Scientists had long argued that supernova explosions were the source, but now it looks like it was the collision of 2 giant Neutron Stars that formed the heavy Elements including Gold, Platinum and lead ...
"These neutron star collisions produce all elements heavier than iron and they do it efficiently enough that they can account for all the gold that's been produced in the universe." ( - Smithsonian Magazine)
Pt= Platinum (78)
Au = Gold (79)