New understanding of feldspar elasticity may explain seismic discontinuity
A Florida State University geology researcher is going deep below the Earth's surface to understand how some of the most abundant minerals that comprise the Earth's crust change under pressure.
In a paper published today in Scientific Reports, Assistant Professor of Geology Mainak Mookherjee explores how feldspar, one of the most important minerals in the Earth's crust, changes under pressure. Typically, materials become stiffer when pressure is applied, but Mookherjee found that these pale-colored crystals actually become softer under extreme pressures.
"I am interested in exploring these materials at extreme conditions," Mookherjee said. "Feldspar is very abundant in the earth's crust so we need to understand its elastic property."
Mookherjee's work shows that at a depth of about 30 kilometers from the Earth's surface, feldspar decomposes to denser mineral phases such as pyroxene and quartz. The densification of feldspar could partially explain a scientific observation called seismic discontinuity across the Earth's crust and mantle.
This seismic discontinuity, also called Mohorovicic discontinuity, is the boundary between the Earth's crust and mantle. It was first observed in 1909 by a Croatian scientist Andrija Mohorovicic who realized that seismograms from shallow-focus earthquakes had two sets of waves -- one that followed a direct path near the Earth's surface, i.e., crust, and the other arriving faster and probably refracted from the underlying higher-velocity medium mantle.
"This is the first study of the elastic properties of feldspar at high pressure," Mookherjee said. "And it provides very new insight and a novel way of accounting for the sharp Mohorovicic discontinuity."
Scientists have been working since the late 1950s to understand the Mohorovicic discontinuity that separates the Earth's outermost layer -- oceanic and continental crust -- with the underlying mantle. Last year, researchers from the drill ship JOIDES Resolution made attempts to drill a bore hole across the discontinuity, but fell short. Further drilling attempts are planned for future.
"We care about the mineral structures in the deep Earth and how they transform to denser crystal structures within the Earth," Mookherjee said. "Through a thorough understanding of the atomic scale structures at extreme conditions and how they influence the properties of the Earth materials, it is possible to gain valuable insight into deep Earth dynamics."
Mookherjee did his work through computer simulations at the FSU Research Computing Center and facilities at Argonne National Laboratory. The research was funded by the National Science Foundation.
Other researchers contributing to the article are Dhenu Patel, a Tallahassee high school student who interned in Mookherjee's lab last summer; Olle Heinonen from Argonne National Laboratory; Anant Hariharan from Cornell University; Ketan Maheshwari from University of Pittsburgh; and David Mainprice from Université de Montpellier.
Kathleen Haughney | EurekAlert!
In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Power and Electrical Engineering
25.09.2017 | Health and Medicine
25.09.2017 | Physics and Astronomy