Scientists recently concluded an expedition aboard the research vessel JOIDES Resolution to learn more about Atlantis Massif, an undersea mountain, or seamount, that formed in a very different way than the majority of the seafloor in the oceans.
This is a map of Atlantis Massif, showing the fault that borders this Atlantic Ocean seamount.
Unlike volcanic seamounts, which are made of the basalt that's typical of most of the seafloor, Atlantis Massif includes rock types that are usually only found much deeper in the ocean crust, such as gabbro and peridotite.
The expedition, known as Integrated Ocean Drilling Program (IODP) Expedition 340T, marks the first time the geophysical properties of gabbroic rocks have successfully been measured directly in place, rather than via remote techniques such as seismic surveying.
With these measurements in hand, scientists can now infer how these hard-to-reach rocks will "look" on future seismic surveys, making it easier to map out geophysical structures beneath the seafloor.
"This is exciting because it means that we may be able to use seismic survey data to infer the pattern of seawater circulation within the deeper crust," says Donna Blackman of the Scripps Institution of Oceanography in La Jolla, Calif., co-chief scientist for Expedition 340T.
"This would be a key step for quantifying rates and volumes of chemical, possibly biological, exchange between the oceans and the crust."
Atlantis Massif sits on the flank of an oceanic spreading center that runs down the middle of the Atlantic Ocean.
As the tectonic plates separate, new crust is formed at the spreading center and a combination of stretching, faulting and the intrusion of magma from below shape the new seafloor.
Periods of reduced magma supplied from the underlying mantle result in the development of long-lived, large faults. Deep portions of the crust shift upward along these faults and may be exposed at the seafloor.
This process results in the formation of an oceanic core complex, or OCC, and is similar to the processes that formed the Basin and Range province of the Southwest United States.
"Recent discoveries from scientific ocean drilling have underlined that the process of creating new oceanic crust at seafloor spreading centers is complex," says Jamie Allan, IODP program director at the U.S. National Science Foundation (NSF), which co-funds the program.
"This work significantly adds to our ability to infer ocean crust structure and composition, including predicting how ocean crust has 'aged' in an area," says Allan, "thereby giving us new tools for understanding ocean crust creation from Earth's mantle."
Atlantis Massif is a classic example of an oceanic core complex.
Because it's relatively young--formed within the last million years--it's an ideal place, scientists say, to study how the interplay between faulting, magmatism and seawater circulation influences the evolution of an OCC within the crust.
"Vast ocean basins cover most of the Earth, yet their crust is formed in a narrow zone," says Blackman. "We're studying that source zone to understand how rifting and magmatism work together to form a new plate."
The JOIDES Resolution first visited Atlantis Massif about seven years ago; the science team on that expedition measured properties in gabbro.
But they focused on a shallower section, where pervasive seawater circulation had weathered the rock and changed its physical properties.
For the current expedition, the team did not drill new holes.
Rather, they lowered instruments into a deep existing hole drilled on a previous expedition, and made measurements from inside the hole.
The new measurements, at depths between 800 and 1,400 meters (about 2,600-4,600 feet) below the seafloor, include only a few narrow zones that had been altered by seawater circulation and/or by fault slip deformation.
The rest of the measurements focused on gabbroic rocks that have remained unaltered thus far.
The properties measured in the narrow zones of altered rock differ from the background properties measured in the unaltered gabbroic rocks.
The team found small differences in temperature next to two sub-seafloor faults, which suggests a slow percolation of seawater within those zones.
There were also significant differences in the speed at which seismic waves travel through the altered vs. unaltered zones.
"The expedition was a great opportunity to ground-truth our recent seismic analysis," says Alistair Harding, also from the Scripps Institution of Oceanography and a co-chief scientist for Expedition 340T.
"It also provides vital baseline data for further seismic work aimed at understanding the formation and alteration of the massif."
The Integrated Ocean Drilling Program (IODP) is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring and monitoring the subseafloor.
The JOIDES Resolution is a scientific research vessel managed by the U.S. Implementing Organization of IODP (USIO). Texas A&M University, Lamont-Doherty Earth Observatory of Columbia University and the Consortium for Ocean Leadership comprise the USIO.
Two lead agencies support the IODP: the U.S. National Science Foundation and Japan's Ministry of Education, Culture, Sports, Science and Technology.
Additional program support comes from the European Consortium for Ocean Research Drilling, the Australia-New Zealand IODP Consortium, India's Ministry of Earth Sciences, the People's Republic of China's Ministry of Science and Technology, and the Korea Institute of Geoscience and Mineral Resources.
For more information on the expedition, please visit the IODP Expedition 340T Photos.
Cheryl Dybas | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine