autolith

(from the article `xenolith`) ...magma while it was still fluid, may be located near their original positions of detachment or may have settled deep into the intrusion, if their ... ...directly related to that of their host are known as xenoliths, and those representing broken-up and detached older parts of the same igneous body ... ...
Found on http://www.britannica.com/eb/a-z/a/128

autolith

autolith 1. A fragment of igneous rock enclosed in another igneous rock of later consolidation, each being regarded as a derivative from a common parent magma. 2. A round, oval, or elongated accumulation of iron-magnesium minerals of uncertain origin in granitoid rock.
Found on http://www.wordinfo.info/words/index/info/view_unit/262/10
No exact match found