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We present a new determination of the intergalactic CIV mass density at 4.3 <z < 6.3. Our constraints are derived from high signal-to-noise spectra of sevenquasars at z > 5.8 obtained with the newly commissioned FIRE spectrograph onthe Magellan Baade telescope, coupled with six observations of northern objectstaken from the literature. We confirm the presence of a downturn in the CIVabundance at <z>=5.66 by a factor of 4.1 relative to its value at <z>=4.96, asmeasured in the same sightlines. In the FIRE sample, a strong system previouslyreported in the literature as CIV at z=5.82 is re-identified as MgII at z=2.78,leading to a substantial downward revision in $\Omega_{CIV}$ for these priorstudies. Additionally we confirm the presence of at least two systems withlow-ionization CII, SiII, and OI absorption but relatively weak signal fromCIV. The latter systems systems may be of interest if the downward trend in$\Omega_{CIV}$ at high redshift is driven in part by ionization effects.

Constraints on the Universal CIV Mass Density at z~6 from Early IR Spectra Obtained with the Magellan FIRE Spectrograph