Depleted mantle beneath an oceanic island arc: New insights into peridotites of the RasKoh ophiolite, western Pakistan

The Slide Mountain Terrane consists of Devonian to Permian siliceous and detrital sediments in which are interbedded basalts and dolerites. Locally, ultramafic cumulates intrude these sediments. The Slide Mountain Terrane is considered to represent a back-arc basin related to the Quesnellia Paleozoic arc-terrane. However, the Slide Mountain mafic volcanic rocks exposed in central British Colombia do not exhibit features of back-arc basin basalts (BABB) but those of mid-oceanic ridge (MORB) and oceanic island (OIB) basalts. The N-MORB-type volcanic rocks are characterized by light rare-earth element (LREE)-depleted patterns, La/Nb ratios ranging between 1 and 2. Moreover, their Nd and Pb isotopic compositions suggest that they derived from a depleted mantle source. The within-plate basalts differ from those of MORB affinity by LREE-enriched patterns; higher TiO2, Nb, Ta, and Th abundances; lower εNd values; and correlatively higher isotopic Pb ratios. The Nd and Pb isotopic compositions of the ultramafic cumulates are similar to those of MORB-type volcanic rocks. The correlations between εNd and incompatible elements suggest that part of the Slide Mountain volcanic rocks derive from the mixing of two mantle sources: a depleted N-MORB type and an enriched OIB type. This indicates that some volcanic rocks of the Slide Mountain basin likely developed from a ridge-centered or near-ridge hotspot. The activity of this hotspot is probably related to the worldwide important mantle plume activity that occurred at the end of Permian times, notably in Siberia.

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The country rocks of Devonian magmatism in the North Patagonian Massif and Chaitenia

Andean geology ◽

10.5027/andgeov45n3-3117 ◽

2018 ◽

Vol 45 (3) ◽

pp. 301 ◽

Cited By ~ 11

Author(s):

Francisco Hervé ◽

Mauricio Calderón ◽

Mark Fanning ◽

Robert Pankhurst ◽

Carlos W. Rapela ◽

...

Keyword(s):

Metamorphic Grade ◽

Oceanic Island ◽

Detrital Zircons ◽

Island Arc ◽

Ultramafic Rocks ◽

The West ◽

Metasedimentary Rocks ◽

The North ◽

The Andes ◽

Late Neoproterozoic

Previous work has shown that Devonian magmatism in the southern Andes occurred in two contemporaneous belts: one emplaced in the continental crust of the North Patagonian Massif and the other in an oceanic island arc terrane to the west, Chaitenia, which was later accreted to Patagonia. The country rocks of the plutonic rocks consist of metasedimentary complexes which crop out sporadically in the Andes on both sides of the Argentina-Chile border, and additionally of pillow metabasalts for Chaitenia. Detrital zircon SHRIMP U-Pb age determinations in 13 samples of these rocks indicate maximum possible depositional ages from ca. 370 to 900 Ma, and the case is argued for mostly Devonian sedimentation as for the fossiliferous Buill slates. Ordovician, Cambrian-late Neoproterozoic and “Grenville-age” provenance is seen throughout, except for the most westerly outcrops where Devonian detrital zircons predominate. Besides a difference in the Precambrian zircon grains, 76% versus 25% respectively, there is no systematic variation in provenance from the Patagonian foreland to Chaitenia, so that the island arc terrane must have been proximal to the continent: its deeper crust is not exposed but several outcrops of ultramafic rocks are known. Zircons with devonian metamorphic rims in rocks from the North Patagonian Massif have no counterpart in the low metamorphic grade Chilean rocks. These Paleozoic metasedimentary rocks were also intruded by Pennsylvanian and Jurassic granitoids.

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A crustal section of an intra-oceanic island arc: The Late Jurassic-Early Cretaceous Guanajuato magmatic sequence, central Mexico

Earth and Planetary Science Letters ◽

10.1016/0012-821x(92)90060-9 ◽

1992 ◽

Vol 108 (1-3) ◽

pp. 61-77 ◽

Cited By ~ 48

Author(s):

H LAPIERRE ◽

L ORTIZ ◽

W ABOUCHAMI ◽

O MONOD ◽

C COULON ◽

...

