Geochemical aspects of back-arc spreading in the Scotia Sea and western Pacific

1981 ◽  
Vol 300 (1454) ◽  
pp. 263-285 ◽  
Keyword(s):  
Island Arc ◽  
Calc Alkaline ◽  
Volcanic Arc ◽  
Scotia Sea ◽  
Marginal Basin ◽  
Early Stages ◽  
Enriched Mantle ◽  
Mantle Sources ◽  
History Of ◽  
Back Arc

The results of recent geochemical investigations of several island arc - marginal basin systems in the Scotia Sea area and in the western Pacific are outlined. Marginal basins in different stages of evolution are represented, from those in the initial stages of formation to those with an extensive and multiple history of back-arc spreading. Some are completely intraoceanic, others have developed at continental margins. Basalts erupted at back-arc spreading centres seem to be as geochemically varied as those from normal mid-ocean ridges, and record evidence for similar processes of partial melting, fractional crystallization and magma mixing in their genesis. They appear to have been derived from mantle sources with incompatible trace element characteristics ranging from ‘depleted’ to ‘enriched’, but with the ‘enriched’ mantle sources being sampled during the earlier stages of back-arc spreading. Submarine back-arc basalts are more vesicular than their normal ocean ridge equivalents, and their corresponding glasses have higher water contents. This, together with other geochemical features such as the higher ratios of lithophile to high field strength elements in some back-arc basalts, suggests that a component from the subducted slab may be involved in their petrogenesis. The chemistry of the corresponding arc volcanics is described in relation to the subduction and extensions history of marginal basin development. In intraoceanic arcs the early stages of arc magmatism are dominated by the eruption of large volumes of island arc tholeiites and subsidiary high-Mg andesites. In the Mariana region, after the initial volcanic arc is split and separated by back-arc spreading, the later frontal arc volcanics have calc-alkaline characteristics. Basalts erupted during the early stages of back-arc spreading more commonly have arc-like geochemical features when the marginal basin has developed through splitting of a calc-alkaline volcanic arc. The secular variation in the geochemistry of the arc volcanics may be related to the progressive development of a lithophile element enriched mantle source beneath the arc. This source contributes to the basalts produced during the early stages of arc rifting and back-arc spreading. Ophiolite complexes which represent marginal basin floor may well carry these arc-like geochemical features.

Depositional and geotectonic history of the Gala area, eastern Southern Uplands, Scotland

1993 ◽  
Vol 84 (2) ◽  
pp. 161-173 ◽  
Author(s):  
A. M. Kassi ◽  
J. A. Weir
Keyword(s):  
Late Stage ◽  
Large Scale ◽  
Strike Slip ◽  
Upper Ordovician ◽  
Volcanic Arc ◽  
History Of ◽  
Back Arc

AbstractThe Ordovician and Silurian successions between Falahill and Galashiels encompass six flysch-dominated formations: the Upper Ordovician Portpatrick and Shinnel Formations representing the Leadhills Group, the Llandovery Mindork, Garheugh, and Buckholm Formations together comprising the Gala Group, and a formation indeterminate of age within the Hawick Group. Southward ensialic andesitic volcanic arc and northward low- to medium-grade sialic sources contributed sediment, whilst ophiolitic and subduction-related sources made minor contributions. Deposition took place firstly, in a SE-migrating back-arc basin bordering the northerly source, the Laurentian continent. Subsequent NW-directed underthrusting led to formation out of the back-arc basin of an imbricate thrust stack which migrated southeastwards. Ultimately a foreland successor basin formed ahead of the rising thrust stack.Flysch units are typically associated with linear outcrops of Moffat Shales which are the loci of major steep SE-translating reverse faults, two of which participate in a late-stage sinistral strike–slip duplex with large-scale imbrication. The faults divide the succession into a sequence of tectonostratigraphic blocks, successively younger to the SE. At least six of the ten blocks customarily recognised in the Southern Uplands, Blocks 3–8, are represented, some of which coincide with single or complete formations.

Variation in the geochemistry of mantle sources for tholeiitic and calc-alkaline mafic magmas, Western Sunda volcanic arc, Indonesia

1980 ◽  
Vol 30 (3) ◽  
pp. 177-199 ◽  
Author(s):  
I.A. Nicholls ◽  
D.J. Whitford ◽  
K.L. Harris ◽  
S.R. Taylor
Keyword(s):  
Calc Alkaline ◽  
Volcanic Arc ◽  
Mantle Sources ◽  
Mafic Magmas

Igneous history of the Andean Cordillera and Patagonian plateau around latitude 46°S

