This document does not contain any text to summarize. A summary requires content in order to extract the key points and essential information in 3 sentences or less.
2015 Broken Hill Resources Investment Symposium - Geological Survey of New South Wales - Glen Phillips
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?
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.
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