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  • richardmitnick 3:08 pm on February 12, 2022 Permalink | Reply
    Tags: "Mineral dating reveals new clues about important tectonic process", , , , , Obduction: the oceanic plate ends up atop the more buoyant continental plate instead of diving below it., , Subduction occurs when two tectonic plates collide and one is forced under the other.,   

    From The Pennsylvania State University : “Mineral dating reveals new clues about important tectonic process” 

    Penn State Bloc

    From The Pennsylvania State University

    February 08, 2022
    Matthew Carroll

    1
    Minerals are visible in rock samples from the coast of Oman. Scientists said these rocks may reveal new information about subduction, an important tectonic process on Earth. Credit: Joshua Garber / Penn State. Creative Commons.

    Ancient rocks on the coast of Oman that were once driven deep down toward Earth’s mantle may reveal new insights into subduction, an important tectonic process that fuels volcanoes and creates continents, according to an international team of scientists.

    “In a broad sense this work gives us a better understanding of why some subduction zones fail while others set up as long-term, steady-state systems,” said Joshua Garber, assistant research professor of geosciences at Penn State.

    Subduction occurs when two tectonic plates collide and one is forced under the other. Where oceanic and continental plates meet, the denser oceanic plates normally subduct and descend into the mantle, the scientists said.

    Occasionally, oceanic plates move on top, or obduct, forcing continental plates down toward the mantle instead. But the buoyancy of the continental crust can cause the subduction to fail, carrying the material back toward the surface along with slabs of oceanic crust and upper mantle called ophiolites, the scientists said.

    “The Samail Ophiolite on the Arabian Peninsula is one of the largest and best exposed examples on the surface of the Earth,” Garber said. “It’s one of the best studied, but there have been disagreements about how and when the subduction occurred.”

    The team, led by Penn State scientists, investigated the timing of the subduction using nearby rocks from the Saih Hatat formation in Oman, which was subducted under the Samail Ophiolite, according to the researchers.

    Heat and pressure from the process created garnet, zircon and rutile crystals in a key suite of highly metamorphosed rocks that saw the most extreme conditions during subduction. Using state-of-the-art dating techniques, including measuring isotopic dates and trace elements, the scientists determined these minerals all formed at roughly the same time 81 to 77 million years ago.

    “What’s interesting about this is that they were all dated by slightly different methods, but they all gave us essentially the same results,” Garber said. “This tells us that all the minerals in the rocks have a coherent story. They all record the same metamorphic episode at the same time.”

    The findings, published in the Journal of Geophysical Research: Solid Earth, dispute previous results that estimated the event began 110 million years ago and happened in separate phases, the scientists said.

    “What our findings suggest is that this continental material was not subducted deep into the mantle a long time before the ophiolite formed as previously thought,” Garber said. “Our data supports a nice sequence of events that happened in a tighter window and that makes more geological sense.”

    The scientists said the subduction of the continental margin occurred after the obduction of the Samail Ophiolite. The most deeply subducted continental material was likely anchored to more dense rocks, and when this anchor broke, the buoyant continental rocks exhumed, first quickly, and then slowly during a lengthy residence in the lower to middle crust. It eventually become exposed in tectonic windows through the ophiolite.

    “Subduction is a really big part of plate tectonics on Earth,” Garber said. “It’s the major recycling mechanism for surface material to the deeper mantle, so understanding how they eventually evolve into stable subduction zones or how they end very quickly is of great interest. I think here we’ve nailed down why this subduction zone ended and the sequence of events that came with it.”

    Also contributing to this work from Penn State was Andrew Smye, assistant professor of geosciences.

    Matthew Rioux, assistant teaching professor, Bradley Hacker, professor emeritus, and Andrew Kylander-Clark, senior development engineer, at the University of California- Santa Barbara; Michael Searle, professor at The University of Oxford (UK); Jeff Vervoort, professor at The Washington State University (US); and Clare Warren, professor at The Open University(UK) also contributed.

    See the full article here .

