2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/104854Let Γbe a geometrically finite tree lattice. We prove a Khintchine-Sullivan type theorem for the Hausdorff measure of the points at infinity of the tree that are well approximated by the parabolic fixed points of G. Using Bruhat-Tits trees, an application is given for the Diophantine approximation of formal Laurent series in the variable 1/X over the finite field Fq by rational fractions in X over Fq, satisfying some congruence properties11 pages, a minor revision, to appear in Archiv der MathematikGroup TheoryMetric Geometry20E08, 11J61, 20G25text