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GSA Specialist Group in Economic Geology Facets of Exploration Feb Webinar

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A monthly series of talks from industry professionals covering many aspects of exploration.

About this Event

The GSA Specialist Group in Economic Geology invites you to attend the Facets of Exploration Webinar on 12.00 pm WST, Wednesday 10 March 2021.

Our speaker is Caroline Perring (Principal Geologist, BHP’s WA Iron Ore Division), who will be presenting the talk 'South Flank: Anatomy of a BIF-hosted Martite-Goethite Ore System from the Hamersley Basin'.

Time:

WST: 12.00pm – 1.00pm (WA)

AEST: 2.00pm - 3.00pm (QLD)

ACST :1.30pm - 2.30pm(NT)

ACDT: 2.30pm – 3.30pm (SA)

AEDT: 3.00pm - 4.00pm (ACT, NSW, TAS, VIC)

Abstract:

South Flank is BHP Western Australian Iron Ore’s exciting new mining development in the Hamersley Province of Western Australia. Development of this >1.9 Gt resource began in 2018 with the first ore scheduled for 2021 and an expected mine life of over 25 years.

This talk will discuss a proposed new model for the genesis of supergene, martite-goethite, BIF-hosted mineralisation. The model was developed using exploration drilling data, 2D geophysical datasets, 3D modelling and ore petrography to understand the controls on ore development from the camp- to the grain-scale.

A fluid and mass flux model is proposed which envisages a three stage process.

• Leaching of Fe from BIF in the vadose zone by reduced, acidic, meteoric-derived fluids.

• Penetration of a Fe-rich supergene-fluid plume, driven by gravity and focussed by bedding-parallel permeability, effecting non-redox mimetic replacement of magnetite by hematite and of the gangue minerals (carbonate, silicate and chert) by goethite and coupled with the release of silica into the fluid phase.

• A change from silica leaching to possible silica deposition on the down-dip margins of the system, before the ore-fluid plume is eventually diluted and becomes indistinguishable from the surrounding body of groundwater.

This process produces a distinct compositional zonation.

At the grain-scale, the mineralisation appears to take place in three stages with a fourth stage represented by the lateritic weathering overprint. Three different textural types of goethite are identified at South Flank and have distinct positions in the paragenetic sequence. They are tentatively interpreted as ochreous, brown and vitreous goethite. These goethite types have distinctly different chemical and physical characteristics and behave differently during downstream processing, from the crushing and transporting phases through to sintering and smelting. An understanding of ore genesis thus provides a critical first stage in the exploration for and development of high-grade, direct-shipping iron ore deposits.

Bio:

Caroline Perring was educated at Cambridge University and the Royal School of Mines, but has spent most of her career working in the Archaean Yilgarn craton of Western Australia. She completed a PhD at the University of Western Australia in the field of mesothermal Au mineralisation, before joining the Commonwealth Scientific Research Organisation to work with the Magmatic Ore Deposits group. Apart from a brief stint at James Cook University, working on Fe-oxide Cu-Au deposits, she spent the next 25 years studying magmatic Ni-Cu sulphide mineralisation and komatiite volcanism, latterly with Western Mining Corporation and then BHP Billiton Nickel West. She is now a Principal Geologist with BHP’s WA Iron Ore division.

We look forward to seeing you on March 10! Attendees will be sent a link to attend the Webinar on the morning of the talk.

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