(Press-News.org) Contact information: Dr. Tim E. Johnson
tjohnson@uni-mainz.de
49-613-139-26825
Johannes Gutenberg Universitaet Mainz
Earth's crust was unstable in the Archean eon and dripped down into the mantle
Model calculations indicate that the extreme density of the base of the thickened primary crust caused it to subside into the Earth's mantle
Earth's mantle temperatures during the Archean eon, which commenced some 4 billion years ago, were significantly higher than they are today. According to recent model calculations, the Archean crust that formed under these conditions was so dense that large portions of it were recycled back into the mantle. This is the conclusion reached by Dr. Tim Johnson who is currently studying the evolution of the Earth's crust as a member of the research team led by Professor Richard White of the Institute of Geosciences at Johannes Gutenberg University Mainz (JGU). According to the calculations, this dense primary crust would have descended vertically in drip form. In contrast, the movements of today's tectonic plates involve largely lateral movements with oceanic lithosphere recycled in subduction zones. The findings add to our understanding of how cratons and plate tectonics, and thus also the Earth's current continents, came into being.
Because mantle temperatures were higher during the Archean eon, the Earth's primary crust that formed at the time must have been very thick and also very rich in magnesium. However, as Johnson and his co-authors explain in their article recently published in Nature Geoscience, very little of this original crust is preserved, indicating that most must have been recycled into the Earth's mantle. Moreover, the Archean crust that has survived in some areas such as, for example, Northwest Scotland and Greenland, is largely made of tonalite–trondhjemite–granodiorite complexes and these are likely to have originated from a hydrated, low-magnesium basalt source. The conclusion is that these pieces of crust cannot be the direct products of an originally magnesium-rich primary crust. These TTG complexes are among the oldest features of our Earth's crust. They are most commonly present in cratons, the oldest and most stable cores of the current continents.
With the help of thermodynamic calculations, Dr. Tim Johnson and his collaborators at the US-American universities of Maryland, Southern California, and Yale have established that the mineral assemblages that formed at the base of a 45-kilometer-thick magnesium-rich crust were denser than the underlying mantle layer. In order to better explore the physics of this process, Professor Boris Kaus of the Geophysics work group at Mainz University developed new computer models that simulate the conditions when the Earth was still relatively young and take into account Johnson's calculations.
These geodynamic computer models show that the base of a magmatically over-thickened and magnesium-rich crust would have been gravitationally unstable at mantle temperatures greater than 1,500 to 1,550 degrees Celsius and this would have caused it to sink in a process called 'delamination'. The dense crust would have dripped down into the mantle, triggering a return flow of mantle material from the asthenosphere that would have melted to form new primary crust. Continued melting of over-thickened and dripping magnesium-rich crust, combined with fractionation of primary magmas, may have produced the hydrated magnesium-poor basalts necessary to provide a source of the tonalite–trondhjemite–granodiorite complexes. The dense residues of these processes, which would have a high content of mafic minerals, must now reside in the mantle.
###
Image:
http://www.uni-mainz.de/bilder_presse/09_geowissenschaften_archaikum.jpg
Computer simulation of the processes in the Earth's mantle
Ill.: Institute of Geosciences, JGU
Publication:
Tim E. Johnson et al.
Delamination and recycling of Archaean crust caused by gravitational instabilities
Nature Geoscience 7, 47–52. Published online 1 December 2013
DOI: 10.1038/ngeo2019
Contact:
Dr. Tim E. Johnson
Metamorphic Geology division
Institute of Geosciences
Johannes Gutenberg University Mainz
D 55099 Mainz, GERMANY
phone +49 6131 39-26825
e-mail: tjohnson@uni-mainz.de
http://www.geowiss.uni-mainz.de/843_ENG_HTML.php
Professor Dr. Boris Kaus
Geophysics division
Institute of Geosciences
Johannes Gutenberg University Mainz
D 55099 Mainz, GERMANY
phone +49 6131 39-24527
e-mail: kaus@uni-mainz.de
http://www.geowiss.uni-mainz.de/934_ENG_HTML.php
Related links:
http://www.geowiss.uni-mainz.de/360_DEU_HTML.php (Geophysics and Geodynamics at Mainz University)
Earth's crust was unstable in the Archean eon and dripped down into the mantle
Model calculations indicate that the extreme density of the base of the thickened primary crust caused it to subside into the Earth's mantle
2013-12-30
ELSE PRESS RELEASES FROM THIS DATE:
Hebrew University researchers reach breakthrough on understanding persistent bacteria
2013-12-30
Hebrew University researchers reach breakthrough on understanding persistent bacteria
Work can lead to improved therapies in the future
Jerusalem, Dec. 29, 2013 – The mechanism by which some bacteria are able to survive antibacterial treatment ...
