Experimental modeling of mantle metasomatism coupled with eclogitization of crustal material in a subduction zone

Abstract. The exhumation of high and ultra-high pressure rocks is ubiquitous in Phanerozoic orogens created during continental collisions, and is common in many ocean-ocean and ocean-continent subduction zone environments. Three different tectonic environments have previously been reported, which exhume deeply buried material by different mechanisms and at different rates. However it is becoming increasingly clear that no single mechanism dominates in any particular tectonic environment, and the mechanism may change in time and space within the same subduction zone. In order for buoyant continental crust to subduct, it must remain attached to a stronger and denser substrate, but in order to exhume, it must detach (and therefore at least locally weaken) and be initially buoyant. Denser oceanic crust subducts more readily than more buoyant continental crust but exhumation must be assisted by entrainment within more buoyant and weak material such as serpentinite or driven by the exhumation of structurally lower continental crustal material. Weakening mechanisms responsible for the detachment of crust at depth include strain, hydration, melting, grain size reduction and the development of foliation. These may act locally or may act on the bulk of the subducted material. Metamorphic reactions, metastability and the composition of the subducted crust all affect buoyancy and overall strength. Subduction zones change in style both in time and space, and exhumation mechanisms change to reflect the tectonic style and overall force regime within the subduction zone. Exhumation events may be transient and occur only once in a particular subduction zone or orogen, or may be more continuous or occur multiple times.

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Composition of barian mica in multiphase solid inclusions from orogenic garnet peridotites as evidence of mantle metasomatism in a subduction zone setting

Contributions to Mineralogy and Petrology ◽

10.1007/s00410-018-1534-6 ◽

2018 ◽

Vol 173 (12) ◽

Cited By ~ 5

Author(s):

Renata Čopjaková ◽

Jana Kotková

Keyword(s):

Subduction Zone ◽

Mantle Metasomatism

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Geochemical and isotopic (Nd, O, and Pb) constraints on granite sources in the Humber and Dunnage zones, Gaspésie, Quebec, and New Brunswick: implications for tectonics and crustal structure

Canadian Journal of Earth Sciences ◽

10.1139/e94-030 ◽

1994 ◽

Vol 31 (2) ◽

pp. 323-340 ◽

Cited By ~ 12

Author(s):

Joseph B. Whalen ◽

George A. Jenner ◽

Ernst Hegner ◽

Clément Gariépy ◽

Frederick J. Longstaffe

Keyword(s):

Subduction Zone ◽

Incompatible Element ◽

Crustal Material ◽

Early Paleozoic ◽

Isotopic Data ◽

Geologic History ◽

Seismic Reflection Data ◽

Crustal Rocks ◽

Isotopic Compositions ◽

Reflection Data

Siluro–Devonian granitoids span a wide compositional range (~50–76% SiO2) and can be subdivided into two groups: (i) monzonitic or incompatible element enriched with affinities to within-plate magmatism (WPG); and (ii) calc-alkalic or incompatible element depleted with supra-subduction zone affinities (VAG). Granitoid εNd(T = 0.4 Ga) values range from −1 to +5.5; most lie between +3 and +5.5. 207Pb/204Pb isotopic compositions range from 15.52 to 15.61; most fall between ~15.55 and 15.59. Most δ18O values lie between +5.5 and +8‰. No well-established trends exist between SiO2 and isotopic composition, and isotopic compositions do not differ between the two trace element defined granitoid groups.Though Pb isotopic data are consistent with a major contribution to the granitoids from Proterozoic-aged Laurentian plate rocks (i.e., Grenville basement), Nd and O isotopic data are not. These isotopic data are consistent with major source components derived from early Paleozoic depleted or supra-subduction zone affected mantle and (or) crustal rocks derived from the early Paleozoic mantle(s). These protoliths would not have seen significant interaction with time-integrated old crustal material or surficial processes. Granitoid Pb isotopic data can be reconciled with an early Paleozoic mantle–crust origin, but it may also be that the Pb isotopes are decoupled from other isotopic systems. In either case, Nd and O isotopic data clearly prohibit the involvement of significant amounts of Grenville crust and suggest that seismic-reflection data do not define crustal blocks, or at least not blocks having a tectonic and geologic history easily related to the surface geology.

