(Press-News.org) The plate tectonic theory has been primarily developed in three stages. (1) From continental drift and seafloor spreading to oceanic subduction, laying a physical foundation of the plate tectonic theory. This was achieved by the recognitions that continents would be assembled to build a supercontinent Pangea with subsequent breakup to yield the present configuration, lithospheric plates buoyantly move on the asthenospheric mantle, and oceanic crust is subducted along trenches into the mantle. (2) From oceanic subduction to continental subduction and collision orogeny, with the first round of revolution to the plate tectonic theory due to the recognition of continental deep subduction to mantle depths. While deeply subducted oceanic crust was processed in the mantle and the returned to the surface by mafic magmatism, deeply subducted continental crust underwent ultrahigh pressure metamorphism at mantle depths and then exhumed to the surface as coherent mélanges. This provides a geodynamic framework of tectonic processes for continental accretion and assemblage through arc-continent and continent-continent collision orogenies. (3) From continental collision and marginal orogeny to intracontinental reworking, emphasizing the inheritance of orogenic materials in postcollisional stages. While continental collision results in continental accretion through marginal orogeny, intercontinental orogens are converted to intracontinental orogens. The deeply subducted continental crust is processed in subduction channel underlying the mantle wedge, with partial return to the surface. These have thrown new lights on developing the plate tectonic theory to encompass the continental tectonics, and thus directed further study toward solution to such questions as how thinning of the orogenic lithosphere and upwelling of the asthenospheric mantle affect postcollisional reworking of the intracontinental materials.
Finding of ultrahigh pressure index minerals such as coesite and diamond in metamorphic rocks of continental supercrustal protolith demonstrate that these rock were subducted to mantle depths for ultrahigh pressure metamorphism and then returned back to the surface. The recognition of continental deep subduction by Earth scientists has not only developed the plate tectonic theory, but also expanded the chemical geodynamics focusing on the recycling of crustal material. The study of ultrahigh pressure metamorphic rocks has made prominent progress in many aspects, achieving the recognitions that the processes of continental seduction and exhumation have caused not only various types of structural deformation and mineralogical reaction but also different extents of metamorphic dehydration and partial melting (Fig. 1). By means of studying various rocks in continental collision orogens, Earth scientists have set the geodynamic link between the subduction and exhumation of continental crust and the building of collision orogens. Furthermore, it is established that bulk melting of the deeply subducted continental crust gives rise to granitic rocks whereas partial melting of the subducting supracrustal rocks produces felsic melt that reacts with the overlying mantle wedge peridotite to generate fertile and enriched mantle sources for mafic magmatism after their storage in different periods.
A research team at School of Earth and Space Sciences in University of Science and Technology of China has taken the rocks of continental collision orogens as the object, and performed a great deal of investigations from field observations and laboratory analyses. This leads to a tectonic analysis of geological processes in continental subduction factory, which is published in Chinese Science Bulletin 2013 (26) in the title "Continental subduction channel processes: Plate interface interaction during continental collision". Leader of this team is Professor ZHENG Yongfei, Academician of the Chinese Academy of Sciences at Key Laboratory of Crust-Mantle Materials and Environments. Major participants are Prof. ZHAO Zifu and Dr. CHEN Yixiang. Earth scientists of China have made a series of prominent progresses in the forefront and hotspot field of subduction channel, and their studies have exemplified successful applications of new techniques, new methods and new ideas to development of the plate tectonic theory.
The recognition of continental deep subduction and ultrahigh pressure metamorphism has provided not only a turning point in developing the plate tectonic theory, but also an excellent opportunity to study the time and mechanism of reworking continental lithosphere. It is intriguing to ask the following questions: (1) how are crustal slices detached at different depths and exhumed during continental subduction? (2) how do physical mixing and chemical reaction proceed between the deeply subducted crust and the overlying mantle wedge? (3) how are energy exchange and matter transfer realized at the plate interface of subduction zone? Prof. Zheng said, to study subduction channel processes, to determine the physical mixing and chemical reaction between the deeply subducted crust and the overlying mantle wedge under ultrahigh pressure conditions, and to understand the interaction at the plate interface of continental subduction zone and its associated fluid action and element transport, are a key to unravel such mysteries of Earth.
INFORMATION:
Source article:
Zheng Y F, Zhao Z F, Chen Y X. Continental subduction channel processes: Plate interface interaction during continental collision. Chinese Science Bulletin, 2013, 58, doi: 10.1007/s11434-013-6066-x
Website: http://link.springer.com/article/10.1007/s11434-013-6066-x
Science China Press Co., Ltd. (SCP) is a scientific journal publishing company of the Chinese Academy of Sciences (CAS). For 50 years, SCP takes its mission to present to the world the best achievements by Chinese scientists on various fields of natural sciences researches.
http://www.scichina.com/
Subduction channel processes: New progress in plate tectonic theory
2013-09-16
ELSE PRESS RELEASES FROM THIS DATE:
Study shows projected climate change in West Africa not likely to worsen malaria situation
2013-09-16
CAMBRIDGE, MA -- As public-health officials continue to fight malaria in sub-Saharan Africa, researchers are trying to predict how climate change will impact the disease, which infected an estimated 219 million people in 2010 and is the fifth leading cause of death worldwide among children under age 5.
