Featured Research

from universities, journals, and other organizations

Diffusive Infiltration May Explain Strange Behavior In Magma

Date:
March 8, 2000
Source:
University Of Illinois At Urbana-Champaign
Summary:
Recent experiments by a University of Illinois researcher have shed light on how glassy materials -- melts that have been quickly frozen -- are formed in exotic chunks of mantle called xenoliths, and how ascending magmas in the mantle can affect the lava output at Earth's surface through chemical, rather than thermal, reactions.

CHAMPAIGN, Ill. -- Recent experiments by a University of Illinois researcher have shed light on how glassy materials -- melts that have been quickly frozen -- are formed in exotic chunks of mantle called xenoliths, and how ascending magmas in the mantle can affect the lava output at Earth's surface through chemical, rather than thermal, reactions.

Related Articles


"Sodium in ascending magma can quickly diffuse into the surrounding mantle at lower pressures, fundamentally altering the process by which the mantle melts," said Craig Lundstrom, a UI professor of geology. "Sodium infiltration can account for the creation of silica-rich glasses in xenoliths, and for the anomalous mineralogical composition of mantle found beneath mid-ocean ridges."

Xenoliths are pieces of mantle that get ripped off and are carried to the surface during a volcanic eruption. Within the xenoliths are former melts -- now found as glasses -- which differ radically from the magma that typically emanates from the mantle, basalt. The glasses reside between the two primary silicate minerals of the uppermost mantle, olivine and orthopyroxene.

"Xenoliths have been found in alkali-rich magmas from ocean island and continental volcanic settings worldwide," Lundstrom said. "But the origin of the glassy regions, and why they have peculiar elemental compositions, have been poorly understood."

To study the potential chemical interaction, Lundstrom first synthesized samples of magma found deep in the mantle and of mantle lying much closer to the surface in a high-temperature, high-pressure apparatus. He then placed these samples together in the same apparatus and "cooked" them for 10 minutes. After cooling the samples, he separated them and analyzed their mineralogical compositions.

"We generally think of magmas as moving very slowly and geological processes as occurring over hundreds of thousands of years, so it's really amazing how much happens in just 10 minutes," Lundstrom said. "In that brief time, considerable migration occurred as sodium diffused through the melt between mineral grains, significantly altering the composition of the material."

In a positive-feedback loop, the infiltrating sodium causes orthopyroxene to break down into olivine plus the peculiar composition melt. This melt, in turn, causes even more sodium to be pulled in. The increase in olivine and the decrease in orthopyroxene within the diffusively infiltrated piece of mantle may explain another perplexing observation: the anomalous ratio of these minerals found in the shallow mantle region beneath mid-ocean ridges.

"We tend to think of volcanic edifices -- like the Hawaiian Islands -- as resulting from hot spots in the mantle," Lundstrom said. "But these results show that sodium-rich, silica-poor magma can cause the surrounding mantle to melt through a chemical reaction without invoking huge quantities of heat."

The diffusion process could also be important to melting the cold lithospheric "plates" that cover the earth, said Lundstrom, who reported his findings in the Feb. 3 issue of the journal Nature.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "Diffusive Infiltration May Explain Strange Behavior In Magma." ScienceDaily. ScienceDaily, 8 March 2000. <www.sciencedaily.com/releases/2000/03/000307090435.htm>.
University Of Illinois At Urbana-Champaign. (2000, March 8). Diffusive Infiltration May Explain Strange Behavior In Magma. ScienceDaily. Retrieved January 31, 2015 from www.sciencedaily.com/releases/2000/03/000307090435.htm
University Of Illinois At Urbana-Champaign. "Diffusive Infiltration May Explain Strange Behavior In Magma." ScienceDaily. www.sciencedaily.com/releases/2000/03/000307090435.htm (accessed January 31, 2015).

Share This


More From ScienceDaily



More Earth & Climate News

Saturday, January 31, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Rare Clouds Fill Grand Canyon

Raw: Rare Clouds Fill Grand Canyon

AP (Jan. 29, 2015) For the second time in two months, a rare weather phenomenon filled the Grand Canyon with thick clouds just below the rim on Wednesday. (Jan. 29) Video provided by AP
Powered by NewsLook.com
Senate Passes Bill for Keystone XL Pipeline

Senate Passes Bill for Keystone XL Pipeline

AP (Jan. 29, 2015) The Republican-controlled Senate has passed a bipartisan bill approving construction of the Keystone XL oil pipeline. (Jan. 29) Video provided by AP
Powered by NewsLook.com
"Cloud Inversion" In Grand Canyon

"Cloud Inversion" In Grand Canyon

Reuters - US Online Video (Jan. 29, 2015) Time lapse video captures a blanket of clouds amassing in the Grand Canyon -- the result of a rare meteorological process called "cloud inversion." Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Why Researchers Say We Should Cut Back On Biofuels

Why Researchers Say We Should Cut Back On Biofuels

Newsy (Jan. 29, 2015) Biofuels aren&apos;t the best alternative to fossil fuels, according to a new report. In fact, they&apos;re quite a bad one. Video provided by Newsy
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