yes might be liquid inside copper pipe leaked, but i dont think cause to much for rx 470 card which is low power gpu, might be some bent in mounting and die not connecting evenly in heatsink
this happen on many vegas gpu. trying to replace with new heatsink to costly for gpu already fall in price
In my case it was a RX580, but same series basically.
I did notice on this particular model (MSI Armor) that when you take the heat sink off the GPU, on the backside there is a small copper tube inset in the block with the two aluminum tubes connected one each end. I wonder if this is why this particular brand/model leaks more. I have other similar GPUs from that era that have a similar design that use solid aluminum throughout with the piping (tubes) all being one piece instead of two.
Anyway, I assume that what ever fluid they use inside these tubes, or heat pipes, boiled away over time and now they are just empty tubes of air acting more like an insulator than a conductor of heat. All that is left is the direct metal contact of the remaining portion of the heat sink which will transfer some but not all of the heat away.
MSI Armor is a reliable video card in terms of elements, but it has very poor fans and cooling radiator. If there is overheating, it is usually due to gas escaping from the radiator tubes.
On the secondary market, these radiators are bad and they cost 80% or more of the cost of the used video card. My video cards mine the Kawpow algorithm with a temperature of 90 degrees with a bad heatsink and they are still alive.