Regional Controls on Mineralisation in the Eyre Peninsula, South
Australia
Supervisors
Research Affiliations
Degree Type/Name
Pre-requisites
Student Support
Collaboration
Prof Mike Dentith and Prof Peter Cawood
Centre for Exploration Targeting, Tectonics Special Research
Centre
Ph.D, M.Sc or Honours - Geology, Earth Science, Minerals
Geoscience
Degree in Geology or Geophysics or other kinds Geoscience
degree.
The student undertaking this project is eligible for financial
support provided by the UWA Geoscience Foundation.
UWA only
Skills
This research project provides the opportunities for research students to obtain skills and
experience in the enhancement and interpretation geophysical data an its integration with
geological information, skills highly regarded in resource exploration companies, as well as
forming a firm basis for a research or academic career.
Project Description
The Eyre Pensinsula, located on the south-central coast of South Australia, is composed of
Palaeo to Mesoproterozoic crystalline basement unconformably overlain by
unmetamorphosed Neoproterozoic sedimentary rocks. Away from the coast exposure is poor,
but what exposure there is has been studied in some detail. Various generations of
aeromagnetic data are available and these data have been reprocessed and merged, and
now await interpretation. Geological problems that could be addressed include:

Important deposits of hydrothermal graphite occur at the southern end of the
Peninsula, near Port Lincoln. Deposit-scale studies show mineralisation is
stratabound and structurally controlled. Detailed mapping of coastal exposures has
allowed a sequence of structural/metamorphic events to be recognised. The
opportunity now exists to use the very high quality aeromagnetic data to extrapolate
the geological data from the coast in land, and study the semi-regional geological
context of the graphite deposits. Such a geological synthesis of the area is of both
economic and scientific interest. Data from the area are shown below.

The Middleback Ranges, located in to the northeast of the Pensinsula are an
important source of iron ore, feeding the smelters in near by Whyalla. Mineralisation
is structurally controlled within one or two (depending on stratigraphic model) units of
banded iron formation. A recent reinterpretation of the area, based primarily on a
structural analysis of the rocks exposed further south, suggests the Middleback
Ranges comprise a large-scale sheath fold. This model requires only one iron
formation unit. Alterative models involve thrust repetition of a single iron formation
horizon. In contrast, yet another interpretation is based on two original iron formation
units, and hence no need for a structural explanation of the two units seen in the field.
Using high-resolution gravity and magnetic data from the region, it is proposed to
model the observed responses to ascertain whether they can resolve the debate.

In the extreme northeast of the Eyre Peninsula Neoproterozoic sedimentary rocks
hosting copper mineralisation occur, comprising the Myall Creek prospect. Extensive
drilling in the 1960s to 1980s has allowed variations in grade, thickness and metal
content to be mapped in the area. However, the poor quality aeromagnetic and
gravity data available at the time meant the cause of these variations remained
unexplained. High quality data from the area now allow these questions to be
addressed. These data allow the structure of the crystalline basement and also
volcanic units within the Neoproterozoic succession to be mapped with confidence
(see figure below). Basement structure and topographic relief related to differential
erosion of volcanic units are likely to be the principal controls on the type and
distribution of the copper mineralisation, because they in turn control facies in the
sedimentary succession. Thus, the opportunity exists to understand the economic
geology of the area through the integration of geological exploration data and
geophysics.

Also located in the northeastern part of the peninsula is a large complex of fault
scarps created by pre-historic earthquakes. The area is currently not especially
seismically active, so the presence of so many scarps is enigmatic. Bedrock is very
poorly exposed in this area, but high quality aeromagnetic data are available. Since
most intra-plate earthquakes, such as formed the fault scarps, involve reactivation of
existing basement structures, the key to understanding the scarps probably lies the
bedrock geology. Careful interpretation of the aeromagnetic data is needed to
establish which of the many structures present is the youngest/related to the scarps
and why these structures were reactivated. The ultimate aim of any such study is to
ascertain whether the seismic hazard in the area has been underestimated.
This multifaceted research project provides opportunities for research students to integrate
geological and geophysical data to address problems and acquire skills relevant to the mining
sector, as well as forming a firm basis for a research or academic career. A Ph.D study could
combine all the components above, whilst M.Sc and Honours projects can be constructed
from selected components.
Recommended Reading
Dentith, M. and Cowan, D., 2003. Unconformity-related copper mineralisation on the Stuart
Shelf, South Australia: Geophysical responses of mineralisation and the mineralised
environment. In: Dentith, M.C., (editor). Geophysical Signatures of South Australian Mineral
Deposits. Centre for Global Metallogeny Publication No.31, Australian Society of Exploration
Geophysicists Special Publication No.12, pp 197-212.
Vassallo, J.J. and Wilson, C.J.L., 2001. Structural repetition of the hutchison Group
metasediments, Eyre Peninsula, South Australia. Australian journal of Earth Sciences, 48,
331-345.
Vassallo J J. Wilson C J L, 2002. Palaeoproterozoic regional-scale non-coaxial deformation;
an example from eastern Eyre Peninsula, South Australia. Journal of Structural Geology, 24,
1-24.