Keyword(s):

Early Cretaceous ◽

Late Jurassic ◽

Oceanic Island ◽

Island Arc ◽

Central Mexico

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Oceanic island arc stratigraphy in the Caribbean region: don't take it for granite

Sedimentary Geology ◽

10.1016/0037-0738(91)90069-p ◽

1991 ◽

Vol 74 (1-4) ◽

pp. 289-308 ◽

Cited By ~ 17

Author(s):

D.K. Larue ◽

A.L. Smith ◽

J.H. Schellekens

Keyword(s):

Oceanic Island ◽

Island Arc ◽

Caribbean Region ◽

The Caribbean

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Lithogeochemistry of volcano-plutonic assemblages of the southern Hanson Lake Block and southeastern Glennie Domain, Trans-Hudson Orogen: evidence for a single island arc complex

Canadian Journal of Earth Sciences ◽

10.1139/e98-037 ◽

1999 ◽

Vol 36 (2) ◽

pp. 209-225 ◽

Cited By ~ 11

Author(s):

Ralf O Maxeiner ◽

Tom II Sibbald ◽

William L Slimmon ◽

Larry M Heaman ◽

Brian R Watters

Keyword(s):

Volcanic Rocks ◽

Volcanic Belt ◽

Oceanic Island ◽

Island Arc ◽

Island Arcs ◽

Calc Alkaline ◽

East Central ◽

South Central ◽

Volcaniclastic Rocks ◽

Flin Flon

This paper describes the geology, geochemistry, and age of two amphibolite facies volcano-plutonic assemblages in the southern Hanson Lake Block and southeastern Glennie Domain of the Paleoproterozoic Trans-Hudson Orogen of east-central Saskatchewan. The Hanson Lake assemblage comprises a mixed suite of subaqueous to subaerial dacitic to rhyolitic (ca. 1875 Ma) and intercalated minor mafic volcanic rocks, overlain by greywackes. Similarly with modern oceanic island arcs, the Hanson Lake assemblage shows evolution from primitive arc tholeiites to evolved calc-alkaline arc rocks. It is intruded by younger subvolcanic alkaline porphyries (ca. 1861 Ma), synvolcanic granitic plutons (ca. 1873 Ma), and the younger Hanson Lake Pluton (ca. 1844 Ma). Rocks of the Northern Lights assemblage are stratigraphically equivalent to the lower portion of the Hanson Lake assemblage and comprise tholeiitic arc pillowed mafic flows and felsic to intermediate volcaniclastic rocks and greywackes, which can be traced as far west as Wapawekka Lake in the south-central part of the Glennie Domain. The Hanson Lake volcanic belt, comprising the Northern Lights and Hanson Lake assemblages, shows strong lithological, geochemical, and geochronological similarities to lithotectonic assemblages of the Flin Flon Domain (Amisk Collage), suggesting that all of these areas may have been part of a more or less continuous island arc complex, extending from Snow Lake to Flin Flon, across the Sturgeon-Weir shear zone into the Hanson Lake Block and across the Tabbernor fault zone into the Glennie Domain.

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Podiform chromitite-bearing ultrabasic rocks from the Bragança Massif, northern Portugal: fragments of island arc mantle?

Geological Magazine ◽

10.1017/s0016756800011419 ◽

1995 ◽

Vol 132 (1) ◽

pp. 39-49 ◽

Cited By ~ 18

Author(s):

J. C. Bridges ◽

H. M. Prichard ◽

C. A. Meireles

Keyword(s):

Island Arc ◽

Silicate Mineral ◽

Melt Extraction ◽

Partial Melt ◽

Arc Magmas ◽

Northern Portugal ◽

Depleted Mantle ◽

High Degree ◽

Podiform Chromitite ◽

Phase Relationships

AbstractThe Upper Allochthonous Thrust Complex (UATC) of the Bragança massif in northern Portugal contains a set of ultrabasic rocks interthrust with granulites. The ultrabasic rocks have refractory silicate mineral and whole rock compositions which indicate an origin as depleted mantle. Phase relationships of harzburgite samples suggest that they formed in equilibrium with high-Mg picritic melts created through a high degree of mantle partial melt extraction. Chromite in small podiform deposits has 100 Cr/(Cr + Al) ratios of 62–85, which are consistent with crystallization from such melts. Most of the chromite composition parameters are similar to those of ophiolite deposits except for the high ferric iron contents (2.77–8.95 wt% Fe2O3). Such enrichment is a feature of chromite from island arc magmas. It is suggested that the extensive partial melt extraction and chromite mineralization in the ultrabasic rocks occurred in the upper few kilometres of island arc mantle. The ultrabasic rocks were tectonically emplaced into a granulite and eclogite-bearing arc-continent collision complex during the Early Ordovician and subsequently, in the mid-Devonian emplaced over the Central-Iberian terrane.

