2015 broken hill resources investment symposium rosemary hegarty

Reducing explora0on risk along covered Curnamona margins: experiences from the Southern Thomson Orogen Collabora0ve Project.

Rosemary Hegarty Regional Mapping & Exploration Geoscience

•  Overview of Southern Thomson NCF Project 2013 – 2015 surveys and invesAgaAons

•  HighlighAng things that have worked well so far

•  Future project plans for southern Thomson region

•  Considering parts of the Curnamona Province where similar techniques could promote exploraAon effort

Acknowledgements to many other co-‐workers and project partners

Curnamona , Delamerian and southern Thomson share the challenge to…. •  understand cover sequences •  measure accurate dtb surfaces •  recognise prospecAvity for interpreted (oPen unknown) rock units and structures •  help locate tangible targets in basement

Southern Thomson Project – overview

IdenAfied as prospecAve covered region with early surveys: o  GSNSW 2005 gravity and deep seismic, o  CRC LEME surface geochemistry, o  GSNSW 2009 DTB, regolith mapping & basement interpretaAon o  ExploraAon acAvity peaked 2012

v  AddiAonal surface geochemistry v  New geophysical acquisiAon v  Mineral systems study v  Geochronology v  Structural synthesis v  Solid geology map compilaAon

Impact: To provide the mineral explora:on industry with pre-‐compe::ve data, and knowledge that reduces risk and encourages investment in the region.

CollaboraAve NCF between Geoscience Australia, GSNSW and GSQ commenced Dec 2013

I. Roach, Digging Deeper 2014

Airborne electromagne0c survey

New AEM data:

•  Regional survey at 5 km line spacing over the Eulo Ridge

•  Single lines along the MT-‐gravity traverses

Phase 1 (Contractor-‐supplied) data released 18 August 2014

Phase 2 (GA inversions) data released December 2014

All data are available from the Geoscience Australia website: www.ga.gov.au

1220

EULO

LOUTH

YOWAH

BYROCK

BOURKE

TINDAREY

GUMBALIE

ENNGONIA

COOLABAH

GONGOLGON

BARRINGUNHUNGERFORD

YANTABULLA

CUNNAMULLA

BREWARRINA

GIRILAMBONE

FORDS BRIDGE

THARGOMINDAH

146°E145°E144°E

28°S

29°S

30°S

31°S

! Towns-settlements

AEM-MT-gravity traverses

Regional AEM survey lines

MT-gravity traverses

State border

0 100 km

QLD

NSW

QLDNTWA SA

NSWVIC TAS

GeoTech Airborne Ltd: VTEM plus®


AEM inversion algorithms

New AEM inversion algorithms developed at GA:

•  GA Layered Earth Inversion •  GA Monte Carlo inversion

Extend understanding of the contractor-‐delivered data

Clearer inversions, clearer interpretaAons, greater risk reducAon in regional assessment

B. Line 1220 EM Flow® CDI section log stretch

C. Line 1220 GA-LEI SBS conductivity section log stretch

D. Line 1220 rj-McMC conductivity section linear stretch

E. Line 1220 Geological interpretation cross-section

1

10

100

0.1

1000Conductivity mS/m

200

300

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100

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A. Line 1220 total magnetic intensity first vertical derivative (TMI 1VD) map

235000 mE 240000 mE 245000 mE 250000 mE

235000 mE 240000 mE 245000 mE 250000 mE

-100

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mASL300

1220

6795

000

mN

-100

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mASL

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Contact metamorphic rocks

granite 2granite 1

Cenozoic cut-and-fill

Contactmmic

rocksMesozoic sedimentary rocks

Mesozoic sedimentary rocks and Cenozoic sand sheet

Faul

t or

intru

sive

con

tact

Discrete conductor

TMI 1VD map

EM Flow®

GA-‐LEI SBS

Rj-‐McMC

Interp


Regional AEM survey results

Regional AEM survey:

•  Depth of cover mapping over Eulo Ridge

•  IdenAfy unmapped resisAve and conducAve basement terrains

•  Risk reducAon for further EM and drilling

QLD

NSW

Subcrop basement rises

Hungerford Granite

Iden0fying basement highs in NSW

NSW

QLD

•  Variability means 5 km line spacing is too wide for gridding in this zone •  ResisAve basement highs do correlate with shallow bore intercepts

1VD image

Yantabulla example


Magnetotelluric (MT) & Gravity surveys

AcquisiAon now complete

•  Broadband MT (lithospheric depth)

