We present new experiments of particle-driven turbulent plumes issuing from a constant source of dense particle-laden fluid, with buoyancy flux,
$B$
, in a uniform horizontal current,
$u$
. Experiments show that a turbulent, well-mixed plume develops, in which the downward vertical speed
$w$
decreases with depth
$z$
according to
$w = 0.76 (B/uz)^{1/2}$
while the horizontal speed rapidly asymptotes to the current speed
$u$
, provided that the Stokes settling speed of the particles
$v<0.92 w$
. For
$v > 0.92 w$
, the particles separate from the plume fluid, and their depth
$z$
increases according to the simple sedimentation trajectory
$\textrm {d}z/{\textrm {d}\kern0.7pt x} = v/u$
. As the particles sediment, they form clusters of particles, which lead to fluctuations in the particle load with position, but do not appear to change the time-average sedimentation speed. We explore the impact of these results for deep-sea mining, in which the fate of the plume water as well as the particles is key for assessing potential environmental impacts.