Here's a (very) rough estimate until someone can find out anything more specific.
According to Intamin, Millennium Force trains weigh 27 tons each, that is 24,494 kilos. Each train seats 36 people. (source:
https://coasterbuzz.com/Forums/Topic/weight-of-a-train).
Fury 325 trains seat 32 people per train but has a zero car.
Assuming it's a fully packed train thats 32 x 70kg = 2,240 kilos. Plus the weight of the train equals
26,734 kilos.
Again, this is very rough maths but it would be interesting how close this quick calculation is to the actual answer.