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INTRUSION-RELATED GOLD SYSTEMS IN THE NEW ENGLAND FOLD BELT:. The Tooloom Example. Brett McKay. Malachite Resources NL. MALACHITE RESOURCES NL. Classification of Intrusion-related gold systems Geological model The Tooloom Example Phoenix - PowerPoint PPT Presentation
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Malachite Resources NLMalachite Resources NL
INTRUSION-RELATED GOLD SYSTEMS IN INTRUSION-RELATED GOLD SYSTEMS IN THE NEW ENGLAND FOLD BELT:THE NEW ENGLAND FOLD BELT:
Brett McKayBrett McKay
The Tooloom ExampleThe Tooloom Example
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
• Classification of Intrusion-related gold systemsClassification of Intrusion-related gold systems
• Geological modelGeological model
• The Tooloom ExampleThe Tooloom Example
– PhoenixPhoenix
• Intrusion-related gold systems in the New Intrusion-related gold systems in the New
England England Fold BeltFold Belt
– metallogeny of NEFBmetallogeny of NEFB
– comparison with LFBcomparison with LFB
• Newly recognised prospectivity of NEFBNewly recognised prospectivity of NEFB
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
Intrusion-related gold system (IRGS) characteristics:Intrusion-related gold system (IRGS) characteristics:
• Au variably combined with Bi, Te, W, Mo, Sb, As
• Low sulphide content (<5%)
• Reduced mineral assemblage (Po, As, Py, Ilm, no Mag/Hem)
• Deposit and metal assemblage zoning: lateral & vertical
• Reduced I-type intrusives
• Intermediate to felsic
• WSnMo provinces
• Continental tectonic setting
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
Intrusion-related gold system (IRGS) characteristics:Intrusion-related gold system (IRGS) characteristics:
• Sheeted veins, stockworks, breccias, disseminations, skarns,
replacements, fissure veins
• Lateral and vertical metal zoning
– proximal Au-Bi-Te > Au-As > As-Sb-Au > Ag-Pb-Zn distal
– W±Mo at depth
– Au-Bi-Sb at shallower levels
• Examples:
– Donlin Creek: 28.5 Moz (measured & indicated resource)
– Pogo: 7 Moz (probable reserve)
– Fort Knox: 2.4 Moz (proven and probable reserve)
Modified from Hart et al., 2002
IRGS MODELIRGS MODEL
Modified from Lang et al., 2000
IRGS IRGS MODELMODEL
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
MAJOR IRGS DISTRICTS:MAJOR IRGS DISTRICTS:
Lang & Baker, 2001
Paleo-Tethys Closure Tintina Gold Belt
Eastern Australia
Bolivia
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
THE TOOLOOM EXAMPLE:THE TOOLOOM EXAMPLE:
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
THE TOOLOOM STORYTHE TOOLOOM STORY
• Hard rock sources barely touched
• Abandoned around 1870 Gympie
• Slipped into obscurity – few official records
• Minor alluvial gold mining continued until 2001
• Phoenix first recognised as a prospect in 2003
HISTORYHISTORY• Tooloom is a major goldfield, long forgotten
• First discovered in 1857 – 10,000 alluvial miners
• Coarse gold – many nuggets: largest 140 ozs
1 cm
Nuggets Nuggets from from
TooloomTooloom
DISCOVERY OF PHOENIX GOLD DEPOSIT IN 2005DISCOVERY OF PHOENIX GOLD DEPOSIT IN 2005
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
Simplified geological map of the Tooloom area
Intrusive centres
CullensCullensPhoenixPhoenix
Joes Joes GullyGully
FrasersFrasers
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
$1JOES GULLY INTRUSIVE JOES GULLY INTRUSIVE
CENTRECENTRE
• extensive alluvial deposits
• coarse Au intergrown with qtz
• sheeted qtz vein and stockworks outcropping upstream
• minor outcropping intrusives and dykes
• Frasers, Nine Mile, Back Creek
• extensive alluvial Au worked – Eight Mile
• Au-bearing qtz veins upstream
• visible Au in outcrop
• nearby intrusives hydrothermal system?
1 cm
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
20 c
Sheeted auriferous Sheeted auriferous quartz veinsquartz veins
FRASERS INTRUSIVE CENTREFRASERS INTRUSIVE CENTRE
GOLD
MALACHITE RESOURCES NLMALACHITE RESOURCES NLPHOENIX INTRUSIVE SYSTEMPHOENIX INTRUSIVE SYSTEM
• followup of multiple +20 ppb Au BLEG anomalies
• discovery of Phoenix Breccia
• 0.2 – 0.4 g/t Au from initial rock chips
• patchy Au in soils, low tenor
• coincident As-Sb-Bi-Cu soil anomaly, 1 km diameter
• large annular IP chargeability anomaly, > 400 m depth
• 2 km diameter aeromagnetic low
• Creek Zone → Au-Bi-As-Cu soil anomaly
• hornfelsed Emu Ck Fm sedimentary rocks contact aureole
• diss. and veinlet pyrrhotite-pyrite-arsenopyrite elevated Au
• 26 RC and diamond holes
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
AuAu AsAs
CuCu SbSb
PHOENIX SOIL PHOENIX SOIL GEOCHEMISTRYGEOCHEMISTRY
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
PHOENIX PROSPECTPHOENIX PROSPECT
Bi soil geochemistryBi soil geochemistry
• Bi in soil over breccia Bi in soil over breccia ==
gold at depthgold at depth
Breccia
The Creek Zone:The Creek Zone: larger but weaker Bi larger but weaker Bi anomaly (+Au-As-Sb)anomaly (+Au-As-Sb)
6837500 mN
44
40
00
mE
6835500 mN
44
20
00
mE
LEGEND
Au soil anomaly
outline of IP anomaly
road, track
river, creek
metres
0 400m
Enhanced heli-magimage, IP and gold
soil geochem atPhoenix Prosepct
GDA94/MGA Zone 56
drill hole with down hole trace
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
PHOENIX PROSPECTPHOENIX PROSPECT
Breccia pipe
Main gold in soil anomaly
IP anomaly
Shear zone (controlling position of Phoenix Breccia?)
