Characteristics of Characteristics of Porphyry Cu-Au Porphyry Cu-Au Systems in the Systems in the

Ordovician Macquarie Ordovician Macquarie Arc of NSWArc of NSW

Bruce Mowat & Stuart SmithBruce Mowat & Stuart Smith

OutlineOutline► IntroductionIntroduction

History of exploration and researchHistory of exploration and research Distribution of systemsDistribution of systems

►Review key geological aspects of the Review key geological aspects of the major depositsmajor deposits

►Characteristics of the Temora Characteristics of the Temora porphyry systemsporphyry systems

►Future challenges of explorationFuture challenges of exploration

► 1976 Geopeko/North identifies porphyry 1976 Geopeko/North identifies porphyry style Cu-Au in the Goonumbla areastyle Cu-Au in the Goonumbla area

► Initial Research, (Paul Heithersay, John Initial Research, (Paul Heithersay, John Walshe)Walshe)

► AGSO, NSW DMR (Doon Wyborn)AGSO, NSW DMR (Doon Wyborn)► Newcrest identify Cadia Hill porphyry Newcrest identify Cadia Hill porphyry

system system ► AMIRA P425 (Gregg Morrison, Phil Blevin) AMIRA P425 (Gregg Morrison, Phil Blevin) ► SPIRT (Dave Cooke, Tony Crawford, Dick SPIRT (Dave Cooke, Tony Crawford, Dick

Glen)Glen)► Ongoing research by Newcrest teamOngoing research by Newcrest team

HistoryHistory

Macquarie ArcMacquarie Arc

►Macquarie Macquarie Arc is a Arc is a component component of the of the Lachlan Lachlan OrogenOrogen

►Ordovician to Ordovician to early Silurian early Silurian Volcanic Volcanic ProvinceProvince

Sydney

Melbourne

Macquarie ArcMacquarie Arc

► Four Separate Four Separate BeltsBelts

► Junee-Junee-Narromine Narromine (JNVB)(JNVB)

► Molong (MVB)Molong (MVB)► Rockley-Rockley-

Gulgong Gulgong (RGVB)(RGVB)

► Kiandra (KVB)Kiandra (KVB)

14

9 °

14

7 °

-3 2 °

-3 4 °

1000

km

SydneySydney

Parkes

Temora

Orange

Narromine

JNVB

MVB

RGVB

KVB

Distribution of SystemsDistribution of Systems► 24 porphyry 24 porphyry

systemssystems► Most (22) occur Most (22) occur

within definable within definable districtsdistricts

► 17 including all 17 including all operations within operations within Cadia and Cadia and NorthparkesNorthparkes

► Districts defined Districts defined by coherent by coherent geological geological charactercharacter

► ClusteredClustered

14

9 °

14

7 °

-3 2 °

-3 4 °

1000

km

SydneySydney

Parkes

Temora

Orange

Narromine

Cadia District

Rain Hill District

Northparkes District

Cowal District

Temporal DistributionTemporal Distribution

Macquarie Arc – Summary Time-Space Plot

Northparkes District

Copper Hill

Cargo

Cadia

Lake Cowal

► Macquarie arc - Australia's only economic Macquarie arc - Australia's only economic porphyry provinceporphyry province

Key Features of the DistrictsKey Features of the Districts

►Higher proportion of intrusive rocks Higher proportion of intrusive rocks ►More complex (but not unique) More complex (but not unique)

magnetic signatures - most related to magnetic signatures - most related to intrusive activityintrusive activity

►Gravity lowsGravity lows►Overall more felsicOverall more felsic►Overall more potassicOverall more potassic

Age of the SystemsAge of the Systems

►455 Ma455 Ma E43, Cargo, Copper Hill,E43, Cargo, Copper Hill, Low K, dacite associationLow K, dacite association adakitesadakites

►440 Ma440 Ma Cadia District, Northparkes, Rain HillCadia District, Northparkes, Rain Hill Medium to High K, monzonite associationMedium to High K, monzonite association

480

465

Nelungaloo Volcs and Mitchell Fmn- - Hi-K calc-alk and shoshonitic

450

440

Narromine and Cowal Middle Ord Intrusive Monzodiorites etc (hi-K CA)

Middle Ord high-K to (higher) shoshonitic lavas

Copper Hill-type adakitic dacite-gdt suites

Evolved shoshonitic lavas suites

Late intrusive shoshonites (monz)

LFB

Igneous CharacterIgneous Character

► Macquarie Arc dominated by basalts and Macquarie Arc dominated by basalts and andesite compositions andesite compositions

► Productive districts tend to be more felsic on Productive districts tend to be more felsic on averageaverage

► E43, Cargo and Copper Hill low-K Calc-alkalineE43, Cargo and Copper Hill low-K Calc-alkaline Dacite porphyry association (adakites)Dacite porphyry association (adakites)

