Cu mineralisation in the Middleback Ranges: conditions of mineralisation
Date
2010
Authors
Jones, R. S. W.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Thesis
Citation
Statement of Responsibility
Conference Name
Abstract
The Moola Prospect situated within the Middleback Ranges on the northern Eyre
Peninsula, South Australia, is comprised of potential IOCG-style, Cu mineralisation which
appears to share some geological and mineralogical affinities with other IOCG deposits
throughout the Gawler Craton. This recently identified mineralisation represents a new
exploration region within the southern extent of the Olympic Cu-Au province which has
proven to be highly lucrative with the recent discovery of the Hillside deposit in the
neighbouring Yorke Peninsula. A broad investigation into host rock lithology, alteration
and mineralisation paragenesis, as well as paleotemperature-pressure conditions of the
deposit was carried out on drill core from OneSteel’s inaugural exploratory diamond drill
hole.
The mineralisation is hosted within the Paleoproterozoic Myola Volcanics, a package of
rhyolites, rhyodacites and felsic gneisses which are intruded by amphibolite sills and
granitic intrusives, assumed to be the neighbouring Wertigo granite. Prominently vein
hosted, the mineralisation is localised around a north-northeast trending shear zone
inferred to be an expression of the Kimban aged, Kalinjala shear zone which is located ~60
Km west of the Middleback Ranges. The alteration mineralogy present is divisible into two
main assemblages, an early albite-epidote assemblage which has experienced extensive
overprinting by the main mineralising phase associated with a quartz-carbonate-sericite±
hematite-sulphide assemblage. Ore mineral paragenesis occurs as a transition of
overlapping minerals that record coprecipiation. The first mineral to form was magnetite
which was later extensively martitised during the transition to hematite precipitation
which is preceded by a transition to pyrite, then finally chalcopyrite. A later phase of
native copper mineralisation is recorded within the transecting shear zone which
represents a supergene enrichment interpreted to have occurred as meteoric water
gained access to depth via the structural weakness of the shear zone and remobilised any
sulphides present, which were redeposited as native copper.
The temperature of mineralisation was established by TitaniQ thermometry which
provided a precise temperature range between 415-530 °C with the peak at ~475 °C,
which represents the conditions at which the paragenically linked quartz and
mineralisation formed. Chlorite thermometry was also performed to obtain a temperature
of mineralisation, with a few samples corresponding with the conditions established by
the TitaniQ thermometer; however a majority of the data overestimates the temperature
range by an unacceptable amount. Pressure conditions were reconstructed using the
much more reliable TitaniQ temperature range inconjuntion with fluid inclusion data to
establish the pressure conditions of mineralisation which ranged between ~5-7 kbar, and
indicated mineralisation occurred at a deep crustal setting.
Fluid and mineralisation characteristics indicate a moderate salinity inferred from the fluid
inclusions study, with NaCl ranging between 27.5-7.5 equiv wt%, along with a sulphur
isotopic signature corresponding with magmatically derived fluids with the δ34S ranging
between -10.5 and -1.2 ‰. Which corresponds with other IOCG style mineralisation
present throughout the Craton, with the Moola Prospect also being spatially associated to
the interpreted source of these fluids within the Galwer Craton, the Hiltaba Suite
granitoids? Even though the Moola Prospect shares affinities with IOCG style
mineralisation this study cannot definitively identify its model of genesis as it also
comprises characteristics that contradict this model, indicating that further study is
required to better understand the extent and nature of this mineralising system.
School/Discipline
School of Physical Sciences
Dissertation Note
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2010
Provenance
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses.
Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the author of this thesis and do not wish it to be made publicly available, or you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals
Description
This item is only available electronically.