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Platinum-Group-Element Systematics of Peridotites from Ophiolite Complexes of Northwest Anatolia, Turkey: Implications for Mantle Metasomatism by Melt Percolation in a Supra-subduction Zone Environment

International Geology Review ◽

10.2747/0020-6814.48.5.420 ◽

2006 ◽

Vol 48 (5) ◽

pp. 420-442 ◽

Cited By ~ 15

Author(s):

Ercan Aldanmaz ◽

Necla Koprubasi

Keyword(s):

Subduction Zone ◽

Platinum Group Element ◽

Mantle Metasomatism ◽

Group Element ◽

Melt Percolation ◽

Platinum Group

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New constraints on the geometry of the subducting African plate and the overriding Aegean plate obtained from P receiver functions and seismicity

Solid Earth Discussions ◽

10.5194/sed-5-427-2013 ◽

2013 ◽

Vol 5 (1) ◽

pp. 427-461 ◽

Cited By ~ 4

Author(s):

F. Sodoudi ◽

A. Bruestle ◽

T. Meier ◽

R. Kind ◽

W. Friederich ◽

...

Keyword(s):

Subduction Zone ◽

Mantle Wedge ◽

Receiver Functions ◽

Moho Depth ◽

Crustal Material ◽

Mantle Lithosphere ◽

African Plate ◽

Western Turkey ◽

Hellenic Subduction Zone ◽

Eastern Aegean

Abstract. New combined P receiver functions and seismicity data obtained from the EGELADOS network employing 65 stations within the Aegean constrained new information on the geometry of the Hellenic subduction zone. The dense network and large dataset enabled us to accurately estimate the Moho of the continental Aegean plate across the whole area. Presence of a negative contrast at the Moho boundary indicating the serpentinized mantle wedge above the subducting African plate was clearly seen along the entire forearc. Furthermore, low seismicity was observed within the serpentinized mantle wedge. We found a relatively thick continental crust (30–43 km) with a maximum thickness of about 48 km beneath the Peloponnesus Peninsula, whereas a thinner crust of about 27–30 km was observed beneath western Turkey. The crust of the overriding plate is thinning beneath the southern and central Aegean (Moho depth 23–27 km). Moreover, P receiver functions significantly imaged the subducted African Moho as a strong converted phase down to a depth of 180 km. However, the converted Moho phase appears to be weak for the deeper parts of the African plate suggesting reduced dehydration and nearly complete phase transitions of crustal material into denser phases. We show the subducting African crust along 8 profiles covering the whole southern and central Aegean. Seismicity of the western Hellenic subduction zone was taken from the relocated EHB-ISC catalogue, whereas for the eastern Hellenic subduction zone, we used the catalogues of manually picked hypocenter locations of temporary networks within the Aegean. P receiver function profiles significantly revealed in good agreement with the seismicity a low dip angle slab segment down to 200 km depth in the west. Even though, the African slab seems to be steeper in the eastern Aegean and can be followed down to 300 km depth implying lower temperatures and delayed dehydration towards larger depths in the eastern slab segment. Our results showed that the transition between the western and eastern slab segments is located beneath the southeastern Aegean crossing eastern Crete and the Karpathos basin. High resolution P receiver functions also clearly resolved the top of a strong low velocity zone (LVZ) at about 60 km depth. This LVZ is interpreted as asthenosphere below the Aegean continental lithosphere and above the subducting slab. Thus the Aegean mantle lithosphere seems to be 30–40 km thick, which means that its thickness increased again since the removal of the mantle lithosphere about 15 to 35 Ma ago.

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Receiver function images of the Hellenic subduction zone and comparison to microseismicity

Solid Earth ◽

10.5194/se-6-135-2015 ◽

2015 ◽

Vol 6 (1) ◽

pp. 135-151 ◽

Cited By ~ 12

Author(s):

F. Sodoudi ◽

A. Brüstle ◽

T. Meier ◽

R. Kind ◽

W. Friederich ◽

...

