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Growth of continental crust in intra-oceanic and continental-margin arc systems: Analogs for Archean systems

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Science China Earth Sciences 2022年第9期65卷 1615-1645页

作者： timothy kusky Lu WANG State Key Lab for Geological Processes and Mineral Resources Center for Global TectonicsSchool of Earth SciencesChina University of GeosciencesWuhan 430074China Badong National Observatory and Research Station for Geohazards China University of GeosciencesWuhan 430074China

Earth’s continental crust has grown and been recycled throughout geologic history along convergent plate *** main locus of continental crustal growth is in intra-oceanic and continental-margin arc systems in Archean time. In arc systems, oceanic lithosphere is subducted to the deeper mantle, and together with its overlying sedimentary sequence is in some cases off-scraped to form accretionary prisms. Fluids are released from the subducting slab to chemically react with the mantle wedge, forming mafic-ultramafic metasomatites, whose partial melting generates mafic melts that rise up to form arcs. In intraoceanic arcs, they produce dominantly basaltic lavas, with a mid-crust that includes variably-developed vertically-walled intermediate plutons and higher-level dikes and sills. In continental-margin arcs, different petrogenetic processes cause assimilation and fractionation of basaltic magmas, partial melting/reworking of juvenile basaltic rocks, and mixing of mantle-and crust-derived melts, so they produce andesitic calc-alkaline melts but still have a mid-crust dominated by vertically-walled felsic plutons, which form 3-D dome-and-basin structures, akin to those in some Archean terranes such as parts of the Pilbara and Zimbabwe cratons. Notably, the continental crust of Archean times is dominated by tonalite-trondhjemite-granodiorite(TTG)plutons, similar to that of the mid-crust of these arc systems, suggesting that early continental crust may have formed largely by the amalgamation of multiple arc systems. The patterns of magmatism, in terms of petrogenesis, rock types, duration of magmatic and accretionary events, and the spatial scales of deformation and magmatism have remained essentially the same throughout geological history, demonstrating that plate tectonic processes characterized by subduction and arc magmatism have been in operation at least as long as recorded by the preserved geologic record, since the Eoarchean. However, the early Earth was dom

关键词： Oceanic arc Continental arc Accretionary orogen Archean Crustal growth

Comparison of Results of Recent Seismic Profiles with Tectonic Models of the North China Craton

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Journal of Earth Science 2011年第2期22卷 250-259页

作者： timothy M kusky State Key Laboratory of Geological Processes and Mineral Resources Three Gorges Research Center for Geo-hazardMinistry of EducationChina University of Geosciences

The geometry and timing of amalgamation of the North China craton（NCC） have been controversial,with three main models with significantly different interpretations of regional structure,geochronology,and geological *** model of Zhao G C et *** that the eastern and western blocks of the NCC formed separately in the Archean,and an active margin was developed on the eastern block between 2.5 and 1.85 Ga,when the two blocks collided above an east dipping subduc-tion *** model of kusky et *** that the eastern block rifted from an unknown larger continent at circa 2.7 Ga,and experienced a collision with an arc（perhaps attached to the western block） above a west-dipping subduction zone at 2.5 Ga,and the 1.85 Ga metamorphism is related to a collision along the northern margin of the craton when the NCC joined the Columbia *** model of Faure et *** two collisions in the central orogenic belt,at 2.1 and 1.88 *** seismic results support both the models of kusky et *** Faure et al.,showing that subduction be-neath the central orogenic belt（COB） was west-directed,and that there is a second,west-dipping pa-leosubduction zone located to the east of the COB dipping beneath the western block（Ordos craton）.The boundaries identified through geophysics do not correlate with the boundaries of the Trans-North China orogen suggested in the Zhao et ***,and the subduction polarity is opposite that predicted by that *** seismic profiles are consistent with an Archean collision above a west-dipping sub-duction zone beneath the COB predicted by the models of kusky et al.,and the second west-dipping subduction zone is consistent with the two events suggested in the Faure et ***.

关键词： North China craton Archean tectonics geophysics.

