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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 devel

关键词： Plate tectonics Exoplanets Planetary science Intelligent life

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 *** 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 *** 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 *** subsequent evolution of this new subduction zone is revealed by integrating data for arcrelated igneous rocks of the Lhasa terrane and Xigaze forearc basin *** 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

Ophiolites:Identification and tectonic significance in space and time

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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 *** 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 *** 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 *** igneous rocks have either ocean-ridge basalt or immature oceanic arc basalt chemical *** 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 *** do not become geographically widespread until after 900 Ma,and most ophiolites of all ages formed in a forearc(subduction initiation)tectonic *** ophiolite production requires plate tectonics,subduction must have begun at least locally by 2700 Ma but did not become widespread until after 2000 *** abundance of ophiolites after 900 Ma may reflect better preservation of subduction-related ophiolites,or to an increasing global network of interconnected *** 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

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

关键词： Stagnant lid Solar system Plate tectonics Planets Moons

Significance of a highly refractory source during subduction initiation to form the Izu-Bonin-Mariana Arc

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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

俯冲带火山活动的氧和锶同位素研究——以Volcano岛弧和Mariana岛弧为例

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宝石和宝石学杂志(中英文) 1987年第1期 55-60页

作者： Emi Ito robert j.stern 李增田

为了确定岩浆的来源,我们分析了大洋区内的Mariana和Volcano岛弧近代新鲜火山岩的O和Sr同位素组成.为了比较,也分析了Mariana-Volcano岛弧外围地区的非岛弧新鲜火山岩和一些深海钻探计划沉积物(DSDP sediments).岛弧间熔岩的氧同位索比... 详细信息

为了确定岩浆的来源,我们分析了大洋区内的Mariana和Volcano岛弧近代新鲜火山岩的O和Sr同位素组成.为了比较,也分析了Mariana-Volcano岛弧外围地区的非岛弧新鲜火山岩和一些深海钻探计划沉积物(DSDP sediments).岛弧间熔岩的氧同位索比值显示出较小幅度的变化,这种变化无法完全用分离结晶作用来解释,但其锶同位素组成具显著的均一性(Mariana为0.70332-0.70394).为了解释观察到的同位素特征,我们考虑了三种模式:(1)MORB型地幔与(a)俯冲沉积物,(b)俯冲洋壳(不包括沉积物)的总体混合熔融;(2)沉积物衍生的流体与洋岛型或热点型地幔所组成的混合物的熔融.其中最后一种模式对已得资料吻合得最好.最后的结论是,需要有少许不等量的沉积物衍生流体(≤1%)来解释观察到的岛间氧同位素变异特征,这个观点与其它同行们应用不同的同位素和微量元素方法所得出的结论一致.Mariana-Volcano岛弧岩浆的形成过程中只有很少量的沉积物卷入,Mariana熔岩的源区在同位素方面与热点玄武岩没有什么差别.

关键词：岛弧熔岩流体火山岩板块深海钻探计划喷出岩火成岩断块 Volcano Mariana 俯冲带锶同位素

Petrogenesis and tectonic implications of Late Carboniferous A-type granites and gabbronorites in NW Iran:Geochronological and geochemical constraints

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Petrogenesis and tectonic implications of Late Carboniferous...

Devonian to Permian evolution of the Paleo-Tethys Ocean:New evidence from U–Pb zircon dating and Sr–Nd–Pb isotopes of the Darrehanjir–Mashhad “ophiolites”,NE Iran

中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： Hadi Shafaii Moghadam Xian-Hua Li Xiao-Xiao Ling robert j.stern jose F.Santos Guido Meinhold Ghasem Ghorbani Shirin Shahabi State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences School of Earth Sciences Damghan University Geosciences Dept. University of TX at Dallas Geobiotec Departamento de GeociênciasUniversidade de Aveiro Geowissenschaftliches Zentrum der Universit?t G?ttingen

