Characterising the mineralisation, alteration, and temporal evolution of the Neoarchean Gokona Au deposit, Tanzania

Routleff, Charles 2024. Characterising the mineralisation, alteration, and temporal evolution of the Neoarchean Gokona Au deposit, Tanzania. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Numerous world-class Neoarchean gold occurrences are proposed to be genetically associated with coeval magmatic intrusive complexes. However, this is highly contentious, and the significance of magmatic ore-forming fluid contributions to greenstone belt Au inventories is poorly understood. The Tanzanian Lake Victoria Goldfields hosts several major Neoarchean gold deposits of late, syn-orogenic timing (c. 2660-2640 Ma). Among these, the 10+ Moz Gokona Au deposit is enigmatic, displaying characteristics inconsistent with the regional mineralisation paradigm. At Gokona, mineralisation predates regional deformation and occurs in a highly dynamic near-surface setting. The deposit is associated with intense wholesale K-feldspar alteration, anomalous base metal and telluride enrichments, and cryptic structural control that is only apparent at the camp scale. The complexly intercalated and thrusted host sequence, comprising andesitic porphyry and tuffaceous-ignimbrite equivalents, shares a common enriched mantle source geochemistry with the regional Kuria Porphyry Complex. In this study, the post-subduction Au-rich porphyry-epithermal system signature is investigated. A rigorous paragenetic framework is established and augmented with complementary fluid inclusion micro-thermometry, stable isotope analyses (δD, δ18O, and δ34S), ID-TIMS geochronological constraints, and zircon trace element geochemistry to establish a genetic association the KPC as the metallogenetic driver. The well-preserved stratigraphic sequence permits the development of a detailed deposit model, classifying Gokona as a Neoarchean low-sulphidation epithermal system and providing novel insights into the role of magmatism within Archean greenstone belts. The growing recognition of geochemically and temporally analogous ore-related porphyries spatially associated with world-class Au deposits, both locally and globally, hints at the broader applicability of this contribution.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Earth and Environmental Sciences
Funders:	NERC GW4+ DTP
Date of First Compliant Deposit:	24 January 2025
Last Modified:	24 Jan 2025 14:34
URI:	https://orca.cardiff.ac.uk/id/eprint/175555

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