•  Some Audio MT (high-‐resoluAon, near-‐surface)

•  Gravity along traverses @ 333 m spacing ~3600 new gravity staAons

Combined AEM, MT & gravity data will be used to model Thomson-‐Lachlan boundary and lithospheric architecture

•  New U-‐Pb SHRIMP mounts from industry drill core: magmaAc ages

•  New Ar-‐Ar, K-‐Ar ages plus XRD on mineral separates for age of metamorphism on Culgoa Lineament

•  New S and Pb isotopic data on mineralisaAon

•  Ages will be released as a new GA Record on southern Thomson-‐northern Lachlan 2015

Isotopic da0ng


New data on magmaAc, metamorphic and mineralisaAon ages build on recent NGA Geochron in NSW and QLD

NSW

Cunaburra area Culgoa area

QLD STO

KB

LO

Mineral Systems •  New S and Pb isotope analyses from Cunaburra

drill core to bener define mineralisaAon events

•  Compare Culgoa and Fifield ultramafic intrusions for PGEs

•  Explore links between W-‐Mo and Au-‐basemetal mineral systems in Cobar and Lachlan Orogen and southern Thomson Orogen

•  Reassess prospecAvity of southern Thomson Orogen based on new isotopic data and structural interpretaAons

Structural Synthesis •  Mapping structures using aeromagneAc,

gravity and seismic data

•  DaAng fabrics using K-‐Ar & Ar-‐Ar

•  PotenAal field modelling of Paka Tank Trough

•  Developing geodynamic interpretaAons

Solid Geology NSW & Qld

•  Merged geophysical–geological interpretaAon across border •  Development of unit descripAons and naming •  Constrained by lack of lithologic informaAon and few age dates •  Inclusion of prospecAve rocks in NSW (Late Silurian & Early Devonian) •  Provides structural framework for kinemaAc studies

NSW 2010

Immediate benefits from the first year!

Geophysics •  AEM acquired and released for explorers and researchers; gravity and magnetotellurics asap •  AEM conducAvity changes resulAng from variaAons within groundwater and bedrock, with penetraAon

typically to about 250m depth below ground – useful to locate shallow bedrock areas

Geochronological age constraints on some poorly understood metasedimentary and volcaniclasAc rocks from basement drillholes (such as Paka Tank Tough area) which is helping to consolidate geological history and correlaAons

Isotopic studies for mineral systems at GA have uAlised exisAng and company drill cores to relate to established mineral systems in the region

Compiling the collaboraAve cross-‐border basement geology and analysis of seismic secAons is developing mapping and understanding of basement rock units and structures for the first Ame

Our GSNSW endeavours in the southern Thomson region within NSW have been greatly boosted by partnering with the scienAfic capabiliAes of GA and the interacAons with GA and Queensland geoscienAsts

Now to get it all out there…

Project Plans looking forward…

ARC Linkage

2014 2015 2016 2017 NCF

WRAPPING UP NCF 1 & PREPARING NCF 2

2009 FormaAon of the E-‐W trending segment of the STO by “Benambran” ENE-‐WSW compression at 440-‐430 Ma. According to this model, Cambro-‐Ordovician turbidites were squeezed against the Precambrian salient of the Curnamona block, and extruded south (Burton, 2009).

2012 Paleozoic oroclinal deformaAon (Cayley, 2012). According to this scenario, the enAre Lachlan Orogen was folded into a Z-‐shaped orocline that more than doubled its width.

2013 An E-‐W oriented dextral strike-‐slip fault system at the southern margin of a westward retreaAng subducAon margin (Glen et al., 2013). This geodynamic sesng was dictated by the geometry of a Neoproterozoic backarc system.

New Arc Linkage CollaboraAve Research Agreement with University of Newcastle:

“Understanding STO origin and evoluAon is thus criAcal to understanding Tasmanides geodynamics”

Chief InvesAgators -‐ University of Newcastle Also – University of Queensland, Queensland University of Technology Partner InvesAgators – GSQ, GSNSW

1.  SystemaAc age determinaAon of key lithostraAgraphic units across the STO,

both sedimentary, igneous and metamorphic;

2.  Detrital zircon age spectra of major sedimentary units for provenance analysis;

3.  KinemaAc analysis and Ar-‐Ar age determinaAon of major fault structures and syn-‐kinemaAc intrusions, where possible;

“TESTING HYPOTHESIS“ APPROACH Designed to increase understanding of key areas based on mapping, core logging, geochronology, & geochemistry.

NW NSW Basement -‐ Banling the same monsters….

