"educing exploration risk along covered Curnamona margins: experiences from the Southern Thomson Orogen Collaborative Project." Rosemary Hegarty, Senior Geophysicist, Geological Survey of New South Wales. Technical presentation at 2015 Broken Hill Resources Investment symposium.

1. Reducing
explora0on
risk
along
covered
Curnamona
margins:
experiences
from
the
Southern
Thomson
Orogen
Collabora0ve
Project.
Rosemary Hegarty
Regional Mapping & Exploration Geoscience

2. • Overview
of
Southern
Thomson
NCF
Project
2013
–
2015
surveys
and
invesAgaAons
• HighlighAng
things
that
have
worked
well
so
far
• Future
project
plans
for
southern
Thomson
region
• Considering
parts
of
the
Curnamona
Province
where
similar
techniques
could
promote
exploraAon
effort
Acknowledgements
to
many
other
co-­‐workers
and
project
partners

3. Curnamona
,
Delamerian
and
southern
Thomson
share
the
challenge
to….
• understand
cover
sequences
• measure
accurate
dtb
surfaces
• recognise
prospecAvity
for
interpreted
(oPen
unknown)
rock
units
and
structures
• help
locate
tangible
targets
in
basement

4. Southern
Thomson
Project
–
overview
IdenAfied
as
prospecAve
covered
region
with
early
surveys:
o GSNSW
2005
gravity
and
deep
seismic,
o CRC
LEME
surface
geochemistry,
o GSNSW
2009
DTB,
regolith
mapping
&
basement
interpretaAon
o ExploraAon
acAvity
peaked
2012
v AddiAonal
surface
geochemistry
v New
geophysical
acquisiAon
v Mineral
systems
study
v Geochronology
v Structural
synthesis
v Solid
geology
map
compilaAon
Impact:
To
provide
the
mineral
explora:on
industry
with
pre-­‐compe::ve
data,
and
knowledge
that
reduces
risk
and
encourages
investment
in
the
region.
CollaboraAve
NCF
between
Geoscience
Australia,
GSNSW
and
GSQ
commenced
Dec
2013

5. I. Roach, Digging Deeper 2014
Airborne
electromagne0c
survey
New
AEM
data:
• Regional
survey
at
5
km
line
spacing
over
the
Eulo
Ridge
• Single
lines
along
the
MT-­‐gravity
traverses
Phase
1
(Contractor-­‐supplied)
data
released
18
August
2014
Phase
2
(GA
inversions)
data
released
December
2014
All
data
are
available
from
the
Geoscience
Australia
website:
www.ga.gov.au
1220
EULO
LOUTH
YOWAH
BYROCK
BOURKE
TINDAREY
GUMBALIE
ENNGONIA
COOLABAH
GONGOLGON
BARRINGUNHUNGERFORD
YANTABULLA
CUNNAMULLA
BREWARRINA
GIRILAMBONE
FORDS BRIDGE
THARGOMINDAH
146°E145°E144°E
28°S
29°S
30°S
31°S
! Towns-settlements
AEM-MT-gravity traverses
Regional AEM survey lines
MT-gravity traverses
State border
0 100 km
QLD
NSW
QLD
NT
WA
SA
NSW
VIC
TAS
GeoTech
Airborne
Ltd:
VTEM
plus®

6. I. Roach, Digging Deeper 2014
AEM
inversion
algorithms
New
AEM
inversion
algorithms
developed
at
GA:
• GA
Layered
Earth
Inversion
• GA
Monte
Carlo
inversion
Extend
understanding
of
the
contractor-­‐delivered
data
Clearer
inversions,
clearer
interpretaAons,
greater
risk
reducAon
in
regional
assessment
B. Line 1220 EM Flow® CDI section log stretch
C. Line 1220 GA-LEI SBS conductivity section log stretch
D. Line 1220 rj-McMC conductivity section linear stretch
E. Line 1220 Geological interpretation cross-section
1
10
100
0.1
1000
Conductivity mS/m
200
300
400
0
500
Conductivity mS/m
100
1
10
100
0.1
1000
Conductivity mS/m
A. Line 1220 total magnetic intensity first vertical derivative (TMI 1VD) map
235000 mE 240000 mE 245000 mE 250000 mE
235000 mE 240000 mE 245000 mE 250000 mE
-100
0
100
200
mASL
300
1220
6795000mN
-100
0
100
200
0
100
200
mASL
mASL
-100
0
100
200
mASL
Contact metamorphic rocks
granite 2granite 1
Cenozoic cut-and-fill
Contact
mmic
rocks
Mesozoic sedimentary rocks
Mesozoic sedimentary rocks and Cenozoic sand sheet
Faultor
intrusivecontact
Discrete conductor
TMI
1VD
map
EM
Flow®
GA-­‐LEI
SBS
Rj-­‐McMC
Interp