Nicotine exploits COPI to foster addiction
2013-12-30
Nicotine exploits COPI to foster addiction
New innovation by NUS researchers enhances information storage in electronics
2013-12-30
New innovation by NUS researchers enhances information storage in electronics
Innovative Magnetoresistive Random Access Memory technology enables bigger and longer lasting memory in electronic systems
A team of researchers from the Department of Electrical & ...
Meloidogyne mali: A new invasive plant parasitic nematode in Europe
2013-12-30
Meloidogyne mali: A new invasive plant parasitic nematode in Europe
Following its recent synonymisation with Meloidogyne ulmi, a species known to parasitize elm trees in Europe, it has become clear that M. mali has been in the Netherlands for more than fifty years.
Evidences ...
Alcohol leaves its mark on youngsters' DNA
2013-12-30
Alcohol leaves its mark on youngsters' DNA
A preliminary study led by a UPV/EHU-University of the Basque Country researcher in collaboration with the Autonomous University of Nayarit, in Mexico, indicates that weekend alcohol consumption may affect DNA
This news release ...
Researchers say fructose does not impact emerging indicator for cardiovascular disease
2013-12-30
Researchers say fructose does not impact emerging indicator for cardiovascular disease
However, overconsumption of calories from fructose can have substantial adverse effects on health
TORONTO, Dec. 30, 2013—Fructose, the sugar often blamed for the obesity ...
Testosterone in male songbirds may enhance desire to sing but not song quality
2013-12-30
Testosterone in male songbirds may enhance desire to sing but not song quality
For the male canary, the ability to sing a pitch-perfect song is critical to wooing female canaries. As the seasons change, so does song quality and frequency. The hormone testosterone ...
Study identifies potential new strategy to improve odds of corneal transplant acceptance
2013-12-30
Study identifies potential new strategy to improve odds of corneal transplant acceptance
DALLAS – Dec. 30, 2013 – For the estimated 10 percent of patients whose bodies reject a corneal transplant, the odds of a second transplant succeeding ...
Plan to delist gray wolf endangers other threatened species, researchers find
2013-12-30
Plan to delist gray wolf endangers other threatened species, researchers find
Scientists say proposal to end wolf protection across US disregards science, history, threats
COLUMBUS, Ohio – The federal government's proposal to discontinue protection for the gray ...
Tell me your barcode, and I will tell you what palm you are
2013-12-30
Tell me your barcode, and I will tell you what palm you are
Reliable and cost-effective species recognition is the dream of many scientists, and has important applications. While the use of morphological features is often uncertain, and can lead to misidentification, species ...
LAST 30 PRESS RELEASES:
MSU team develops scalable climate solutions for agricultural carbon markets
Playing an instrument may protect against cognitive aging
UNM study finds link between Grand Canyon landslide and Meteor Crater impact
Ultra-hot Jupiter’s death spiral could reveal stellar secrets
You only get one brain! The best helmet material for protecting your noggin
Neurodegeneration and stroke after GLP-1RAs in diabetes and obesity
Pediatric COVID-19 hospitalization trends by race and ethnicity, 2020-2023
Research spotlight: New genetic roadmap offers insights into obesity and diabetes
Fred Hutch leads new Vanguard Study for Cancer Screening Research Network
‘Mismatched’ transplants now safe, effective for blood cancer patients, study finds
New research helps narrow down uncertainties in near-term precipitation projections for the Asian Water Tower
AI tool accurately detects tumor location on breast MRI
Researchers use OCT imaging to uncover how the fallopian tube transports embryos
PolyU secures RGC theme-based research scheme funding to develop cost-effective and sustainable Co-GenAI model
Van Andel Institute scientists develop technique for high-resolution single cell epigenetic analysis
The Lundquist Institute wins multi-year NIH grant exceeding $11 million to transform diagnosis and treatment of deadly mucormycosis
Review suggests ending adult boosters for tetanus, diphtheria
ESMT Berlin welcomes Rebecca Schaumberg to faculty
Blocking a little-known protein may offer new hope for devastating lung disease
Medieval medicine was smarter than you think – and weirdly similar to TikTok trends
FAU receives NIH grant to investigate amphetamine addiction
Realizing on-site carbon nanotube photo-thermoelectric imaging
Most of us love memes. But are they a form of comics?
Novel biosensor allows real-time monitoring of sucrose uptake in plants
Korea University researchers reveal revealing how WEE1 drives cancer resistance to immunotherapy
Pusan National University researchers develop breakthrough deep learning model that enhances handheld 3D medical imaging
SLAS Discovery and SLAS Technology demonstrate research impact with 2024 impact factors
Disease-causing bacteria can deal with stink as long as they get a meal
Mapping the metabolism of blood stem cells
UK air quality improved since 2015 but targets still missed
[Press-News.org] Earth's crust was unstable in the Archean eon and dripped down into the mantleModel calculations indicate that the extreme density of the base of the thickened primary crust caused it to subside into the Earth's mantle