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Ophiolites:Identification and tectonic significance in space and time

Geoscience Frontiers 2023年第6期14卷 380-385页

作者： Kent C.Condie robert j.stern Department of Earth&Environmental Science New Mexico Institute of Mining and TechnologySocorroNM 87801USA Geosciences Department University of Texas at DallasRichardsonTX 75080USA

Ophiolites are fragments of oceanic lithosphere that are produced at spreading centers at ocean ridges,back arc basins,or forearcs during subduction initiation,and are key indicators of plate tectonics.Although it is widely agreed that ophiolites are remnants of oceanic crust and associated depleted mantle preserved in orogens,the recognition of ophiolites and their tectonic significance is still a topic of discussion and disagreement.We propose that ophiolites can be recognized in the geologic record by some combination of genetically related pillow basalt,layered gabbro,sheeted dykes,podiform chromite,harzburgite or/and dunite.Mafic igneous rocks have either ocean-ridge basalt or immature oceanic arc basalt chemical compositions.Using a scoring system of 1–11 for ophiolite confidence level,scores of8 are considered confident,6–8 probable,andstern China at 2550 Ma,and the oldest well documented sheeted dykes occur in the jormua and Purtuniq ophiolites at 2000–1950 Ma.Ophiolites do not become geographically widespread until after 900 Ma,and most ophiolites of all ages formed in a forearc(subduction initiation)tectonic setting.If ophiolite production requires plate tectonics,subduction must have begun at least locally by 2700 Ma but did not become widespread until after 2000 Ma.The abundance of ophiolites after 900 Ma may reflect better preservation of subduction-related ophiolites,or to an increasing global network of interconnected plates.Ophiolite frequency peaks in the geologic record partially reflect geographic regions where ophiolites have been extensively studied rather than monitoring the production rate of ophiolites,but the scarcity of>900 Ma ophiolites is probably real.

关键词： Ophiolite Plate tectonics Subduction initiation Forearc Ocean ridge Tectonic setting Supercontinent

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高度难熔源区在俯冲起始形成伊豆-小笠原-马里亚纳岛弧中的意义

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Science Bulletin 2022年第2期67卷 119-121,M0003页

作者： Scott A.Whattam robert j.stern Department of Geosciences King Fahd University of Petroleum and MineralsDhahran 31261Saudi Arabia Department of Geosciences University of Texas at DallasRichardsonTX 75083-0688USA

The ascendent theory that unifies the Earth Sciences is Plate Tectonics, a regime which is unique to Earth. Other convectively active, solid silicate bodies of our Solar System (Venus, Mars, and Io) are encased in a single deforming "lid";on these, multiple plates and hence plate motions do not exist [1]. As Earth’s tectonic plates are driven by the sinking of old and cold oceanic lithosphere at subduction zones, understanding how new subduction zones originate is vital for a complete plate tectonic theory. Proposed mechanisms of subduction initiation (SI) are controversial but can be either spontaneous, i.e., caused by forces originating at the SI site, or induced by ongoing plate motions [2].

关键词： Earth tectonic Solar

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The Orosirian(1800–2050 Ma)plate tectonic episode:Key for reconstructing the Proterozoic tectonic record

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Geoscience Frontiers 2023年第3期14卷 1-9页

作者： robert j.stern Geosciences Dept. U Texas at DallasRichardsonTX 75083-0688United States

Eight lines of evidence indicate that the Orosirian Period in mid-Paleoproterozoic time was characterized by plate tectonics:ophiolites,low T/P metamorphism including eclogites,passive margin formation,tall mountains,paleomagnetic constraints,ore deposits,abundant S-type granites,and seismic images of paleo-subduction zones.This plate tectonic episode occurred about 1 billion years earlier than the present plate tectonic episode began in Neoproterozoic time.The two plate tectonic episodes bracket the‘Boring Billion’,which may have been a protracted single lid tectonic episode that began when the supercontinent Nuna or Columbia formed.Recognition of multiple lines of evidence for Orosirian plate tectonics demonstrates that Earth’s tectonic style can be reconstructed with some confidence back to at least Early Paleoproterozoic time,and thus the absence of compelling evidence for Mesoproterozoic plate tectonics is not obvious due to poor preservation.A tectono-magmatic lull2.3 Ga suggests an earlier episode of single lid tectonics.Evidence for two episodes of plate tectonics and two episodes of single lid tectonics indicates that Earth switched between single lid and plate tectonics multiple times during the last 2.4 Ga.

关键词： Plate tectonics Single lid tectonics Urey ratio Paleoproterozoic

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Is plate tectonics needed to evolve technological species on exoplanets?

