We present the results of a detailed abundance analysis of one of the confirmed building blocks of the Milky Way stellar halo , a kinematically-coherent metal-poor stellar stream .
We have obtained high resolution and high S/N spectra of 12 probable stream members using the MIKE spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory and the 2dCoude spectrograph on the Smith Telescope at McDonald Observatory .
We have derived abundances or upper limits for 51 species of 46 elements in each of these stars .
The stream members show a range of metallicity ( - 3.4 < [ Fe/H ] < - 1.5 ) but are otherwise chemically homogeneous , with the same star-to-star dispersion in [ X/Fe ] as the rest of the halo .
This implies that , in principle , a significant fraction of the Milky Way stellar halo could have formed from accreted systems like the stream .
The stream stars show minimal evolution in the \alpha or Fe-group elements over the range of metallicity .
This stream is enriched with material produced by the main and weak components of the rapid neutron-capture process and shows no evidence for enrichment by the slow neutron-capture process .