  We present elemental abundances for 855 red giant branch (RGB) stars in the
globular cluster Omega Centauri (w Cen) from spectra obtained with the Blanco
4m telescope and Hydra multifiber spectrograph. The sample includes nearly all
RGB stars brighter than V=13.5, and span's w Cen's full metallicity range. The
heavy alpha elements (Si, Ca, and Ti) are generally enhanced by ~+0.3 dex, and
exhibit a metallicity dependent morphology that may be attributed to mass and
metallicity dependent Type II supernova (SN) yields. The heavy alpha and
Fe-peak abundances suggest minimal contributions from Type Ia SNe. The light
elements (O, Na, and Al) exhibit >0.5 dex abundance dispersions at all
metallicities, and a majority of stars with [Fe/H]>-1.6 have [O/Fe], [Na/Fe],
and [Al/Fe] abundances similar to those in monometallic globular clusters, as
well as O-Na, O-Al anticorrelations and the Na-Al correlation in all but the
most metal-rich stars. A combination of pollution from intermediate mass
asymptotic giant branch (AGB) stars and in situ mixing may explain the light
element abundance patterns. A large fraction (27%) of w Cen stars are O-poor
([O/Fe]<0) and are preferentially located within 5-10' of the cluster center.
The O-poor giants are spatially similar, located in the same metallicity range,
and are present in nearly equal proportions to blue main sequence stars. This
suggests the O-poor giants and blue main sequence stars may share a common
origin. [La/Fe] increases sharply at [Fe/H]>-1.6, and the [La/Eu] ratios
indicate the increase is due to almost pure s-process production.