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Geoscience Frontiers 2016年第4期7卷 573-580页

作者： robert j.stern Geoscience Department University of Texas at Dallas

As we continue searching for exoplanets, we wonder if life and technological species capable of communicating with us exists on any of them. As geoscientists, we can also wonder how important is the presence or absence of plate tectonics for the evolution of technological species. This essay considers this question, focusing on tectonically active roclw （silicate） planets, like Earth, Venus, and Mars. The development of technological species on Earth provides key insights for understanding evolution on exoplanets, including the likely role that plate tectonics may play. An Earth-sized silicate planet is likely to experience several tectonic styles over its lifetime, as it cools and its lithosphere thickens, strengthens, and becomes denser. These include magma ocean, various styles of stagnant lid, and perhaps plate tectonics. Abundant liquid water favors both life and plate tectonics. Ocean is required for early evolution of diverse single-celled organisms, then colonies of cells which specialized further to form guts, ap- pendages, and sensory organisms up to the complexity of fish （central nervous system, appendages, eyes）. Large expanses of dry land also begin in the ocean, today produced above subduction zones in juvenile arcs and by their coalescence to form continents, although it is not clear that plate tectonics was required to create continental crust on Earth. Dry land of continents is required for further evolution of technological species, where modification of appendages for grasping and manipulating, and improve- ment of eyes and central nervous system could be perfected. These bioassets allowed intelligent crea- tures to examine the night sky and wonder, the beginning of abstract thinking, including religion and science. Technology arises from the exigencies of daily living such as tool-making, agriculture, clothing, and weapons, but the pace of innovation accelerates once it is allied with science. Finally, the importance of plate tectonics for developing a technological species is examined via a

关键词： Plate tectonics Exoplanets Planetary science Intelligent life

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Early Cretaceous subduction initiation beneath southern Tibet caused the northward flight of India

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Geoscience Frontiers 2020年第4期11卷 1123-1131页

作者： Haoyu Hu robert j.stern Geosciences Department University of Texas at DallasRichardsonTX75083-0688USA

Collision between the Indian and Eurasian plates formed the ~2500 km long Yarlung Zangbo Suture Zone and produced the Himalaya mountains and Tibetan plateau.Here we offer a new explanation for tectonic events leading to this collision:that the northward flight of India was caused by an Early Cretaceous episode of subduction initiation on the southern margin of Tibet.Compiled data for ophiolites along the Yarlung Zangbo Suture Zone show restricted ages between 120 Ma and 130 Ma,and their supra-subduction zone affinities are best explained by seafloor spreading in what became the forearc of a north-dipping subduction zone on the southern margin of Tibet.The subsequent evolution of this new subduction zone is revealed by integrating data for arcrelated igneous rocks of the Lhasa terrane and Xigaze forearc basin deposits.Strong slab pull from this new subduction zone triggered the rifting of India from East Gondwana in Early Cretaceous time and pulled it northward to collide with Tibet in Early Paleogene time.

关键词： Cretaceous northward subduction

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Stagnant lid tectonics:Perspectives from silicate planets,dwarf planets, large moons,and large asteroids

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Geoscience Frontiers 2018年第1期9卷 103-119页

作者： robert j.stern Taras Gerya Paul j.Tackley Geosciences Department University of Texas at Dallas Department of Earth Sciences ETH-Zurich

To better understand Earth's present tectonic style-plate tectonics—and how it may have evolved from single plate(stagnant lid) tectonics, it is instructive to consider how common it is among similar bodies in the Solar System. Plate tectonics is a style of convection for an active planetoid where lid fragment(plate) motions reflect sinking of dense lithosphere in subduction zones, causing upwelling of asthenosphere at divergent plate boundaries and accompanied by focused upwellings, or mantle plumes;any other tectonic style is usefully called "stagnant lid" or "fragmented lid". In 2015 humanity completed a 50+ year effort to survey the 30 largest planets, asteroids, satellites, and inner Kuiper Belt objects,which we informally call "planetoids" and use especially images of these bodies to infer their tectonic activity. The four largest planetoids are enveloped in gas and ice(jupiter, Saturn, Uranus, and Neptune)and are not considered. The other 26 planetoids range in mass over 5 orders of magnitude and in diameter over 2 orders of magnitude, from massive Earth down to tiny Proteus; these bodies also range widely in density, from 1000 to 5500 kg/m^3. A gap separates 8 silicate planetoids with ρ = 3000 kg/m^3 or greater from 20 icy planetoids(including the gaseous and icy giant planets) with ρ = 2200 kg/m^3 or less. We define the "Tectonic Activity Index"(TAI), scoring each body from 0 to 3 based on evidence for recent volcanism, deformation, and resurfacing(inferred from impact crater density). Nine planetoids with TAI = 2 or greater are interpreted to be tectonically and convectively active whereas 17 with TAI <2 are inferred to be tectonically dead. We further infer that active planetoids have lithospheres or icy shells overlying asthenosphere or water/weak ice. TAI of silicate(rocky) planetoids positively correlates with their inferred Rayleigh number. We conclude that some type of stagnant lid tectonics is the dominant mode of heat loss and that plate tectonics is unusual. To make progress understanding Earth

