Serializing document fragment without using extensions

Hello,

I need to put a document fragment (probably held by a temporary tree) into
a CDATA section. So I am looking for a way to serialize it. All I could
find were extensions - e.g. saxon:serialize() - doing the job. Sadly I
will not be able to use them. Is there a way to get this done with XSLT
2.0 without using extensions?

Thanks, Heiko