Zinc-copper-lead metallogeny of the eastern Arunta · Roland Maas Sue Golding Colleagues at GA and...

Australian Government

Geoscience Australia

Zinc-copper-lead metallogeny of the eastern Arunta

David L Huston1, Kelvin Hussey2

and Max Frater3

1Geoscience Australia2Arafura Resources NL (formerly Northern Territory Geological Survey)

3Northern Territory Geological Survey

Geoscience AustraliaNAP-wrap 2006

Acknowledgments

Jon Claoué-Long

Shen-Su Sun

Tim Munson

Roland Maas

Sue Golding

Colleagues at GA and NTGS


SignificantZn-Cu-Pb(Ag-Au)

Mineralisationrestricted to:

(1) SE Aileron Province (1810-1800 Ma &

1765 Ma)

(2) Warumpi Province (1620-1610 Ma)


Zn-Cu & Cu-Au – Arunta-Tennant-Tanami

StrangwaysStokes Yard, UlpurutaOonagalabi

Jervois

Home of BullionMt Hardy

White’s Yard

Silver King

Johnnies

TennantCreek

Rover

WA NT NT

Strangways RangeWarumpi ProvinceGeoscience Australia

Zn-Cu & Cu-Au prospects – Strangways Range

Geoscience AustraliaGeoscience Australia

Zn-Cu & Cu-Au prospects – Strangways Range

Type Element assemblage

Host Alteration assemblages

Age (Ma)

Origin

Utnalanama Zn-Pb-Cu(Ag-Au-Bi-Cd)

Marble and calc-silicate after marble.

Qz-crd±opxrock > massive amp±spn±cpx rock

1810-1800

VHMS

Oonagalabi Zn-Cu-Pb(Ag-Au-Bi)

Marble →calc-silicate → massive anthophyllite.

Qz-gt rock. 1765 Carbonate replacement or VHMS

Johnnies Cu-Au-Pb(Zn-Ag-Bi-Mo-Mn-Ca-HFSE-REE)

Mt-cpx-am±qz rock (after marble).

Qz-bt-gtgneiss in structural footwall to lode rock.

1795-1770

IOCG


Characteristics of Utnalanama-type deposits

Mineralisation hosted by marble lenses within the Lower Strangways Metamorphic Complex (Ongeva package)

Age of host: 1810-1800 Ma

Psammo-pelitic sequence; volcaniclastic component

Size and grade of known deposits: to ~5 Mt at 2-4% Zn+Cu+Pb with Ag and Au credits

Dominant alteration: asymmetric quartz-cordierite rock;Lesser (minor) amphibole-rich assemblages;

Minor magnetiteGeoscience Australia

Utnalanama-type deposits – Edwards Creek


Edwards Creek – Host sequenceMostly banded, felsic gneiss (includes massive felsic gneiss)Lesser mafic gneiss (sills) and micaceous schistForsterite marble and calc-silicate host mineralisation


Local “clastic” textures

Local “quartz-eye” textures

Edwards Creek – Mineralisation and siliceous cap


Surface assays (n = 11):to 3.3% Zn, 0.7% Pb, 0.8% Cu

(anomalous Bi & Cd)

Mineralised marble

Ore mineralogy:Sp > py ~ gn ~ cp > gh ~ mt


(anomalous Ag, Bi, Cd, Mn & Bi)

Siliceous capTertiary weathering of marble

Hornblende-gahnite rock150 m along strike; up to 5 m wideTo 11.7% Zn (anomalous Bi, Cu,

Pb, Sn, Th and REEs)

Edwards Creek – Alteration assemblagesDominant meta-assemblage: cordierite-quartz rock (gneiss)

with local orthopyroxeneporphyroblasts

Minor meta-assemblage: gedrite-hercynite rock andmassive anthophyllite rock


Edwards Creek – alteration geochemistry


Talc

Quartz-cordierite rock & gedrite-hercynite rock:

Enriched in Fe(II), Mg, and, locally, Pb

Depleted in Na, Ca, Sr, Cu and, locally, K and Rbδ18O = 1.8-4.4‰

Quartz-cordierite rockGedrite-hercynite rockMassive tremolite rockHornblende-gahnite rock

Massive tremolite rock:Enriched in Mg and Ca

Depleted in Na, K and Rb

Pre-metamorphic alteration assemblagesQuartz-cordierite rock & gedrite-hercynite rock: Quartz-chlorite-muscovite & massive chlorite, respectivelyMassive tremolite rock: Talc-chlorite-carbonate

Utnalanama-type deposits – generalised model

500-1500+ m

Psammo-pelitic gneiss; quartzofeldspathic gneiss

Mafic gneiss

Quartz-cordierite rock (+Mg, Fe; -Na, Ca, K)

