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Confidentiality-I#-A#
Dr Kate Robertson
Senior Geophysicist – Lithospheric Architecture
Geological Survey of South Australia
Department of the Premier and Cabinet, South Australia
Geometry and origin of the Curnamona
Conductivity Anomaly from AusLAMP
magnetotelluric data
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A# Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
• In SA as a collaborative
project between GSSA,
GA and UoA
• Victoria complete
• Tasmania complete
• SA almost complete
• NSW underway
In SA funding from GSSA,
NCRIS/ANSIR, GA
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
• 73 sites
• Average spacing around 55 km
• NeoProterozoic Ikara-Flinders Ranges
• Paleo-Mesoproterozoic Curnamona Province
• Intraplate deformation
• High heat flow and elevated seismicity
SURVEY AREA
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
MAGNETOTELLURICS (MT)
• Passive electromagnetic method
• Measurement of naturally
occurring magnetic and electric
fields at the earths surface
• We use long period MT here
(deep sounding)
• Obtain information on the
electrical resistivity structure of
the subsurface (down to 100’s of
km’s)
Fluxgate Magnetometer
(Hx, Hy, Hz)
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
PHASE TENSOR ELLIPSESInterpreting ellipses:
Colour
Red: increasing conductivity with depth
Blue: decreasing conductivity with depth
Shape
Circle= 1D resistivity, ellipse = 2- or 3D resistivity structure
Orientation
Orientation along direction of preferred current flow
Crust Upper mantleLower
lithosphere
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
Yellow circles- locations of diamondiferous
kimberlites
Black dots- earthquakes
Blue triangles- MT site locations
Black lines- tectonic zone boundaries
Blue regions are resistive, red are conductive
• No obvious correlations of earthquakes with
conductors
• Conductive sediments at 1 km of Murray and
Cooper Basins
• Conductive anomalies apparent at 10 km
and greater.
3D INVERSION RESULTS
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CURNAMONA EAST-WEST 03GA-CU1
0
0.5
3
1
1.5
2
2.5
Yarramba
Warrakimbo
Lo
g r
esis
tivity (
oh
m.m
)
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08GA-C1 DEEP
REFLECTION
SEISMIC
SURVEY
NORTHSOUTH
0
0.5
3
1
1.5
2
2.5
YarrambaWarrakimbo??
Log r
esis
tivity (
ohm
.m)
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
CRUSTAL FLUIDS
NORTH SOUTH
o Stable, old region only minor reworking at
edges from Delamerian Orogeny
o Seismic tomography models show cratonic
signatures
o From geochemistry, lithospheric thinning in
Broken Hill Domain resulted in primitive,
depleted melts in partial melt
o Less thinning in Olary Domain, refertilised
from Olarian subduction?
o Saline sediments and fluids/fossil fluids
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
CURNAMONA INFILL TRANSECT
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
ACKNOWLEDGEMENTS
• Field personnel
• Landholders and Traditional Owners for
land access
• Goran Boren for technical assistance
• GSSA for funding
• Geoscience Australia for logistical
assistance
• Gary Egbert, Anna Kelbert and Naser
Meqbel for ModEM, and Naser Meqbel for
3D grid
Presentation for UNCOVER, Curnamona 26 July 2017
Confidentiality-I#-A#
DisclaimerThe information contained in this presentation has been compiled by the Department of State
Development (DSD) and originates from a variety of sources. Although all reasonable care has
been taken in the preparation and compilation of the information, it has been provided in good faith
for general information 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.
DSD 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 information for any loss or damage however caused
(including negligence) which may be directly or indirectly suffered as a consequence of use of these
materials. DSD reserves the right to update, amend or supplement the information from time to
time at its discretion.
www.minerals.statedevelopment.sa.gov.au
Confidentiality-I#-A#
Contact
www.minerals.statedevelopment.sa.gov.au
Department of State Development - Mineral Resources Division
Geological Survey of South Australia
Dr Kate Robertson: [email protected]
Level 4, 101 Grenfell Street
Adelaide, South Australia 5000
GPO Box 320
Adelaide, South Australia 5001
T: +61 8 8463 3000
