scholarly journals Crustal Evolution of a Paleozoic Intra-oceanic Island-Arc-Back-Arc Basin System Constrained by the Geochemistry and Geochronology of the Yakuno Ophiolite, Southwest Japan

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Yoshimitsu Suda ◽  
Yasutaka Hayasaka ◽  
Kosuke Kimura
Keyword(s):  
East Asian ◽  
Oceanic Island ◽  
Island Arc ◽  
Geochemical Data ◽  
Southwest Japan ◽  
Asian Continent ◽  
Initial Stage ◽  
Back Arc ◽  
Shrimp Zircon ◽  
Analytical Errors

The Yakuno ophiolite in southwest Japan is considered to have been obducted by the collision between an intra-oceanic island-arc-back-arc basin (intra-OIA-BAB) system and the East Asian continent during the late Paleozoic. New SIMS (SHRIMP) zircon U-Pb determinations for amphibolite and metagabbro of BAB origin within the Yakuno ophiolite yield ages of 293.4 ± 9.5 Ma and 288 ± 13 Ma, respectively. These ages are slightly older (however, overlapping within analytical errors) than the magmatic age of arc granitoids (ca. 285–282 Ma) that intruded into the mafic rocks of BAB origin. Results from geochronological and geochemical data of the Yakuno ophiolite give rise to the following tentative geotectonic model for the Paleozoic intra-OIA-BAB system: the initial stage of BAB rifting (ca. 293–288 Ma) formed the BAB crust with island-arc basalt (IAB) signatures, which was brought to the OIA setting, and generated the arc granitoids (ca. 285–282 Ma) by anatexis of the BAB crust. A later stage of BAB rifting (<ca. 285 Ma) formed the BAB crust with IAB to MORB signatures, on which the Permian sediments were conformably deposited. These components collided with the eastern margin of the East Asian continent during the early Mesozoic.

Geochemistry of the upper Snooks Arm Group basalts, Burlington Peninsula, Newfoundland: evidence against formation in an island arc

1980 ◽  
Vol 17 (7) ◽  
pp. 888-900 ◽  
Author(s):  
G. A. Jenner ◽  
B. J. Fryer
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
Sedimentary Rocks ◽  
Oceanic Islands ◽  
Oceanic Island ◽  
Island Arc ◽  
Geochemical Data ◽  
Basaltic Rocks ◽  
Arc Setting ◽  
Back Arc

The Snooks Arm Group of the Newfoundland Appalachians, which includes the Betts Cove ophiolite at its base, has been interpreted as oceanic crust overlain by island arc volcanic and sedimentary rocks. The limited geochemical data available on the upper Snooks Arm Group basalts have been used as evidence for and against their formation in an island arc environment.Reinvestigation of the chemistry of the basaltic rocks of the upper Snooks Arm Group establishes them as large ion lithophile enriched tholeiites. Similar basalts have been found in oceanic islands, on aseismic ridges, and possibly in back-arc basins. Chemically analogous rocks are notably lacking from island arc settings.The geochemistry and geology of the upper Snooks Arm Group suggest that these rocks may have formed in either an oceanic island setting or, as recently suggested by Upadhyay and Neale, as part of a marginal basin. It is not possible to distinguish between these alternate models, although the most similar basaltic rocks occur in the former environment. It is most unlikely that these rocks formed in an early island arc setting and indeed there may be no need for them to be associated with a major subduction zone.

scholarly journals The Kohistan between Gilgit and Chilas, northern Pakistan: regional tectonic implications

1996 ◽  
Vol 14 ◽  
Author(s):  
T. Khan ◽  
M. A. Khan ◽  
M. Q. Jan ◽  
M. Latif
Keyword(s):  
Sedimentary Rocks ◽  
Oceanic Island ◽  
Island Arc ◽  
Northern Pakistan ◽  
The Past ◽  
Volcanic Group ◽  
The North ◽  
Regional Tectonic ◽  
Back Arc ◽  
Field Geology