7. I. Roach, Digging Deeper 2014
Regional
AEM
survey
results
Regional
AEM
survey:
• Depth
of
cover
mapping
over
Eulo
Ridge
• IdenAfy
unmapped
resisAve
and
conducAve
basement
terrains
• Risk
reducAon
for
further
EM
and
drilling
QLD
NSW
Subcrop
basement
rises
Hungerford
Granite

8. Iden0fying
basement
highs
in
NSW
NSW
QLD
• Variability
means
5
km
line
spacing
is
too
wide
for
gridding
in
this
zone
• ResisAve
basement
highs
do
correlate
with
shallow
bore
intercepts
1VD
image
Yantabulla
example

9. I. Roach, Digging Deeper 2014
Magnetotelluric
(MT)
&
Gravity
surveys
AcquisiAon
now
complete
• Broadband
MT
(lithospheric
depth)
• Some
Audio
MT
(high-­‐resoluAon,
near-­‐surface)
• Gravity
along
traverses
@
333
m
spacing
~3600
new
gravity
staAons
Combined
AEM,
MT
&
gravity
data
will
be
used
to
model
Thomson-­‐Lachlan
boundary
and
lithospheric
architecture

10.
• New
U-­‐Pb
SHRIMP
mounts
from
industry
drill
core:
magmaAc
ages
• New
Ar-­‐Ar,
K-­‐Ar
ages
plus
XRD
on
mineral
separates
for
age
of
metamorphism
on
Culgoa
Lineament
• New
S
and
Pb
isotopic
data
on
mineralisaAon
• Ages
will
be
released
as
a
new
GA
Record
on
southern
Thomson-­‐northern
Lachlan
2015
Isotopic
da0ng
I. Roach, Digging Deeper 2014
New
data
on
magmaAc,
metamorphic
and
mineralisaAon
ages
build
on
recent
NGA
Geochron
in
NSW
and
QLD
NSW
Cunaburra
area
Culgoa
area
QLD
STO
KB
LO

11. Mineral
Systems
• New
S
and
Pb
isotope
analyses
from
Cunaburra
drill
core
to
bener
define
mineralisaAon
events
• Compare
Culgoa
and
Fifield
ultramafic
intrusions
for
PGEs
• Explore
links
between
W-­‐
Mo
and
Au-­‐basemetal
mineral
systems
in
Cobar
and
Lachlan
Orogen
and
southern
Thomson
Orogen
• Reassess
prospecAvity
of
southern
Thomson
Orogen
based
on
new
isotopic
data
and
structural
interpretaAons
Structural
Synthesis
• Mapping
structures
using
aeromagneAc,
gravity
and
seismic
data
• DaAng
fabrics
using
K-­‐Ar
&
Ar-­‐Ar
• PotenAal
field
modelling
of
Paka
Tank
Trough
• Developing
geodynamic
interpretaAons

12. Solid
Geology
NSW
&
Qld
• Merged
geophysical–geological
interpretaAon
across
border
• Development
of
unit
descripAons
and
naming
• Constrained
by
lack
of
lithologic
informaAon
and
few
age
dates
• Inclusion
of
prospecAve
rocks
in
NSW
(Late
Silurian
&
Early
Devonian)
• Provides
structural
framework
for
kinemaAc
studies
NSW
2010