1981 ◽  
Vol 303 (1474) ◽  
pp. 105-149 ◽  
Keyword(s):  
Calc Alkaline ◽  
Alkali Basalts ◽  
Cinder Cones ◽  
Andean Cordillera ◽  
The Pacific ◽  
Igneous Activity ◽  
History Of ◽  
Pacific Margin ◽  
Rhyolite Volcanism ◽  
Back Arc

From the Middle Jurassic onwards persistent igneous activity in the southern Andes around 46 °S was controlled by easterly dipping subduction along the Pacific margin. Cogenetic plutonic rocks belonging to the Patagonian batholith, and calc-alkaline volcanics ranging from basaltic andesites to rhyolitic tuffs and ignimbrites are the principal products. Erosion of the primary volcanics has led at various times to the development of thick volcaniclastic sequences, for example in the Cretaceous-Lower Tertiary Divisadero formation. The Coyhaique region marks the northerly extension of a narrow back-arc basin in which the marine Neocomian successions accumulated. Volcaniclastics from the island arc, which presumably lay to the west, are intercalated with the sediments. Although the marine basin was short-lived a mildly extensional back-arc regime may have existed through much of Mesozoic-Recent times. Widespread basalt-rhyolite volcanism on the eastern side of the cordillera seems to have been associated with this tectonic environment. Remnants of the Patagonian basalt plateau at latitude 45-47 °S extend from the Argentine-Chile frontier to Lago Colhue Huapi. Four principal age and compositional groups have been distinguished in the lavas, (i) The oldest, which are about 80 Ma, occur in sections at Senguerr and Morro Negro. They are almost exclusively tholeiitic, but show some calc-alkaline affinities and resemble in other respects basalts from marginal basins, (ii) The second group (57-43 Ma) occur in the lower part of the Chile Chico section with a compositional spread from olivine tholeiites through alkali basalts to one occurrence of a basanite. (iii) The upper part of the main plateau sequence, where the flows are in the range 25-9 Ma, are dominantly of alkali basalt composition, (iv) Post-plateau flows from small cinder cones on the surface of the plateau range in age from ca. 4 Ma to 0.2 Ma or less. They are mostly highly undersaturated basanites, with occasional leucite basanites, enriched in incompatible elements. A few of the earlier tholeiites with calc-alkali traits may have been closely associated with subduction or marginal basin processes. The younger lavas are more alkalic intraplate types generated in the remote back-arc extensional zone.

The Ordovician volcanics of the Elmtree–Belledune inlier and their relationship to volcanics of the northern Miramichi Highlands, New Brunswick

1992 ◽  
Vol 29 (7) ◽  
pp. 1430-1447 ◽  
Author(s):  
J. A. Winchester ◽  
C. R. van Staal ◽  
J. P. Langton
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Volcanic Arc ◽  
Middle Ordovician ◽  
Marginal Basin ◽  
Tectonic Mélange ◽  
Back Arc

An investigation of the geology and chemistry of the basic igneous rocks in the Elmtree and Belledune inliers in northern New Brunswick shows that the bulk of the Middle Ordovician rocks of the ophiolitic Fournier Group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back-arc basin southeast of a volcanic arc. The oceanic back-arc-basin igneous rocks form the basement to renewed arc-related basaltic volcanism in late Middle to Late Ordovician time. The Fournier Group is separated from the structurally-underlying, shale-dominated Elmtree Formation of the Tetagouche Group by an extensive tectonic melange, which incorporates lenses of serpentinite, mafic volcanic rocks, and sedimentary rocks of both the Tetagouche and Fournier groups. The mafic volcanic rocks in the Elmtree Formation correlate best with those intercalated with the lithologically similar sediments of the Llandeilian–Caradocian Boucher Brook Formation in the northern Miramichi Highlands. The melange and the present structural amalgamation of the Tetagouche and Fournier groups result from closure of the marginal basin by northward-directed subduction at the end of the Ordovician. Most mafic suites in the Elmtree and Belledune inliers can be chemically correlated with similar suites in the northern Miramichi Highlands, showing that the two areas are not separated by a terrane boundary.

Contribution a l'etude du volcanisme de l'arc des Nouvelles-Hebrides; caracterisation de deux series magmatiques de l'ile d'Erromango

1979 ◽  
Vol S7-XXI (5) ◽  
pp. 631-641 ◽  
Author(s):  
G. Marcelot ◽  
C. Lefevre ◽  
P. Maillet ◽  
R. C. Maury
Keyword(s):  
Fractional Crystallization ◽  
Basaltic Magma ◽  
Island Arc ◽  
Calc Alkaline ◽  
Early Stages ◽  
New Hebrides ◽  
Volcanic Series