In this paper, we present geological description of an area located between Gilgit and Chilas within the Kohistan terrane. This terrane has been considered an intra-oceanic island arc, formed due to northward subduction of the Neo-tethyan lithospheric plate. At present, it is squeezed between the Karakoram­ Asian and Indian continental plates. Both the contacts are marked by suture zones, that is, Shyok (MKT) in the north and Indus (MMT) sutures in the south, respectively. The investigated area consists of plutonic, metamorphosed volcanic and sedimentary rocks, the Chilas Complex, and the Kamila Amphibolite. The metamorphosed volcanic and sedimentary rocks are packaged into the Jagfot Group. This group comprises basal turbiditic sediments, intercalated with amphibolites and calc-silicates (the Gilgit Formation), followed upward by the Gashu-Confluence Volcanics = Chait Volcanic Group, and finally the Thelichi Formation = Yasin Group of Aptian-Albian age. The Thelichi Formation comprises a volcanic base (Majne volcanics) and overlying turbidites, local intercalation of marbles, volcaniclastics and lava flows. Greenschist and amphibolite facies are common in the Jaglot Group, and particularly the sillimanite in the Gilgit Formation. A pair of anticline (the Gilgit anticline) and syncline (the Jaglot syncline) make up the structural scenario. On the basis of field geology, we conclude that the entire Jaglot Group and its equivalents, the Yasin Group, Chait Volcanic Group in Kohistan, and Burjila Formation, Bauma Harel Formation and Katzarah Formation in Ladakh show intra-oceanic back-arc basin rather than island arc affinities as suggested in the past.

scholarly journals PALEOGEODYNAMICAL RECONSTRUCTIONS AND MINERAGENY OF EARLY-JURASSIC BASALT-ULTRABASITIC FIAGDONSKIY COMPLEX (REPUBLIC NORTHERN OSSETIA-ALANIA, CAUCASUS, RF) ON PETROCHEMICAL, GEOCHEMICAL AND, ISOTOPIC DATA

2017 ◽  
Author(s):  
А.Г. Гурбанов ◽  
В.М. Газеев ◽  
А.Б. Лексин ◽  
А.Я. Докучаев ◽  
Ю.В. Гольцман ◽  
...  
Keyword(s):  
Early Jurassic ◽  
Island Arc ◽  
Geochemical Data ◽  
Isotopic Data ◽  
Suprasubduction Zone ◽  
Marginal Sea ◽  
Ore Mineralization ◽  
Back Arc ◽  
Content Of Gold

В статье приведены впервые полученные изотопно-геохимические данные, позволившие уточнить геодинамическую обстановку при образовании пород раннеюрского Фиагдонского комплекса (ФК). Раннеальпийские магматические комплексы, изучавшиеся в середине и конце ХХ века, практически не были охарактеризованы изотопно-геохимическими данными. Этот пробел восполнен полученными нами принципиально новыми данными, на основе которых сделаны следующие выводы: – на диагностических диаграммах породы ФК сконцентрированы в полях: базальтов СОХ, окраинных морей; или в зоне перекрытия полей базальтов MORB и IAT; – сравнение мультиэлементных спектров и спектров распределения REE с эталонами N-MORB указало на их близость к толеитовым базальтам задуговых бассейнов, занимающих промежуточное положение между MORB и IAT – энсиматических островных дуг; – величины 87Sr / 86Sr в породах ФК, варьируют в пределах от 0,7038 до 0,7057 и сопоставимы по этим величинам с базальтами IAT и окраинных морей; – геодинамическая обстановка, в которой сформировались породы ФК, определена как надсубдукционная офиолитовая (suprasubduction zone ophiolites). Резко повышенные содержания золота (от 0,2 до 3?7 г / т) в лиственитизированных серпентинитах, позволили предполагать, что выявлен новый для Большого Кавказа золото-лиственитовый с шеелитом тип рудной минерализации. The firstly obtained isotope-geochemical data, allows to specify the geodynamics situation in the course of origin of Fiagdon complex (FC) rocks are reported in this article. Early Alpine magmatic complexes, which have been investigated during middle-and end of XX century, were not described by modern isotope-geochemical data. This flaw was supply by on principle new data obtained, on base of which the following conclusions were done: – on the diagnostic diagrams the rocks of FC are concentrated in the fields of basalts of MORB, marginal sea or in zone of overlapping fields basalts MORB and IAT; – comparison of multielements spectrums and spectrums of distribution of REE with N-MORB standart, shown its closeness to tholeitic basalt of the back arc basins, which are intermediate between МОRВ and IAT; – value of 87Sr / 86Sr in basalts and picrites of FC are vary in the range from 0,7038 to 0,7057 and correlated with basalts of ensimatical island arc and marginal sea; – geodynamics conditions of origin of FC rocks are correspond as suprasubduction zone; The radically increased content of gold (from 0,2 tо 3?7 ppm) in serpentinite with process of listvenitization alteration suggests that a new for the Great Caucasus gold-listvenitical type with scheelite of ore mineralization was revealed.

