  We present an [O/Fe] ratio of a luminous galaxy GN-z11 at $z=10.60$ derived
with the deep public JWST/NIRSpec data. We fit the medium-resolution grating
data with the model spectra consisting of BPASS-stellar and CLOUDY-nebular
spectra in the rest-frame UV wavelength ranges with Fe absorption lines,
carefully masking out the other emission and absorption lines in the same
manner as previous studies conducted for lower redshift ($z\sim 2-6$) galaxies
with oxygen abundance measurements. We obtain an Fe-rich abundance ratio
$\mathrm{[O/Fe]}=-0.39^{+0.59}_{-0.36}$ that is confirmed with the independent
deep prism data as well as by the classic 1978 index method. This [O/Fe]
measurement is lower than that at $z\sim 2-3$ and comparable with those at
$z\sim 6$. Because $z=10.60$ is an early epoch after the Big Bang ($\sim 430$
Myr) and the first star formation (likely $\sim 200$ Myr), there is a
difficulty in efficiently producing Fe by Type Ia supernovae (SNeIa) requiring
sufficient delay time for white-dwarf formation and gas accretion. The Fe-rich
abundance ratio in GN-z11 suggests that the delay time is short, or that the
major Fe enrichment is not accomplished by SNeIa but bright hypernovae (BrHNe)
and/or pair-instability supernovae (PISNe), where the yield models of BrHNe and
PISNe explain Fe, Ne, and O abundance ratios of GN-z11. The [O/Fe] measurement
is not too low to rule out the connection between GN-z11 and globular clusters
(GCs) previously suggested by the nitrogen abundance, but rather confirms the
connection with a GC population at high [N/O] if a metal dilution process
exists.
