Forearc magmatic evolution during subduction initiation: Insights from an Early Cretaceous Tibetan ophiolite and comparison with the Izu-Bonin-Mariana forearc

2020 ◽  
Author(s):  
Jin-Gen Dai ◽  
Cheng-Shan Wang ◽  
Robert J. Stern ◽  
Kai Yang ◽  
Jie Shen
Keyword(s):  
Early Cretaceous ◽  
Plate Tectonics ◽  
Early Stage ◽  
Published Data ◽  
Magmatic Evolution ◽  
Southern Tibet ◽  
Subduction Initiation ◽  
Suprasubduction Zone ◽  
Depleted Mantle ◽  
Mariana Forearc

Subduction initiation is a key process in the operation of plate tectonics. Our understanding of melting processes and magmatic evolution during subduction initiation has largely been developed from studies of the Izu-Bonin-Mariana forearc. Many suprasubduction zone ophiolites are analogous to the Izu-Bonin-Mariana forearc sequence. However, whether there are differences between Izu-Bonin-Mariana subduction initiation sequences and suprasubduction zone ophiolites remains unclear. Here, we report field geological, geochemical, and geochronological data from mafic and felsic rocks in the Xigaze ophiolite (southern Tibet) mantle and crustal section; the same types of published data from both this ophiolite and the Izu-Bonin-Mariana forearc are compiled for comparison. The ophiolite section is intruded by various late-stage dikes, including gabbroic pegmatite, diabase, basalt, and plagiogranite. The compositions of clinopyroxene and amphibole suggest that gabbroic pegmatite formed from hydrous high-SiO2 depleted melts, while whole-rock compositions of basaltic and diabase dikes show negative Nb and Ta anomalies, suggesting flux melting of depleted mantle. Along with the mafic rocks, plagiogranite has a roughly constant content of La and Yb with increasing SiO2 contents, implying hydrous melting of mafic amphibolite. Early-stage pillow basalts exhibit geochemical affinities with Izu-Bonin-Mariana forearc basalts, but they are slightly enriched. Synthesized with the regional geological setting and compared with Izu-Bonin-Mariana forearc magmatism, we propose that the transition from mid-ocean ridge basalt−like lavas to subduction-related mafic and felsic dikes records an Early Cretaceous subduction initiation event on the southern flank of the Lhasa terrane. However, the mantle sources and the magmatic evolution in the Xigaze ophiolite are more variable than those for the Izu-Bonin-Mariana forearc.

scholarly journals Supplemental Material: Forearc magmatic evolution during subduction initiation: Insights from an Early Cretaceous Tibetan ophiolite and comparison with the Izu-Bonin-Mariana forearc

2020 ◽  
Author(s):  
Jin-Gen Dai ◽  
et al.
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Early Cretaceous ◽  
Analytical Methods ◽  
Major And Trace Elements ◽  
Magmatic Evolution ◽  
Isotopic Data ◽  
Subduction Initiation ◽  
Mariana Forearc

Detailed analytical methods in Text S1, major- and trace-element compositions of clinopyroxene, orthopyroxene, and amphibole, whole-rock major and trace elements, Sr-Nd isotopic data, and zircon U-Pb and Lu-Hf data in Tables S1–S7; Figures S1–S5.

scholarly journals Supplemental Material: Forearc magmatic evolution during subduction initiation: Insights from an Early Cretaceous Tibetan ophiolite and comparison with the Izu-Bonin-Mariana forearc

2020 ◽  
Author(s):  
Jin-Gen Dai ◽  
et al.
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Early Cretaceous ◽  
Analytical Methods ◽  
Major And Trace Elements ◽  
Magmatic Evolution ◽  
Isotopic Data ◽  
Subduction Initiation ◽  
Mariana Forearc

Detailed analytical methods in Text S1, major- and trace-element compositions of clinopyroxene, orthopyroxene, and amphibole, whole-rock major and trace elements, Sr-Nd isotopic data, and zircon U-Pb and Lu-Hf data in Tables S1–S7.

scholarly journals Supplemental Material: Forearc magmatic evolution during subduction initiation: Insights from an Early Cretaceous Tibetan ophiolite and comparison with the Izu-Bonin-Mariana forearc

2020 ◽  
Author(s):  
Jin-Gen Dai ◽  
et al.
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Early Cretaceous ◽  
Analytical Methods ◽  
Major And Trace Elements ◽  
Magmatic Evolution ◽  
Isotopic Data ◽  
Subduction Initiation ◽  
Mariana Forearc

Detailed analytical methods in Text S1, major- and trace-element compositions of clinopyroxene, orthopyroxene, and amphibole, whole-rock major and trace elements, Sr-Nd isotopic data, and zircon U-Pb and Lu-Hf data in Tables S1–S7; Figures S1–S5.

