Here is an short history of the Icelandic hotspot for the past 65 million years. But it is believed to be around that old. Based on current studies into it.
Iceland hotspot during past ~65 million years. Copyright unknown, but belongs to it’s author. But the picture is from this web site here.
There is a lot of debate about the hotspot under Iceland. If it exist, or how it works. A lot of unanswered question remains. But with time and study. I am sure that some of them are going to be answered.
More information (short version)
Iceland hotspot (Wikipedia)
The water content of olivines from the North Atlantic Volcanic Province (SicenceDirect, Paywalled)