Mantle wedge control on back-arc crustal accretion

Nature ◽  
2002 ◽  
Vol 416 (6879) ◽  
pp. 417-420 ◽  
Author(s):  
Fernando Martinez ◽  
Brian Taylor
Keyword(s):  
Mantle Wedge ◽  
Crustal Accretion ◽  
Back Arc

scholarly journals Ophiolitic Pyroxenites Record Boninite Percolation in Subduction Zone Mantle

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 565 ◽  
Author(s):  
Véronique Le Roux ◽  
Yan Liang
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Mantle Wedge ◽  
Major Element ◽  
Early Stage ◽  
Diffusion Modeling ◽  
Melt Infiltration ◽  
Melt Percolation ◽  
Back Arc ◽  
Parental Melts

The peridotite section of supra-subduction zone ophiolites is often crosscut by pyroxenite veins, reflecting the variety of melts that percolate through the mantle wedge, react, and eventually crystallize in the shallow lithospheric mantle. Understanding the nature of parental melts and the timing of formation of these pyroxenites provides unique constraints on melt infiltration processes that may occur in active subduction zones. This study deciphers the processes of orthopyroxenite and clinopyroxenite formation in the Josephine ophiolite (USA), using new trace and major element analyses of pyroxenite minerals, closure temperatures, elemental profiles, diffusion modeling, and equilibrium melt calculations. We show that multiple melt percolation events are required to explain the variable chemistry of peridotite-hosted pyroxenite veins, consistent with previous observations in the xenolith record. We argue that the Josephine ophiolite evolved in conditions intermediate between back-arc and sub-arc. Clinopyroxenites formed at an early stage of ophiolite formation from percolation of high-Ca boninites. Several million years later, and shortly before exhumation, orthopyroxenites formed through remelting of the Josephine harzburgites through percolation of ultra-depleted low-Ca boninites. Thus, we support the hypothesis that multiple types of boninites can be created at different stages of arc formation and that ophiolitic pyroxenites uniquely record the timing of boninite percolation in subduction zone mantle.

scholarly journals First magmatism in the New England Batholith, Australia: forearc and arc–back-arc components in the Bakers Creek Suite gabbros

Solid Earth ◽  
2017 ◽  
Vol 8 (2) ◽  
pp. 421-434 ◽  
Author(s):  
Seann J. McKibbin ◽  
Bill Landenberger ◽  
C. Mark Fanning
Keyword(s):  
New England ◽  
Mantle Wedge ◽  
Accretionary Prism ◽  
Granitic Rocks ◽  
Magmatic Evolution ◽  
Lachlan Orogen ◽  
Eastern Australia ◽  
Granitic Intrusion ◽  
Back Arc ◽  
New England Orogen

Abstract. The New England Orogen, eastern Australia, was established as an outboard extension of the Lachlan Orogen through the migration of magmatism into forearc basin and accretionary prism sediments. Widespread S-type granitic rocks of the Hillgrove and Bundarra supersuites represent the first pulse of magmatism, followed by I- and A-types typical of circum-Pacific extensional accretionary orogens. Associated with the former are a number of small tholeiite–gabbroic to intermediate bodies of the Bakers Creek Suite, which sample the heat source for production of granitic magmas and are potential tectonic markers indicating why magmatism moved into the forearc and accretionary complexes rather than rifting the old Lachlan Orogen arc. The Bakers Creek Suite gabbros capture an early ( ∼  305 Ma) forearc basalt-like component with low Th ∕ Nb and with high Y ∕ Zr and Ba ∕ La, recording melting in the mantle wedge with little involvement of a slab flux and indicating forearc rifting. Subsequently, arc–back-arc like gabbroic magmas (305–304 Ma) were emplaced, followed by compositionally diverse magmatism leading up to the main S-type granitic intrusion ( ∼  290 Ma). This trend in magmatic evolution implicates forearc and other mantle wedge melts in the heating and melting of fertile accretion complex sediments and relatively long ( ∼  10 Myr) timescales for such melting.