•  Basement platorm •  BHP Minerals held brave EL in 1992 -‐ 1993 •  First basement interpretaAon by B. Stevens •  Several local invesAgaAons, no further drilling

The Tindara Zone – northeastern Curnamona Province – where Willyama Group and Neoproterozoic units extend north under cover

Geophysical – Geological Basement Interpreta0ons to extend Curnamona and Delamerian prospec0vity

Density of Drillholes

MILP

CL

BH

NW NSW Basement -‐ Banling the same monsters….

Geophysical – Geological Basement Interpreta0ons to extend Curnamona and Delamerian prospec0vity

BH

In parAcular for … •  Nth Koonenberry Belt •  Grasmere Knee Zone •  Kars Loch Lily Belt

The maps greatly extend information on basement in areas where Mesozoic and/or Cenozoic cover units are extensive, presenting the region as though cover has been removed. The interpretation maps include several tectonic provinces – the northern extension of the Curnamona Craton in the Tindara Zone and the Bancannia Trough of the Darling Basin and the Koonenberry Belt and Thomson Orogen. Care has been taken to ensure the true amount of outcrop and the depth of cover is evident to map users.

Cobham Lake & Milparinka 1:250 000 InterpretaAon (Maps & GS2011/0790 InterpretaAon Notes)

DTB 100 m contours Tindara Zone

Neoproterozoic straAgraphy relies on Fowlers Gap mapping (Torrowangee) and the basal Wilangee Basalt

BHP Minerals drill-tested 10 magnetic target areas

TD9210 & TD 93001 Roof zone of pyritic quartz mica schist, pegmatite, mica greisen, and magnetite-bearing hornfels overlying (Delamerian) granite: 6m @ 2730 ppm Zn + 3m @ 180 ppm Cu + 4m @ 620 ppm Zn (these values in the weathered schist and pegmatite)

TD 9204 intersected upward-facing proximal turbidites with single cleavage at 20 – 30 degrees to bedding. Pyrrhotite (< 5%) on shale cleavage planes and disseminated within sandstone and quartzite units. Sulphides noted in 12 m wide shear zone.

Tindara Zone

TD 9209 intersected tourmalinised graphitic quartz-muscovite schist with blue quartz interbeds: correlated with Paragon Group on basis of 2 cleavages developed, graphitic nature, metamorphic grade, and presence of tourmaline.

Encountered mainly basalt, dolerite and Adelaidean sedimentary units.

Old petroleum seismic, water bores and magnetic modelling indicate that the Tindara Zone bedrock platform under the Smithville 1:100 000 sheet deepens from

•  about 170 m at southern boundary, out to

•  about 400m at the north-eastern edges of the Tindara Zone.

172 m 350 m

300 m

Depth to Basement

•  Core Tail at Ten Mile Bore (Border Downs) basement intersected at 442m – 457m TD

•  Metasiltstone and metamudstone with contorted bedding. Metal sulphides (pyrite, galena) in fractures and in zone of becciaAon Cu 28 – 40 ppm, Pb 50 – 5000ppm

GS2010/0173 Core tails report by Dick & Simpson

•  The depth indicators suggest a fairly consistent surface and the highlighted features could be expected to lie around the 250 to 350 m below surface.

Core tail sample

(Geoscience Australia Record 2012/40)

Depth to Basement – Tindara Example from the Frome airborne electromagneAc survey, SA

AEM Go Map illustraAng signal penetraAon over a region. This DOI grid can reduce the risk of exploraAon using EM surveys, making EM surveying a more anracAve tool for mineral exploraAon

Benagerie Ridge

Loca:on of bedrock and bedrock-‐derived colluvium in the vicinity of Teilta homestead in the southwest of COBHAM LAKE, showing onlap of sand dune field in the northwest (SPOT 5 image).

Addi:onal bedrock exposures shown in yellow in the west of the image around Teilta and Joulnie homesteads were iden:fied by Steve Hill (2004) during regolith mapping by CRC LEME.

Depth to Basement -‐ Tindara

In Summary…..

•  First stage of NCF Southern Thomson Project is almost completed and all results due mid-‐2015 and Second stage of NCF Project is being planned to undertake straAgraphic drilling in coming years

•  ARC Linkage Project is funded and will focus on key aspects with detailed academic studies in the next 3 years

•  Pursue no-‐impact techniques such as the AEM and basement studies also to covered Curnamona Province and Delamerian Orogen.

Education

2015 broken hill resources investment symposium rosemary hegarty