Using Sloan Digital Sky Survey ( SDSS ) early data release spectra , we have identified 370 Mg ii absorption systems with Mg ii \lambda 2796 rest equivalent widths \geq 1 Å and redshifts z = 0.9 - 2.2 .
From our previous and ongoing HST UV spectroscopic studies , we estimate that the mean neutral hydrogen column density of a system selected in this manner is N _ { HI } = 3.6 \pm 1.3 \times 10 ^ { 20 } atoms cm ^ { -2 } , which corresponds to the damped Ly \alpha ( DLA ) regime .
We have formed high signal-to-noise ratio composite spectra using 223 of these systems with z = 0.9 - 2.0 
in order to study the strength of the Zn ii and Cr ii absorption lines corresponding to this mean neutral hydrogen column density .
After making a correction for missed DLAs , overall we find that [ Zn/H ] = -1.13 \pm 0.19 .
We find [ Cr/Zn ] = -0.45 \pm 0.13 , which indicates that \approx 65 % of the Cr is depleted on to grains , but this does not correct for the missed DLAs .
We have also derived Zn and Cr abundances in two kinematic regimes , and within each regime we consider two redshift intervals .
We find trends which indicate that metallicities are higher in the composites where the absorption has larger velocity spreads as measured by Mg ii \lambda 2796 rest equivalent width .
Larger velocity spreads may correspond to deeper gravitational potential wells which represent more massive and chemically evolved structures , and/or regions associated with winds from starbursting galaxies , also leading to kinematically broad structures of chemically enriched gas .
Within the large velocity spread regime , we find that at lower redshifts the Zn metallicity is larger and more Cr is depleted on to grains .