I think using dtype
where there is a name row is confusing the routine. Try
>>> r = np.genfromtxt(fname, delimiter=',', names=True)
>>> r
array([[ 6.11882430e+02, 9.08956010e+03, 5.13300000e+03,
8.64075140e+02, 1.71537476e+03, 7.65227770e+02,
1.29111196e+12],
[ 6.11882430e+02, 9.08956010e+03, 5.13300000e+03,
8.64075140e+02, 1.71537476e+03, 7.65227770e+02,
1.29111311e+12],
[ 6.11882430e+02, 9.08956010e+03, 5.13300000e+03,
8.64075140e+02, 1.71537476e+03, 7.65227770e+02,
1.29112065e+12]])
>>> r[:,0] # Slice 0'th column
array([ 611.88243, 611.88243, 611.88243])