The Bathurst Metallogenic map

Geological Survey Technical Talks
1st June 2016, Orange
The Bathurst Metallogenic
map and transition to a new
generation mineral potential
mapping in NSW
Peter Downes
Joel Fitzherbert
Phillip Blevin

End of an era….
 Warwick-Tweed Heads:
last of the 250k 1st edition
series (published 2014).
 25 maps, >15,000
occurrences, 40 years.
 Extensive explanatory
notes and datasheets.
 Focus on “Where”
 Focus on surface geology

Metallogenic map of NSW
(1:1,500,000 scale)
 Used NSW mineral system
schema,
 Used AUD prices Jan 2009,
 Deposits grouped into 126
districts,
 Only districts with metal
endowment > $10 M shown,
 Based on ~3500 deposits with
size,
 Only 425 individual deposits
shown (as part of districts),
 Best selling map for GSNSW!

Bathurst 1:250,000 scale
metallogenic map (2nd edition)
schema,
 Updated time-space plot
with mineralising events,
 Updated Macquarie Arc &
granite geology,
 311 deposits / mines shown,
 Over 1900 sites considered,
 Only sites with production ±
resources included,
 Back of map
 mining history,
 geological history,

building the Bathurst metallogenic map
Starting point — East
Lachlan GIS (Glen et al
2007)
Stage 1 — update
Ordovician
geology & include “Phases”
from Glen & co-workers
Stage 2— review, group &
simply granite supersuites
Stage 3 — add post
Carboniferous cover
sequences and make semi-
transparent
Stage 4 — add classified
mineral deposits including
mineralised placers

Metallogenic mapping, commodity and
mineral potential studies
 Metallogenic maps >> need to understand mineral system drivers
 Timing of mineralisation
 Source of metals/fluids
 Temperature of fluid and fluid sources
 Traps >> redox, temperature etc
 Mineral system models (process based)
 Commodity studies >> better understand metal endowment vs deposit
models and metal/fluid sources
 Mineral potential studies >> define realistic mineral potential tracts that
are geologically defensible
 Develop a series of mineral system models from state to regional scale.
Where When Why Where else?
(Mineral systems model: Wyborn et al. 1994)

500k scale Metallogenic Syntheses
 Broken Hill 250k – done
 Cobar – underway
 New England – preliminaries
 Macquarie Volcanic Province
 S.E. LFB
 ERIV to follow on from mapping
Intrusion related &
Orogenic Au–Sb
Cobar “style’’ Porphyry Cu-Au
Broken Hill
VAMS
Orogenic Au

Broken Hill Metallogenic Map
 New synthesis including all
elements of Broken Hill geology
(Willyama, Adelaidean & regolith),
 First complete time-space plot for
BH including mineralising events,
schema,
 239 deposits & mines shown
although ~3500 sites reviewed,
 Inserts showing metamorphic
isograds for both Olarian and
Delamerian events,
 Two supporting Quarterly Notes
with back of map aimed at general
public.

Yanco Glen (W)
Waukeroo (Sn)
Euriowie (Sn)
Kantappa (Sn)
Stratigraphic control has been inferred
Lower sill complex (W) Hores Gneiss
Upper pegmatite field (Sn) Paragon Group
Lower layered sill complex (W)
Amphbolite facies
Upper pegmatite field (Sn)
Greenschist facies
Pegmatite/quartz
vein hosted
Olarian Orogeny (1600-1580 Ma)
Example: Sn-W-bearing pegmatites

Syn to post D1
Lower sill complex in
amphibolite facies
Upper pegmatite field
(upper greenschist facies)
Metamorphic field gradient is essentially stratabound
Intrusive phases are essentially stratabound
Yanco Glen (W)
Waukeroo (Sn)
Euriowie (Sn)
Kantappa (Sn)
BUT… Stevens 2006

Sawyer (1998)
Fitzherbert (1998)
Lower sill complex = pooling
small volume melt batches at
or below solidus.
Level of the Hores Gneiss and
sill-Kspar-partial melt isograd
Small fractionated melt
batches, enriched in fluxing
elements (F, Li, B)
Amblygonite (Li, F)
Flouroapatite (F)
Lepidolite (Li)
Tourmaline (B)
Depressed solidus promotes
intrusion at considerably
higher levels in the Paragon
Group
Li

Cobar Metallogenic Project
http://cdn.business2community.com/wp-
content/uploads/2014/05/newsboy._anchorage_al
aska._1918-1920.jpg

New Cobar 500K basement interpretation
• New Basement interpretation
– Incorporates new GSNSW mapping from Sussex-
Byrock, Coolabah, Cargelligo, Nymagee
• Focus on:
– basement subdivisions/faults
– middle Silurian stitching plutons and
– controls on Cobar Basin opening & inversion.
• Combine with metamorphic facies/isograd and
lithostratigraphic maps to help refine prospective
areas through the basin.
Peperitic rhyolite margin
with sphalerite-rich
replacement on its
margins. Mallee Bull

New petrographic and hyperspectral work
conducted on selected prospects and deposits,
(e.g. Nymagee, Hera, Lowan, Mount Allen,
Browns Reef, Mallee Bull, May Day, Manuka,
Yellow Mountain, Mineral Hill, Great Central,
Mount Solar). Reassessment of all historic
GSNSW thin sections from many of the other
deposits.
actinolite/biotite. Nymagee stilpnomelane. Nymagee
Cobar – metamorphic map

Reassessed GSNSW thin sections from past
projects for Mount Hope Group, Rast Group,
Kopyje Group, Amphitheatre Group, Nurri
Group, Mouramba Group, Ootha Group.
Plagioclase-phyric dacitic lava -
Babinda Volcanics (Ettamogah Tuff
Member).
Rhyolite with flow foliation -
Florida Volcanics
Compelling evidence that the rhyolites were
erupted first with a change to dacitic composition
occurring at a higher stratigraphic level.