The Neoarchean Ophiolite in the North China Craton:Early Precambrian Plate Tectonics and Scientific Debate

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Journal of Earth Science 2012年第3期23卷 277-284页

作者： timothy M kusky 翟明国 Three Gorges Research Center for Geo-hazards Ministry of EducationChina University of Geosciences State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences

Archean greenstone belts and their possible inclusion of fragments of ophiolites is an im-portant research subject, since it is correlated with the nature of early oceanic crust, and can yield in-formation on the nature of early planetary lithospheres, the origin of TTG （tonalite-trondhjemite-granodiorite） continental crust, the formation of early cratons and continents, and is related to when plate tectonics started in the Earth＇s evolutionary history. This article briefly reviews the North China craton＇s Archean ophiolite argument and proposes further studies aimed at understanding the genera- tion of greenstone belts and Archean ophiolites, and suggests some key scientific questions that remain to be answered.

关键词： Archean ophiolite greenstone belt North China craton.

Déjàvu:Might Future Eruptions of Hunga Tonga-Hunga Ha'apai Volcano be a Repeat of the Devastating Eruption of Santorini,Greece(1650 BC)?

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Journal of Earth Science 2022年第2期33卷 229-235页

作者： timothy M.kusky Center for Global Tectonics Three Gorges Research Center for Geo-HazardsChina University of GeosciencesWuhan 430074China

The remote Pacific islands nation of Tonga(about 170 islands,with a population of 105000),and surrounding countries,are suffering from the damage from one of the largest,most explosive volcanic eruptions in at least several decades,at least since the 1991 eruption of Pinatubo in the *** data is still coming in from the Jan.15,2022 *** reports show(remarkably)few casualties,but the islands are still(as of this writing)inaccessible because of thick volcanic ash coverings。

关键词： volcanic eruption thick

Environmental Monitoring of Bombetoka Bay and the Betsiboka Estuary,Madagascar,Using Multi-temporal Satellite Data

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Journal of Earth Science 2010年第2期21卷 210-226页

作者： Tsilavo Raharimahefa timothy M kusky Department of Earth Sciences Laurentian University Three Gorges Research Center for Geo-hazard Ministry of EducationChina University of Geosciences(Wuhan) State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences(Wuhan)

The causes and consequences of soil erosion in Madagascar have been the focus of recent environmental debates. The Betsiboka, Madagascar＇s largest river stretching 600 km from the high central plateau to the northwest coast on the Mozambique Channel, is a major conduit for transporting lateritic soils and sediments derived from the highlands of Central Madagascar to the sea. These en- trained lateritic sediments color the river a blood-red hue, as if the life of the island is being drained away. In this study, Landsat visible and near infrared spectral bands are used to map the underwater sediments especially under the sea and in the interface between seawater and freshwater. Band color composites, single bands and band ratios are used to improve the detection of underwater sediments including sand bars and delta lobes. We show the evolution of the bay, coastline, delta, and change detection results derived from Landsat satellite images recorded in 1973, 1989, 1999, 2000 and 2003, respectively. Results indicate that sedimentary transport and suspension in Bombetoka Bay has significantly changed during the past 30 years, with a dramatic increase in the amount of sediment moved by the river, and deposited in the estuary and in offshore delta lobes. These changes have adversely affected agriculture, fisheries, and transportation for one of Madagascar＇s largest ports. The changes are attributed to increased erosion following large-scale deforestation, bush fires, and overgrazing in the river basin.

关键词： environment monitoring Madagascar delta remote sensing Landsat.

ASTER Analysis for Locating REE-Bearing Granites in Arid Regions:Example from the Arabian Shield

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Journal of Earth Science 2022年第5期33卷 1114-1123页

作者： Reda Amer timothy M.kusky Department of Earth and Space Sciences Lamar UniversityBeaumontTX77710USA State Key Laboratory of Geological Processes and Mineral Resources Center for Global TectonicsSchool of Earth SciencesBadong National Observatory and Research Station for GeohazardsChina University of GeosciencesWuhan430074China

