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1. The Delamerian orogenic
cycle:
inferences from the provenance
record of the Koonenberry Belt
Glen Phillips1,2 & Emma Johnson2,3
1 Regional Mapping & Exploration Geosciences, Geological Survey NSW
2 Discipline of Earth Sciences, The University of Newcastle
3 Research School Earth Sciences, The Australian National University

2. The
Delamerian
Orogenic
cycle
is
the
oldest
of
the
Tasmanides.
It
defines
the
onset
of
over
500
million
years
of
subduc:on-­‐related
tectonism
along
the
eastern
margin
of
Australia.
It
was
responsible
for
the
genera:on
of
major
known
ore
deposits
(Cadia,
Western
Victoria).
The
Tasmanides
&
the
Delamerian

3.
Given
that
our
explora:on
tenement
is
the
whole
state
of
NSW;
we
need
mineralisa:on
models
at
that
scale.
In
part,
regional-­‐scale
models
such
as
these
are
underpinned
by
geodynamic
reconstruc:ons.
The
Tasmanides
&
the
Delamerian

4. A.
To
some
degree.
But
a
major
gap
in
our
understanding
is
the
:me
and
the
mechansism(s)
responsible
for
the
onset
of
the
Delamerian
orogen.
Antarc7ca
Passive
margin
in
eastern
Australia
Q.
Do
we
understand
the
Delamerian?

5. Koonenberry
perspec7ve
Glen
(2013)
AJES
Greenfield
et
al.
(2011)
GR
520-­‐500
Ma

7. Arrowsmith
Volcanics
Unconformity:
passive
to
ac:ve
margin
sediments
Mount
Wright
Volcanics
Turbidites
–
Teltawongee
Gp.
No
detrital
mica
(Kara
Fm.)
Lots
of
detrital
mica
(Teltawongee
Gp.)

8. Samples
Samples
are
from
the
Kara
Forma7on
Detritus
shedding
into
passive
margin
basins.
(or
incipient
ac:ve
margin?)
Samples
are
from
the
Teltawongee
and
Ponto
Groups
Detritus
shedding
into
the
ac:ve
margin
basins.
Should
be
arc
related?
Samples
are
from
the
Kayrunnera
and
Mutawintji
Gp.
Detritus
shedding
into
foreland
basins.

9. Johnson
et
al.
(in
review)

10. Detrital
Zircon
–
Igneous
and
Metamorphic
records
Huh?
Passive
margin
(Kara
Forma7on)
Detritus
sourced
from
con:nental
interior
Ac7ve
margin
(Teltawongee
&
Ponto
Gp.)
Detritus
sourced
from
the
margin
Foreland
Basin
(Kayrunnera
&
Mutawintji
Gp.)
Detritus
sourced
from
the
orogen
n=198
n=397
n=299
n=198

11. Detrital
Ru7le
–
Metamorphic
Record
Passive
margin
(Kara
Forma7on)
Detritus
sourced
from
con:nental
interior
Ac7ve
margin
(Teltawongee
&
Ponto
Gp.)
Detritus
sourced
from
the
margin
Foreland
Basin
(Kayrunnera
&
Mutawintji
Gp.)
Detritus
sourced
from
the
orogen
Huh?

12. Backarc
basin
Koonenberry
Belt
Forearc
Cawood
et
al.
(2012)
Sediment
provenance
and
geodynamics

13. Implica7ons
1
Geodynamic
SeWng
1. The
provenance
of
sediments
deposited
in
the
ac:ve
margin
basins
during
the
Cambrian
(i.e.,
Teltawongee
and
Ponto
groups)
is
not
consistent
with
the
postulated
forearc
seYng.
2. The
provenance
of
these
rocks
is
more
consistent
with
deposi:on
in
a
back-­‐arc
seYng.
Re-­‐assess
the
reconstruc7on
SubducFon
zone
further
to
the
east.
What
are
the
Mount
Wright
Volcanics?

14. Implica7ons
2
Source
of
the
550-­‐600
Ma
detrital
zircons
Two
possibili:es
:
1. A
local
source.

15. Inconsistencies
with
the
local
source
hypothesis
1. No
significant
igneous
/
metamorphic
complex
of
this
age
in
eastern
Australia.
2. Sediment
and
geochemical
record
is
consistent
with
a
passive
margin
seYng
along
eastern
Australia
between
600-­‐550
Ma
–
not
a
renowned
seIng
for
zircon
producFon

16. Two
possibili:es
:
2. A
distant
source
from
the
interior
of
Gondwana
Implica7ons
2
Source
of
the
550-­‐600
Ma
detrital
zircons
Two
possibili:es

17. If
the
sediments
are
derived
from
a
local,
now
concealed
source:
1. U-­‐Pb
in
zircon
defines
the
longevity
of
the
tectonothermal
event
-­‐
posing
the
ques7on:
is
the
Delamerian
orogen
older
than
520
Ma?
2. Hf
in
zircon
informs
us
on
the
crustal
evolu:on
of
the
Neoproterozoic
source
–
what
were
the
magma:c
and
geodynamic
condi:ons
prior
to
the
Delamerian?

18. 700-­‐620
Ma
No
change
through
:me
and
minimal
zircon
produced.
620-­‐580
Ma
Rapid
departure
toward
–ve
values;
mel:ng
evolved
crust.
570-­‐540
Ma
Returning
towards
+ve
values;
increased
juvenile
input.
Zircon
produc7on
through
7me

19. 520-­‐490
Ma
Delamerian
Orogen
Strong
juvenile
input
–
development
of
an
external
orogen.
Zircon
produc7on
through
7me

20. What
could
this
mean
(assuming
a
proximal
source
for
detritus)
1. Crustal
mel:ng
in
a
ria
environment
2. Introduc:on
of
more
isotopically
depleted
rocks
during
riaing
3. Magma:c
break
–
crustal
thickening?
4. Development
of
an
external
orogen
1
2
3
4

21. Intracratonic
extension
Ac:ve
margin
Subduc:on
ini:a:on

22. A
closing
remark