  The production and distribution of metals in the diffuse intergalactic medium
(IGM) have implications for galaxy formation models and the baryon (re)cycling
process. The relative abundance of metals in high versus low-ionization states
has also been argued to be sensitive to the Universe's reionization history.
However, measurements of the background metallicity of the IGM at z~4 are
sparse and in poor agreement with one another, and reduced sensitivity in the
near-IR renders detecting individual metal absorbers nearly impossible. We
present a new clustering-based technique that enables the detection of these
weak IGM absorbers by statistically averaging over all spectral pixels, here
applied to the C IV forest. We simulate the z=4.5 IGM with different models of
inhomogeneous metal distributions and investigate its two-point correlation
function (2PCF) using mock skewers of the C IV forest. The 2PCF demonstrates a
clear peak at the doublet separation of the C IV line. The peak amplitude
scales quadratically with metallicity, while enrichment morphology affects both
the shape and amplitude of the 2PCF. The effect of enrichment topology can also
be framed in terms of the metal mass- and volume-filling factors, and we show
their trends as a function of the enrichment topology. For models consistent
with the distribution of metals at z~3, we find that we can constrain [C/H] to
within 0.2 dex, log$\,M_{\rm{min}}$ to within 0.4 dex, and $R$ to within 15%.
We show that strong absorbers arising from the circumgalactic medium of
galaxies can be easily identified and masked, allowing one to recover the
underlying IGM signal. The auto-correlation of the metal-line forest presents a
new and compelling avenue to simultaneously constrain IGM metallicity and
enrichment topology with high precision at z>4, thereby pushing such
measurements into the Epoch of Reionization.

Astrophysics of Galaxies