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Tectonic setting of late Archean bimodal volcanism in the Michipicoten (Wawa) greenstone belt, Ontario

Canadian Journal of Earth Sciences ◽

10.1139/e87-109 ◽

1987 ◽

Vol 24 (6) ◽

pp. 1120-1134 ◽

Cited By ~ 44

Author(s):

Paul J. Sylvester ◽

Kodjo Attoh ◽

Klaus J. Schulz

Keyword(s):

Greenstone Belt ◽

Tectonic Setting ◽

Volcanic Rocks ◽

Depositional Environments ◽

Oceanic Island ◽

Island Arc ◽

Basaltic Rocks ◽

Bimodal Volcanism ◽

Continental Arc ◽

Convergent Plate Margin

The tectono-stratigraphic relationships, depositional environments, rock associations, and major- and trace-element compositions of the late Archean (2744–2696 Ma) bimodal basalt–rhyolite volcanic rocks of the Michipicoten (Wawa) greenstone belt, Ontario, are compatible with an origin along a convergent plate margin that varied laterally from an immature island arc built on oceanic crust to a more mature arc underlain by continental crust. This environment is similar to that of the Cenozoic Taupo–Kermadec–Tonga volcanic zone. Michipicoten basaltic rocks, most of which are proximal deposits compositionally similar ([La/Yb]n = 0.63–1.18) to modern oceanic island-arc tholeiites, are interpreted as having formed along the largely submerged island arc. Voluminous Michipicoten rhyolitic pyroclastic rocks ([La/Yb]n = 4.3–18.7, Ybn = 5.7–15.9) probably erupted subaerially from the continental arc, with distal facies deposited subaqueously on the adjacent oceanic island arc and proximal facies deposited in subaerial and shallow subaqueous environments on, or along the flanks of, the continental arc. The compositional similarity between the lower (2744 Ma) and upper (2696 Ma) volcanic sequences of the belt suggests that this island- and continental-arc configuration existed for at least 45 Ma. The Michipicoten belt may be a remnant of a larger, laterally heterogeneous volcanic terrane that also included the Abitibi greenstone belt.

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Evolution of porphyry copper mineralization in an oceanic island arc; Panama; a reply

Economic Geology ◽

10.2113/gsecongeo.73.5.985 ◽

1978 ◽

Vol 73 (5) ◽

pp. 985-0

Author(s):

S. E. Kesler

Keyword(s):

Porphyry Copper ◽

Oceanic Island ◽

Island Arc ◽

Copper Mineralization ◽

Porphyry Copper Mineralization

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Chromite in greenstone lavas from the Kanakasu area, Nanjo Massif of the Mesozoic Mino terrane, central Japan

Mineralogical Magazine ◽

10.1180/0026461026640050 ◽

2002 ◽

Vol 66 (4) ◽

pp. 575-590 ◽

Cited By ~ 4

Author(s):

T. Agata ◽

I. Hattori

Keyword(s):

Chemical Composition ◽

Oceanic Island ◽

Island Arc ◽

Basalt Magma ◽

Central Japan ◽

Compositional Zoning ◽

Oceanic Ridge ◽

Host Magma ◽

Alkalic Basalt ◽

Alkalic Basalts

AbstractChromite occurs together with olivine as phenocrysts in basalts of the Kanakasu greenstone body. Chromite forms inclusions within olivine phenocrysts; it also constitutes discrete phenocrystic grains scattered in the groundmass. The Cr and Ni contents of chromite-bearing olivine basalts are unusually high relative to the MgO content. This is probably due to the presence of phenocrystic chromite and olivine. The mineralogy suggests that the groundmass of the basalts is hawaiitic in composition. Chromite, generally, is unlikely to crystallize from differentiated magma such as hawaiite melt. The chromite and associated olivine phenocrysts are probably xenocrysts. Discrete chromite commonly shows compositional zoning that resulted from reaction with host magma; some chromite evidently changed in composition. Chromite embedded in olivine was shielded from reaction with host magma, and has preserved the original chemical composition. The composition of embedded chromite ranges: Mg/(Mg+Fe2+) 0.37–0.58, Cr/(Cr+Al) 0.47–0.64, Fe3+ 0.16–0.47 p.f.u., and Ti 0.034–0.13 p.f.u. The relatively high Ti and Al contents suggest that chromite crystallized from an alkalic basalt magma. The Cr/(Cr+Al) ratio is relatively high when compared to those of chromite in mid-oceanic ridge and island-arc alkalic basalts; the Kanakasu embedded chromite is chemically identical to chromite from Hawaiian alkalic basalts. The Kanakasu chromite was probably formed in an intraplate oceanic island.

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