Geologist makes rare discovery in Dominican Republic

Grenville Draper, professor of geology and associate director of Liberal Studies at FIU, has discovered fragments of mantle plume rocks in the northern Dominican Republic.

A mantle plume is a mass of abnormally hot rock that rises up through the Earth’s mantle. Many scientists believe these plumes explain the existence of volcanoes that are outside of tectonic plate boundaries, such as the volcanoes in Hawaii.

FIU Professor Grenville Draper, center, explores fragments of mantle plume rocks recently discovered in the Dominican Republic.

While a small group of geoscientists have questioned whether mantle plumes actually exist, Draper’s latest discovery provides evidence of their existence. Adding to the intrigue of the discovery, mantle plumes usually do not occur at plate boundaries. But the plume rocks discovered by Draper were found in an area that once was a convergent plate boundary. It is also the first time fragments have ever been discovered that appear to have lifted to the Earth’s surface and not contained in the lava of volcano.

“As the rocks have come from a depth of over 110 kilometers, their passage to the surface would need some special tectonic process that we don’t yet understand,” Draper said. “It is just one more example of the Caribbean region’s geologic complexity and what I like to call its geodiversity. I’ve worked in the Caribbean all my career, and I never cease to be amazed at its geologic history.”

Draper’s study Garnet-bearing ultramafic rocks from the Dominican Republic: Fossil mantle plume fragments in an ultra high-pressure oceanic complex? was co-published with Esteban Gazel of Columbia University and Richard N. Abbott Jr. of Appalachian State University. It can be found in Lithos, an international journal dedicated to publishing papers on mineralogy, petrology and geochemistry.

“Given our recent findings of the mantle plumes, our next step is to apply for funding from the National Science Foundation to look further into their composition and age,” Draper said.