We present abundance measurements , based on high-resolution optical spectroscopic data obtained with the Ultraviolet and Visual Echelle Spectrograph mounted on Kueyen ( Very Large Telescope UT2 ) , for ten stars in the extended blue horizontal branch of the Galactic globular cluster NGC 1904 ( M79 ) .
In agreement with previous findings for other clusters , we obtain normal abundances for stars cooler than T _ { eff } \sim 11 000 K , and largely anomalous abundances for hotter stars : large He depletions , and overabundances of Fe , Ti , Cr , P and Mn .
The abundances of Mg , Si and Ca are roughly normal , in the hot stars as well as in the cooler ones .
This abundance pattern can be attributed to the onset of diffusion and to radiation pressure in the stable atmospheres of hot horizontal branch stars .