new understanding and mineral endowment of the archaean ... · endowment of the archaean,...
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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
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
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
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
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
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
• 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)
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
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.
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
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)
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
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
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
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)
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
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.)
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
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)
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
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:
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
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
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
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
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
• 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
?
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
• Niflheim thrust• Supracrustal units of the
Kuummuit Terrane
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
~
Niflheim Thrust; Archaean orthogneisses in amphibolite (footwall) and in granulite facies (hangingwall); 2733±5Ma and 2705±15Ma respectively.
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
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
Marble and graphitic schist from the air
Palaeoproterozoic graphitic schist, paragneiss and marble; 1 wide belt north of Heilheim Gletcher.
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
Complex history with nappe formation, large domes and synformal
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
Large scale isoclinal folding
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
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
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
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
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
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
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
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
Anorthosite enclaves in migmatiticorthogneiss
Granite invaded orthogneiss
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
Large ultramafic lens, followed by granite and with amphibolitesequence in the background
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
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
.
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
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
Ammassalik Intrusive Complex:Diorite of ~1885 MaContact metamorphic aureole of diatexites
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
Supracrustals and diatexites in the contact aureole
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
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
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
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
Peaks of the Ammassalik Batholith; granite, granodiorite, diorite, norite, gabbro
Diorite1634±14 Ma
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
~1600 Ma granite intrusion
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
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
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
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
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
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
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
Thank you
For more information, please contact Bo M. Stensgaard([email protected])
Greenland Day Perth, Dec. 9th, 2015
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
the end...
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
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
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
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
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
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
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
D1 in the Isertoq TerraneWhat is the nature and timing of the early SE-vergent deformation in the Isortoq Terrane?
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
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 ?