Chemical properties of distant Milky Way halo stars from current and future spectroscopic surveys

The study of elemental abundances of long-lived individual stars is one of the pillars of Galactic Archaeology, as a powerful way for retrieving information on the stars birth environment.
Through this approach, it has already been established that the inner Milky Way halo cannot have formed solely from the disruption of satellite galaxies experiencing as low an initial star formation rate as in the surviving Milky Way satellites.
However, the growing observational evidence for a dual nature of the Milky Way stellar halo raises the question of whether the elemental abundances of inner halo stars can be considered as representative of the whole Milky Way halo and if the inner and outer halo were formed through different dominant mechanisms.
In this talk I will present our investigation of the
chemical properties of the outer Milky Way halo, based on abundances of large samples of distant halo stars, both from SDSS-DR13
and proprietary spectroscopic campaigns at VLT, Magellan and HET. I will conclude with a
discussion of the prospects that future Galactic Archaeology surveys such as with the WHT/WEAVE spectrograph will open up for the study of the Milky Way halo properties.