13.
Immediate
benefits
from
the
first
year!
Geophysics
• AEM
acquired
and
released
for
explorers
and
researchers;
gravity
and
magnetotellurics
asap
• AEM
conducAvity
changes
resulAng
from
variaAons
within
groundwater
and
bedrock,
with
penetraAon
typically
to
about
250m
depth
below
ground
–
useful
to
locate
shallow
bedrock
areas
Geochronological
age
constraints
on
some
poorly
understood
metasedimentary
and
volcaniclasAc
rocks
from
basement
drillholes
(such
as
Paka
Tank
Tough
area)
which
is
helping
to
consolidate
geological
history
and
correlaAons
Isotopic
studies
for
mineral
systems
at
GA
have
uAlised
exisAng
and
company
drill
cores
to
relate
to
established
mineral
systems
in
the
region
Compiling
the
collaboraAve
cross-­‐border
basement
geology
and
analysis
of
seismic
secAons
is
developing
mapping
and
understanding
of
basement
rock
units
and
structures
for
the
first
Ame
Our
GSNSW
endeavours
in
the
southern
Thomson
region
within
NSW
have
been
greatly
boosted
by
partnering
with
the
scienAfic
capabiliAes
of
GA
and
the
interacAons
with
GA
and
Queensland
geoscienAsts
Now
to
get
it
all
out
there…

14. Project
Plans
looking
forward…
ARC
Linkage
2014
2015
2016
2017
NCF
WRAPPING
UP
NCF
1
&
PREPARING
NCF
2

15. 2009
FormaAon
of
the
E-­‐W
trending
segment
of
the
STO
by
“Benambran”
ENE-­‐WSW
compression
at
440-­‐430
Ma.
According
to
this
model,
Cambro-­‐Ordovician
turbidites
were
squeezed
against
the
Precambrian
salient
of
the
Curnamona
block,
and
extruded
south
(Burton,
2009).
2012
Paleozoic
oroclinal
deformaAon
(Cayley,
2012).
According
to
this
scenario,
the
enAre
Lachlan
Orogen
was
folded
into
a
Z-­‐shaped
orocline
that
more
than
doubled
its
width.
2013
An
E-­‐W
oriented
dextral
strike-­‐
slip
fault
system
at
the
southern
margin
of
a
westward
retreaAng
subducAon
margin
(Glen
et
al.,
2013).
This
geodynamic
sesng
was
dictated
by
the
geometry
of
a
Neoproterozoic
backarc
system.
New
Arc
Linkage
CollaboraAve
Research
Agreement
with
University
of
Newcastle:
“Understanding
STO
origin
and
evoluAon
is
thus
criAcal
to
understanding
Tasmanides
geodynamics”

16. Chief
InvesAgators
-­‐
University
of
Newcastle
Also
–
University
of
Queensland,
Queensland
University
of
Technology
Partner
InvesAgators
–
GSQ,
GSNSW
1. SystemaAc
age
determinaAon
of
key
lithostraAgraphic
units
across
the
STO,
both
sedimentary,
igneous
and
metamorphic;
2. Detrital
zircon
age
spectra
of
major
sedimentary
units
for
provenance
analysis;
3. KinemaAc
analysis
and
Ar-­‐Ar
age
determinaAon
of
major
fault
structures
and
syn-­‐kinemaAc
intrusions,
where
possible;
“TESTING
HYPOTHESIS“
APPROACH
Designed
to
increase
understanding
of
key
areas
based
on
mapping,
core
logging,
geochronology,
&
geochemistry.

17. NW
NSW
Basement
-­‐
Banling
the
same
monsters….
• Basement
platorm
• BHP
Minerals
held
brave
EL
in
1992
-­‐
1993
• First
basement
interpretaAon
by
B.
Stevens
• Several
local
invesAgaAons,
no
further
drilling
The
Tindara
Zone
–
northeastern
Curnamona
Province
–
where
Willyama
Group
and
Neoproterozoic
units
extend
north
under
cover
Geophysical
–
Geological
Basement
Interpreta0ons
to
extend
Curnamona
and
Delamerian
prospec0vity
Density
of
Drillholes
MILP
CL
BH

18. NW
NSW
Basement
-­‐
Banling
the
same
monsters….
Geophysical
–
Geological
Basement
Interpreta0ons
to
extend
Curnamona
and
Delamerian
prospec0vity
BH
In
parAcular
for
…
• Nth
Koonenberry
Belt
• Grasmere
Knee
Zone
• Kars
Loch
Lily
Belt

