David is undertaking doctoral research into the geochemistry of rocks of the Northern Volcanic Zone of the Andes in Colombia and related rocks in the Panama isthmus as possible analogues for the Earth’s first stable continents.
How and why the first continents formed on Earth is an open question in geoscience. The majority of continental crust preserved from early Earth history (4.0 – 3.0 Ga) is composed of a suite of rocks known as trondjhemites, tonalities and granodiorites (TTG).
The geological setting for generation of this material remains controversial. Though some workers favour remelting of basalt at the base of thickened crust, most workers view a subduction setting as more likely. This is partly based on the fact that the TTG suite has a distinct chemical composition similar to rare modern arc lavas known as adakites.
Recent work in Jamaica has described a sub-type of adakites derived from underplating of arc crust by oceanic plateau. Underplating or subduction of oceanic plateau is increasingly seen as a likely mechanism for generation of the earliest (4.0 – 3.6 Ga) continental crust. As the Caribbean plate is largely composed of oceanic plateau, material with a similar origin and geochemistry could exist elsewhere in the Caribbean and the margin of South America. This could provide a possible large scale analogue for production of the earliest TTG, and therefore the first stable continents.
David has conducted extensive fieldwork in both Panama and Colombia as part of this research.