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Type: Thesis
Title: Pyrite in the Pepegoona, Pepegoona West and Pannikan uranium deposits, Lake Eyre Basin, S.A.: implications for regional uranium exploration
Author: Ingham, E.
Issue Date: 2012
School/Discipline: School of Earth and Environmental Sciences
Abstract: The common sulphide mineral pyrite is abundant throughout sedimentary uranium systems at Pepegoona, Pepegoona West and Pannikan, South Australia. No in-depth geochemical and textural characterisation of this important mineral has previously been conducted. Multiple micro-analytical techniques have successfully constrained textural and chemical patterns within the pyrite. Results point to variation in fluid composition, sulphur source and precipitation conditions during a protracted mineralisation event. In-situ micron-scale sulphur isotope analysis of pyrite demonstrated broad-scale isotopic heterogeneity (delta34S= -43.9 to +32.4‰CDT), indicative of complex, multi-faceted pyrite evolution and sulphur derived from two or more sources. Preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation. Authigenic, pre-ore pyrite underwent prolonged evolution and recrystallisation, evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra. Secondary hydrothermal pyrite commonly displayed hyperenrichment of several trace elements (Mn, Co, Ni, As, Se, Mo, Sb, W and Tl) in ore-bearing horizons. Hydrothermal fluids of magmatic and meteoric origin supplied metals to the system but the geochemical signature of pyrite suggests a dominant granitic source and influence of mafic lithologies. Irregular variation in 34S, coupled with oscillatory trace element zonation in secondary pyrite, is interpreted in terms of continuous variations in fluid composition and possible cycles of diagenetic recrystallisation. A late-stage oxidising fluid, which mobilised selenium from pre-existing pyrite, caused ongoing pyrite re-crystallisation and precipitation of native selenium. These results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at Beverley North. Insight into depositional conditions and sources of both sulphide and uranium mineralisation allow for a preliminary paragenetic scheme for the ore systems. This new understanding of pyrite geochemistry can also underpin an effective vector for uranium exploration, not only at Beverley North, but throughout the sedimentary systems of the Lake Eyre Basin.
Dissertation Note: Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2012
Where: Lake Eyre Basin, South Australia
Keywords: Honours; Geology; pyrite; Beverley North; uranium exploration; sulphur isotopes; trace elements; Eyre Formation
Description: This item is only available electronically.
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:
Appears in Collections:School of Physical Sciences

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