éventail de dispersion

CONT: Une répartition variable de la teneur en métal, diminuant ou s'élargissant à peu près en forme de triangle et apparemment orientée vers une source, s'appelle éventail de dispersion.

OBS: secondary dispersion: ... Secondary patterns are those formed at the earth's surface by weathering, erosion, or surface transportation. Secondary patterns have been classified more in detail as halos, fans, and trains, depending on the characteristic shape of the pattern and its geometric relationship to the ore deposit ...