Riddle of how Reef gold ore was formed is solved

THE story of Johannesburg is, after 130 years, a story well told: George Harrison, an Australian prospector, stumbled on a rocky outcrop, determined it was gold ore, and declared open season on what scientists and industrialists would eventually realise was the largest gold repository in the world.

What hasn’t been told is how gold ore got there to begin with.

A new study from a team of Canadian scientists and Geomar Helmholtz Centre of Ocean Research in Kiel, Germany, has helped solve part of that riddle.

“For decades scientists have been trying to answer this question,” said Sebastian Fuchs, the lead author on the study.

Fuchs and his team took samples from the Witwatersrand basin, took images of them with an electron microscope and then used new 2D and 3D modelling software to visualise them on a computer screen. The models revealed a previously unknown process for ore-formation.

South African surface rock is far older than similar rock in the rest of the world.

The sea and river water that covered South Africa 3 billion years ago contained gold and uranium that, this study found, collected on the rock into ore that Harrison would find eons later.

The study found much of the dissolved gold and uranium particulate – essentially dust – formed ore through a structure called “oil-water emulsions”.

Oil formed from the remains of the earth’s oldest living organisms, formed a vinaigrette- like combination that settled on the rock floor and became the ore that would one day supply the world.