  We report the first detection of a pair of correlated emission lines in the
X-ray spectrum of black hole candidate 4U 1630-47 during its 1996 outburst,
based on RXTE observations of the source. At the peak plateau of the outburst,
the emission lines are detected, centered mostly at $\sim$5.7 keV and $\sim$7.7
keV, respectively, while the line energies exhibit random variability $\sim$5%.
Interestingly, the lines move in a concerted manner to keep their separation
roughly constant. The lines also vary greatly in strength, but with the
lower-energy line always much stronger than the higher-energy one. The measured
equivalent width ranges from $\sim$50 eV to $\sim$270 eV for the former, and
from insignificant detection to $\sim$140 eV for the latter; the two are
reasonably correlated.
  The correlation between the lines implies a causal connection --- perhaps
they share a common origin. Both lines may arise from a single $K_{\alpha}$
line of highly ionized iron that is Doppler-shifted either in a Keplerian
accretion disk or in a bi-polar outflow or even both. In both scenarios, a
change in the line energy might simply reflect a change in the ionization state
of line-emitting matter. We discuss the implication of the results and also
raise some questions about such interpretations.
