  N51D (= DEM L 192) appears at first glance as a nearly circular, 120pc
diameter bubble of ionized gas around the LMC OB association LH 54. A deeper
look reveals a complex web of filaments and deviations from radial expansion.
Using a deep XMM-Newton X-ray pointing centered on N51D we find that diffuse
soft X-ray emitting gas fills the whole superbubble as delineated by the
H-alpha filaments. Contrary to recent findings for galactic winds, the
correlation between H-alpha and X-ray surface brightness is not good. The X-ray
spectrum of this diffuse gas cannot be fitted with the LMC abundance pattern,
but implies an overabundance of at least oxygen and neon, consistent with
recent enrichment from supernovae type II. Some indications for enhanced mixing
at the brightest region of the H-alpha shell and for a beginning outflow of the
hot gas were also detected.
