Overview

East Riverina Project Location
East Riverina Project Location (red box). Background image comprises the first vertical derivative of total magnetic intensity underlain by Bouguer gravity

The East Riverina Mapping Project is providing up-to-date data to aid mineral exploration and to enable informed regional land-use planning decisions. The area is prospective for a range of deposit styles, including intrusion-related tin–tungsten (e.g. Ardlethan), gold and porphyry-style copper–gold systems, as well as orogenic gold. The region also has increasing land use pressures, particularly from new residential zones around Wagga Wagga and along the Hume Highway corridor.

The project commenced in 2014, with field work completed in 2018. It will replace the existing Wagga Wagga and Narrandera 1:250 000 geological maps which were released in the late 1960s, before the development of modern mapping techniques that allow interpretation below deep alluvial cover and the advent of precise whole rock and mineral dating technologies.

The project area is in the central Lachlan Orogen and includes the Wagga part of the Wagga–Omeo metamorphic belt. Major geological units comprise Ordovician metasedimentary rocks of the Adaminaby and Bendoc groups, Silurian S-type granites of the Koetong and Tom Groggin suites, Silurian volcanic rocks (e.g. Gidginbung and Temora volcanics), Siluro-Devonian sedimentary rocks such as the Ootha Group, Early Devonian Gurragong and Walleroobie volcanics, Devonian I-type granites (e.g. Holbrook) and Devonian quartz-rich sandstones of the Cocoparra Group. Major structures include the Gilmore and Kancoona fault zones.

Systematic field mapping has been integrated with specialist studies such as mineral systems, geochronology (with Geoscience Australia), palaeontology, spectral analysis, geophysical modelling, reinterpretation of seismic lines, 3D modelling of geology and fluid flow, and hydrogeochemistry (with CSIRO).

Products include 1:100 000 (or better) geological mapping that will be incorporated into the NSW Seamless Geology geodatabase, observations, measurements and analytical data that will be available in MinView, annual technical reports, and specialist reports on aspects of the geology and mineral systems.

Work completed

Field mapping

Field Observations
Field Observations (green circles) to date in the project area over the Lachlan Orogen province layer from the NSW Seamless Geology geodatabase

Systematic field mapping began in 2014. All observations and measurements were captured in FieldObs and are available online through the Geoscientific Data Warehouse using the ERIV project prefix: https://minview.geoscience.nsw.gov.au/

Reports outlining results and preliminary findings from field work are in DIGS:

Reports on volcanic facies in the Gurragong Volcanics (GS2015/1290), and Walleroobie Volcanics (GS2016/0968) by Dr Kate Bull are available in DIGS. A report on volcanic rocks in the Walbundrie area is available (GS2017/0149).

Two palaeontology reports identifying graptolites, conodonts and other fossils from the project area are available in DIGS as GS2016/1119 (by Dr Ian Percival) and GS2018/1001 (by Dr Yong Yi Zhen and Zoe Wyllie).

Three project talks were presented at the granites2017@benalla symposium on 25–28 September 2017. Abstracts are on the conference website: http://www.sjsresource.com.au/geoscientist-symposia-past-events.html

  • Revisions to the magmatic history in the project area following mapping and geochronology (by Dr Lorraine Campbell)
  • New insights into volcanic rocks through the Central Lachlan (by Dr Kate Bull)
  • Tin mineralisation at Ardlethan (by Dr Phil Blevin).

Geochronology

SHRIMP U–Pb dating of zircon from the project area was undertaken in conjunction with Dr Simon Bodorkos and others at Geoscience Australia. The results and geochronological interpretations are in a series of reports:

A final report with results from FY2016–17, FY2017–18 and FY2018–19 is due for publication in late 2019 as:

  • Bodorkos S., Waltenberg K., Bull K.F., Eastlake M.A., Gilmore P.J., Campbell L.M., Trigg S.J., Blevin P.L., Deyssing L., & Williams B.J., in prep. New SHRIMP U–Pb zircon ages from the Lachlan Orogen, New South Wales: East Riverina Project, July 2016–June 2019. Geoscience Australia Record 2019/XX; Geological Survey of New South Wales Report GS2019/1089.

A further suite of samples were submitted to James Cook University and Macquarie University for LA ICPMS U-Pb geochronology. The results from these samples will be available in late 2019 as:

  • Huang H. 2019. Zircon U–Pb dating of magmatic and detrital zircon samples. East Riverina geochronology. EGRU report 1815. Geological Survey of NSW Report GS2019/0445.
  • Tilhac R. 2019. Zircon U–Pb dating: TerraneChron report to the Geological Survey of NSW (TC-182). Geological Survey of NSW Report GS2019/0446.

