Saturday, September 7, 2019

Mystery of the Pilbara gold nugget

An old-school gold rush kicked off in the Pilbara goldfields in 2017 with the discovery of hundreds of gold nuggets shaped like watermelon seeds. Since then, the mystery of the source has grown. Two competing theories try to explain ‘Pilbara nuggets.’

Nuggets ranged in size and shape, suggesting they may have been caused by a ‘rough and tumble’ life in ancient riverbeds in a sedimentary process. This involves weathering and erosion and squashed into another form of rock, called conglomerate. An alternative theory is the gold conglomerate may have been transformed and modified through hydrothermal events. These occur when hot fluids seep through faults and cracks in the rock causing the metal to deform under high temperature and pressure.
Scientists have examined the geology and geochemistry of samples taken from the region, with imaging results of the 2.8 billion-year-old rocks revealing information.
Data suggested a clear hydrothermal influence at some point in their history, however, whether the nuggets were originally formed through sedimentary processes can't be confirmed.