Tania Dhu - NT Geological Survey

www.nt.gov.au

Geophysical programs to

support exploration under the

CORE initiativeTania Dhu, Manager Geophysics and Remote

Sensing

Northern Territory Geological Survey

15 September 2015DEPARTMENT OF PRIMARY INDUSTRY AND RESOURCES

www.nt.gov.au

• Maximise opportunities for the exploration, discovery and development of new mineral and petroleum resources

• Targeting the greater McArthur Basin, Arnhem Province, Arunta Region and Amadeus Basin

NTGS Regional Geoscience Programs

greater McArthur Basin

Arnhem Province

Amadeus Basin

Arunta Region

greater McArthur Basin Amadeus Basin

Arunta Region

Arnhem Province Palaeo-Mesoproterozoic Orogens

Archaean

Palaeo-Mesoproterozoic Basins

Mesozoic-Cenozoic

Neoproterozoic-Palaeozoic

www.nt.gov.au

• Understand the outcropping and undercover extent of the McArthur Basin and its stratigraphic correlatives in the BirrinduduBasin and Tomkinson Province

• Investigate basin architecture and evolution, copper ± base metal and hydrocarbon systems

• Programs include:

– Characterisation and correlation of stratigraphy

– Systematic hydrocarbon source rock analysis

– Acquisition of regional-scale geophysical data

– Construction of 3D geological models

Palaeo-Mesoproterozoic greater McArthur Basin

Carpentaria BasinBirrindudu Basin

McArthur Basin

Tomkinson Province


Arunta Region


Archaean


Mesozoic-Cenozoic


www.nt.gov.au

• Framework studies to understand stratigraphic, structural, metamorphic and magmatic evolution and potential correlations with the highly prospective Pine Creek Orogen


– 1:100k 1st edition geological maps and explanatory notes

Arnhem Province

Pine Creek OrogenMcArthur Basin

Arnhem Province

CarpentariaBasin


Arunta Region


Archaean


Mesozoic-Cenozoic


www.nt.gov.au

Jervois (Cu-Pb-Zn)

• Framework studies to understand stratigraphic, structural, metamorphic and magmatic evolution of the Arunta Region

• Investigate resource potential of the Palaeoproterozoic Aileron Province


– Characterisation of Cu ± polymetallicmineral systems

– 1:100k 1st edition maps and explanatory notes

Arunta Region

Clark (Cu)

Mount Hardy (Cu-Zn-Pb)

Rock Hill (Cu)

Home of Bullion (Cu-Zn-Pb-Ag-Au)

Strangways VHMS

Jericho (W-Cu-Ag-Pb-Zn)

Bonya (Cu)

Molyhil (W-Mo)


Arunta Region


Archaean


Mesozoic-Cenozoic


www.nt.gov.au

• Understand basin architecture, evolution and resource potential


– Neoproterozoic stratigraphic characterisation and correlation

– 1:100k and 1:250k geological maps and explanatory notes

– New regional scale gravity data

– CSIRO COBRA project (construct 3D model from potential field data; integrate geochemistry, sedimentology, isotopic analysis, ASTER to undertake resource assessment of the basin)

Amadeus Basin

Warumpi Province Arunta Region

Aileron Province

Eromanga Basin

Amadeus Basin

Musgrave Province

IrindinaProvince


Arunta Region


Archaean


Mesozoic-Cenozoic


www.nt.gov.au

• Range of geophysical and remote

sensing projects:

– Improving pre-competitive

geophysical and remote sensing

datasets

– Interpretation and modelling of

new and existing data

– Integration of data and

construction of 3D models

Geophysics and Remote Sensing

www.nt.gov.au

• Increasing ground gravity resolution to 4 km

spacing or better

• Regional spacing – suitable for interpreting

regional-scale geology and basin architecture

• Prior to 2013 approximately 45% of NT

mainland covered by modern 4 km ground

spaced gravity

Ground Gravity Pre 2013 NT wide Bouguer anomaly (historical 11 km spaced data shaded)

www.nt.gov.au

Bouguer anomaly images of new surveys (historical 11 km spaced data shaded, pre-existing modern data faded)