70K Tonalite
Emu Creek Fm sedimentary rocks
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
PHOENIX PROSPECT:PHOENIX PROSPECT:
Phoenix Breccia:Phoenix Breccia:
• 85 m true width, +300 m outcrop length
• elongate, pipe-like geometry
• eg. 48 m @ 2.21 g/t Au
• polymictic, angular to subrounded clasts
• was up to 20% open-space
• qtz-carb-sulphide infill, at least two episodes
• jig-saw textured, limited vertical movement
• weak to locally intense Se alteration → Au grades
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
The Phoenix breccia The Phoenix breccia in outcropin outcrop
PHOENIX PROSPECTPHOENIX PROSPECT
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
PHOENIX PHOENIX PROSPECTPROSPECT
The Phoenix The Phoenix breccia in drill corebreccia in drill core
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
PHOENIX PROSPECTPHOENIX PROSPECT
Late stibnite veins
Sulphide infill of open-space in breccia
The Phoenix breccia in The Phoenix breccia in drill coredrill core
MALACHITE RESOURCES NLMALACHITE RESOURCES NLIRGS CHARACTERISTICS OF PHOENIX SYSTEM:IRGS CHARACTERISTICS OF PHOENIX SYSTEM:
• Au-Bi-Sb-As association
• reduced mineral assemblage → Po-As-Py, no Mag/Hem
• low sulphide content <5%
• possible vertical metal zoning: Sb-Py, slight Au with depth
• located in mineralised contact aureole of buried intrusive?
• I-type, mod. reduced, felsic-intermediate intrusives in project area
• continental tectonic setting, post-orogenic
• W-Sn-Mo province (NEFB)
• mid-way between proximal and distal
• potential for range of other deposits
PHOENIX is part of a large Intrusion-related Gold SystemPHOENIX is part of a large Intrusion-related Gold System
Modified from Lang et al., 2000
Phoenix
IRGS IRGS MODELMODEL
Present erosional level at Phoenix
MALACHITE RESOURCES NLMALACHITE RESOURCES NLIRGS in NEW IRGS in NEW ENGLAND FOLD BELTENGLAND FOLD BELT
• Au, W, Sb, Sn, Mo and base metal occurrences
• Associated with intrusives:
– post orogenic
– I-type
– reduced
– felsic to intermediate
– low magnetic
– mid-Permian to early Triassic
• Veins, stockworks, pipes, disseminations, greisens, skarns
Tooloom
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
IRGS in NEW ENGLAND FOLD BELTIRGS in NEW ENGLAND FOLD BELT
Favourable granite geochemistry:Favourable granite geochemistry:
• Clarence River Supersuite → Tooloom
• Moonbi Supersuite → Timbarra; Tooloom?
• Uralla Supersuite
• Nundle Supersuite
• Gundle Belt
• Coastal Belt
• Various unnamed leucogranite intrusives
Various deposits associated with intrusives:Various deposits associated with intrusives:
• Kingsgate Mo-Bi; Glen Eden Mo-W-Sn; Taronga Sn
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
IRGS in the NEW ENGLAND FOLD BELTIRGS in the NEW ENGLAND FOLD BELT
Eg. TimbarraTimbarra
– best studied IRGS in NEFB (Mustard, 2001 & 2004)
– disseminated Au in miarolitic carapace of monzogranite of
Moonbi Supersuite
– strong Au correlation with Bi, Ag, Te
– weak Au correlation with Sb, Mo, As
– proximal i.e. within mineralising pluton
– only 60 km south-southwest of Phoenix
– Moonbi Supersuite outcrops in vicinity of Tooloom
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
IRGS in the NEW ENGLAND FOLD BELTIRGS in the NEW ENGLAND FOLD BELT
Comparison of NEFB LFB
LFBLFB::
• Intensive exploration for porphyry Cu in 1960-70’s
• Arizona ‘light-bulb’ model
• unprospective for large Cu deposits
• later success with application of new model
Ordovician shoshonitic intrusives
Northparkes, Cadia
MALACHITE RESOURCES NLMALACHITE RESOURCES NL
IRGS in the NEW ENGLAND FOLD BELTIRGS in the NEW ENGLAND FOLD BELT
Comparison of NEFB LFB
NEFBNEFB::
• Very little exploration though application of wide-ranging
geological model
• Large Au deposits in Qld part Cracow, Mt Morgan, Gympie
• NSW part regarded as unprospective
• IRGS will rediscover the NEFB as prospective for large Au
deposits
PHOENIX could do for the NEFB what Northparkes did for the LFB!PHOENIX could do for the NEFB what Northparkes did for the LFB!
Malachite Resources NLMalachite Resources NL
INTRUSION-RELATED GOLD SYSTEMS IN INTRUSION-RELATED GOLD SYSTEMS IN THE NEW ENGLAND FOLD BELT:THE NEW ENGLAND FOLD BELT:
Brett McKayBrett McKay
The Tooloom ExampleThe Tooloom Example