Back-arc underplating provided crustal accretion affecting topography and sedimentation in the Adria microplate

2021 ◽  
pp. 105470
Author(s):  
Paolo Mancinelli ◽  
Vittorio Scisciani ◽  
Cristina Pauselli ◽  
Gérard M. Stampfli ◽  
Fabio Speranza ◽  
...  
Keyword(s):  
Crustal Accretion ◽  
Back Arc

Uncertainties in the stability field of UHP hydrous phases (10-A phase and phase E) and deep-slab dehydration: potential implications for fluid migration and water fluxes at subduction zones

2020 ◽  
Author(s):  
Nestor G. Cerpa ◽  
José Alberto Padrón-Navarta ◽  
Diane Arcay
Keyword(s):  
Lithospheric Mantle ◽  
Subduction Zones ◽  
Mantle Wedge ◽  
Numerical Models ◽  
Stability Field ◽  
Fluid Migration ◽  
Water Fluxes ◽  
Water Release ◽  
The Stability ◽  
Back Arc

<p>The subduction of water via lithospheric-mantle hydrous phases have major implications for the generation of arc and back-arc volcanism, as well as for the global water cycle. Most of the current numerical models use Perple_X [Connolly et al., 2009] to quantify water release from the slab and subsequent fluid migration in the mantle wedge. At UHP conditions, the phase diagrams generated with this thermodynamic code suggest that the breakdown of serpentine and chlorite leads to the near complete dehydration of the lithospheric mantle before reaching a 200-km depth. Laboratory experiments, however, have observed the stability of the 10-Å phase and the phase E in natural bulk compositions, which may hold moderate amounts of water, beyond the stability field of serpentine and chlorite [Fumagalli and Poli, 2005; Maurice et al., 2018]. Here, using 2D thermo-mechanical models, we explore to what extent the presence of these hydrous phases may favor a deeper subduction of water than those predicted by Perple_X.</p><p>We perform end-member models in terms of slab temperature and thickness of hydrated lithospheric mantle entering at trench. The computed geotherms within the uppermost subducted mantle show that the stability field of mantle hydrous phases around 600-800°C and 6-8 GPa is crucial for predictions of water fluxes. We point out that the lack of systematic experiments at these P-T conditions, as well as the absence of 10-Å and E phases in current thermodynamic databases, prevent accurate estimates of deep water transfers. We nonetheless build a phase diagram based on current experimental constraints that includes approximations of their stability field and qualitatively discuss the potential implications for fluid migration in the back-arc mantle wedge and water fluxes.</p>

Spatial variations of magmatic crustal accretion during the opening of the Tyrrhenian back-arc from wide-angle seismic velocity models and seismic reflection images

2016 ◽  
Vol 30 ◽  
pp. 124-141 ◽  
Author(s):  
Manel Prada ◽  
Valenti Sallares ◽  
César R. Ranero ◽  
Montserrat G. Vendrell ◽  
Ingo Grevemeyer ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Seismic Velocity ◽  
Spatial Variations ◽  
Wide Angle ◽  
Crustal Accretion ◽  
Velocity Models ◽  
Back Arc

scholarly journals Magmatic Evolution Following Damp Tholeiitic and Wet Calc-alkaline Liquid Lines of Descent: An Eastern Pontides (NE Turkey) Example

2020 ◽  
Author(s):  
Ze Liu ◽  
Di-Cheng Zhu ◽  
Oliver Jagoutz ◽  
Hervé Rezeau ◽  
Qing Wang ◽  
...  
Keyword(s):  
Mantle Wedge ◽  
Spatial Relationship ◽  
Oceanic Lithosphere ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Eastern Pontides ◽  
Isotopic Compositions ◽  
Intrusive Rocks ◽  
Lines Of Descent ◽  
Back Arc