Life cycle of an Archean subduction zone from initiation to arc–polarity reversal: Insights from the Zunhua ophiolitic mélange, North China Craton 

2021 ◽  
Author(s):  
Wenbin Ning ◽  
Timothy Kusky ◽  
Junpeng Wang ◽  
Lu Wang ◽  
Hao Deng ◽  
...  
Keyword(s):  
Life Cycle ◽  
Subduction Zone ◽  
North China Craton ◽  
Plate Tectonics ◽  
North China ◽  
Polarity Reversal ◽  
Iron Formation ◽  
Arc Magmatism ◽  
Subduction Initiation ◽  
Depleted Mantle

<p>Subduction initiation and arc–polarity reversal have rarely been recognized in the Archean rock record. We document Neoarchean subduction initiation, fore-arc magmatism, and an arc–polarity reversal event from the Zunhua structural belt along the eastern margin of the Central Orogenic Belt (COB) of the North China Craton (NCC). The Zunhua ophiolitic mélange within the Zunhua structural belt is a mappable unit characterized by blocks of metamorphosed harzburgite/lherzolite, podiform chromite –bearing dunite, pyroxenite, amphibolite, metabasites (basalt and diabase) with rare intermediate volcanics, chert, and tectonic lenses of banded iron formation in a strongly sheared metapelitic matrix. New geochronological and geochemical analyses of magmatic blocks within the ophiolitic mélange show that the crustal magmatic rocks were produced in a fore-arc region at 2.55–2.52 Ga from depletion of the harzburgitic–lherzolitic mantle tectonites. Chemical, petrological, and temporal links between the depleted mantle blocks, and the suite of magmatic blocks derived from partial melting and metasomatism of these depleted mantle blocks, unequivocally shows that they represent part of the same original Neoarchean fore-arc ophiolite suite. After formation and accretion in the oceanic realm, the mélange was emplaced on the continental margin of the Eastern Block between 2.52–2.50 Ga, and underwent two stages of metamorphism at ca. 2.48–2.46 Ga and 1.81 Ga. Metamorphosed intermediate–mafic volcanic blocks exhibit systematic successive geochemical variations, from MORB-like to volcanic arc-like, and the N-MORB-like meta-basalts show remarkable similarity with the subduction initiation-related Izu–Bonin–Mariana (IBM) fore-arc basalts. We suggest that the Zunhua fore-arc complex records continuous geodynamic processes from subduction initiation to arc magmatism. The Zunhua ophiolitic mélange is part of a ca. 2.5 Ga suture between an oceanic arc of the COB and Eastern Block of the NCC. After the arc–continent collision, an arc–polarity reversal event has been proposed to initiate a new eastward–dipping subduction zone on the western side of the COB. This arc–polarity reversal can be traced for more than 1,600 km along the length of the orogen, similar in scale, geometry, and duration between collision and polarity flip to the present-day arc–polarity reversal of the Sunda–Banda arc during its ongoing collision with the Australia continent. This indicates that a life cycle of an Archean subduction zone, including birth (subduction initiation), maturity (arc magmatism), death (arc-continent collision) and re-birth (arc–polarity reversal), is recorded in the Zunhua ophiolitic mélange, and the geodynamics of plate tectonics at the end of the Archean was similar to that of today.</p><p> </p>

Intra-oceanic subduction initiation recorded by the metamorphic sole of the New Caledonia ophiolite: petrological, structural and age constraints

2020 ◽  
Author(s):  
Bénédicte Cenki-Tok ◽  
Derya Gürer ◽  
Vasileios Chatzaras ◽  
Julien Collot ◽  
Fernando Corfu ◽  
...  
Keyword(s):  
Plate Tectonics ◽  
New Caledonia ◽  
Time History ◽  
Mineral Chemistry ◽  
Published Data ◽  
Spreading Ridge ◽  
Plate Interface ◽  
Subduction Initiation ◽  
Grain Size Distributions ◽  
History Of

