The geochemical processes involved in phosphorous enrichment of volcanic rocks under shallow seawater are not yet fully understood. As a contribution to this problematic, a detailed chemical characterization of phosphatized basaltic hyaloclastites assigned at Sal Island, Cape Verde archipelago, was undertaken using synchrotron radiation X-ray fluorescence. The mineralogical constitution of the samples was characterized by combining X-ray diffraction and electron microprobe data. Micromappings of metallogenetically significant components and other mobile chemical species were obtained. A positive correlation between Br plus Sr, on one side, and As plus Cr and Zn, on the other, is pointed out and brief comments are presented on the selective up-take of chemical elements in close dependence from the mineral assemblage formed by phosphatization.