Let's say a field of stars all die within a short amount of time. Just
for argument's sake they produce a debris field of iron ( or any other
heavy element). Provided that there is enough time the debris will
agglomerate, we know this.
My question: Given enough mass, will this agglomeration of heavy
elements fuse into even heavier elements?
Short answer, no, as others have said. At least, not in the stellar fusion sense, because heavier than Iron doesn't fuse in stellar fusion. Heavier than Iron fuses in supernova explosions.
Quick Source: http://curious.astro.cornell.edu/copyright-notice/85-the-universe/supernovae/general-questions/418-how-are-elements-heavier-than-iron-formed-intermediate
More info here: Origin of elements heavier than Iron (Fe)
To be plain, I am not talking about stellar fusion or whether there is
enough latent energy to continue fusion at an already existing core. I
want to know if there was enough collective mass in the debris field,
could the field itself, coalesce to the point where the heavy elements
Lets examine what happens when the iron coalesces, and in reality, it's unlikely that you'd have Iron and nothing else. It's hard to imagine a share of hydrogen, helium, carbon, etc, wouldn't be present, but assuming just Iron:
First, you get something similar to a planet or a planet core. That gets bigger as more coalesces. Then something cool happens (or, well, hot more specifically), but it's kinda neat. At a certain point, the planet stops getting bigger and starts getting smaller, and as it gets smaller, it gets hotter, not from fusion, just the energy of coalescing. In time, it could glow hot like the sun, but much smaller than a sun. If I was to guess, the peak size might be around the size of Neptune. (Peak hydrogen planet size is about the size of Jupiter, peak Iron planet size would, I would think, be a fair bit smaller).
Eventually, with enough mass, you get something something similar to a white dwarf. Iron white dwarfs don't exist because stars that become white dwarfs don't get to the Iron creation stage. There's some metallicity, but essentially, white dwarfs are carbon/Oxygen, or, smaller ones can be made of Helium and sometimes, there's some Neon, Magnesium - more on that here: https://en.wikipedia.org/wiki/White_dwarf
Your scenario would essentially become an Iron white dwarf.
Then, as with any white dwarf, at a certain mass, it reaches the Chandrasekhar limit and the inside of the star would begin to degenerate into a Neutron Star and once that process begins, it moves quickly and you basically have a really really really big boom and a type 1a supernova. And during the supernova, a lot of the Iron would fuse into heavier elements, but it would kind of happen all of a sudden, in the reasonably short period of time.