► Rain Hill District medium to high-K Calc-Rain Hill District medium to high-K Calc-alkalinealkaline

► Cadia and Northparkes districts are high-K to Cadia and Northparkes districts are high-K to shoshonitic in character, the most potassic shoshonitic in character, the most potassic regions in the arcregions in the arc Monzonite, syenite, latite, trachyteMonzonite, syenite, latite, trachyte

AlterationAlteration► Core: Core:

potassic (biotite-mt; orthoclase-qtz-sulphide-potassic (biotite-mt; orthoclase-qtz-sulphide-hematite) hematite)

calc-sodic (act-mt-ab)calc-sodic (act-mt-ab) Phyllosilicate (sericite, hm, ab)Phyllosilicate (sericite, hm, ab)

► Distal: Distal: propylitic (chl-carb-epi-ab-hm) propylitic (chl-carb-epi-ab-hm) sodic (ab-chl-tm)sodic (ab-chl-tm) Phyllosilicate (sericite, albite)Phyllosilicate (sericite, albite)

► Late faults: Late faults: phyllic (QSP-carbonate-base metals) phyllic (QSP-carbonate-base metals)

► Distinctive pink rock hematite alt of Distinctive pink rock hematite alt of intrusions & volcanicsintrusions & volcanics

GOONUMBLASchematic Intrusives -

Alteration - MineralisationG Morrison & P Blevin 3/96

K Feldspar-quartz

K Feldspar destructive

Sericitic

Kf network +biotite spots

MMZc

MMZpMMZa

GRp

MMZc

MZD

DI

MMZp

MZD

MMZmMMZp

Ap

MZp

MMZa

ALTERATION

Northparkes potassic Northparkes potassic alterationalteration

Northparkes Potassic AltNorthparkes Potassic Alt

Sericite Albite AlterationSericite Albite Alteration

►Cadia East, Ridgeway, E26, E48 have Cadia East, Ridgeway, E26, E48 have sericite and/or albite bearing zonessericite and/or albite bearing zones These can beThese can be

►Central and directly associated with oreCentral and directly associated with ore►Proximal and directly associated with oreProximal and directly associated with ore►Peripheral and not associated with orePeripheral and not associated with ore►Minor associated with narrow fault zonesMinor associated with narrow fault zones

Distinguishing these is critical but can Distinguishing these is critical but can be very difficult be very difficult

500m

Skarn

Reg Prop

Skarn Prop

Alb-ser

Alb-qz-hem

Calc-sodic

Inner Prop

Outer calc-pot

Inner calc-pot

After Tedder et al., 2001After Tedder et al., 2001

Cadia EastCadia East

► Extensive alb-ser-Extensive alb-ser-tour-py-hem zonetour-py-hem zone Above and Above and

peripheral to peripheral to orebodyorebody

Obscures outcrop of Obscures outcrop of the orebodythe orebody

Albite Sericite Tourmaline AltAlbite Sericite Tourmaline Alt

E26E26► Widespread and Widespread and

generally high level generally high level qtz-ser-py-albqtz-ser-py-alb

► Highly bleachedHighly bleached

Strong mt-bi

Weak mt-bi

Strong K-fs

Weak K-fs

Qtz-ser-py-alb

Unaltered or Propylitic

Central Sericite AlterationCentral Sericite Alteration► E26 & E48 both have a core zone of E26 & E48 both have a core zone of

magmatically derived sericite +/-albite, magmatically derived sericite +/-albite, alunitealunite Associated directly with bornite, Associated directly with bornite,

chalcocite, covellite, digenite, tennantite, chalcocite, covellite, digenite, tennantite, enargiteenargite

Generally > 2%Cu

E48 Proximal He-Se-CarbE48 Proximal He-Se-Carb

Propylitic AlterationPropylitic Alteration

►One of the greatest unknowns in One of the greatest unknowns in Macquarie Arc porphyriesMacquarie Arc porphyries Cadia has both distal and proximalCadia has both distal and proximal Northparkes, possibly has distalNorthparkes, possibly has distal Strong and very widespread regional Strong and very widespread regional

assemblage that is definitely unrelated to assemblage that is definitely unrelated to mineralisationmineralisation