Over 11 000 petrographic observations
available plus some 15,000 field
observations
Can query these to make maps of primary
and secondary mineral assemblages,
metamorphic textures (e.g. granoblastic,
hornfels)
Collate all historical temperature control
(CAI, mica crystallinity, mica chemistry,
fluid inclusion), field observations and
past metamorphic mapping for the area.

cordierite
distribution of secondary minerals
(from petrographic database)
distribution of textural information
(from field observations database)
Query data to extract
index minerals &
observations to create
maps of:
 primary mineral
assemblages
 secondary mineral
assemblages
 metamorphic textures
biotite
chlorite

• Cobar Basin — mostly diagenetic to anchizonal, very
low grade metamorphic conditions during burial and
basin inversion, with the exception of Glen’s Zone 1 — a
high strain zone through Cobar
• Disconnect between the highest grades of overprinting
metamorphism and deformation.
• Highest grade alteration systems (pre-fabric, high-T
potassic, calc-potassic to calcsilicate alteration) are best
preserved in lesser deformed sequences.
• Strong thermal contrast between the host rocks and
metasomatic mineral associations.
• i.e. rocks 10’s to 100’s of meters away have sub
greenschist facies (~200oC) basinal rocks.
• Suggestive hot, proximal heat source to
mineralised zones/structures.
• Thermal highs spatially associated with Devonian
intrusions.

The basin rocks…
Detrital biotite and muscovite are
very well preserved and the effects
of deformation are weak. All noted
by Pogson (Nymagee 100K)
Some sandstones preserve diagenetic
textures and primary porosity

Approaching mineralisation…
(but only tens of metres away)
Biotite flooding of sandstone/siltstones and
crosscutting biotite veins (note they are
subsequently deformed).
Early biotite porphyroblasts
enveloped by chloritic foliation
Hera

Mineralisation…
Calcsilcate alteration (garnet–tremolite
(retrogressed to chlorite–plagioclase)
intimately associated with mineralisation.
Also identified from Nymagee using Hylogger.
Garnet-rich veins from Hera, along
with abundant garnet with sulfide.
(courtesy of Adam McKinnon, Aurelia)

The high temperature connection
In the pipeline:
 Hylogging for CSA, Peak,
Endeavor, followed by new
petrographic work.
 Sm-Nd dating of garnet from
high-T alteration systems at
Nymagee and Hera.
 dO-dD of tremolite in high-T
alteration zones from
Nymagee and Hera.
 Possible garnet fluid inclusion
work for Nymagee and Hera.Stegman, 2000,
Cobar conf. vol.
cpy-po–stipnomelane vein crosscutting
early mag–chl alt – Great Cobar

● Canbelego-Mineral Hill Belt
● Kopyje Shelf
● Cobar Basin
● Mount Hope Trough
● Winduck Shelf
Pb-isotopes: mineralisation related data
Notes — data sources
• 2012/14 = this study
• pmdcrc
• CSIRO (selected only)
2012/14 and pmdcrc studies have higher
precision than older analyses
Background: LFB major metallogenic events
from Carr et al (1995)
Ordovician (basement)-dominant
signature: Mallee Bull, Mineral Hill,
Blind Calf, Bobadah
mid-late Silurian-dominant
signature: Hera, Nymagee,
Wagga Tank, Shuttleton, part
Manuka
Early Devonian
signature
Sandy Creek, part
Manuka, Wagga Tank

S-isotopes: mineralisation related data
W E
Pb & S
Pb & S
Pb & S
Basinal Fluids
Basement Fluids
Fluid mixing
zones
siliciclastics
greywackes &
mafics
Cobar
Basin
Girilambone
Basement
Hera Nymagee
ShuttletonMallee Bull Sandy Creek
d34S >8
d34S <~8
Pb Zn Ag
Cu Au
Pb Zn Ag Cu Au

Aims
 Build a virtual core library of the mines at Cobar (CSA, Endeavor, Peak)
 Document regional metamorphism & changes to host rock mineralogy
distal to mineralised zones;
 Document alteration associated with mineralising event(s);
 Support other big picture projects e.g. deep seismic;
Cobar HyLogger project FY15/16
NCRIS funding for “scanning”
of 9,000m of core from Cobar

Cobar Metallogenic map progress

Charlotte Barry and Michael Nelson
Neodymium Map of NSW

Questions
Thank you
and no
I have not been
photo-shopped
Cupiferous shingleback
Nymagee copper mine

The Bathurst Metallogenic map

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