Abstract Associations between tholeiitic and calc-alkaline arc magmatism with close spatial and temporal relationships can provide critical constraints on magma genesis and allow the reconstruction of subduction polarity at convergent margins. This study identifies two compositionally distinct intrusive series from the Yusufeli region in the Eastern Pontides arc, NE Turkey. The intrusive rocks from the Yusufeli intrusive complex were emplaced at 179–170 Ma and are dominated by the low- to medium-K tholeiitic series, with depleted Hf isotopic compositions. In contrast, the intrusive rocks from the Camlikaya intrusive complex were emplaced at 151–147 Ma and are characterized by the medium- to high-K calc-alkaline series, with relatively enriched Hf isotopic compositions. The Al-in-hornblende geobarometer reveals that the magmas of both two intrusive complexes crystallized at upper crustal levels (∼150–250 MPa, ∼5–8 km). The presence of patchy-textured plagioclase and the widespread occurrence of coeval dykes and magmatic mafic enclaves (MMEs) indicate that two intrusive complexes are derived from multiple magma pulses in open magmatic systems. The mineral crystallization order of amphibole and plagioclase, the trace elemental signatures (e.g. Sr/Y and Y), and rare-earth element modeling collectively suggest that the Yusufeli intrusive complex was dominated by plagioclase and clinopyroxene fractionation with earlier plagioclase crystallization than amphibole, whereas the Camlikaya intrusive complex was dominated by the fractionation of amphibole accompanied by co-crystallization of plagioclase. Such significant differences in the fractionating mineral assemblages at comparable intrusion pressures can be attributed to different initial H2O contents of the Yusufeli and Camlikaya parental magmas, which ultimately control their distinct liquid lines of descent (LLD). In accord with thermodynamic modeling results derived using the Rhyolite-MELTS software, we propose that the Yusufeli intrusive rocks are derived from damp (∼1–2 wt.% H2O) parental magmas formed dominantly by decompression melting of mantle wedge in a back-arc setting. In contrast, the wet parental magmas (>∼2 wt.% H2O) of Camlikaya intrusive rocks are more hydrous and formed through flux melting of supra subduction zone mantle wedge. Combined with the back-arc basin related Jurassic sedimentary and structural records previously determined in the Southern Zone of the Eastern Pontides, the geochemical compositions and spatial relationship of the Yusufeli and Camlikaya intrusive complexes are preferred to be explained by the southward subduction of the Paleotethys oceanic lithosphere in the Early to Late Jurassic.

Lithospheric mantle, asthenosphere, slab and crustal contribution to petrogenesis of Eocene to Miocene volcanic rocks from the west Alborz Magmatic Assemblage, SE Ahar, Iran

2020 ◽  
pp. 1-32
Author(s):  
Ahmad Ahmadvand ◽  
Mohammad Reza Ghorbani ◽  
Mir Ali Asghar Mokhtari ◽  
Yi Chen ◽  
William Amidon ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Mantle Wedge ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
The West ◽  
Nw Iran ◽  
Enriched Mantle ◽  
Basement Rocks ◽  
Cenozoic Volcanism ◽  
Back Arc

Abstract Significant uncertainty remains regarding the exact timing and nature of subduction events during the closure of the Tethyan seas in what is now NW Iran. This study thus presents new geochemical compositions and U–Pb ages for a suite of volcanic rocks emplaced during Cenozoic volcanism in the west Alborz Magmatic Assemblage, which is commonly regarded as the back-arc of the Neotethyan magmatism in Central Iran. The subalkali basalts and andesites are dated to 57 ± 1.2 Ma, and are likely derived from a supra-subduction mantle wedge. Later, trachytic A-type rocks erupted from ~42 to 25 Ma during an anorogenic (extensional) stage triggered by slab retreat and associated asthenospheric mantle influx. A-type melts were at least partly concurrent with lithospheric mantle magmatism implied by eruption of subalkali basalts–andesites around 26–24 Ma. Next, Amp-Bt trachybasaltic volcanism with high-Nb basaltic affinity at ~19 Ma likely records slab deepening and slab partial melting, which reacted with the mantle wedge to produce the source material for the high-Nb basalts. Sr–Nd isotopic ratios for SE Ahar mafic as well as A-type rocks imply rather enriched mantle source(s). Some crustal contamination is implied by the presence of inherited zircons dominated by those derived from Neoproterozoic–Cambrian basement rocks and Carboniferous magmatism. Rhyolitic rocks with adakitic affinity probably mark the final volcanism in the study area. The adakitic rocks show crustal signatures such as high K and Th, probably formed as a consequence of higher temperature gradients, at crustal levels, imposed by both slab and mantle partial melts.

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