19. The maps greatly extend information on basement in areas where Mesozoic
and/or Cenozoic cover units are extensive, presenting the region as though
cover has been removed. The interpretation maps include several tectonic
provinces – the northern extension of the Curnamona Craton in the Tindara
Zone and the Bancannia Trough of the Darling Basin and the Koonenberry
Belt and Thomson Orogen. Care has been taken to ensure the true amount of
outcrop and the depth of cover is evident to map users.
Cobham
Lake
&
Milparinka
1:250
000
InterpretaAon
(Maps
&
GS2011/0790
InterpretaAon
Notes)
DTB
100
m
contours
Tindara
Zone

20. Neoproterozoic
straAgraphy
relies
on
Fowlers
Gap
mapping
(Torrowangee)
and
the
basal
Wilangee
Basalt

21. BHP Minerals drill-tested 10 magnetic target areas
TD9210 & TD 93001 Roof zone of pyritic quartz mica schist,
pegmatite, mica greisen, and magnetite-bearing hornfels overlying
(Delamerian) granite:
6m @ 2730 ppm Zn + 3m @ 180 ppm Cu + 4m @ 620 ppm Zn
(these values in the weathered schist and pegmatite)
TD 9204 intersected upward-facing proximal turbidites with single
cleavage at 20 – 30 degrees to bedding. Pyrrhotite (< 5%) on
shale cleavage planes and disseminated within sandstone and
quartzite units. Sulphides noted in 12 m wide shear zone.
Tindara
Zone
TD 9209 intersected tourmalinised graphitic quartz-muscovite
schist with blue quartz interbeds: correlated with Paragon
Group on basis of 2 cleavages developed, graphitic nature,
metamorphic grade, and presence of tourmaline.
Encountered
mainly
basalt,
dolerite
and
Adelaidean
sedimentary
units.

22. Old petroleum seismic, water bores and
magnetic modelling indicate that the Tindara
Zone bedrock platform under the Smithville
1:100 000 sheet deepens from
• about 170 m at southern boundary, out to
• about 400m at the north-eastern edges of
the Tindara Zone.
172
m
350
m
300
m
Depth
to
Basement

23. • Core
Tail
at
Ten
Mile
Bore
(Border
Downs)
basement
intersected
at
442m
–
457m
TD
• Metasiltstone
and
metamudstone
with
contorted
bedding.
Metal
sulphides
(pyrite,
galena)
in
fractures
and
in
zone
of
becciaAon
Cu
28
–
40
ppm,
Pb
50
–
5000ppm
GS2010/0173
Core
tails
report
by
Dick
&
Simpson
• The
depth
indicators
suggest
a
fairly
consistent
surface
and
the
highlighted
features
could
be
expected
to
lie
around
the
250
to
350
m
below
surface.
Core
tail
sample

24.
(Geoscience
Australia
Record
2012/40)
Depth
to
Basement
–
Tindara
Example
from
the
Frome
airborne
electromagneAc
survey,
SA
AEM
Go
Map
illustraAng
signal
penetraAon
over
a
region.
This
DOI
grid
can
reduce
the
risk
of
exploraAon
using
EM
surveys,
making
EM
surveying
a
more
anracAve
tool
for
mineral
exploraAon
Benagerie
Ridge

25. Loca:on
of
bedrock
and
bedrock-­‐derived
colluvium
in
the
vicinity
of
Teilta
homestead
in
the
southwest
of
COBHAM
LAKE,
showing
onlap
of
sand
dune
field
in
the
northwest
(SPOT
5
image).
Addi:onal
bedrock
exposures
shown
in
yellow
in
the
west
of
the
image
around
Teilta
and
Joulnie
homesteads
were
iden:fied
by
Steve
Hill
(2004)
during
regolith
mapping
by
CRC
LEME.
Depth
to
Basement
-­‐
Tindara

26. In
Summary…..
• First
stage
of
NCF
Southern
Thomson
Project
is
almost
completed
and
all
results
due
mid-­‐2015
and
Second
stage
of
NCF
Project
is
being
planned
to
undertake
straAgraphic
drilling
in
coming
years
• ARC
Linkage
Project
is
funded
and
will
focus
on
key
aspects
with
detailed
academic
studies
in
the
next
3
years
• Pursue
no-­‐impact
techniques
such
as
the
AEM
and
basement
studies
also
to
covered
Curnamona
Province
and
Delamerian
Orogen.