Cordierite rock;gedrite-spinel rock

Mineralised marble (Zn-Cu-Pb(Ag-Au-Cd-Bi)Tremolite rock

50-2

50 m

Inferred origin: volcanic-hosted massive sulphideGeoscience Australia

Characteristics of Oonagalabi-type deposits

Mineralisation hosted by marble lenses within the Bungitina Metamorphics (Ledan package)

Age of host: <1765 Ma

Psammo-pelitic sequence; volcaniclastic component

Size and grade of known deposits: to “25 Mt at 1%Zn and 0.5% Cu” with Au and Ag credits

Dominant alteration: massive anthophyllite rock;Quartz-garnet rock (in psammo-pelitic rocks);

Minor magnetite and quartz-cordierite


Geoscience AustraliaGeoscience Australia

Oonagalabi-type deposits – Oonagalabi

Oonagalabi – Host sequenceUnit A: Banded, biotite-quartzo-feldspathic gneiss with minor1-3 mm garnet porphyroblasts. Host to mineralised carbonate lens.


Unit B: Biotite-rich quartzo-feldspathic gneiss with distintive5-30 mm K-feldspar porphyro-blasts. Structurally underlies unit A.


Oonagalabi – Mineralisation


(anomalous Cd)

Mineralised marble

Ore mineralogy:Sp > po ~ cp > gn > gh ~ py

Surface and core assays (n = 7):to 2.9% Zn, 0.2% Pb, 2.7% Cu (anomalous Bi, Mo, Cd & Sn)

Massive anthophyllite rock

ParagenesisMarble → calc-silicate → massive

anthophyllite

Oonagalabi – Alteration assemblagesDominant meta-assemblage:

garnet-quartz rockRestricted in distribution: <20 m

from mineralised rock


Minor meta-assemblages: Orthoamphibole-

orthopyroxene-magnetite-spinel rock, cordierite-quartz

rock andgahnite-quartz rock

Oonagalabi – Alteration geochemistry

Quartz-garnet rock:Enriched in Si, Fe(II), Mg, and,

locally, PbDepleted in Na, K, Ca, Sr, K and

Rb

Massive anthophyllite rock:Enriched in Mg, Fe and FDepleted in Na, K and Rb

Quartz-garnet rock: Quartz-rich quartz-chlorite altered unit A

Massive anthophyllite rock: Talc-quartz altered marble

Pre-metamorphic alteration assemblages


Oonagalabi – Structure


Tight, NE-plunging F3 folds on relatively flat form surface

Oonagalabi-type deposits – generalised model

Biotite-rich pelitic gneiss (unit B)

Mineralised marble

Quartzo-feldspathic gneiss (unit A)

Mineralisedanthophyllite rock

Calc-silicate

Garnet-quartz rock

100 m

Mafic gneiss

Inferred origin: carbonate-replacementGeoscience Australia

Zn-Pb-Cu prospects – Warumpi ProvinceNT

Iwupataka Metamorphic Complex

Host: Iwupataka Metamorphic ComplexAmphibolite-facies quartz-muscovite schist, calc-silicates

and amphibolites

Age: 1620-1610 MaExtensional/transtensional basins formed after accretion

of Warumpi Province onto North Australian CratonGeoscience Australia

N

020 m

DDH 1-3

DDH 4Pegmatite

Calc-silicate breccia

Amphibolite

leuco-gneiss

meta-pelite/psammite

1971-72 Five DDHs drilled by NTGS to test the mineralisation at depth.

Glen Helen Metamorphics

Stokes Yard Prospect

Stokes Yard

Mineralisation in N-S mylonite and breccia zone.

Surface Pb-Zn mineralisation occurs in calc-silicate.

1972 drilling program intersected narrow Cu mineralisation in altered amphibolite in breccia zone.

Surface Pb-Zn mineralisation not intersected.

Local geology, mineral association and alteration suggest the prospect is a deformed skarn occurrence.


Lead isotopes

15.36

15.37

15.38

15.39

15.40

15.41

15.42

15.75 15.80 15.85 15.90 15.95 16.00206Pb/204Pb

207 Pb

/204 Pb

Utnalanama

Johnnie’s

Oonagalabi

Warumpi

Strangways evolutioncurve

Geoscience AustraliaMinerals Exploration Seminar 2003

ConclusionsThree styles and ages of Zn-Cu-Pb deposits in eastern

Aileron and Warumpi Provinces:Utnalanama-type: VHMS deposits hosted by 1810-1800 Ma

Ongeva packageOonagalabi-type: Carbonate replacement deposits hosted by

~1765 Ma Ledan packageStokes type: Skarn deposits hosted by 1620-1610 Ma Iwupataka

Metamorphics

All deposits closely associated with carbonate lenses

In Utnalanama- and Oonagalabi-type deposits, host has a volcaniclastic component


Lead isotope data indicate the source of lead becomes progressively more primitive with younger age.

Zinc-copper-lead metallogeny of the eastern Arunta · Roland Maas Sue Golding Colleagues at GA and...

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