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    Penn State Campus

    The The Pennsylvania State University is a public state-related land-grant research university with campuses and facilities throughout Pennsylvania. Founded in 1855 as the Farmers’ High School of Pennsylvania, Penn State became the state’s only land-grant university in 1863. Today, Penn State is a major research university which conducts teaching, research, and public service. Its instructional mission includes undergraduate, graduate, professional and continuing education offered through resident instruction and online delivery. In addition to its land-grant designation, it also participates in the sea-grant, space-grant, and sun-grant research consortia; it is one of only four such universities (along with Cornell University, Oregon State University, and University of Hawaiʻi at Mānoa). Its University Park campus, which is the largest and serves as the administrative hub, lies within the Borough of State College and College Township. It has two law schools: Penn State Law, on the school’s University Park campus, and Dickinson Law, in Carlisle. The College of Medicine is in Hershey. Penn State is one university that is geographically distributed throughout Pennsylvania. There are 19 commonwealth campuses and 5 special mission campuses located across the state. The University Park campus has been labeled one of the “Public Ivies,” a publicly funded university considered as providing a quality of education comparable to those of the Ivy League.

    Annual enrollment at the University Park campus totals more than 46,800 graduate and undergraduate students, making it one of the largest universities in the United States. It has the world’s largest dues-paying alumni association. The university offers more than 160 majors among all its campuses.

    Annually, the university hosts the Penn State IFC/Panhellenic Dance Marathon (THON), which is the world’s largest student-run philanthropy. This event is held at the Bryce Jordan Center on the University Park campus. The university’s athletics teams compete in Division I of the NCAA and are collectively known as the Penn State Nittany Lions, competing in the Big Ten Conference for most sports. Penn State students, alumni, faculty and coaches have received a total of 54 Olympic medals.

    Early years

    The school was sponsored by the Pennsylvania State Agricultural Society and founded as a degree-granting institution on February 22, 1855, by Pennsylvania’s state legislature as the Farmers’ High School of Pennsylvania. The use of “college” or “university” was avoided because of local prejudice against such institutions as being impractical in their courses of study. Centre County, Pennsylvania, became the home of the new school when James Irvin of Bellefonte, Pennsylvania, donated 200 acres (0.8 km2) of land – the first of 10,101 acres (41 km^2) the school would eventually acquire. In 1862, the school’s name was changed to the Agricultural College of Pennsylvania, and with the passage of the Morrill Land-Grant Acts, Pennsylvania selected the school in 1863 to be the state’s sole land-grant college. The school’s name changed to the Pennsylvania State College in 1874; enrollment fell to 64 undergraduates the following year as the school tried to balance purely agricultural studies with a more classic education.

    George W. Atherton became president of the school in 1882, and broadened the curriculum. Shortly after he introduced engineering studies, Penn State became one of the ten largest engineering schools in the nation. Atherton also expanded the liberal arts and agriculture programs, for which the school began receiving regular appropriations from the state in 1887. A major road in State College has been named in Atherton’s honor. Additionally, Penn State’s Atherton Hall, a well-furnished and centrally located residence hall, is named not after George Atherton himself, but after his wife, Frances Washburn Atherton. His grave is in front of Schwab Auditorium near Old Main, marked by an engraved marble block in front of his statue.

    Early 20th century

    In the years that followed, Penn State grew significantly, becoming the state’s largest grantor of baccalaureate degrees and reaching an enrollment of 5,000 in 1936. Around that time, a system of commonwealth campuses was started by President Ralph Dorn Hetzel to provide an alternative for Depression-era students who were economically unable to leave home to attend college.

    In 1953, President Milton S. Eisenhower, brother of then-U.S. President Dwight D. Eisenhower, sought and won permission to elevate the school to university status as The Pennsylvania State University. Under his successor Eric A. Walker (1956–1970), the university acquired hundreds of acres of surrounding land, and enrollment nearly tripled. In addition, in 1967, the Penn State Milton S. Hershey Medical Center, a college of medicine and hospital, was established in Hershey with a $50 million gift from the Hershey Trust Company.