Use with extreme caution Use with extreme caution

Propylitic AlterationPropylitic Alteration

500m

Skarn

Reg Prop

Skarn Prop

Alb-ser

Alb-qz-hem

Calc-sodic

Inner Prop

Outer calc-pot

Inner calc-pot

After Tedder et al., 2001After Tedder et al., 2001

200m

After Wilson et al., 2003After Wilson et al., 2003

PotassicPotassicCalc-PotassicCalc-Potassic

Inner PropyliticInner PropyliticOuter PropyliticOuter Propylitic

Garnet-silicaGarnet-silica

Albite-pyriteAlbite-pyrite

RidgewayRidgewayCadia EastCadia East

►eg. Cadia Easteg. Cadia East

500m

Skarn

Reg Prop

Skarn Prop

Alb-ser

Alb-qz-hem

Calc-sodic

Inner Prop

Outer calc-pot

Inner calc-pot

Extensive alb-ser-Extensive alb-ser-tour-py alteration tour-py alteration

Regional vs Distal Regional vs Distal PorphyryPorphyry

► Some clues - but a lot more work neededSome clues - but a lot more work needed Fracture controlFracture control Overlap with most distal magnetite-biotiteOverlap with most distal magnetite-biotite Any low level CuAny low level Cu Prehnite/actinolitePrehnite/actinolite

Distal Porphyry ep-chl-Distal Porphyry ep-chl-prehpreh

Regional ep-chl-calcRegional ep-chl-calc

Fe-OxideFe-OxideDistributionDistribution

Magnetite DistributionMagnetite Distribution

► Magnetics is the second most common Magnetics is the second most common targeting tool (behind simple Cu & Au targeting tool (behind simple Cu & Au geochemistry)geochemistry)

► How well do we understand the controls on How well do we understand the controls on magnetite distribution and therefore the magnetite distribution and therefore the types of signatures to expecttypes of signatures to expect

► What are the controlsWhat are the controls Primary magnetitePrimary magnetite Magnetite constructive alterationMagnetite constructive alteration Magnetite destructive alterationMagnetite destructive alteration

Alteration MagnetiteAlteration Magnetite

►Magnetite constructive alterationMagnetite constructive alteration Occurs in ALL systems, but location is not Occurs in ALL systems, but location is not

always the samealways the same All Macquarie arc systems share an early All Macquarie arc systems share an early

mt alteration stagemt alteration stage►Associated with early intrusions - can be Associated with early intrusions - can be

widespread -several 100 m from intrusionswidespread -several 100 m from intrusions

Distal magnetite-biotiteDistal magnetite-biotite

►Cadia systemsCadia systems Ridgeway - direct association with oreRidgeway - direct association with ore

Magnetite & Alteration

After Harper, 2000After Harper, 2000

Ridgeway Cross SectionRidgeway Cross SectionContoured Magnetic Contoured Magnetic Susceptibility values; 10Susceptibility values; 10--

55SISI

NorthparkesNorthparkes►Fundamentally different characterFundamentally different character

In all known systems the ore-bearing In all known systems the ore-bearing stage overprints and destroys earlier stage overprints and destroys earlier magnetite constructive stagemagnetite constructive stage

Amount of early magnetite Amount of early magnetite ANDAND the the degree of magnetite destruction is degree of magnetite destruction is variablevariable

►Mt alteration is in part function of host rock Mt alteration is in part function of host rock compositioncomposition

►Intermediate hosts develop large mt halosIntermediate hosts develop large mt halos►In felsic hosts low 1In felsic hosts low 1o o Fe content results in Fe content results in

lesser mtlesser mt

Ore-stage Mt DestructionOre-stage Mt Destruction

► E26E26 Major ore stage is Major ore stage is

associated with associated with intense K-feldspar intense K-feldspar alterationalteration

This overprints and This overprints and destroys much of the destroys much of the magnetite-biotite magnetite-biotite alterationalteration

►E26 - magnetite destructive K-feldsparE26 - magnetite destructive K-feldspar

Weak

Moderate

Intense

Remnant bi-mt alterationRemnant bi-mt alteration

Magnetite and OreMagnetite and Ore

►Directly associated with OreDirectly associated with Ore RidgewayRidgeway

►Magnetite destruction with OreMagnetite destruction with Ore E26E26

►Felsic host less MtFelsic host less Mt NorthparkesNorthparkes

►Mafic to intermediate host more MtMafic to intermediate host more Mt Cadia RegionCadia Region

Metal ZoningMetal Zoning

►Cu-AuCu-Au Pipe-like systems (eg NPM, Ridgeway) Pipe-like systems (eg NPM, Ridgeway)

show a strong zoning with Au increasing show a strong zoning with Au increasing toward corestoward cores

Can be used as an exploration tool - slight Can be used as an exploration tool - slight systematic increase in Au:Cu should systematic increase in Au:Cu should encourage further drillingencourage further drilling

Metal ZoningMetal Zoning► Systems have traditional Cu, Zn zoningSystems have traditional Cu, Zn zoning

Cu anomaly much larger than the systemsCu anomaly much larger than the systemsLows within major ?peripheral Zn anomalyLows within major ?peripheral Zn anomaly

From Heithersay & Walshe, 1995From Heithersay & Walshe, 1995

PreservationPreservation► Remarkably intact, little deformationRemarkably intact, little deformation► NorthparkesNorthparkes