scholarly journals Discovery of Ancient Volcanoes in the Okhotsk Sea (Russia): New Constraints on the Opening History of the Kurile Back Arc Basin

Geosciences ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 442
Author(s):  
Reinhard Werner ◽  
Boris Baranov ◽  
Kaj Hoernle ◽  
Paul van den Bogaard ◽  
Folkmar Hauff ◽  
...  
Keyword(s):  
Trace Element ◽  
Island Arc ◽  
Kurile Island ◽  
Geochemical Data ◽  
Magma Source ◽  
Published Data ◽  
Kurile Island Arc ◽  
History Of ◽  
Spreading Rates ◽  
Back Arc

Here we present the first radiometric age and geochemical (major and trace element and isotope) data for samples from the Hydrographer Ridge, a back arc volcano of the Kurile Island Arc, and a newly discovered chain of volcanoes (“Sonne Volcanoes”) on the northwestern continental slope of the Kurile Basin on the opposite side of the arc. The 40Ar/39Ar age and geochemical data show that Hydrographer Ridge (3.2–3.3 Ma) and the “Sonne Volcanoes” (25.3–25.9 Ma) have very similar trace element and isotope characteristics to those of the Kurile Island Arc, indicating derivation from a common magma source. We conclude that the age of the “Sonne Volcanoes” marks the time of opening of the Kurile Basin, implying slow back arc spreading rates of 1.3–1.8 cm/y. Combined with published data from the Kurile fore arc, our data suggest that the processes of subduction, Kurile Basin opening and frontal arc extension occurred synchronously and that extension in the rear part and in the frontal part of the Kurile Island Arc must have been triggered by the same mechanism.

scholarly journals CARACTERIZAÇÃO GEOTECTÔNICA DO SETOR SETENTRIONAL DO CINTURÃO RIBEIRA: EVIDÊNCIA DE ACRESÇÃO NEOPROTEROZÓICA NO LESTE DE MINAS GERAIS, BRASIL.

1995 ◽  
Author(s):  
Antônio Gilberto Costa ◽  
Carlos Alberto Rosiére ◽  
Luciano Melo Moreira ◽  
Daniele Piuzana
Keyword(s):  
Continental Margin ◽  
Oceanic Lithosphere ◽  
Minas Gerais ◽  
Island Arc ◽  
Geochemical Data ◽  
Magmatic Arc ◽  
High K ◽  
Alternative Hypotheses ◽  
Back Arc ◽  
Early Neoproterozoic

