Ancient rock under Haiti came from 1,000+ miles away, 1 billion years older than previously thought

[Judi Lynn]

Ancient rock under Haiti came from 1,000+ miles away, 1 billion years older than previously thought
July 12, 2011 by Jean Feingold

Two University of Florida geologists are part of a team that found lavas on the Caribbean island of Hispaniola – home to Haiti and the Dominican Republic — that suggest the area is underlain by rocks almost a billion years older than previously believed. Until now geologists thought Hispaniola was relatively young from a geological perspective and rocks there should be no older than the Jurassic period, around 150 million to 160 million years ago.

An article published Sunday on the Nature Geoscience website reports the team found that unusual lavas resulting from relatively recent volcanic activity had occurred in the region of the same fault system that caused the January 2010 earthquake in Haiti. The existence of this volcanic activity, which probably occurred less than 1 million years ago, is unexpected as it postdates the previously known active volcanism in this part of the Caribbean by at least 40 million years, said Michael R. Perfit, a professor and chairman of UF's department of geological sciences.

The most surprising discovery came from chemical analyses of the lavas which were found to have compositions similar to lavas found inside stable interior parts of continents. A detailed examination of the chemical data suggests that the source for these lavas is derived from mantle rock that originated at least 1,000 miles away.

"We can use the trace element and isotope information recorded in lavas and other environmental samples as sort of 'inorganic DNA' to trace their origin, migratory pathways and age," said George D. Kamenov, a UF associate in geology. The department's state-of-the-art plasma mass spectrometer was used to measure precisely the abundances of lead, strontium and neodymium isotopes in the lavas.

More:
http://www.physorg.com/news/2011-07-ancient-haiti-miles-billion-years.html