<p>Subduction initiation is commonly identified as a major enigma in plate tectonics. Attention to subduction initiation is growing in the community, as is our understanding of the sequences of geologic events that precede and postdate this critical stage of the Wilson cycle. Nevertheless, the direct triggers of subduction initiation and their regional to global consequences remain uncertain. The New Caledonia ophiolite has formed in a supra-subduction zone setting in the vicinity of an active spreading centre. The metamorphic sole, which represents the ancient subduction interface, is locally preserved beneath the ophiolite. Unravelling its tectono-metamorphic record is essential in order to determine the timing of subduction initiation and the tectonic processes operating at the plate interface during the early stages of subduction.  We have sampled and studied amphibole-bearing rocks of the metamorphic sole that crop out in three newly found and three previously known localities that are scattered across the island (160 km * 50 km in size). The amphibolites form laterally discontinuous meter-size lenses that crop out within or beneath the serpentinite sole at the base of the ophiolite nappe.  Preliminary U-Pb zircon ID-TIMS geochronology yields a crystallization age of 56±1 Ma in agreement, but with a narrower timespan compared to previously published data (Cluzel et al., 2012).  We use whole-rock geochemistry, mineral chemistry and thermodynamic modelling to constrain the Pressure-Temperature-time history of the amphibolites.  Microstructural data such as dominant deformation mechanisms, crystallographic preferred orientations, grain size distributions determined by EBSD allow to constrain the deformation processes and rheological behavior of the amphibolites during subduction infancy.</p><p> </p><p>Cluzel, D., Jourdan, F., Meffre, S., Maurizot, P., and Lesimple, S., 2012. The metamorphic sole of New Caledonia ophiolite: 40Ar/39Ar, U-Pb, and geochemical evidence for subduction inception at a spreading ridge. Tectonics, VOL. 31, TC3016, doi:10.1029/2011TC003085.</p>

Accretionary orogenesis in the Lake Superior region, USA: modern-like tectonics during the Paleoproterozoic

2020 ◽  
Author(s):  
Daniel R. Viete ◽  
Robert M. Holder
Keyword(s):  
Plate Tectonics ◽  
Lake Superior ◽  
Oceanic Lithosphere ◽  
Ocean Basin ◽  
Length Scale ◽  
Subduction Initiation ◽  
Suprasubduction Zone ◽  
Lithospheric Extension ◽  
Rapid Switching ◽  
Terrane Accretion

<p>Terrane accretion and tectonothermal activity associated with the Penokean and Yavapai Orogenies are recorded in various geologic elements of the Lake Superior region, USA, including: (1) mafic–ultramafic terranes comprising tholeiitic basalts and gabbros, boninites and calc-alkaline volcanics and intrusives (e.g., the Pembine–Wausau Terrane), and (2) multiple and distinct, short-length-scale (5–15 km) chlorite–biotite–garnet–staurolite–(kyanite–)sillimanite regional metamorphic isograd sequences. These geologic associations reflect development of a suprasubduction zone system (subduction initiation?) within a Paleoproterozoic ocean in the Orosirian Period, followed by episodes of short-duration (limited-length-scale) tectonometamorphism during accretionary orogenesis in the Statherian Period.</p><p>The geologic processes recorded in the Paleoproterozoic terranes of the Lake Superior region are very common in the Phanerozoic. We suggest that Paleoproterozoic tectonism in the Lake Superior region may reflect a West Pacific-type setting, involving distinct, short-lived tectonothermal events marking periods of subduction rollback and lithospheric extension, punctuated by episodes of arc/microcontinent collision, terrane accretion and lithospheric shortening.</p><p>The apparent operation of modern-like plate tectonics—accretionary tectonics involving rapid switching between lithospheric extension and shortening—in the Paleoproterozoic requires that a scenario of temporally-varying buoyancy forces at the subduction zone (spatially-varying density of the subducting slab?) be reconciled with the thicker (slower-densifying) oceanic lithosphere expected for a hotter Earth. Such a scenario may be explained by: (1) an anomalously cool mantle (producing anomalously thin oceanic crust) beneath the ocean basin whose closure led to the accretionary orogenesis recorded in the Lake Superior region, or (2) an incredibly long-lived (>> 100 Myr) ocean basin that allowed widespread development of critically-overdense lithosphere prior to subduction initiation and onset of accretionary orogenesis associated with the Penokean and Yavapai Orogenies.</p><p>We are currently investigating geologic associations in the Lake Superior region and their potential tectonic origins, using whole-rock geochemistry to test for the tectonic origins of the Pembine–Wausau Terrane, and <sup>40</sup>Ar/<sup>39</sup>Ar geochronology/geospeedometry to constrain time scales for the tectonometamorphism that produced the metamorphic isograd sequence in the region of Republic, Michigan. Results will provide new insights into accretionary tectonics during the Paleoproterozoic, and processes controlling the emergence and evolution of plate tectonics on Earth.</p>

scholarly journals The Spongtang Massif in Ladakh, NW Himalaya: An Early Cretaceous record of spontaneous, intra-oceanic subduction initiation in the Neotethys

2018 ◽  
Vol 63 ◽  
pp. 226-249 ◽  
Author(s):  
Solomon Buckman ◽  
Jonathan C. Aitchison ◽  
Allen P. Nutman ◽  
Vickie C. Bennett ◽  
Wanchese M. Saktura ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Nw Himalaya ◽  
Subduction Initiation
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