Page 11: of Marine Technology Magazine (May 2006)

www.seadiscovery.com Marine Technology Reporter 11

He said, "The size and geometry of the melt lens affects not only the composition and thermal structure of the ocean crust, but also the vigor of hydrothermal circula- tion of seawater through the crust." Alt explains that such systems lead to spectacu- lar black-smoker vents ancient copper deposits, and oases in the deep ocean that support exotic life.

Jamie Allan, IODP program director at the U.S. National Science Foundation, said, "These results, from drilling into the structural heart of Pacific crust, are exciting and confirm ideas from seismologic inter- pretation about how fast-spreading oceanic crust is built. They further refine our understanding of the relationship between seismic velocity and crustal rock composi- tion, and open new vistas for investigating the origin of lower oceanic crust that can best be addressed by deeper drilling."

Geophysical theories have projected that oceanic magma chambers freeze to form coarse-grained, black rocks known as gab- bros, commonly used for facing stones on buildings and kitchen countertops.

Although gabbros have been sampled else- where in the oceans, where faulting and tec- tonic movement have brought them closer to the seafloor, this is the first time that gabbros have been recovered from intact ocean crust. "Drilling this deep hole in the eastern

Pacific is a rare opportunity to calibrate remote geophysical measurements such as seismic travel time or magnetic field with direct observations of real rocks," said geo- physicist Doug Wilson, University of

California, Santa Barbara. Co-chief scien- tist on an earlier expedition to the same news

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