Intrusives vertical, 30 degree dip volcanicsIntrusives vertical, 30 degree dip volcanics

► CadiaCadia Intrusives vertical, stratigraphy flatIntrusives vertical, stratigraphy flat

► CowalCowal intactintact

► Rain HillRain Hill Devonian shear zone overprintDevonian shear zone overprint

Temora Porphyry DistrictTemora Porphyry District

►Goldminco Corporation holds majority Goldminco Corporation holds majority of Districtof District

► Junee-Narromine Volcanic BeltJunee-Narromine Volcanic Belt

►6 identified systems so far6 identified systems so far The Dam, Mandamah, Culingerai, Estoril, The Dam, Mandamah, Culingerai, Estoril,

Harold Bell, YiddahHarold Bell, Yiddah

TemoraTemoraGeologyGeology

TemoraTemoraMagneticMagnetic

ssCurrumburramaVolcanics

10

Gidginbung

BoonabahVolcanics

BelimebungVolcanics

0

kilometres

5

Rain HillMonzodiorite

GidginbungVolcanics

Temora Porphyry Temora Porphyry CharacteristicsCharacteristics

► Porphyry mineralisation clustered around Porphyry mineralisation clustered around margin of Rain Hill Monzodioritemargin of Rain Hill Monzodiorite Similar setting to NorthparkesSimilar setting to Northparkes

► Medium to high-K calc-alkalineMedium to high-K calc-alkaline► Mineralisation associated with high level Mineralisation associated with high level

porphyritic monzodiorite dykes and plugsporphyritic monzodiorite dykes and plugs 435 Ma age on syn to post mineral dyke435 Ma age on syn to post mineral dyke

► Andesitic volcanics and volcaniclasticsAndesitic volcanics and volcaniclastics No felsic volcanicsNo felsic volcanics Qtz poor volcanics and intrusivesQtz poor volcanics and intrusives

Temora Porphyry Temora Porphyry MineralisationMineralisation

►MineralisationMineralisation Early classic qtz-mt-py-cpy seam veinsEarly classic qtz-mt-py-cpy seam veins Late coarse qtz-carb-chl-cpy veinsLate coarse qtz-carb-chl-cpy veins

►AlterationAlteration Core mt-hm-biot-chlCore mt-hm-biot-chl±K-feldspar±K-feldspar Distal phyllic ab-ser-pyDistal phyllic ab-ser-py Late propylitic chl-ep-carbLate propylitic chl-ep-carb Devonian ser-py shear overprintDevonian ser-py shear overprint

Estoril porphyry Au-Cu Estoril porphyry Au-Cu systemsystem

Qz-mt-ksp-cpy veinsChl-mt-bi alt volc

Qz-mt-cpy seam vein

Ep-chl overprintingEarly mt-ksp alt

Estoril porphyry Au-Cu systemEstoril porphyry Au-Cu system

Qz-mt-cpy veins inDiorite host rock

Sheeted qz-mt-cpy veins

Andesite and MZDRIntrusive host rock

Qz-mt-ksp-cpy veins

He-mt alt MZDR

Local intense He-mtAlteration

MZDR

Similarities to other systemsSimilarities to other systems

► Geological SettingGeological Setting Similar to Northparkes settingSimilar to Northparkes setting

► AgeAge Late Ordovician early SilurianLate Ordovician early Silurian

► Similar alteration faciesSimilar alteration facies Inner Potassic and overprinting phyllicInner Potassic and overprinting phyllic

► Igneous characterIgneous character Oxidised High-K intrusivesOxidised High-K intrusives

► MineralisationMineralisation Qtz-mt-cpy seam veinsQtz-mt-cpy seam veins Alteration and ore stage mtAlteration and ore stage mt

Differences to current economic Differences to current economic systemssystems

►No Felsic rocksNo Felsic rocks Lack of the felsic suites (monz, trach, Lack of the felsic suites (monz, trach,

latite)latite)

►Limited hematiteLimited hematite Much less alteration hematite than Much less alteration hematite than

NorthparkesNorthparkes

►Post mineral tectonicsPost mineral tectonics Overprinted by Devonian shear zonesOverprinted by Devonian shear zones

Future ExplorationFuture Exploration►Ordovician SystemsOrdovician Systems

Current model prefers the current 4 Current model prefers the current 4 productive districts (tightly held)productive districts (tightly held)

Under cover Narromine-JuneeUnder cover Narromine-Junee Variations on current model (Less Variations on current model (Less

oxidised systems)oxidised systems)

►Other AgesOther Ages Siluro-Devonian Systems (Yeoval, Siluro-Devonian Systems (Yeoval,

Bald Hill, Vic, Bushranger)Bald Hill, Vic, Bushranger)