacement of the pegmatite takes place with well-developed mineral zoning, culminating in a biotite zone, followed by a zone with black amphibole + pink to purple ruby-sapphire.

• Ruby-sapphire is rare, but large (locally up to 5 cm in diameter), anhedral in shape with only little fractures.

• The genetic model works; new discoveries made, however more work is needed; potential for larger systems?

Pou

lsen

et a

l. 20

13; P

ouls

en&

Hin

sber

g 20

14; P

ouls

enet

al.

2015

.



Ammassalik Intrusive Complex:Diorite of ~1885 MaContact metamorphic aureole of diatexites


Supracrustals and diatexites in the contact aureole


Ni‐Cu‐PGEOrthomagmatic Ni‐Cu‐PGE mineralisation in AIC

Mineral endowment:

• Earlier discoveries by NunaOil A/S in the anatectic supracrustal zone outside the AIC; komatiite-nickel exploration model

2014 GEUS-CET-BMP work• Conduit-type model;

orthomagmatic• New discovery of semi-massive

sulphide mineralisation withingabbro-norite-tonaliteof the AIC

A.

A.

Johansen (in preb.), Kolb et al. 2015



Peaks of the Ammassalik Batholith; granite, granodiorite, diorite, norite, gabbro

Diorite1634±14 Ma


~1600 Ma granite intrusion









RAECraton

NAC


Palaeogene intrusive suite• Kialineq District, Kap Gustav Holm• 50 Ma old gabbro and a comparatively young suite of

intrusions (40-35 Ma) dominated by dioritic to syeniticand granitic compositions.

• No discovered mineralisation; although a conceptualpotential for magmatic Au-PGE may or exhalative/ hydrothermal mineralising systems may be presents

Schweizerland Terrane

RAECraton

Palaeogene Intrusive Suite

Map after Brooks 2011

Younger granites in Skrækkens Bugt

Diorite by cut by pink syenitic veins in Skrækkens Bugt


SEGMENT; South-East Greenland Mineral ENdowment Task• An interesting geological model unfolds for entire

South-East Greenland • The Tasiilaq – and, perhaps to a lesser extend the

Skjoldungen region – comprise a potential for different mineral resources

• The ongoing work by GEUS and MMR will continue into 1st half of 2016 – with more results pending

• Final mineral endowment report and a digital GIS data package to be presented early 2016

• A likely workshop – including summary of new model and data – will be announced in 2016

• Stream sediment geochemistry and indicator mineral data as well as new regional aeromagnetic data are already available

• Few licenses are currently claimed in the region; interested in knowing more – come and talk with us…

Overall purpose


Thank you

For more information, please contact Bo M. Stensgaard([email protected])

Greenland Day Perth, Dec. 9th, 2015


the end...


Lommen‐Jættefjord Ni‐CuOrthomagmatic Ni‐Cu mineralisation in ultramafic rocks

Mineral endowment:

Layers of ultramafic and mafic granulites• Interpreted to be intrusions

in the lowermost part of the crust

Green peridotite and black pyroxenite; mingling. Mafic granulite

Leucosome

Peridotite

Sequence of peridotite, pyroxenite, mafic granulite and Ni-Cu mineralisation


425m

800m

AIC contact

Sulphide Showing

Ni‐Cu‐PGEOrthomagmatic Ni‐Cu‐PGE mineralisation in AIC

Mineral endowment:

PolheimShowing

• Discovered 1996 by NunaOil/NunaMineralsA/S

• concordant lens trending 310º and dipping 70º NE; Isocline fold axis plunging 127º/38º

• Hosted in partly serpentinised ultramafic rock - discontinuous rusty lineament ultramafic pods or boudins parallel to the contact of the AIC

• 90-100 m on surface and varies in width from 1 to 8 m; NiTenor 4.72%, CuTenor 1.56%

• Revisited in 2014 during GEUS fieldwork

Main Mineralisation

Qorqortoq Showing

PolheimShowing

New Showing

TASIILAQ

The Main Mineralisation

21stNorthNi Cu Co Au Pd Pt1.39 pct 0.46 pct 757 ppm 108 ppb 29 ppb 219 ppb

NiTenor CuTenor

4.72 pct 1.56 pct


Old and exposed for a long timeExhumation history

2694±4 Ma

• U/Pb dating on zircons of pegmatites with miaroliticcavities provides constraints on the exhumation.

• No major vertical movements since Archean time

Miarolitic cavities in syn-magmatic intrusions and pegmatites in Skjoldungen. Evidence of intrusion at shallow levels (1-2 kb max pressure)

2632±7 Ma

Ruinnæsset intrusion

Metasediments

Relics of TimmiarmoutOrogen

2740 Ma

2694 Ma

2740 Ma Granulite facies metamorphism ca 0.8 GPa

2632 MaPegmatite Ruinnæssetca <0.15 GPa (≤ 3 km)

2694 Ma Pegmatite of the Ruinnæsset intrusions; emplaced at ca <0.15 GPa (≤ 3 km)

Dep

th [k

m]

Pre

ssur

e [G

pa]

2750 Ma 2700 Ma 2650 Ma

1

0.5

0 0

15

30

Berger et al. 2014


D1 in the Isertoq TerraneWhat is the nature and timing of the early SE-vergent deformation in the Isortoq Terrane?


Kuummiut Terrane

How is the complex evolution of different metamorphic units, i.e. eclogite facies orthogneiss and mafic dykes and amphibolite facies Síportôq Supracrustal Association, in the Kuummiut terrane ?What is the nature and timing of the late Niflheim Thrust, one of the youngest structural features in the orogen ?

Documents

New Understanding and mineral endowment of the Archaean ... · endowment of the Archaean, Palaeoproterozoic and Palaeogene of ... Ccp, Pn; up to 20%, ... Nugget-effects may be causing