Nucleosynthetic signatures of primordial origin around supermassive
  black holes
  If primordial black holes (PBHs) seeded the supermassive black holes (SMBHs)
at the centers of high-redshift quasars, then the gas surrounding these black
holes may reveal nucleosynthetic clues to their primordial origins. We present
predictions of altered primordial abundances around PBHs massive enough to seed
SMBHs at z~6-7.5. We find that if PBHs with initial masses of ~10^5 M$_{\odot}$
are responsible for such SMBHs, they may produce primordial Deuterium and
Helium fractions enhanced by >~ 10%, and Lithium abundance depleted by >~10%,
at distances of up to ~ a comoving kiloparsec away from the black hole after
decoupling. We estimate that ~ 10^8 M$_{\odot}$ of gas is enhanced (or
depleted) by at least one percent. Evidence of these modified primordial
Deuterium, Helium, and Lithium abundances could still be present if this
circum-PBH gas remains unaccreted by the SMBH and in or near the host galaxies
of high-redshift quasars. Measuring the abundance anomalies will be
challenging, but could offer a novel way to reveal the primordial origin of
such SMBH seeds.
