Petrogenesis of Lavas along the Solomon Island Arc, SW Pacific: Coupling of Compositional Variations and Subduction Zone Geometry

Abstract —Analysis of geochemical, geochronological, and new geophysical data on metasedimentary and igneous rocks of the Ol’khon region has made it possible to substantiate: (1) the absence of products of the Caledonian suprasubduction magmatism from the adjacent part of the Siberian craton and (2) the presence of a product of this magmatism in the Anga–Talanchan island arc, namely, the Krestovsky massif with gabbro-diorite to granite phases. This suggests subduction of the Paleoasian oceanic crust under the island arc before the collision. The geophysical data showed a steep sinking of the Siberian craton margin. This sinking and the supposed contrary movement and rotation of the Siberian craton prevented the appearance of a subduction zone beneath the craton during the collision but caused the wide development of fault plates in the fold belt at the late collision stage. The residue of oceanic crust slab was pressed out along the fault planes near the surface and formed a row of gabbro-pyroxenite massifs of the Birkhin Complex in the fold belt, where syncollisional granitic melts (Sharanur Complex) formed at the same time. The interaction of two contrasting melts gave rise to the Tazheran and Budun alkaline syenite massifs and alkaline metasomatites of the Birkhin and Ulanganta gabbroid massifs.

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The Imbert Formation of northern Hispaniola: a tectono-sedimentary record of arc-continent collision and ophiolite emplacement in the northern Caribbean subduction-accretionary prism

Solid Earth Discussions ◽

10.5194/sed-7-1827-2015 ◽

2015 ◽

Vol 7 (2) ◽

pp. 1827-1876 ◽

Cited By ~ 2

Author(s):

J. Escuder-Viruete ◽

A. Suárez-Rodríguez ◽

J. Gabites ◽

A. Pérez-Estaún

Keyword(s):

Subduction Zone ◽

Continental Margin ◽

Middle Eocene ◽

Accretionary Prism ◽

Island Arc ◽

Caribbean Island ◽

Stratigraphic Sequence ◽

Oblique Collision ◽

The Caribbean ◽

Ophiolitic Complex

Abstract. In northern Hispaniola, the Imbert Formation (Fm) has been interpreted as an orogenic "mélange" originally deposited as trench-fill sediments, an accretionary (subduction) complex formed above a SW-dipping subduction zone, or the sedimentary result of the early oblique collision of the Caribbean plate with the Bahama Platform in the middle Eocene. However, new stratigraphical, structural, geochemical and geochronological data from northern Hispaniola indicate that the Imbert Fm constitutes a coarsening-upward stratigraphic sequence that records the transition of the sedimentation from a pre-collisional forearc to a syn-collisional piggy-back basin. This piggy-back basin was transported on top of the Puerto Plata ophiolitic complex slab and structurally underlying accreted units of the Rio San Juan complex, as it was emplaced onto the North America continental margin units. The Imbert Fm unconformably overlies different structural levels of the Caribbean subduction-accretionary prism, including a supra-subduction zone ophiolite, and consists of three laterally discontinuous units that record the exhumation of the underlying basement. The distal turbiditic lower unit includes the latest volcanic activity of the Caribbean island arc; the more proximal turbiditic intermediate unit is moderately affected by syn-sedimentary faulting; and the upper unit is a (caotic) olistostromic unit, composed of serpentinite-rich polymictic breccias, conglomerates and sandstones, strongly deformed by syn-sedimentary faulting, slumping and sliding processes. The Imbert Fm is followed by subsidence and turbiditic deposition of the overlying El Mamey Group. The 40Ar / 39Ar plagioclase plateau ages obtained in gabbroic rocks from the Puerto Plata ophiolitic complex indicate its exhumation at ∼ 45–40 Ma (lower-to-middle Eocene), contemporaneously to the sedimentation of the overlying Imbert Fm. These cooling ages imply the uplift to the surface and submarine erosion of the complex to be the source of the ophiolitic fragments in the Imbert Fm, during of shortly after the emplacement of the intra-oceanic Caribbean island-arc onto the continental margin.

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Subduction-related magmatic imprint of most Philippine ophiolites: implications on the early geodynamic evolution of the Philippine archipelago

BSGF - Earth Sciences Bulletin ◽

10.2113/175.5.443 ◽

2004 ◽

Vol 175 (5) ◽

pp. 443-460 ◽

Cited By ~ 53

Author(s):

Rodolfo A. Tamayo* ◽

René C. Maury* ◽

Graciano P. Yumul ◽

Mireille Polvé ◽

Joseph Cotten ◽

...

Keyword(s):

