The Winu Cu-Au-Ag discovery – first seen from space

In the first part of 2018 rumours began to circulate in the Australian exploration industry that Rio Tinto had made a significant Cu-Au discovery in a remote part of Western Australia. The discovery, called Winu, was located 130km north of Newcrest’s Telfer gold-copper mine.

Major mining houses can remain tight-lipped about such discoveries until a proper resource evaluation program has been completed.  (Because of their massive market capitalisation the news of a single discovery is hardly material to the company share price, and there is then no obligation for public disclosure to the market). However in this case, public-domain satellite imagery gave the rest of us a peek (albeit low-resolution) at what was going on.

The spatial resolution of the freely available Sentinel-2 optical imagery satellite data varies from 10m to 60m. Never the less, the ground disturbance from six drill pads in a 200m x 100m drill pattern, which suddenly appeared in the Paterson Desert in November-December 2017, could be picked up in the public domain Sentinel-2 satellite data.

Sentinel-2 data is updated every few weeks, so it was interesting to see a camp structure being erected in May 2018, along with ten or so follow-up drill sites, marking the start of a significant drill program, which would have been designed to evaluate just exactly what Rio Tinto had uncovered.

Only the following year, in February 2019, did Rio Tinto go public with the Winu discovery, releasing an additional statement in August.

The Winu deposit contains copper, gold, and silver in metamorphic basement under less than 60m-100m of cover. The thickest intersection reported to date is a 763m hit from 46m depth grading 0.44% copper, 0.65g/t gold and 2.88g/t silver. These are not bonanza grades, but there is an awful lot of it under quite shallow cover, yielding just the type of deposit that a major mining house can develop and run with profit for years and years.

No exploration had occurred in the area before Rio Tinto came on the scene in 2016. Geophysics would have played a major part in the discovery. The deposit is associated with a distinct magnetic expression in the public domain Anketell aeromagnetic and radiometric survey data set. In addition Rio Tinto has carried out a number of geophysical surveys over the deposit area including airborne electromagnetics, ground gravity, induced polarisation/resistivity, and passive seismic. 

Showing the way of the digital future in mineral exploration and mining they have also had the very good sense to run downhole density, gamma, conductivity, resistivity, induced polarisation, magnetic susceptibility and acoustic televiewer in the drill holes, and hyperspectral and high-resolution core imagery is being collected using a CoreScan hyperspectral core imager. I really look forward to see a published case study from all this work!

I have compiled an animation, showing the discovery of Winu and the subsequent resource evaluation drilling activity as it looked from Sentinel-2 imagery from September 2017 to April 2018.

Visually the Australian desert is red sand mixed in with a lot of red dust – so I had to apply Nordic Geoscience in-house data enhancements to the raw Sentinel-2 imagery to bring out the drill pads as much as possible. I found that old-school grey-scale imaging and filtering worked best for red-on-red desert satellite imagery.

The 2.5 years have been compressed into less than 2 minutes. I hope you enjoy it!

Thanks for watching, for now stay at home and stay safe!

Asbjorn Norlund Christensen is a consulting geophysicist at Nordic Geoscience, a geoscience consultancy with bespoke solutions in exploration geophysics and data science – www.nordicgeoscience.com

 PS:

To download the relevant Sentinel-2 images I have used the excellent RemotePixel viewer software by Vincent Sarago  at https://remotepixel.ca/

Here are the links to Rio Tinto’s market releases concerning Winu:

https://www.riotinto.com/news/releases/Exploration-update-Paterson

https://www.riotinto.com/en/news/releases/Project-update-Winu