    Modern era

    In the 1970s, the university became a state-related institution. As such, it now belongs to the Commonwealth System of Higher Education. In 1975, the lyrics in Penn State’s alma mater song were revised to be gender-neutral in honor of International Women’s Year; the revised lyrics were taken from the posthumously-published autobiography of the writer of the original lyrics, Fred Lewis Pattee, and Professor Patricia Farrell acted as a spokesperson for those who wanted the change.

    In 1989, the Pennsylvania College of Technology in Williamsport joined ranks with the university, and in 2000, so did the Dickinson School of Law. The university is now the largest in Pennsylvania. To offset the lack of funding due to the limited growth in state appropriations to Penn State, the university has concentrated its efforts on philanthropy.

    Research

    Penn State is classified among “R1: Doctoral Universities – Very high research activity”. Over 10,000 students are enrolled in the university’s graduate school (including the law and medical schools), and over 70,000 degrees have been awarded since the school was founded in 1922.

    Penn State’s research and development expenditure has been on the rise in recent years. For fiscal year 2013, according to institutional rankings of total research expenditures for science and engineering released by the National Science Foundation (US), Penn State stood second in the nation, behind only Johns Hopkins University (US) and tied with the Massachusetts Institute of Technology (US), in the number of fields in which it is ranked in the top ten. Overall, Penn State ranked 17th nationally in total research expenditures across the board. In 12 individual fields, however, the university achieved rankings in the top ten nationally. The fields and sub-fields in which Penn State ranked in the top ten are materials (1st), psychology (2nd), mechanical engineering (3rd), sociology (3rd), electrical engineering (4th), total engineering (5th), aerospace engineering (8th), computer science (8th), agricultural sciences (8th), civil engineering (9th), atmospheric sciences (9th), and earth sciences (9th). Moreover, in eleven of these fields, the university has repeated top-ten status every year since at least 2008. For fiscal year 2011, the National Science Foundation reported that Penn State had spent $794.846 million on R&D and ranked 15th among U.S. universities and colleges in R&D spending.

    For the 2008–2009 fiscal year, Penn State was ranked ninth among U.S. universities by the National Science Foundation, with $753 million in research and development spending for science and engineering. During the 2015–2016 fiscal year, Penn State received $836 million in research expenditures.

    The Applied Research Lab (ARL), located near the University Park campus, has been a research partner with the Department of Defense (US) since 1945 and conducts research primarily in support of the United States Navy. It is the largest component of Penn State’s research efforts statewide, with over 1,000 researchers and other staff members.

    The Materials Research Institute was created to coordinate the highly diverse and growing materials activities across Penn State’s University Park campus. With more than 200 faculty in 15 departments, 4 colleges, and 2 Department of Defense research laboratories, MRI was designed to break down the academic walls that traditionally divide disciplines and enable faculty to collaborate across departmental and even college boundaries. MRI has become a model for this interdisciplinary approach to research, both within and outside the university. Dr. Richard E. Tressler was an international leader in the development of high-temperature materials. He pioneered high-temperature fiber testing and use, advanced instrumentation and test methodologies for thermostructural materials, and design and performance verification of ceramics and composites in high-temperature aerospace, industrial, and energy applications. He was founding director of the Center for Advanced Materials (CAM), which supported many faculty and students from the College of Earth and Mineral Science, the Eberly College of Science, the College of Engineering, the Materials Research Laboratory and the Applied Research Laboratories at Penn State on high-temperature materials. His vision for Interdisciplinary research played a key role in creating the Materials Research Institute, and the establishment of Penn State as an acknowledged leader among major universities in materials education and research.

    The university was one of the founding members of the Worldwide Universities Network (WUN), a partnership that includes 17 research-led universities in the United States, Asia, and Europe. The network provides funding, facilitates collaboration between universities, and coordinates exchanges of faculty members and graduate students among institutions. Former Penn State president Graham Spanier is a former vice-chair of the WUN.

    The Pennsylvania State University Libraries were ranked 14th among research libraries in North America in the 2003–2004 survey released by The Chronicle of Higher Education. The university’s library system began with a 1,500-book library in Old Main. In 2009, its holdings had grown to 5.2 million volumes, in addition to 500,000 maps, five million microforms, and 180,000 films and videos.