Carboniferous igneous rocks constitute volumetrically minor components of Iranian crust but preserve important information about the magmatic and tectonic history of SW *** granites and gabbronorites in NW Iran comprise a bimodal magmatic suite that intruded Ediacaran–Cambrian gneiss and are good representatives of carboniferous igneous *** SIMS U–Pb zircon ages indicate that the gabbronorites and granites were emplaced synchronously at20 *** granites show A-type magmatic affinities,with typical enrichments in alkalis,Ga,Zr,Nb and Y,depletion in Sr and P and fractionated REE patterns showing strong negative Eu *** gabbronorites are enriched in LREEs,Nb,Ta and other incompatible trace elements,and are similar in geochemistry to OIB-type *** and gabbronorites have similarεNd(t)(+1.3 to+3.4 and-0.1 to+4.4,respectively)and zirconεHf(t)(+1.7 to+6.2 and+0.94 to+6.5,respectively).The similar variation in bulk rockεNd(t)and zirconεHf(t)values and radiometric ages for the granites and gabbronorites indicate a genetic relationship between mafic and felsic magmas,either a crystal fractionation or silicate liquid immiscibility process;further work is needed to resolve petrogenetic *** compositional characteristics of the bimodal Ghushchi complex are most consistent with magmatic activity in an extensional tectonic *** extension may have occurred during rifting of Cadomian fragments away from northern Gondwana during early phases of Neotethys opening.

关键词： A-type granite Gabbronorite Carboniferous Zircon U–Pb ages Iran

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Devonian to Permian evolution of the Paleo-Tethys Ocean:New ...

中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： Hadi Shafaii Moghadam Xian-Hua Li Xiao-Xiao Ling robert j.stern Mohamed Zaki Khedr Massimo Chiaradia Ghasem Ghorbani Shoji Arai Akihiro Tamura State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences School of Earth Sciences Damghan University Geosciences Dept. University of Texas at Dallas Department of Earth Sciences Kanazawa University Department of Geology Faculty of ScienceKafrelsheikh University Département de Minéralogie Université de Genève

Middle to Late Paleozoic ophiolites,which are remnants of the Paleo-Tethys Ocean,are aligned in two main zones in northern Iran:Darrehanjir-Fariman-Mashhad,and Rasht in the north and jandagh-Anarak ophiolites to the *** new U-Pb zircon dating results show that the-200 km long Darrehanjir-Mashhad mafic-ultramafic body is not a single ophiolite but a composite igneous complex composed of Permian pillow lavas and pelagic sediments in fault contact with a small outcrop of Devonian intrusive and ultramafic *** intrusive rocks have U-Pb zircon ages of 380.6±3.7 Ma and 382.9±3.7 Ma respectively,-100 Ma older than published ages for gabbros and radiolarites intercalated with lavas near Mashhad and *** peridotites from the Devonian complex contain low Cr#spinel,similar to that in MORB-type *** Darrehanjir gabbros and Permian Mashhad sequences both have boninitic and calc-alkaline signatures,***δOvalues from the Devonian ferrodiorite(δO-4.6±0.3‰)are slightly lower than the 5.2 to5.4‰expected for MORB-type zircons whereas Devonian plagiogranitic zircons mostly haveδO103)and lowεNd(jir-Mashhad rocks are characterized by radiogenicPb/Pb andPb/Pb,indicating the involvement of subducted terrigenous sediments in the *** Mashhad-Darrehanjir mafic-ultramafic complex demonstrates that this part of Paleo-Tethys evolved from oceanic crust formation above a subduction zone in Devonian time to accretionary convergence in Permian *** Paleozoic ophiolites and oceanic igneous complexes along with those of the Caucasus and Turkey in the west and Afghanistan,Turkmenistan

关键词： Paleozoic ophiolites U–Pb zircon dating Zircon εHf(t) Komatiite Supra-subduction zone-type magmatism

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初始俯冲的动力学:二维和三维的数值模拟

初始俯冲的动力学:二维和三维的数值模拟