Keyword(s):

Subduction Zone ◽

Mantle Wedge ◽

Receiver Functions ◽

Moho Depth ◽

Crustal Material ◽

Mantle Lithosphere ◽

African Plate ◽

Data Set ◽

Hellenic Subduction Zone ◽

Hypocentre Locations

Abstract. New combined P receiver functions and seismicity data obtained from the EGELADOS network employing 65 seismological stations within the Aegean constrained new information on the geometry of the Hellenic subduction zone. The dense network and large data set enabled us to estimate the Moho depth of the continental Aegean plate across the whole area. Presence of a negative contrast at the Moho boundary indicating the serpentinized mantle wedge above the subducting African plate was seen along the entire forearc. Furthermore, low seismicity was observed within the serpentinized mantle wedge. We found a relatively thick continental crust (30–43 km) with a maximum thickness of about 48 km beneath the Peloponnese Peninsula, whereas a thinner crust of about 27–30 km was observed beneath western Turkey. The crust of the overriding plate is thinning beneath the southern and central Aegean and reaches 23–27 km. Unusual low Vp / Vs ratios were estimated beneath the central Aegean, which most likely represent indications on the pronounced felsic character of the extended continental Aegean crust. Moreover, P receiver functions imaged the subducted African Moho as a strong converted phase down to a depth of about 100 km. However, the converted Moho phase appears to be weak for the deeper parts of the African plate suggesting nearly complete phase transitions of crustal material into denser phases. We show the subducting African crust along eight profiles covering the whole southern and central Aegean. Seismicity of the western Hellenic subduction zone was taken from the relocated EHB-ISC catalogue, whereas for the eastern Hellenic subduction zone, we used the catalogues of manually picked hypocentre locations of temporary networks within the Aegean. Accurate hypocentre locations reveal a significant change in the dip angle of the Wadati–Benioff zone (WBZ) from west (~ 25°) to the eastern part (~ 35°) of the Hellenic subduction zone. Furthermore, a zone of high deformation can be characterized by a vertical offset of about 40 km of the WBZ beneath the eastern Cretan Sea. This deformation zone may separate a shallower N-ward dipping slab in the west from a steeper NW-ward dipping slab in the east. In contrast to hypocentre locations, we found very weak evidence for the presence of the slab at larger depths in the P receiver functions, which may result from the strong appearance of the Moho multiples as well as eclogitization of the oceanic crust. The presence of the top of a strong low-velocity zone at about 60 km depth in the central Aegean may be related to the asthenosphere below the Aegean continental lithosphere and above the subducting slab. Thus, the Aegean mantle lithosphere seems to be 30–40 km thick, which means that its thickness increased again since the removal of the mantle lithosphere about 15 to 35 Ma ago.

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Cr-spinel records metasomatism not petrogenesis of mantle rocks

Nature Communications ◽

10.1038/s41467-019-13117-1 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 8

Author(s):

Hamed Gamal El Dien ◽

Shoji Arai ◽

Luc-Serge Doucet ◽

Zheng-Xiang Li ◽

Youngwoo Kil ◽

...

Keyword(s):

Subduction Zone ◽

Plate Tectonics ◽

Mantle Metasomatism ◽

Mantle Melting ◽

Ultramafic Rocks ◽

Chromian Spinel ◽

Core Composition ◽

Mid Ocean Ridge ◽

Ocean Ridge ◽

Petrogenetic Indicator

Abstract Mantle melts provide a window on processes related to global plate tectonics. The composition of chromian spinel (Cr-spinel) from mafic-ultramafic rocks has been widely used for tracing the geotectonic environments, the degree of mantle melting and the rate of mid-ocean ridge spreading. The assumption is that Cr-spinel’s core composition (Cr# = Cr/(Cr + Al)) is homogenous, insensitive to post-formation modification and therefore a robust petrogenetic indicator. However, we demonstrate that the composition of Cr-spinel can be modified by fluid/melt-rock interactions in both sub-arc and sub-mid oceanic mantle. Metasomatism can produce Al-Cr heterogeneity in Cr-spinel that lowers the Cr/Al ratio, and therefore modifies the Cr#, making Cr# ineffective as a geotectonic and mantle melting indicator. Our analysis also demonstrates that Cr-spinel is a potential sink for fluid-mobile elements, especially in subduction zone environments. The heterogeneity of Cr# in Cr-spinel can, therefore, be used as an excellent tracer for metasomatic processes.

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