In standard dictionaries, such as Duden and Langenscheidt, the preposition zu is mentioned in sich zu etwas melden, which means to volunteer for something; e.g. "Wer meldet sich freiwillig zum Geschirrspülen?" (quoted from Langenscheidt Großwörterbuch Deutsch als Fremdsprache).
Meanwhile, I read the following example sentence in Farrell's Dictionary of German Synonyms:
Er meldete sich freiwillig für den Dienst im Ausland, doch ließ seine Begeisterung rasch nach.
In this example, the preposition für is used instead of zu. I am wondering whether this usage is really correct and whether there is any difference in meaning in this particular case of sich melden, that arises from the different choice between zu and für?