• Six ground gravity surveys completed and one

currently underway

• NTGS has acquired over 20,000 gravity

stations

• Another ~8500 infill stations acquired by

industry

• Approximately 80% of NT mainland now

covered

Ground Gravity

West Amadeus

North McArthur Basin

South McArthur Basin

South WisoBasin

Victoria Basin

North WisoBasin

Daly Basin

www.nt.gov.au

Bouguer Anomaly (Pre 2013)

Bouguer Anomaly (Post 2013)

Daly Waters ArchDaly Waters Arch

Mallapunyah FaultMallapunyah Fault

Improves definition of regional scale structures

Beetaloo Sub-basin

Beetaloo Sub-basin

BeetalooSub-basin

www.nt.gov.au

• Increasing airborne magnetic and radiometric resolution to 500 m line spacing or better

• Prior to 2013 over 90% of NT mainland covered at this resolution

Airborne Magnetics and Radiometrics

Pre 2013 NT wide TMI RTP (historical data shaded)

www.nt.gov.au

• Two airborne magnetic and radiometric

surveys completed (3 areas)

• Over 200,000 line km of 400 m spaced

magnetic and radiometric data acquired

• Approximately 98% of the NT mainland now

covered

Airborne Magnetics and Radiometrics

Dunmarra

Delamere and Spirit Hills

TMI RTP images of new surveys (historical data shaded, pre-existing modern data faded)

www.nt.gov.au

Total Magnetic Intensity Reduced to Pole

Ternary Radiometrics

Dunmarra

Spirit Hills

Delamere

Dunmarra

Spirit Hills

Delamere

www.nt.gov.au

• PGN Geoscience contracted to provide a regional geophysical interpretation of gravity and magnetic data (DIP015):

– Spatial distribution of main sedimentary packages

– Structural development of the basins

– Fault timing and kinematics

• Produced prior to the North McArthur, North Wiso, Victoria Basin and Daly Basin gravity surveys and Dunmarra, Delamere and Spirit Hills magnetic and radiometric surveys

Gravity and Magnetic Interpretation

Syn-Glydepackage fault systems

www.nt.gov.au

• Collaboration between NTGS and CSIRO focussed on basin

architecture, base metal mineral systems and fluid flow within the


• Studies draw on CSIRO expertise in deformation, fluid flow and

reactive transport modelling, geophysical modelling and inversion,

mineral systems and exploration through cover

• Includes 2 CSIRO post-doctoral researchers (Teagan Blaikie and

Marcus Kunzmann) embedded within NTGS for three years

CSIRO Collaboration


www.nt.gov.au

• Build on PGN Geoscience project

through:

– Structural interpretation

– 2.75D forward modelling

– 3D inversion

• Constrained by known geology,

structure and rock properties

Gravity and Magnetic Interpretation using new data

Low pass (15,000 m), 1st vertical derivative of reduced to pole total magnetic intensity (top). Tilt derivative of Bougueranomaly derived from new gravity surveys acquired under the CORE initiative, overlain on the first vertical derivative of low pass filtered (8000 m) historical Bouguer anomaly grid (bottom).

Area of Interest

Magnetic Image

Gravity Image

www.nt.gov.au

Modelling Kalkarindji flood basalts

• Shallow basalts dominate magnetic expression in the Dunmarra Magnetic and Radiometric Survey

• Modelling of holes in sheet provide estimates of depth of ~270 m and thickness ~265 m (Foss and Dhu, 2016)

• Modelling of similar anomalies ~200 km apart produced comparable results

www.nt.gov.au

• Can Airborne Electromagnetic (AEM) systems

map the Barney Creek Formation:

– In what areas?

– At what depths?

– What is the best survey/system design?

