"Using the cover to uncover the Curnamona". Dr Steve Hill, Director, Geological Survey of South Australia. Technical presentation at 2015 Broken Hill Resources Investment symposium.

1. Using
the
Cover
to
Uncover
the
Curnamona
Steve Hill
Director, Geological Survey of South Australia
May 2015
www.statedevelopment.sa.gov.au

2. The
Cover
Impediment…
•
The
greatest
impediment
for
future
discoveries
in
the
Curnamona
– Ignore
it
– Punch
or
look
through
it
– Use
it
to
help
guide
explora;on

3. The
prize….
• Broken
Hill
and
nearly
all
other
Curnamona
mineral
occurrences
were
found
because
they
stuck
out
of
the
ground
• Notable
excep;ons:
– Sedimentary
uranium
(Beverley,
Four
Mile…)
– Geophysical
targe;ng
under
the
Mundi
Mundi
Plain
• The
reason
we
haven’t
had
more
discoveries
is
that
they
are
under
cover

4. 4
White
dots
=
Major
mineralisa;on
discoveries
=
Bias
towards
areas
with
outcrop
/
shallow
basement
INSPIRATION:
new
exploraGon
search
space
beyond
shallow
cover

5. Australian
Discoveries
under
cover…

6. Geology
of
the
Cover
• We
need
our
geological
brains
working
in
the
cover
…
its
not
the
domain
that
geology
forgot

7. Geological
Processes
in
the
Cover:
• Weathering
/
erosion
/
sediment
and
element
accumula;on
• Element
mobility
–
source,
transport,
accumula;on,
preserva;on
• Supergene
enrichments
• Biogeochemical
processes
• Placer
concentra;on
and
recycling
• Geochemical
footprint
enlargement
• -­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐
• Dilu;on
• Barren
cover
(‘blind”
deposits)
• Erosion
/
poor
preserva;on
7
Weathering
Erosion
SedimentaGon
Preserva;on
Leaching
Denuda;on
Physical
Dispersion
Burial
Re-­‐accumula;on
(“False
anomaly”)
Dynamic
Equilibrium

8. Mapping
Through
and
within
Transported
Cover

9. How
does
cover
geology
work?
(e.g.
Tunkillia)

10. However….
• Perhaps
the
cover
in
itself
is
not
the
real
impediment
to
discovery?
• Could
it
be
that
our
knowledge
and
aNtude
to
the
geology
of
the
cover
that
is
our
biggest
hurdle?

11. Key
points
1. A
becer
geological
context
for
the
Curnamona’s
cover
2. Cover
penetra;on:
some
ways
to
see
through
it
3. Enlarged
mineral
system
footprints
in
the
cover

12. A
becer
geological
context
for
the
cover
• Geological type sections and their associated data have received diminished
attention, particularly since the GSSA work in basin areas in 1970s and 1980s
• These are important reference sections, particularly as exploration moves into
surrounding covered areas.
• Modern data for these sections can include:
• GPS coordinates
• Lithological logging
• Biostratigraphy
• HyLogger mineralogy
• Lithogeochemistry
• Detrital zircon dating
• et al……

13. Trinity
Well
type
sec;on,
Marree
1:250k
mapsheet
13

14. Trinity Well Reference Section
14

15. Deep
cover
atlas
of
SA
(DET
CRC)
…
15

16. 5
other
components
• Detailed
palaeodrainage
and
palaeosurface
reconstruc;on
and
history?
• Regional
regolith
geochemistry
– hydrogeochemistry
has
best
coverage
so
far
• Regional
depth
of
cover?
• Links
between
geophysics
and
cover?
• Cover
expressions
of
key
mineral
systems?

17. Cover
penetra;on:
some
ways
to
see
through
it
• Geophysics
• Mineralogy
• Geochemistry
• Biogeochemistry

18. White
Dam
Cu-­‐Au,
Curnamona
Province,
SA

19. Cu
Topsoil
Cu
BSB

20. Aier
R
E
Smith
&
B
Singh,
2007
Enlarged
mineral
system
footprints
in
the
cover

21. Enlarged
mineral
system
footprints
in
the
cover

22. Scale
of
the
distal
footprint
of
the
Broken
Hill
mineral
system
• Lateral
dispersion
for
>100
km
– High
grade
garnets
in
beach
sands
at
Menindee
Lakes
(>100
km
to
SE)
– Staurolite
and
other
high
grade
metamorphic
minerals
in
sediments
overlying
low-­‐grade
metamorphic
rocks
in
the
Fowlers
Gap
and
Bancannia
Basin
(>100
km
to
N)
– Lateral
dispersion
onto
Mundi
Mundi
Plains
(30-­‐50
km
to
W
and
NW)

23. Catchment
headwaters
within
Barrier
Ranges
Mundi
Mundi
Plains
Umberumberka
Reservoir
Umberumberka
Creek
-­‐
Broken
Hill
(Charloce
Mitchell,
DET
CRC)

24. Catchment
headwaters
within
Barrier
Ranges
Mundi
Mundi
Plains
Umberumberka
Reservoir
Umberumberka
Creek
-­‐
Broken
Hill
(Charloce
Mitchell,
DET
CRC)

25. Mundi
Mundi
Plain
• Lateral
dispersion
and
reaccumula;on

26. Tibooburra
Au
provenance...
Tors
of
Tibooburra
Granodiorite
(photo
S.Hill)

27. Au
hosted
in
basal
Mesozoic
sediments

28. Tibooburra:
Mesozoic
palaeoflow
model
in
rela;on
to
historic
Au
diggings
(Hill
et
al
2009)
Emergent
.The Granites
.
Easter Monday
.
Tunnel Hill
.Six Mile

29. Think
about
the
cover
• Ignore
it
at
your
peril
• We
known
a
licle
about
it
(probably
just
enough
to
be
dangerous)
• Huge
rewards
to
change
our
explora;on
success
in
the
region

30. Disclaimer
The
informaGon
contained
in
this
presentaGon
has
been
compiled
by
the
Department
of
State
Development
and
originates
from
a
variety
of
sources.
Although
all
reasonable
care
has
been
taken
in
the
preparaGon
and
compilaGon
of
the
informaGon,
it
has
been
provided
in
good
faith
for
general
informaGon
only
and
does
not
purport
to
be
professional
advice.
No
warranty,
express
or
implied,
is
given
as
to
the
completeness,
correctness,
accuracy,
reliability
or
currency
of
the
materials.
The
Department
of
State
Development
and
the
Crown
in
the
right
of
the
State
of
South
Australia
does
not
accept
responsibility
for
and
will
not
be
held
liable
to
any
recipient
of
the
informaGon
for
any
loss
or
damage
however
caused
(including
negligence)
which
may
be
directly
or
indirectly
suffered
as
a
consequence
of
use
of
these
materials.
The
Department
of
State
Development
reserves
the
right
to
update,
amend
or
supplement
the
informaGon
from
Gme
to
Gme
at
its
discreGon.
www.statedevelopment.sa.gov.au