The ore-bearing bed of Xiaochangyuan P deposit is Lower Cambrian Yuhucun Formation. The collophanite is composed of sand clast, pebble clast and ooide grain, in porous, pore - base ferro - muddy cementation. The grain form is subrounded, irregular, coarse grain increase evident. The sedimentation ebvironment is in the epeiric sea domain of old land margin. We infer that the sedimentary mineral material mainly results from the weathering -leaching process of old land.