Abstract
Here we derive some further properties of starbursts; namely the amount of matter returned to the interstellar medium by means of supernova explosions from massive stars ( M[*] >= 8Msolar), as a function of time. Following different approximations to stellar evolution we also derive the time dependent oxygen and iron production rates as a function of the starburst mass. The newly created heavy elements clearly enhance the metalicity of the resultant superbubbles, fact that should be taken into consideration when calculating the cooling and the X-ray luminosity of superbubbles. It however will take several times 108 yr for them to enhance the metalicity of the ISM.