The world’s increasing demand for rare earth elements(REEs)highlights the potential for using new multispectral remote sensing techniques to define new exploration targets in arid regions,such as the Kingdom of Saudi Arabia(KSA),Egypt,and regions of central and western *** REEs cannot be detected by satellite multispectral instruments,REEs-bearing alkaline granites can be identified on ASTER ***,we develop a new ASTER band ratio scheme to delineate mineralization-related features of the Ghurayyah REE-bearing peralkaline granite in the northwestern *** Ghurayyah peralkaline stock is located at the intersection of a NW striking segment of the Najd-fault system,and an E-W striking *** is surrounded to the north and west by metavolcanics,from east by the Jabal Dabbagh alkali granite,and from the south by *** mineralogical composition of granitic rocks resulted in spectral variation and causes absorption features at different wavelengths in the shortwave infrared(SWIR).The newly developed band ratios were constructed from(b6+b8)/(b6–b8)in red;(b6+b8)/b4 in green,and(b7–b9)/(b7+b9)in blue,enabling the discrimination between the Ghurayyah REE-bearing peralkaline granite,Jabal Dabbagh alkali granite,monzogranite,and *** work will be carried out to perform higher-resolution drone-based hyperspectral imaging for new high-resolution mapping and evaluate the existing REE deposits,emphasizing field spectral measurements to identify the spectral reflectance of REEs mineralized zones and the absorption features of monazite,columbite-tantalite,and aeschynite-(Y),coupled with rock sampling for petrographical,spectral,and geochemical *** methods have great potential for locating REEs-bearing peralkaline granites in the Arabian shield and elsewhere,such as arid portions of central and western China and adjacent regions.

关键词： remote sensing multispectral imaging rare earth elements Arabian Shield mineral exploration

Origin and Emplacement of Archean Ophiolites of the Central Orogenic Belt, North China Craton

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Journal of Earth Science 2010年第5期21卷 744-781页

作者： timothy M kusky 李江海 State Key Laboratory for Geological Processes and Mineral Resources China University of Geosciences Three Gorges Research Center for Geohazards Ministry of Education China University of Geosciences School of Earth and Space Sciences Peking University

Understanding Archean crustal and mantle evolution hinges upon identification and characterization of oceanic lithosphere. We report and update here more than 10 years work on a complete, yet dismembered and metamorphosed Archcan ophiolite sequence in the North China craton, in the Dongwanzi （东湾子）-Zunhua （遵化） structural belt and correlatives in the Wutaishan （五台山） area. Banded iron formation structurally overlies several tens of meters of variably deformed pillow lavas, mafic flows, and picritic amphibolites. These are in structural contact with a 2 km thick mixed gabbro and dike complex with gabbro screens, exposed discontinuously along strike for more than 20 km. The dikes consist of metamorphosed diabase, basalt, Hb-Cpx-gabbro, and pyroxenite. The dike/gabbro complex is underlain by several kilometers of mixed isotropic and foliated gabbro, which preserve compositional layering approximately 2 km below the dike complex, and then over several hundred meters merge into strongly compositionally layered gabbro and olivine-gabbro. The layered gabbro becomes mixed with layered pyroxenite/gabbro marking a transition zone into emulate ultramaflc rocks including serpentinzed dunite, pyroxenite and wehrlite, and finally into strongly deformed and serpentinized olivine and orthopyroxene-bearing ultraInafic rocks interpreted as depleted mantle harzburgite tectoultes. A U/Pb zircon age of 2.505 Ga from gabbro of the Dongwanzi ophioUte makes it one of the world＇s oldest recognized, laterally. extensive complete ophiolite sequences, though older dismembered ophiolites are recognized in South Africa and Greenland, extending back to 3.8 Ga. This age is confirmed by a ca. 2.6 Ga Re-Os isochron from chromites from the belt, and a number of dated 2.5-2.4 Ga cross-cuttlng younger igneous units. The Dongwanzi ophiolite is one of the largest well-preserved greenstone belts in the central orogenic belt that divides the North China craton into eastern and western blocks. More than 1 000

关键词： North China craton Archcan ophiolite Proterozoic melange podiform chromite.

