I think there are many methods to model Fracture of Rock beside XFEM. Enclosed files maybe help you with better understanding. Hope that my answer is useful for you
I think that it is possible to simulate the mixture you have mentioned above but i don't know whether you ought to use Xfem or not. Because both Rock fracturing and blast is possible to simulate individually. About fracture we have different aspects. One may devide fracture in to predefined path and arbitrary path. Another one can be devided by the initiation and propagation criterion. I attach a file that describe this issues about the fracture.
In order to find more about the blast it is recommended to see part 9.1.8 of "Abaqus Example problems manual".