The early neoproterozoic evolution of eastern Minas Gerais is characterized by a history of a continental margin activity, including the accretion of suspect terranes. The Manhuaçu Terrane is one of those and is represented by a granitic continental plutonic arc and terrigeneous metasediments that reflect a continental margin. A metasedimentary gneiss belt at this margin with shallow to deep marine clastic lithologies as well as metavulcanic and metaplutonic mafic rocks was interpreted as an extensive tectonic segment with suspect development in a back-arc setting. Fragments of a volcanic arc are identified and interpreted as an evidence for a probable island-arc domain. In the studied region the Juiz de Fora and Paraiba do Sul Complexes are domains of these terranes. The distribution of magmatism in the studied region shows from west to east three different suites : 1) tholeiitic, 2) a medium to high-K cal-alkalic and 3) a high-K calc-alcalic/shoshonitic(?) magmatism which attests the evolution of early magmatism arcs (volcanic and plutonic) initially relates to ocean-plate subduction, followed by a continent-continent collision. Petrological, structural and geochemical data of mesoproterozoic/neoproterozoic metamorphic and magmatic suites of rocks are in agreement with the development of an accretionary orogeny. After a vulcanic-(island-arc) and a back-arc basin formation (by rifting of a continental margin with no spreading) in connection with eastward subduction, the island arc was accreted to a continental margin. Further subduction beneath it and a mechanism of flattening of the slab during the subduction process was responsible for the development of as granitic continental plutonic-arc (Andean-type batholith) eastwardly in a compressional setting. Continental plates became sutured and all intervening oceanic lithosphere was subducted beneath one of the converging masses. This resulted in the accretion of the Manhuaçu Microplate to the São Francisco Craton Domain. Plates continued to converge and the inversion of subduction polarity occurs resulting in a new subduction system (westward subduction) to the back of the Manhuaçu Microplate, in a easternward of the Espírito Santo state, with the establishment of a new magmatic arc of late neoproterozoic to eopaleozoic age. In this paper, only the probable early neoproterozoic volcanic (tholeiitic magmatism transitional between N-type MORB and island are basalts) and the plutonic (early continental calc-alkalic magmatism) arcs characterized by rocks with a very particular geochemistry and the back-arc basin setting will be discussed. Two alternative hypotheses to explain the evolution of these terranes may be postulated: 1) an island arc orogeny related to a westward subduction followed by a cordillerean type orogeny. With the advance of the island-arc and continent with offshore sediments, in  different plates, a collision between these domains occurred. The old subduction zone was replaced by another one, eastward directed and the development of a continental magmatic arc occurred. Continental plates became sutured and all intervening oceanic lithosphere was subducted beneath one of the converging masses. Against this model are the presence of metavulcanic basic and intermediate rocks intercalated with marine and continental margin; 2) an extensional ensialic setting (aborted marginal basin) in the continental margin formed during the opening of a rapidly subsiding basin, with moderately rapid mantle upwelling, pronounced thinning of the continental crust and slight crustal contaminanton, without formation of oceanic crust or an island-arc may explain the association of basic metavulcanic rocks with marine and continental metasediments. Here, the low potassium contents of a few studied metavulcanic basic rocks and theire oceanic tholeiitic affinity are not well in agreement with this setting where continental basalts (flood basalts), or rocks ( basalts or basaltics andesites) belong to the high-K calc-alkaline series are expected to occur. Nevertheless, our evidences are not unequivocal enough for theire disapprovals.

Intra-oceanic island arc origin for Iratsu eclogites of the Sanbagawa belt, central Shikoku, southwest Japan

2011 ◽  
Vol 280 (1-2) ◽  
pp. 97-114 ◽  
Author(s):  
Atsushi Utsunomiya ◽  
Bor-ming Jahn ◽  
Kazuaki Okamoto ◽  
Tsutomu Ota ◽  
Hironao Shinjoe
Keyword(s):  
Oceanic Island ◽  
Island Arc ◽  
Southwest Japan
Sign in / Sign up

Export Citation Format

Share Document