The mazurka provided him with a repertoire of motifs, rhythms, and sonorities outside the main Italian, French, and German traditions of European music: he used it to create a series of works within this tradition which are absolutely personal—marginal works which challenge the center.
They are the most eccentric and original of Chopin's works. We shall never know exactly what and how much Chopin took directly from the popular folk tradition and how much he invented, but it does not matter: his originality is revealed as much in what he selected as in what he imagined. The folk dances gave him the possibility of exploring new harmonies, of exploiting the emotional effect of obsessive repetition, and of developing a new form of rubato.

Ch. 7 : Chopin: From the Miniature Genre to the Sublime Style - The Romantic Generation (1995)