What are the Blue Rings in 'Bram Stoker's Dracula'?

The source novel mentions a blue flame barrier but these aren't explained by the author, other than being a sort of general foreshadowing to the fact that "Dracula has mysterious eldritch powers ... WOoooOOoo".

In the film, the flames just appear to be a sort of general mystic forcefield kind of deal, again for much the same effect:

Suddenly, away on our left, I saw a faint flickering blue flame. The driver saw it at the same moment; he at once checked the horses, and, jumping to the ground, disappeared into the dark- ness. I did not know what to do, the less as the howling of the wolves grew closer; but while I wondered the driver suddenly appeared again, and without a word took his seat, and we re- sumed our journey. I think I must have fallen asleep and kept dreaming of the incident, for it seemed to be repeated endlessly, and now looking back, it is like a sort of awful nightmare. Once the flame appeared so near the road, that even in the darkness around us I could watch the driver's motions. He went rapidly to where the blue flame arose it must have been very faint, for it did not seem to illumine the place around it at all and gathering a few stones, formed them into some device. Once there appeared a strange optical effect: when he stood between me and the flame he did not obstruct it, for I could see its ghostly flicker all the same. This startled me, but as the effect was only momentary, I took it that my eyes deceived me straining through the darkness. Then for a time there were no blue flames, and we sped onwards through the gloom, with the howling of the wolves around us, as though they were following in a moving circle.

...

I asked him of some of the strange things of the preceding night, as, for instance, why the coachman went to the places where he had seen the blue flames. He then explained to me that it was commonly believed that on a certain night of the year last night, in fact, when all evil spirits are supposed to have unchecked sway a blue flame is seen over any place where treasure has been concealed. "That treasure has been hidden,"

I know why, for I have proof from the book AND I played the game called Dracula: resurrection. In the book Dracula said that’s where people’s belongings have been buried. In the game the innkeeper lady said it’s where treasure has been buried after Jonathan found the dragon’s ring in the cemetery. In the game the innkeeper said “Did you see blue flames? Blue flames only appear when the demons have broken their chains. They would always point to the spot of the buried treasure! My grandmother would always tell me the stories of the invaders that attacked our country. The peasants decided to bury their belongings instead of watch them fall into the hands of the barbarians. It is said that their gold is cursed! GET THAT RING AWAY FROM ME!” In the book it says:

I asked him of some of the strange things of the preceding night, as, for instance, why the coachman went to the places where he had seen the blue flames. He then explained to me that locals believed that on a certain night of the year last night, in fact, when all evil spirits are supposed to have unchecked sway a blue flame is seen over any place where treasure has been concealed.