Partial Melting ◽

Subduction Zone ◽

Volcanic Rocks ◽

The Philippines ◽

Island Arc ◽

Island Arcs ◽

Geodynamic Evolution ◽

Wide Range ◽

Opening And Closing ◽

Back Arc

Abstract The basement complexes of the Philippine archipelago include at least 20 ophiolites and ophiolitic complexes. These complexes are characterised by volcanic sequences displaying geochemical compositions similar to those observed in MORB, transitional MORB-island arc tholeiites and arc volcanic rocks originating from modern Pacific-type oceans, back-arc basins and island arcs. Ocean island basalt-like rocks are rarely encountered in the volcanic sequences. The gabbros from the ophiolites contain clinopyroxenes and plagioclases showing a wide range of XMg and An values, respectively. Some of these gabbros exhibit mineral chemistries suggesting their derivation from basaltic liquids formed from mantle sources that underwent either high degrees of partial melting or several partial melting episodes. Moreover, some of the gabbros display a crystallization sequence where orthopyroxene and clinopyroxene appeared before plagioclase. The major element compositions of coexisting orthopyroxenes and olivines from the mantle peridotites are consistent with low to high degrees of partial melting. Accessory spinels in these peridotites display a wide range of XCr values as well with some of them above the empirical upper limit of 0.6 often observed in most modern mid-oceanic ridge (MOR) mantle rocks. Co-existing olivines and spinels from the peridotites also exhibit compositions suggesting that they lastly equilibrated under oxidizing mantle conditions. The juxtaposition of volcanic rocks showing affinities with modern MOR and island arc environments suggests that most of the volcanic sequences in Philippine ophiolites formed in subduction-related geodynamic settings. Similarly, their associated gabbros and peridotites display mineralogical characteristics and mineral chemistries consistent with their derivation from modern supra-subduction zone-like environments. Alternatively, these rocks could have, in part, evolved in a supra-subduction zone even though they originated from a MOR-like setting. A simplified scenario regarding the early geodynamic evolution of the Philippines is proposed on the basis of the geochemical signatures of the ophiolites, their ages of formation and the ages and origins of the oceanic basins actually bounding the archipelago, including basins presumed to be now totally consumed. This scenario envisages the early development of the archipelago to be largely dominated by the opening and closing of oceanic basins. Fragments of these basins provided the substratum on top of which the Cretaceous to Recent volcanic arcs of the Philippines were emplaced.

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Contributions from the detrital approach to unravelling the timing of India-Asia collision and Himalayan evolution

10.5194/egusphere-egu21-1916 ◽

2021 ◽

Author(s):

Yani Najman ◽

Shihu Li

Keyword(s):

Subduction Zone ◽

Crustal Deformation ◽

Earth Science ◽

Island Arc ◽

Current Understanding ◽

Indian Plate ◽

Geophysical Research

<p>Knowledge of the timing of India-Asia collision and associated Tethyan closure in the region is critical to advancement of models of crustal deformation.&#160;&#160; One of a number of methods traditionally used to constrain the time of India-Asia collision is the detrital approach. This involves determination of when Asian material first arrived on the Indian plate, with most recent estimates documenting collision at ca 60 Ma (e.g. Hu et al, Earth Science Reviews 2016). However, more recently, such data and a number of other approaches providing data previously used to determine the timing of India-Asia collision, have been controversially re-interpreted to represent collision of India with an Island arc, with terminal India-Asia collision occurring significantly later, ca 34 Ma (e.g. Aitchison et al, J. Geophysical Research 2007). Clearly, for the detrital approach to advance the debate, discrimination between Asian detritus and arc detritus is required. Such a discrimination was proposed in Najman et al (EPSL 2017), dating the timing of terminal India-Asia collision at 54 Ma. However, this evidence is far from universally accepted.&#160; For example, such data are at variance with various palaeomagnetic studies which suggest that an oceanic Transtethyan subduction zone existed 600-2300 kms south of the Eurasian margin in the Paleocene &#160;(e.g. Martin et al, PNAS 2020) and therefore these authors propose different explanations to explain the detrital data.&#160; This presentation will discuss the uncertainties associated with our current understanding of the timing of India-Asia collision.</p>

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Geology, petrology and tectonomagmatic evolution of the plutonic crustal rocks of the Sabzevar ophiolite, NE Iran

Geological Magazine ◽

10.1017/s0016756812000933 ◽

2013 ◽

Vol 150 (5) ◽

pp. 862-884 ◽

Cited By ~ 10

Author(s):

MORTEZA KHALATBARI JAFARI ◽

HASSAN A. BABAIE ◽

MOJTABA MIRZAIE

Keyword(s):

Subduction Zone ◽

Subduction Zones ◽

Island Arc ◽

Magma Chambers ◽

Northern Margin ◽

Crustal Rocks ◽

Microscopic Studies ◽

Element Enrichment ◽

Spider Diagrams ◽

Ocean Ridge

AbstractThe plutonic crustal sequence exposed northeast of Sabzevar is part of the ophiolitic belt of Sabzevar that occurs along the northern margin of the Central Iran micro-continent. The sequence includes olivine and pyroxene gabbro with cumulate characteristics, isotropic gabbro, foliated gabbro and a diabase sheeted dyke complex cut by wehrlite and olivine websterite intrusions, and pegmatite gabbro and plagiogranite as small intrusions and dykes. The sequence is comparable to gabbros in known ophiolite complexes. Microscopic studies show an abundance of the mesocumulate and heteradcumulate textures that represent open system magma chambers, which are common in supra-subduction zones. The olivine → plagioclase → clinopyroxene → ± orthopyroxene → amphibole trend of mineralization in the gabbros, similar to mid-ocean ridge basalt (MORB), and olivine → clinopyroxene → ± orthopyroxene → plagioclase → amphibole, similar to arc rocks, indicate the diversity in the formation of these rocks, and represent petrographic evidence of their formation in a supra-subduction zone. The rocks have calc-alkaline to tholeiitic affinities, and niobium depletion in the spider diagrams of diabase that matches the patterns of island arc magma. These patterns, and the light rare earth element enrichment of the diabase and plagiogranite, suggest the effect and introduction of the fluids, originating from the subducting slab, beneath the mantle wedge. The low titanium compositions, matching those of arc diabase and plagiogranite, plot in the island arc to MORB tectonomagmatic fields, and suggest formation of the Sabzevar ophiolitic plutonic crustal sequence in a supra-subduction zone during Late Cretaceous time.

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