Two OSIRIS/GTC pointings towards Cl0024. The plot has standard orientation: north is at the top and east to the left. Blue symbols correspond to SF galaxies and red ones correspond to AGNs according to the [N ii]/Hα ≥ 0.6 criterion from Ho et al. (1997). Circles correspond to galaxies in the main cluster structure (structure “A” in Sect. 6), squares to those in the infalling group (structure “B”), and triangles to sources in the putative group around z ≈ 0.42 (see Sect. 6). The cyan cross (×) denotes the centre of the cluster (galaxies/BCG) and the large pink circle denotes the virial radius of 1.7 Mpc (Treu et al. 2003). A general alignment of ELGs is observed in the NW SE direction, consistent with a a structure assembling onto the cluster core from the NW with an orientation almost in the plane of the sky (Moran et al. 2007; Zhang et al. 2005; Kneib et al. 2003).