Apparently the name's original spelling is Iracema. So Irasema, with an "S" is definitely a variant. Here is what I have on Iracema,
Iracema: Tupí, meaning "from honey". (The Tupí are Brazilian natives)
Iracema: Anagram of América. Name created by José Martiniano de Alencar. J.M. Alencar is a well know Brazilian writer.
Now, I know who came first (the chicken or the egg...?) with this name. Obviously the Tupí and "from honey" and not writer J.M. de Alencar with his anagram of America. This makes it is clear that the name is a native Brazilian thing. Its definitely not Spanish. I'm not implying that the name is in the Portuguese language either, but just so that you can see how I got some of this info, I am inclosing some lines in Brazilian Portuguese which describes a bit of what posted above,
"Iracema: Anagrama de América. Nome criado por José de Alencar. José Martiniano de Alencar é uma das figuras mais destacadas da literatura brasileira oitocentista."
So this is the part where I suggest you as whom ever gave you your name, were did s/he came up with it, so that you know if you are ither “from honey” or “America” and how come yours has got a “S” and not a “C”