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An Enduring Problem: A multidisciplinary approach to characterise acid and metalliferous drainage at Endurance Mine, NE Tasmania

Citation

Fisher, E and Xuen Heng, W and Wilson, O and Cracknell, MJ and Miller, CB, An Enduring Problem: A multidisciplinary approach to characterise acid and metalliferous drainage at Endurance Mine, NE Tasmania, Geological Society of Australia Earth Science Student Symposium 2020, 12-17 October 2020, Virtual Conference, Online (Australia) (2020) [Conference Extract]

Abstract

The legacy Endurance Mine, an abandoned alluvial tin mine in northeast Tasmania, provides an opportunity to evaluate the production of acid and metalliferous drainage (AMD) in quartz-rich gravel tailings. Almost four decades after mine closure, and despite low observed pyrite content (< 1 wt. %), AMD generated at the Endurance tailings site continues to negatively impact rehabilitation success and the local environment. Three Earth Sciences honours projects at the University of Tasmania aim to embody a collaborative, multidisciplinary approach to mine waste characterisation and rehabilitation using hydrological, geochemical and geophysical methods. Due to the heterogenous nature of mine waste materials, research shows that a combination of disciplines is necessary to effectively characterise a tailings repository. These concurrent studies provide a unique opportunity for integration of results and a more holistic understanding of the Endurance legacy mine site.

Eliza Fisher’s thesis focuses on tailings and lake sediment geochemistry across the Endurance site. Her project has completed a bathymetric survey of Blue Lake, the largest of the three acidic (pH 2.7–4) pit-lakes to study depositional processes and pinpoint the deepest section of at 16.5 meters depth for sediment coring. Lake sediment cores were also collected from Middle Lake and Ruby Lagoon, the latter which is a collection pond for acid and metalliferous drainage. Horizons in the lake sediment cores will be analysed using integrated ICP-MS, XRD and SEM/MLA techniques to characterise the bulk geochemistry, mineralogy and trace metal hosts in the sediments. As the redox and pH sensitivity of authigenic metal-bearing minerals in sub-aqueous environments has implications for metal mobility, the geochemical analysis of these sediment will help to inform suitable remediation techniques.

To better understand the source and pathway of contamination at the former mine site, nine piezometers have been installed for Olivia Wilson’s hydrogeological survey. Surface and groundwater samples collected across the site demonstrate low pH (2.97-5.56), high conductivity, and elevated levels of metals (Al, Fe, Pb, Zn). Shake flask tests have been completed on various tailings materials to assess the solubility of mineral phases when interacting with surface and groundwaters. Analyses will lead to a combined understanding of sources of acid and metalliferous drainage at the legacy tailings site and the fate and transport of metals of concern to the downstream environment.

Wei Xuen Heng’s project focuses on the collecting geophysical observations of the historic tailings landscape using Electromagnetics (EM), Ground Penetrating Radar (GPR), Electrical resistivity imaging (ERI), near-surface seismic and radiometrics. These geophysical methods were used to image the thickness and internal structure of the Endurance tailings site. ERI and seismic methods have helped in estimating the thickness of surface tailings, saturated sediments, and granitic basement. GPR has proven to be a rapid way for defining the depth-to-basement, position of saturated sediments and highlighting the presence of dipping structures within 10 meters of the surface. In addition, this study compared electrical and elastic properties of the near-surface tailings layer based on the integration of inverted models and found that granite has > 2000 m/s P-wave velocity and > 100 Ohm/m resistivity values. These geophysical models are being cross-referenced with observations from the hydrogeological and geochemical surveys, which has the potential to provide an insight into basement topography for on-going hydrological and geochemical studies for future rehabilitation.

The permeable nature of the tailings material, combined with low water pH and high levels of aluminium, present challenges to passive remediation techniques. The collaborative effort of these three honours projects have implications for future remediation approaches at Endurance, which will inform remediation projects in high Al concentration environments across the tin fields of Tasmania’s northeast.

Item Details

Item Type:Conference Extract
Keywords:mining, remediation, acid mine drainage, hydrogeology, geophysics, geochemistry, mineralogy
Research Division:Environmental Sciences
Research Group:Environmental management
Research Field:Natural resource management
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Environmentally sustainable mineral resource activities
Objective Field:Management of solid waste from mineral resource activities
UTAS Author:Cracknell, MJ (Dr Matthew Cracknell)
UTAS Author:Miller, CB (Dr Clare Miller)
ID Code:143903
Year Published:2020
Deposited By:Earth Sciences
Deposited On:2021-04-09
Last Modified:2021-04-30
Downloads:0

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