Positrons from black holes might emit gamma rays.
Gamma radiation arises when positrons annihilate electrons. In an electron cluster this can be explained by the idea that vacancies appear in an electron cluster when positrons annihilate electrons. These vacancies are immediately refilled by neighboring electrons at which point a wave motion with Compton wavelength.
Arthur Compton researched into gamma radiation and received the Nobel Prize for physics in 1927 for his discovery by firing photons at electrons and thereby showing how electrons took on a new wavelength.
This is the same effect as is achieved when electrons begin to move when filling the vacancies in the electron cluster when positrons are annihilated. Gamma radiation is the natural frequency electrons take on in the charge density present in the electron cluster. It does not follow that energy of the gamma radiation comes from the mass of the positrons and the electrons when they annihilate each other according to E = m x c2, since no energy can be created when a positive charge annihilates a negative charge.