Is it possible that in the debris field left over from a neutron star merger (kilonova) there are heavy element sized chuncks of (mostly) neutron matter that undergo rapid beta-decay to become the heavy elements observed? I seem to remember reading about this possibility shortly after the recent LIGO observation, but now everything I see only mentions the R-process. The R-process was a logical explanation for the heavy elements when it was thought they resulted only from supernova events, but is there now a wider range of possibilities?
I assume by "neutron matter" you mean the major component (by mass) of a neutron star - a fluid comprised mainly of neutrons with a small component of protons and electrons in "beta equilibrium".
If so, then this cannot decay into r-process elements like gold and osmium. All it can do is decay into a plasma of protons and electrons.
To build heavy, neutron-rich elements requires the rapid capture of neutrons (the r-process) onto already heavy elements. Such elements exist in the crusts of merging neutron stars. After the rapid neutron capture, the unstable products do undergo beta decay to become the stable "r-process elements".