Some way to go to the world record set in Australia in 2001: over 99,700 tonnes, 682 loaded iron ore hoppers and over four and a half miles long. It needed eight General Electric AC6000 locos to shift it.
I always liked the Sishen - Saldanha train in South Africa, 41400t gross (this may have gone up recently, when they lengthen the trains slightly), 50kv AC, 375 wagons reaching 4km in length. All on 3ft6in track.
I believe it is the heaviest regular train in operation. They use 5 distributed electric loco's controled by 1 driver with an assistant, previously they used a mixed train of electric and diesel with 10 loco's but the new ones are now more powerful.