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Inverse modeling constrained by potential field data, petrophysics, and improved geologic mapping: A case study from prospective northwest Tasmania
journal contribution
posted on 2023-05-20, 18:26 authored by Esmaeil Eshaghi, Anya ReadingAnya Reading, Michael RoachMichael Roach, Duffett, M, Bombardieri, D, Matthew CracknellMatthew Cracknell, Everard, JL, Cumming, G, Kuhn, SDThe 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 2–3 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.
Funding
Australian Research Council
AMIRA International Ltd
BHP Billiton Ltd
Newcrest Mining Limited
History
Publication title
GeophysicsVolume
85Issue
5Pagination
K13-K26ISSN
0016-8033Department/School
School of Natural SciencesPublisher
Soc Exploration GeophysicistsPlace of publication
8801 S Yale St, Tulsa, USA, Ok, 74137Rights statement
Copyright 2020 Society of Exploration GeophysicistsRepository Status
- Restricted