Featured Research

from universities, journals, and other organizations

International drilling mission to lower crust of Pacific yields unexpected clues to ocean mysteries

Date:
December 3, 2013
Source:
University of Houston
Summary:
Geoscientists have revealed new discoveries about Earth's development, following a major international expedition that recovered the first-ever drill core from the lower crust of the Pacific Ocean.

Jonathan Snow (Co-chief Scientist, University of Houston, USA), Kathryn Gillis (Co-chief Scientist, University of Victoria, B.C., Canada) and Chad Broyles (Curatorial Specialist, IODP-USIO/TAMU) work on a core sample in the splitting room.
Credit: Bill Crawford, IODP/TAMU

A University of Houston (UH) geoscientist and his colleagues are revealing new discoveries about Earth's development, following a major international expedition that recovered the first-ever drill core from the lower crust of the Pacific Ocean.

Related Articles


Co-chief scientists Jonathan Snow from UH and Kathryn Gillis from University of Victoria in Canada led a team of 30 researchers from around the world on the $10 million expedition, finding a few surprises upon penetrating the lower crust of the Pacific. Their findings are described in the Dec. 1 issue of Nature in a paper titled "Primitive Layered Gabbros from Fast-Spreading Lower Oceanic Crust."

"The ocean crust makes up two-thirds of the Earth's surface and forms from volcanic magma at mid-ocean ridge spreading centers," Snow said. "The deepest levels of this process are hidden from view due to the miles of upper volcanic crust on top. So, until now we had to make educated guesses about the formation of the lower crust based on seismic evidence and the study of analogous rocks found on land."

Traveling aboard the Integrated Ocean Drilling Program Expedition 345 to the Hess Deep in the Pacific Ocean, the scientific voyagers recovered core sections of lower crustal rocks, called gabbros, that formed more than two miles beneath the sea floor. A large rift valley in the eastern equatorial Pacific, the Hess Deep is like an onion sliced and pulled apart, revealing its deeper layers.

"Hess Deep is like a window into the lower crust of the ocean, where we can drill directly into these lower crustal levels," Snow said. "This is where magma rising up from the Earth's mantle begins to crystallize on its way to eventual eruption at the sea floor."

The two-month expedition, aboard the drilling vessel JOIDES Resolution, confirmed for the first time the widespread existence of layered gabbros in the lower crust. This observation had been predicted by plate tectonic theory and analogies made to fragments of ocean crust found on land, called ophiolites, but only rarely had actual layered rocks been recovered from the ocean floor.

A second surprise discovered by the explorers was akin to "finding gold in a silver mine," according to Snow. By studying thin slices of the gabbros under polarizing microscopes, the scientists identified substantial amounts of the mineral orthopyroxene, a magnesium silicate that was thought to be absent from the lower crust.

"Orthopyroxene by itself is nothing special. Traces of it are often found at late stages of crystallization higher in the crust, but we never in our wildest dreams expected a lot of it in the lower crust," Snow said. "Although this mineral is not economically valuable, the discovery means that basic chemical reactions forming the lower crust will now have to be re-studied."

A third surprise, Snow says, casts doubt on one of the main theories of the construction of the lower ocean crust. It involved the mineral olivine, also a magnesium silicate. This mineral is known to grow in delicate crystals sometimes found in layered intrusions on land, but never expected in the ocean crust. This is because the separation of the tectonic plates was thought to deform the magma like play dough in a partially molten state that would have broken them up. However, Snow says, the last word isn't written on this, because the researchers just cored a small section of the crust in one place on this expedition. To know for sure, they will have to explore the lower crust more, which will require drilling.

The fourth phase of ocean drilling, to be called the "International Ocean Discovery Program," was approved in late November by the National Science Board (NSB). The NSB is the governing board of the National Science Foundation and is responsible for guiding the pursuit of national policies for promoting research and education in science and engineering.


Story Source:

The above story is based on materials provided by University of Houston. The original article was written by Lisa Merkl. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kathryn M. Gillis, Jonathan E. Snow, Adam Klaus, Natsue Abe, Αlden B. Adriγo, Norikatsu Akizawa, Georges Ceuleneer, Michael J. Cheadle, Kathrin Faak, Trevor J. Falloon, Sarah A. Friedman, Marguerite Godard, Gilles Guerin, Yumiko Harigane, Andrew J. Horst, Takashi Hoshide, Benoit Ildefonse, Marlon M. Jean, Barbara E. John, Juergen Koepke, Sumiaki Machi, Jinichiro Maeda, Naomi E. Marks, Andrew M. McCaig, Romain Meyer, Antony Morris, Toshio Nozaka, Marie Python, Abhishek Saha, Robert P. Wintsch. Primitive layered gabbros from fast-spreading lower oceanic crust. Nature, 2013; DOI: 10.1038/nature12778

Cite This Page:

University of Houston. "International drilling mission to lower crust of Pacific yields unexpected clues to ocean mysteries." ScienceDaily. ScienceDaily, 3 December 2013. <www.sciencedaily.com/releases/2013/12/131203191159.htm>.
University of Houston. (2013, December 3). International drilling mission to lower crust of Pacific yields unexpected clues to ocean mysteries. ScienceDaily. Retrieved March 1, 2015 from www.sciencedaily.com/releases/2013/12/131203191159.htm
University of Houston. "International drilling mission to lower crust of Pacific yields unexpected clues to ocean mysteries." ScienceDaily. www.sciencedaily.com/releases/2013/12/131203191159.htm (accessed March 1, 2015).

Share This


More From ScienceDaily



More Earth & Climate News

Sunday, March 1, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Whale-Watching Scientists Spot Baby Orca

Whale-Watching Scientists Spot Baby Orca

AP (Feb. 28, 2015) — Researchers following endangered killer whales spotted a baby orca off the coast of Washington state, the third birth documented this winter but still leaving the population dangerously low. (Feb. 28) Video provided by AP
Powered by NewsLook.com
Bridge Collapses Due to Flooding in Bolivia

Bridge Collapses Due to Flooding in Bolivia

Reuters - News Video Online (Feb. 28, 2015) — Heavy rain and flooding sweep through parts of Bolivia causing damage and leaves more than 2,000 people homeless. Sophia Soo reports. Video provided by Reuters
Powered by NewsLook.com
Death Toll from Afghan Avalanches Tops 200

Death Toll from Afghan Avalanches Tops 200

AFP (Feb. 27, 2015) — More than 200 people have been killed in a series of avalanches triggered by heavy snowfall in Afghanistan. Duration: 00:42 Video provided by AFP
Powered by NewsLook.com
France, Philippines Call for Agreement on Climate Change

France, Philippines Call for Agreement on Climate Change

Reuters - News Video Online (Feb. 27, 2015) — The presidents of France and the Philippines issue a joint appeal for a binding agreement on climate change. Katie Sargent reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins