Crashes and flashes: Deep crustal geophysics for Resource Prospectivity

Crashes and flashes: Deep crustal geophysics for Resource Prospectivity

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  Crashes and flashes: Deepcrustal geophysics for Resource Prospectivity Ned Stolz
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  Tuesday 9 May2017 Parliament House, Sydney GSNSW Deep Crustal geophysics • Flashes – MT and AusLAMP • Crashes - Highlands Seismic • Soft Crashes – Passive Seismic and AusREM • Implications for NSW resource prospectivity
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  Tuesday 9 May2017 Parliament House, Sydney Flashes – How MT works 50 m 50 m Magnetic sensor North electrode East electrode Field Measurement Time series data recording over hours - weeks Data Logger 7 Days Quiet Days Magnetic Storm Magnetic Field Time Series
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  Tuesday 9 May2017 Parliament House, Sydney AusLAMP MT Instrument and Set-up Field vehicle and gear Deployed instrument Dipole electrode 3 component magnetometer Programing the data logger
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  Tuesday 9 May2017 Parliament House, Sydney Processing & Modelling – Its all about Bandwidth Magnetic Field Electric Field Instrument - Time Series hours Resistivity vs Period (=1/f) Resistivity vs Depth Processing Modelling 50km
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  Tuesday 9 May2017 Parliament House, Sydney AusLAMP Overview • Collaboration between Geoscience Australia and State Geological Surveys • Long period MT soundings across the continent • Half – degree (55km) station spacing • Four week deployments image deep crustal conductivity down to 100km depth • Tasmania, Victoria and southern South Australia complete • NSW acquisition funded (~300 sites) and acquisition commenced • Northern Australia funded under the Federal Government $100m Exploring for the Future Program
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  Tuesday 9 May2017 Parliament House, Sydney AusLAMP New South Wales 2016- 2017 • 77 Stations completed • Acquisition by Geoscience Australia staff and by contractors Southern NSW FarWest Southern Thomson Progress, priorities and bottle-necks Western Division 2017 – 18 Plan • Shortage of instruments • Shortage of skilled contractors • Geoscience Australia now focussed on Northern Australia March - November • Acquire Western Division with GAGSNSW staff June - October • Acquire Southern Thomson with contractors December - February • Start on Central NSW in 2018
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  Tuesday 9 May2017 Parliament House, Sydney AusLAMP – the big picture Complete coverage of Southeast Australia will enable large scale modelling of the deep crust Coverage May 2018
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  Tuesday 9 May2017 Parliament House, Sydney AusLAMP – Model results from Victoria 40km depth slice of 3D resistivity model derived from inversion of the AusLAMP Victoria data. Black lines depicts Geological Survey of Victoria major zone boundaries and structural framework. Ohmm
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  Tuesday 9 May2017 Parliament House, Sydney Crashes – Deep Crustal Relection Seismic • Sparse coverage in NSW – especially over prospective areas • No long traverses spanning major zones
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  Tuesday 9 May2017 Parliament House, Sydney Crashes – Deep Crustal Reflection Seismic • More complete east-west coverage in western Victoria • Still covers major structures important to NSW Highlands Seismic
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  Tuesday 9 May2017 Parliament House, Sydney Highlands Seismic Proposed Lines • Crosses major geological zones and regional scale faults • Geological Survey of Victoria, Geoscience Australia and GSNSW • Acquisition commencing March 2018
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  Tuesday 9 May2017 Parliament House, Sydney Highlands Seismic Proposed Lines • Crosses regional scale faults and both sides of major granite (Bega Batholith) • Test for Macquarie Arc beneath the Deddick Zone in Victoria • Crosses complex fault patterns
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  Tuesday 9 May2017 Parliament House, Sydney Soft Crashes – Passive seismic and AusREM • 3D model of seismic properties of the Australian Crust • Compilation by ANU of seismic results collected over many years • High quality dataset “for free” • NSW and Victoria have best coverage • AusLAMP and Highlands Seismic will integrate with these deep crustal data Deep crustal seismic lines and stations in Australia Figures from Salmon et al, 2013Image of Vp @ 5km Australia is the best country to do this stuff . . .
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  Tuesday 9 May2017 Parliament House, Sydney How do Deep Crustal Data help Resource Explorers? • NSW crustal studies by Bob Musgrave • Regional low magnetic zones map out felsic “continental” crust • Regional high magnetic zones map out mafic “oceanic” crust • Macquarie Arc mapped as sitting on continental like crust • Implications for porphyry deposition models – Mineralisation has a juvenile source inconsistent with continental crust – Implies rapid intrusion with no interaction with the crust Regional magnetic interpretations Slide by Bob Musgrave
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  Tuesday 9 May2017 Parliament House, Sydney Comparison with AusREM Seismic Velocity Model • Hay – Booligal Zone mapped as low velocity implying felsic continental style crust • Southwest margin of the Thomson Orogen mapped as low velocity • Some correlation with Bob’s interpretation of continental and oceanic style crust from the magnetics • Discrete zone of low velocity correlates with Lachlan Transverse Zone. Regional Magnetics compared with P-wave velocity at 25km depth 8 5 Vp Km/s Slide by Bob Musgrave
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  Tuesday 9 May2017 Parliament House, Sydney Lachlan Transverse Zone Vs at 25 km depth Copper mineralisation Operating mine • Linearment linking major mineralised zones in the Lachlan Orogen • Cuts across geological trends
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  Tuesday 9 May2017 Parliament House, Sydney Vs at 25 km depth TMI magnetic image Lachlan Transverse Zone - Where is it? Isostatic gravity image
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  Tuesday 9 May2017 Parliament House, Sydney Lachlan Transverse Zone – Look a little deeper • LTZ also sits on a major gradient in the Nd image • Suggests the LTZ is related to a deep crustal feature • What will the AusLAMP model tell us about these fundamental features of NSW geology? AusREM Vp @ 25km
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  Tuesday 9 May2017 Parliament House, Sydney GSNSW Deep Crustal Geophsyics • GSNSW collaborating on new deep crustal data acquisition • Deep crustal investigations and data validate geological models for orogen genesis – Test the hypothesis – Refine orogen geometries and boundaries – Advance mineralisation models and targeting ideas • Build fundamental geological knowledge and understanding of the crust • Provide a window into the deep crust – Understand the source of deep crustal fluids critical to deposition of giant ore deposits
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  Tuesday 9 May2017 Parliament House, Sydney Acknowledgements • Magnetic studies - Bob Musgrave • AusLAMP - Geoscience Australia • AusREM - The ANU Research School of Earth Sciences • Statewide images - Astrid Carlton and Lisa Nix