关键词： Stagnant lid Solar system Plate tectonics Planets Moons

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Necrotic enteritis and antibiotic-free production of broiler chickens:Challenges in testing and using alternative products

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Animal Nutrition 2024年第1期16卷 288-298页

作者： robert j.Moore School of Science RMIT University

The global trend towards raising broiler chickens without the use of in-feed antibiotics(IFAs) means that there is an ongoing need to develop alternative treatments capable of delivering the benefits that IFAs previously provided. IFAs supported the productivity performance of chickens and played a key role in maintaining their health. Necrotic enteritis(NE) is an important disease of broilers that affects health,productivity, and welfare, and was previously well controlled by IFAs. However, with the reduction in IFA use, NE is resurgent in some countries. Vaccines and various feed additives, including pre-, pro-, and postbiotics, phytobiotics, fatty acids, and phage therapies have been introduced as alternative methods of NE control. While some of these feed additives have specific activity against the NE pathogen, Clostridium perfringens, most have the more general goal of reinforcing gut health. Extensive reviews of the effects of many of these feed additives on gut health have been published recently. Hence, rather than cover previously well reviewed areas of research this review focuses on the challenges and pitfalls in undertaking experimental assessment of alternative NE treatments and translating laboratory research to real world commercial production settings. The review is based on the author's particular experience,reading, thoughts, and analysis of the available information and inevitably presents a particular understanding that is likely to be at odds with others thinking on these issues. It is put forward to stimulate thinking and discussion on the issues covered.

关键词： Necrotic enteritis

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Glycolysis and glucose metabolism as a target for bioenergetic and neuronal protection in glaucoma

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Neural Regeneration Research 2024年第8期19卷 1637-1638页

作者： Pete A.Williams robert j.Casson Department of Clinical Neuroscience Division of Eye and VisionSt.Erik Eye HospitalKarolinska InstitutetStockholmSweden Ophthalmic Research Laboratories Discipline of Ophthalmology and Visual SciencesUniversity of AdelaideAdelaideAustralia

Vision is arguably our most valued sense,yet approximately 340 million people globally suffer blindness or moderate visual impairment,highlighting the need to further develop and advance treatments for ophthalmic diseases.Glaucoma refers to a group of ocular disorders united by a clinically characteristic optic neuropathy with associated retinal ganglion cell loss.

关键词： metabolism glaucoma globally

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Does MgSO_(4) protect the preterm brain?Dissecting its role in the pathophysiology of hypoxic ischemic encephalopathy

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Neural Regeneration Research 2024年第9期19卷 1861-1862页

作者： robert Galinsky Laura Bennet Alistair j.Gunn The Ritchie Centre Hudson Institute of Medical ResearchMelbourneVICAustralia Department of Obstetrics and Gynaecology Monash UniversityMelbourneVICAustralia Department of Physiology The University of AucklandAucklandNew Zealand

Mitigating preterm encephalopathy continues to be one of the greatest challenges in perinatal medicine.Preterm encephalopathy is associated with high mortality,serious morbidity,and significant socio-economic impacts on the individuals,their families,and public health sectors and welfare systems that last a lifetime.The cost of disability associated with preterm brain injury continues to rise.Prevention of this injury,and disability,would significantly reduce this socioeconomic burden.

关键词： encephalopathy mortality hypoxic

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Extracellular vesicles and angiotensin-converting enzyme 2 in COVID-19 disease

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BIOCELL 2024年第1期48卷 1-8页

作者： YU LIU robert j.KASPER NATALIE j.S.CHOI Department of Family and Community Medicine Northwestern University Feinberg School of MedicineChicagoIllinois

Extracellular vesicles(EVs)are membranous vesicular structures released from almost all eukaryotic cell types under different physiological or pathological conditions.Growing evidence demonstrates that EVs can serve as mediators of intercellular communication between donor and recipient cells or microorganism-infected and noninfected cells.Coronavirus disease 2019(COVID-19)disease is caused by infection of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)of host cells in the respiratory system and various extra-pulmonary tissue/organs,resulting in complications of multiple organ systems.As the cell surface receptor,angiotensin-converting enzyme 2(ACE2)mediates cellular entry of SARS-CoV-2 into the host cells in patients with COVID-19.Recent studies have found that ACE2 can be released with EVs,which have been shown to interfere with the entry of the virus into host cells and thus may be involved in COVID-19 pathophysiology.In addition,ACE2,neprilysin(NEP),and thimet oligopeptidase(TOP)are the key enzymes that regulate angiotensin metabolism by converting angiotensin II or angiotensin I to angiotensin 1-7,the latter of which has protective effects in counterbalancing the harmful effects of angiotensin II in COVID-19 disease.This review summarizes the recent research progress regarding EV-associated ACE2,NEP,and TOP and the perspectives of their potential involvement in the pathophysiology of COVID-19 disease.

关键词： Extracellular vesicles COVID-19 Angiotensin converting enzyme 2 Thimet oligopeptidase

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