Comparative orotomy of the Archean Superior and Phanerozoic Altaid orogenic systems

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National Science Review 2023年第2期10卷 20-48页

作者： timothy M.kusky A.M.Celal ?eng?r Center for Global Tectonics School of Earth Sciences and State Key Laboratory for Geological Processes and Mineral ResourcesChina University of Geosciences Badong National Observatory and Research Station for Geohazards Ministry of Education China University of Geosciences Department of Geological Engineering Middle East Technical University Eurasia Institute of Earth Sciences Istanbul Technical University Department of Geology Faculty of Mines Istanbul Technical University

We compare and contrast the materials and mechanisms of continental crustal growth in the largest preserved regions of Phanerozoic and Archean juvenile additions to the crust,to test for similarities or differences in the formation of continents through *** accomplish this through a comparison of map patterns,lithological contents,and structural and metamorphic evolution of the Phanerozoic Altaid orogenic system of Asia,with the Archean Superior Province of the North American Craton,using a method termed comparative *** orogenic systems consist of collages of curvilinear belts of eroded arcs,some older continental slivers,and vast tracts of former subduction/accretionary *** contain numerous shreds of portions of the ophiolite suite,slivers of island and continental arcs,and accreted oceanic plateau,all intruded by multiple magmatic suites during or between multiple deformation events,then sliced by large transcurrent fault systems and bent into large oroclinal *** make this comparison because the Superior Province is a typical Archean craton that was later,in the P aleoproterozoic,incorporated into the larger North American Craton,and has occupied a central position in several super continents(*** and Nuna,which then formed the core of Columbia,Rodinia,Laurentia and Pangea) during its *** it is the largest single fragment of Archean continental cratonic lithosphere preserved on Earth,the Superior Province is widely regarded as a testing ground for how Earth’s continental crust was ***,the Altaids encompass the largest region of crustal growth for the *** comparison with the Altaids is needed,as in recent years many myths about how the planet may have responded to higher heat production and flow in the Archean have emerged,because of trends in the science where regional geology is ignored in favor of numerical models,isotopic proxies for assumed models of chemical behavior for crust-for

关键词： Altaids superior province ophiolite subduction strike-slip

On the Role of Dual Active Margin Collision for Exhuming the World's Largest Ultrahigh Pressure Metamorphic Belt

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Journal of Earth Science 2012年第6期23卷 802-812页

作者：王璐 timothy M kusky M Santosh State Key Laboratory for Geological Processes and Mineral Resources China University of Geosciences Three Gorges Geo-hazard Research Center of Ministry of Education China University of Geosciences China University of Geosciences

ABSTRACT： A wide variety of tectonic models have been invoked to explain the exhumation of the world＇s largest ultrahigh pressure （UHP） orogenic belt, the Qinling Dabieshan Sulu belt in China, and its correlatives in Korea. Most of these models assume that the orogen contains one main collisional suture between the North and South China cratons that collided in the Mesozoic. New field data reveal that this model is too simplistic, and that the collision involved an additional mi- croplate, which initially rifted off the Yangtze craton. This continental microplate was partially sub- ducted beneath an active margin on the North China craton, and subsequently an additional active Andean-style margin developed on the southern margin of the Qinling microplate after collision, leav- ing the near-vertical microplate wedged between the two thickened and thermally softened margins. The thermo-mechanical environment of collision thus left a cold, thick, and buoyant microplate wedged between two easily deformed margins, which acted as power-law creep channels, accommodating rapid buoyancy-driven rise of a 2 000 km long wedge of the subducted microplate, which became intimately involved with the collisional process. An addi- tional segment of the northern Yangtze craton was subducted to ~100 kin, and formed a separate wedge that rose alongside the thermally softened margin of the Qinling mieroeontinent, and was bordered on the south by the recently thermally- softened rift zone where the Qinling mieroeonti- nent broke off the Yangtze eraton between Late Devonian and Permian times. Recognizing the dual active margins in Qinling-Dabieshan-Sulu orogen and the thermally-softened power-law creep channels sheds new light on understanding exhumation of the world＇s largest ultrahigh pressure belt. We propose that this model is generally applicable to other UHP belts worldwide.

关键词： ultrahigh-pressure metamorphic belt plate tectonics subduction collision exhumation,Qinling-Dabieshan-Sulu belt.