Actually current modeling has supernovae as being only a small contributor to the measured abundance of heavy nucleii. These guys tend to come from a more exotic source still: material thrown off as a neutron star is tidally disrupted during a merger event with another neutron star or black hole.
The wikipedia page is pretty good, as always: https://en.wikipedia.org/wiki/Nucleosynthesis
Almost everything with mass of 90 or above comes predominantly from neutron star mergers, basically.