Abstract The volcanic series of Mt Rantop and Robertson's Thumb, Erromango Island, New Hebrides, formed by fractional crystallization of orogenic basaltic magma of near-island-arc tholeiitic type. Differentiation was controlled mainly by separation of plagioclase, olivine and clinopyroxene. The Mt Rantop series is predominantly tholeiitic (plagioclase at the liquidus, late appearance of magnetite, pigeonite in microphenocrysts, and Fe and Ti remaining constant or increasing in the early stages of differentiation); those of Robertson's Thumb are mostly calc-alkaline (magnetite at the liquidus, late appearance of plagioclase, olivine quickly becoming unstable, orthopyroxene in phenocrysts and early decrease of Fe and Ti). The compositional differences reflect higher fO <sub>2</sub> and PH <sub>2</sub> O in Robertson's Thumb during fractional crystallization.

Late Paleozoic- Early Mesozoic tectonics of Hainan Island: Key to understanding Paleotethyan geology

2020 ◽  
Author(s):  
Huiying He ◽  
Peter Cawood ◽  
Yuejun Wang
Keyword(s):  
South China ◽  
Tectonic Evolution ◽  
Hainan Island ◽  
Igneous Rocks ◽  
Late Paleozoic ◽  
Calc Alkaline ◽  
Early Mesozoic ◽  
History Of ◽  
Back Arc ◽  
T Values

<p>In Southeast Asia, establishing the origin and associated tectonic setting of Late Paleozoic-Early Mesozoic igneous rocks is complicated by structural overprinting and the complex tectonic evolution of the Paleotethyan regime. Hainan Island, located at the south-eastern margin of the Paleotethys, and lacking significant tectonic overprints is a key to understand amalgamation history of the Indochina and South China blocks and to constraining the tectonic evolution of Paleotethys ocean in southeast Asia.</p><p>The Late Paleozoic-Early Mesozoic record of igneous rocks on Hainan Island includes the following. 1) ca. 350 Ma island arc andesites and ca. 330 Ma metabasites, the latter with both MORB- and arc-like geochemical affinities, positive ε<sub>Nd</sub>(t) values of +5.86 – +9.85 and rare inherited zircons with a zircon age of 1400 Ma inferred to be derived from a MORB source with the input of a slab-derived component. Together with the ~350 Ma island arc andesites, the Carboniferous tectonic environment is supposed to be a continental back-arc basin setting. 2) Late Permian gneiss granitoids (272-252 Ma) characterized by a gneissic foliation and calc-alkaline I-type geochemical affinities with negative Nb-Ta and Ti anomalies, related to metasomatized mantle wedge modified by the sediment-derived component in a continental arc setting. 3) ca. 257 Ma arc-like andesites, which further validate a subduction-related setting. 4) Peraluminious Early-Middle Triassic massive granitoids (251–243 Ma) with slightly high A/CNK ratios, δ<sup>18</sup>O values (up to 11.75 ‰) and Sr/Y ratios, inferred to have formed in a compressive regime from a mixed source of greywacke and metabasite. 5) Middle-Late Triassic (242–225 Ma) high-K calc-alkaline granitoids with high zircon temperatures (842–867°C) and geochemical signatures of A-type granites. They show slightly low whole-rock ε<sub>Nd</sub>(t) and zircon ε<sub>Hf</sub>(t) values, suggestive of the derivation from a metabasite–greywacke source in an extensional setting. 6) ca. 240 Ma gabbro-dolerites showing enrichment in LILEs, depletion in HFSEs, negative ε<sub>Nd</sub> (t)-ε<sub>Hf</sub> (t) values (−8.45 to −1.05 and −5.9 to −2.7, respectively) and crustal-like δ<sup>18</sup>O values (7.26–8.70‰), it is implied that the Hainan Island entered into post-collisional environment in response to the asthenosphere upwelling shortly after the closure of back-arc basin.</p><p>Thus, Hainan Island provides a record of Carboniferous back-arc basin opening, followed by an extended Permian–Triassic history of subduction-related consumption leading to orogenic assembly and extensional collapse between the South China and Indochina blocks. Such a tempo-spatial pattern is consistent with that along the Song Ma–Ailaoshan suture zone rather than the magmatic history of eastern South China and indicates that the Paleotethys extended west to at least Hainan Island in the Late Paleozoic-Early Mesozoic.</p>

Silica-enriched mantle sources of subalkaline picrite-boninite-andesite island arc magmas

2017 ◽  
Vol 199 ◽  
pp. 287-303 ◽  
Author(s):  
A. Bénard ◽  
R.J. Arculus ◽  
O. Nebel ◽  
D.A. Ionov ◽  
S.R.B. McAlpine
Keyword(s):  
Island Arc ◽  
Arc Magmas ◽  
Enriched Mantle ◽  
Mantle Sources

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.

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