    The university’s College of Information Sciences and Technology is the home of CiteSeerX, an open-access repository and search engine for scholarly publications. The university is also the host to the Radiation Science & Engineering Center, which houses the oldest operating university research reactor. Additionally, University Park houses the Graduate Program in Acoustics, the only freestanding acoustics program in the United States. The university also houses the Center for Medieval Studies, a program that was founded to research and study the European Middle Ages, and the Center for the Study of Higher Education (CSHE), one of the first centers established to research postsecondary education.

     
  • richardmitnick 3:30 pm on January 23, 2022 Permalink | Reply
    Tags: "Radiometric Dating Sheds Light on Tectonic Debate", , , , , Obduction-ophiolites-slices of oceanic crust and mantle atop a continental plate—offer uncommon opportunities to view seafloor geology from the comfort of land., Obduction: the oceanic plate ends up atop the more buoyant continental plate instead of diving below it., Subduction: the denser oceanic plate is pushed below the continental plate., The episode occurred approximately 81–77 million years ago when the Arabian continental plate subducted to the northeast below the Samail Ophiolite., The Samail Ophiolite (Oman–United Arab Emirates) is frequently studied as a model of obduction because of its well-exposed and well-studied geology., This conclusion refutes previously published estimates that continental subduction in Oman started 110 million years ago and may have occurred over two distinct episodes.   

    From Eos : “Radiometric Dating Sheds Light on Tectonic Debate” 

    From AGU
    Eos news bloc

    From Eos

    21 January 2022
    Aaron Sidder

    The emplacement of the Samail Ophiolite in Oman has been a source of disagreement among geologists. New state-of-the-art research offers a fresh perspective on its timing and geometry.

    1

    At the far edges of continents, where the continental shelf transitions into the deep ocean, continental and oceanic plates come face to face. At many of these margins, the denser oceanic plate is pushed below the continental plate in a process called subduction. However, in some cases, known as obduction, the oceanic plate ends up atop the more buoyant continental plate instead of diving below it.

    Obduction zones are unique because they foster the recycling of surface continental material to the deep mantle, which happens infrequently, and they have formed almost exclusively in the past billion years of Earth’s history. The resulting ophiolites—slices of oceanic crust and mantle atop a continental plate—offer uncommon opportunities to view seafloor geology from the comfort of land.

    The Samail Ophiolite (Oman–United Arab Emirates), in the northeastern corner of the Arabian Peninsula, is frequently studied as a model of obduction because of its well-exposed and well-studied geology. However, geologists disagree about the timing and geometry of the continental subduction that led to the final emplacement of the ophiolite. Several tectonic models offer hypotheses on the ophiolite’s obduction but differ in their conclusions.

    In a new study, Garber et al. [JGR: Solid Earth] sought to clarify the timing of the obduction episode in Oman. The authors sampled several different rocks from As Sifah, an Omani beach with an outcrop of high-grade continental metamorphic rocks subducted beneath the ophiolite. The studied As Sifah rocks reflect a diverse range of lithologies that all experienced the same metamorphic evolution, the authors say. Samarium-neodymium (Sm-Nd) and uranium-lead (U-Pb) radiometric dating on the garnet, zircon, and rutile crystals in the rocks helped determine the age of the subduction event.

    The findings provide new constraints on the timing of the obduction of the ophiolitic rocks in Oman. The results indicate that the episode occurred approximately 81–77 million years ago when the Arabian continental plate subducted to the northeast below the Samail Ophiolite. The subduction of the Arabian plate to mantle depths occurred at rates similar to those of other small continental subduction events, and the tectonic evolution appears to be similar to that of other ophiolite formations.

    This conclusion refutes previously published estimates that continental subduction in Oman started 110 million years ago and may have occurred over two distinct episodes. Overall, the study provides a meaningful contribution to a long-debated geologic question.

    See the full article here .

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    Please help promote STEM in your local schools.

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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

     
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