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Inverse modeling constrained by potential field data, petrophysics, and improved geologic mapping: A case study from prospective northwest Tasmania

Citation

Eshaghi, E and Reading, AM and Roach, M and Duffett, M and Bombardieri, D and Cracknell, M and Everard, JL and Cumming, G and Kuhn, SD, Inverse modeling constrained by potential field data, petrophysics, and improved geologic mapping: A case study from prospective northwest Tasmania, Geophysics, 85, (5) pp. K13-K26. ISSN 0016-8033 (2020) [Refereed Article]

Copyright Statement

Copyright 2020 Society of Exploration Geophysicists

DOI: doi:10.1190/geo2019-0636.1

Abstract

The Heazlewood-Luina-Waratah area is a prospective region for minerals in northwest Tasmania, Australia, associated with historically important ore deposits related to the emplacement of granite intrusions and/or ultramafic complexes. The geology of the area is poorly understood due to the difficult terrain and dense vegetation. We have constructed an initial high-resolution 3D geologic model of this area using constraints from geologic maps and geologic and geophysical cross sections. This initial model is improved upon by integrating results from 3D geometry and physical property inversion of potential field (gravity and magnetic) data, petrophysical measurements, and updated field mapping. Geometry inversion reveals that the Devonian granites in the south are thicker than previously thought, possibly connecting to deep sources of mineralization. In addition, we identified gravity anomalies to the northeast that could be caused by near-surface granite cupolas. A newly discovered ultramafic complex linking the Heazlewood and Mount Stewart Ultramafic Complexes in the southwest also has been modeled. This implies a greater volume of ultramafic material in the Cambrian successions and points to a larger obducted component than previously thought. The newly inferred granite cupolas and ultramafic complexes are targets for future mineral exploration. Petrophysical property inversion reveals a high degree of variation in these properties within the ultramafic complexes indicating a variable degree of serpentinization. Sensitivity tests suggest maximum depths of 23 km for the contact aureole that surrounds major granitic intrusions in the southeast, whereas the Heazlewood River complex is likely to have a deeper source up to 4 km. We have demonstrated the value of adding geologic and petrophysical constraints to 3D modeling for the purpose of guiding mineral exploration. This is particularly important for the refinement of geologic structures in tectonically complex areas that have lithology units with contrasting magnetic and density characteristics.

Item Details

Item Type:Refereed Article
Keywords:potential field, geophysical inversion, petrophysics, Tasmania
Research Division:Earth Sciences
Research Group:Geophysics
Research Field:Geophysics not elsewhere classified
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Mineral exploration
Objective Field:Mineral exploration not elsewhere classified
UTAS Author:Eshaghi, E (Mr Esmaeil Eshaghi)
UTAS Author:Reading, AM (Professor Anya Reading)
UTAS Author:Roach, M (Dr Michael Roach)
UTAS Author:Cracknell, M (Dr Matthew Cracknell)
UTAS Author:Kuhn, SD (Mr Stephen Kuhn)
ID Code:141243
Year Published:2020
Funding Support:Australian Research Council (IH130200004)
Web of Science® Times Cited:1
Deposited By:Physics
Deposited On:2020-10-07
Last Modified:2020-11-04
Downloads:0

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