Detrital zircons recovered from three samples in the Cocoparra Group and Square Head Formation by Charlotte Barry (Graduate Officer 2016 with the department) were analysed by LA ICPMS at the University of Newcastle to examine their provenance. Results are currently being interpreted.

Results of Ar-Ar analysis by the University of Melbourne) to constrain the age of deformation and metamorphism from mylonite zones in the Yalgogrin Granite and sheared Yiddah Formation were received. The interpretation of these ages is currently being finalised.

Published U–Pb SHRIMP (and other isotopic system) ages from this project and previous work are available through MinView.

Mineral systems

Mineral systems reports from the East Riverina Mapping Project include:

Please refer to Mineral potential mapping webpage for information on mineral potential mapping over the East Riverina Mapping Project area.

In addition, Daniel Cronin was a was lead author on a paper 'Temora copper–gold deposits' published in the AusIMM Australian Ore Deposits monograph (sixth edition).

Hydrogeochemistry

The final report on the collaborative hydrogeochemistry project in the Wagga area between GSNSW and CSIRO, led by Dr David Gray (CSIRO) Hydrogeochemical Investigations in the Wagga Wagga Region is available in DIGS as GS2015/0219.

Research

Collaborative research projects between GSNSW (Dr Glen Phillips and Dr Robert Musgrave) and the University of Newcastle (Dr Alistair Hack, Dr David Boutelier and Prof. Bill Collins) are listed below.

  • Michael Bell is doing a structural mapping (Masters) project to determine kinematics and timing of deformation in the Gilmore Fault Zone. This project will further our understanding of the structural settings influencing fluid flow and mineralisation along the fault zone. Michael presented a poster 'The geodynamic significance of the Gilmore fault zone, Lachlan Orogen: structural characteristics, kinematic history and timing' at the 2016 Australian Earth Sciences Convention. Michael is currently interpreting the results of six samples submitted to the University of Melbourne for Ar–Ar analysis – these analyses will constrain the timing of deformation in different aged rocks along the Gilmore Fault Zone.
  • Deepika Venkataramani's Masters project includes modelling the crust using deep crustal seismic (GA-99AGS-L3, Barmedman area), magnetic and gravity data, along with surface mapping. This will aid our 3D understanding of major structures including the Gilmore Fault Zone, intrusive bodies and Ordovician–Silurian volcanic rocks. Deepika presented the results of her study to date to the 2016 Australian Earth Sciences Convention, and in an extended abstract and talk at the 25th International Geophysical Conference and Exhibition (ASEG). Deepika's findings are published in a paper in Exploration Geophysics here: https://doi.org/10.1071/EG16148
  • Abstract for a poster presented at the Geological Society of Australia (GSA) Specialist Group in Tectonics and Structural Geology 2015 meeting by Brad Williams on the nature and timing of P–T conditions associated with metamorphism in the Holbrook area is available in GSA Abstracts Number 113.
  • A paper on Deepika Venkataramani's potential field and seismic modelling across the Gilmore Fault Zone is available here: https://doi.org/10.1071/EG16148

Publications on the application of remote sensing, spectral and geophysical data to field mapping by Dr Rob Hewson (RMIT University):

  • Using remote sensing, spectral and geophysical information to assist exploration within the Ardlethan and Barmedman 1:100 000 map sheet areas is in DIGS as GS2015/0185.
  • Using ASTER and geophysical mapping for mineral exploration in the Wagga Wagga and Cobar areas, NSW . Quarterly Note 140.
  • Project presentations

    Presentations on aspects of East Riverina Project are available. Contact phil.gilmore@planning.nsw.gov.au if no links are provided.

    • By Cait Stuart at Exploration in the Rocks in May 2019.
    • By Phil Gilmore at Exploration In Another House in May 2018.
    • Presentations and posters to the AGCC conference in Adelaide in October 2018:
      • Revised geology of the Central Lachlan Orogen: new insights from the East Riverina Mapping Project (Phil Gilmore et al.).
      • Devonian twins? The age, stratigraphy and provenance of the Cocoparra and Mulga Downs groups, NSW (Steven Trigg).
      • Old friends reunite: a new proposal for an Ordovician Lachlan Supergroup in the Tasmanides (Liann Deyssing et al.).
    • Phil Gilmore presented a project overview East Riverina mapping project: laying the foundation for resource discovery at Discoveries in the Tasmanides in Orange in September 2017. The extended abstract is available here: https://www.minesandwines.com.au/mw-papers-2017/5_Granites-and-more/2_East-Riverina-Mapping-Project_PGilmore.pdf. Please contact Phil for a copy of the presentation.
    • Sydney Mineral Exploration Discussion Group (SMEDG) in November 2015 is available here: http://www.smedg.org.au/past.html

    More information

    Phil Gilmore, Project Leader phil.gilmore@planning.nsw.gov.au