@IsailedawayfromFR Well, I did a little digging into research done there.
https://bermudageology.com/the-bermuda-volcanic-seamount/Gives a descriptive overview, and the whole book is interesting, but only sheds a little light on the mineralogy of the volcanoes and intrusives involved. That reference is primarily concerned with sedimentary deposits over the eroded volcanic framework, and not as much in the mineralogy of the igneous rocks themselves.
https://pubs.geoscienceworld.org/gsa/books/edited-volume/618/chapter-abstract/3805664/Origin-of-the-Bermuda-volcanoes-and-the-Bermuda?redirectedFrom=fulltext...gets a little deeper (no pun intended) into the mineralogy of the volcanics, and states:
The pillow lavas forming the original Bermuda shield volcano have not been reliably dated, and the three associated smaller edifices have not been drilled or dated. A well-dated (ca. 33–34 Ma) episode of unusually titaniferous sheet intrusion in the Bermuda edifice was either triggered by platewide stress changes or reflects local volcanogenic events deep in the mantle source region. The high Ti and Fe of the Bermuda intrusive sheets probably relate to the very high-amplitude magnetic anomalies discovered on the islands. Numerical models constrained by available geophysical data attribute the Bermuda Rise to some combination of lithospheric reheating and dynamic uplift. While the relative contributions of these two processes cannot yet be wholly separated, three features of the rise clearly distinguish it from the Hawaiian swell: (1) the Bermuda Rise is elongated at right angles to the direction of plate motion; (2) there has been little or no subsidence of the rise and the volcanic edifice since its formation—in fact, rise uplift continued at the same site from the late Middle Eocene into the Miocene; and (3) the Bermuda Rise lacks a clear, age-progressive chain. We infer that the Bermuda Rise and other Atlantic midplate rises are supported by anomalous asthenosphere, upwelling or not, that penetrates the thermal boundary layer and travels with the overlying plate.
I am not sure what effect the high titanium content of the rock has on isostacy, but titanium is roughly 60% of that of iron, and the presence of large amounts may make a difference in the overall density of the underlying igneous and volcanic rock. Lower density rock 'floats' better on the mantle (like the continental plates), and though I cannot state how much of an effect the mineralogy has on the overall density of the underlying igneous rock or the thickness thereof (mainly for lack of data), it would have some, perhaps enough to keep the rise from subsiding like the more iron rich basaltic islands, submarine volcanoes, and seamounts found in the Pacific.
The Abstract goes on to describe fragments of subducted plate causing localized upwelling in the mantle, but without access to the rest of the article, I cannot form an opinion on the conclusions because I do not have all the data.
Keep in mind that this is out of my specific area of expertise.
Without a better description of the mineralogy of the underlying igneous rock, it is difficult to say, and the amount of that is limited, because coring of the rocks has been limited. Because there is no island chain. like the Hawaiian Islands. indicating plate movement over a Mantle hotspot, that may not be the cause (not completely ruled out, but unlikely).
Interesting, though, and thanks for bringing my attention to this.
