I'm willing to be corrected but I believe the rules that apply to national monuments are very different than those that apply to other federal lands, like National Forests (administered by the Department of Agriculture) and other federal lands that are administered by the BLM. Those last two are always leasing land for various industrial uses. National monuments are administered by the National Park Service and I believe that most of the original monument proclamations barred new mineral leases, mining claims, prospecting, exploration activities, and oil, gas, and geothermal leases, subject to existing rights.