But projections of future malaria infection have been hampered by wide variation in rainfall predictions for the region and lack of a malaria-transmission model that adequately describes the effects of local rainfall on mosquitoes, which breed and mature in ephemeral pools ...
Diminishing fear vicariously by watching others
2013-09-16
Phobias — whether it's fear of spiders, clowns, or small spaces — are common and can be difficult to treat. New research suggests that watching someone else safely interact with the supposedly harmful object can help to extinguish these conditioned fear responses, and prevent them from resurfacing later on.
The research, published in Psychological Science, a journal of the Association for Psychological Science, indicates that this type of vicarious social learning may be more effective than direct personal experience in extinguishing fear responses.
"Information about ...
Sharp rise in opioid drugs prescribed for non-cancer pain, reports study in Medical Care
2013-09-16
Philadelphia, Pa. (September 13, 2013) – Prescribing of strong opioid medications for non-cancer pain in the United States has nearly doubled over the past decade, reports a study in the October issue of Medical Care, published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.
At the same time, prescribing of non-opioid pain relievers has been stable or declined, according to the new research by Dr G. Caleb Alexander of Johns Hopkins Bloomberg School of Public Health, Baltimore, and colleagues. Dr Alexander comments, "There is an epidemic of prescription ...
Several common differentially expressed genes between Kashin-Beck disease and Keshan disease
2013-09-15
Kashin-Beck disease (KBD) and Keshan disease (KD) are major endemic diseases in China. Postgraduate Xi Wang et al., under the guidance of Professor Xiong Guo from the Institute of Endemic Diseases of the Faculty of Public Health, Medicine College of Xi'an Jiaotong University, Key Laboratory of Environment and Gene Related Diseases in Ministry of Education, Key Laboratory of Trace Elements and Endemic Diseases of Health Ministry, set out to tackle these two endemic diseases. After several years of innovative research, they have made significant progress in determining the ...
Hypertension researcher encourages colleagues to expand their focus
2013-09-14
Augusta, Ga. – Dr. David Pollock has a simple message for fellow hypertension researchers: think endothelin.
In a country where better than 30 percent of adults have high blood pressure and 50-75 percent of those have salt-sensitive hypertension, he believes the powerful endothelin system, which helps the body eliminate salt, should not be essentially ignored.
However, the research and clinical world focus on suppressing a better-known system, which prompts the body to hold onto salt, said Pollock, Chief of the Section of Experimental Medicine at the Medical College ...
Sleep better, look better? New research says yes
2013-09-14
ANN ARBOR, Mich. — Getting treatment for a common sleep problem may do more than help you sleep better – it may help you look better over the long term, too, according to a new research study from the University of Michigan Health System and Michigan Technological University.
The findings aren't just about "looking sleepy" after a late night, or being bright-eyed after a good night's rest.
It's the first time researchers have shown specific improvement in facial appearance after at-home treatment for sleep apnea, a condition marked by snoring and breathing interruptions. ...
CPAP therapy provides beauty sleep for people with sleep apnea
2013-09-14
DARIEN, IL – A new study suggests that people with obstructive sleep apnea (OSA) are perceived to appear more alert, more youthful and more attractive after at least two months of continuous positive airway pressure (CPAP) therapy.
"This study showed that independent human raters – both medical personnel and members of the community – can perceive improved alertness, attractiveness, and youthfulness in the appearance of sleepy patients with obstructive sleep apnea, after they have been compliant with use of CPAP at home," said lead author and principal investigator Ronald ...
NASA sees Tropical Depression Gabrielle approaching eastern Canada
2013-09-14
Eastern Canada is now expecting some winds and rain from Tropical Depression Gabrielle as it transfers its energy to a cold front. NASA's Aqua satellite captured an infrared image of Gabrielle that showed some very cold cloud top temperatures and strong thunderstorms around its center.
The Atmospheric Infrared Sounder instrument called AIRS that flies aboard NASA's Aqua satellite captured an infrared image of Tropical Depression Gabrielle on Sept. 13 at 06:29 UTC/2:29 a.m. EDT. The AIRS image showed a circular area of very high, cold cloud top temperatures surrounding ...
Fish skin immune responses resemble those of the gut, Penn study finds
2013-09-14
Fish skin is unique in that it lacks keratin, the fibrous protein found in mammalian skin that provides a barrier against the environment. Instead, the epithelial cells of fish skin are in direct contact with the immediate environment: water. Similarly, the epithelial cells that line the gastrointestinal tract are also in direct contact with their immediate milieu.
"I like to think of fish as an open gut swimming," said J. Oriol Sunyer, a professor in the the Department of Pathobiology of the University of Pennsylvania's School of Veterinary Medicine.
Building on this ...
NASA sees system 93L become Tropical Storm Ingrid, now soaking eastern Mexico
2013-09-14
NASA and NOAA satellites have been tracking the progression of low pressure System 93L through the Caribbean Sea and into the southwestern Gulf of Mexico over a week's time, and it became Tropical Storm Ingrid mid-day on Sept. 13. NOAA's GOES-East satellite captured an image of Ingrid's center over the Bay of Campeche.
NOAA's GOES-East satellite sits in a fixed orbit and covers weather over the eastern U.S. and Atlantic Ocean, providing imagery continuously. NASA's GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Md. created an image of Tropical Storm ...