• Analysis and interpretation of industry submitted

AEM data in the Batten Fault Zone (Ley-Cooper

et al 2011)

Batten Fault Zone

Teena (Zn-Pb)

McArthur River (Zn-Pb-Ag)

Batten Fault Zone AEM

www.nt.gov.au

• Over 40,000 line km of data

acquired using 7 different AEM

systems

• Data has been assessed for

suitability for full inversion or

approximate transformation to

estimate conductivity at depth


Area of Interest

www.nt.gov.au

• Final products will include conductivity

depth pseudo-sections and merged

conductivity depth layers

Comparison of EMFlow Conductivity Transform and GA-LEI inversion (left); inverted conductivity derived from 14 different datasets (top)


www.nt.gov.au

3D Modelling in the greater McArthur Basin

• Integrating disparate data in a 3D environment:

– Surface geology

– Geological cross-sections

– Balanced cross-sections

– Seismic interpretation

– Potential field interpretation

– Drillhole data

• Understanding the structural architecture, evolution and depth to prospective stratigraphy of the greater McArthur Basin at different scales

Large model extent

Higher resolution model extent

www.nt.gov.au

• Hyperspectral scanning of

drill core using the

HyLoggerTM instrument

• Rock property

measurements taken at

semi-regular intervals on

drill core

Hyperspectral

www.nt.gov.au

• Over 350 drillholes scanned, more than 100 km of drill core

• Summary reports for over 50 drillholes provided as Hylogger Data Packages (HDP)

Using HyLogger Data

www.nt.gov.au

• The Geophysics and Drilling Collaborations program has been running since 2008 providing co-funding assistance for drilling and geophysical projects

• A range of semi-regional or innovative surveys have been undertaken across the Northern Territory including

– ~54,000 ground gravity stations

– ~30,000 line km of airborne electromagnetic data

– ~1150 line km of sub-audio magnetic data

– ~400 audio magnetotelluric stations

– ~24,000 line km of airborne magnetic and radiometric data

– ~22 line km of seismic surveying

Geophysics and Drilling Collaborations

www.nt.gov.au

MagneticsGravity Radiometrics

Territory-wide geophysical products

www.nt.gov.au

Magnetics

Reduced to Pole Total Magnetic Intensity

Total Magnetic Intensity First Vertical Derivative Total Magnetic Intensity

Total Magnetic Intensity Gradient Strings

www.nt.gov.au

• Geoscience Exploration and Mining Information System (GEMIS): http://geoscience.nt.gov.au/gemis– Digital Information Packages

• 3D Model (DIP012)

• Rock Properties (DIP013)

• PGN Geophysical Interpretation (DIP015)

• COBRA Project (DIP016)

– HyLogger Data Packages

– Geophysical Data – NT Wide Stitches, Individual Survey Data

– Industry submitted geophysical data (including GDC)

• STRIKE Tenure and Geoscience Information: http://strike.nt.gov.au– Spatial datasets

• Geophysical Image Web Server: http://geoscience.nt.gov.au/giws– Geophysical images

• Geophysical Archive Data Delivery System (GADDS): http://www.ga.gov.au/gadds– Geophysical data

Data Delivery

http://geoscience.nt.gov.au/gemis

http://strike.nt.gov.au/

http://geoscience.nt.gov.au/giws

http://www.ga.gov.au/gadds

www.nt.gov.au

Thank you

References• Foss and Dhu, 2016. The bark without a dog – Magnetic Anomalies over Holes in a Volcanic Sheet in the greater McArthur

Basin, NT: in ‘Proceedings of the 25th Geophysical Conference.’ ASEG-PESA-AIG, Australia, Adelaide.• Ley-Cooper AY, Munday T, Ibrahimi T and Cahill K. Analysis and reinterpretation of historical AEM data sets: McArthur

Basin, NT: in Annual Geoscience Exploration Seminar (AGES) Proceedings, Alice Springs, Northern Territory 15-16 March 2016. Northern Territory Geological Survey, Darwin, 21-26.

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Tania Dhu - NT Geological Survey