Composition of fluids during serpentinite breakdown in subduction zones: Evidence for limited boron mobility

Orogenic plateaus have raised abundant attention amongst geoscientists during the last decades, offering unique opportunities to better understand the relationships between tectonics and climate, and their expression on the Earth’s surface.Orogenic plateau margins are key areas for understanding the mechanisms behind plateau (de)formation. Plateau margins are transitional areas between domains with contrasting relief and characteristics; the roughly flat elevated plateau interior, often with internally drained endorheic basins, and the external steep areas, deeply incised by high-discharge rivers. This thesis uses a wide range of structural and tectonic approaches to investigate the evolution of the southern margin of the Central Anatolian Plateau (CAP), studying an area between the plateau interior and the Cyprus arc. Several findings are presented here that constrain the evolution, timing and possible causes behind the development of this area, and thus that of the CAP. After peneplanation of the regional orogeny, abroad regional subsidence took place in Miocene times in the absence of major extensional faults, which led to the formation of a large basin in the northeast Mediterranean. Late Tortonian and younger contractional structures developed in the interior of the plateau, in its margin and offshore, and forced the inversion tectonics that fragmented the early Miocene basin into the different present-day domains. The tectonic evolution of the southern margin of the CAP can be explained based on the initiation of subduction in south Cyprus and subsequent thermo-mechanical behavior of this subduction zone and the evolving rheology of the Anatolian plate. The Cyprus slab retreat and posterior pull drove subsidence first by relatively minor stretching of the crust and then by its flexure. The growth by accretion and thickening of the upper plate, and that of the associated forearc basins system, caused by accreting sediments, led to rheological changes at the base of the crust that allowed thermal weakening, viscous deformation, driving subsequent surface uplift and raising the modern Taurus Mountains. This mechanism could be responsible for the uplifted plateau-like areas seen in other accretionary margins. ISBN: 978-90-9028673-0

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METAMORPHICALLY-INDUCED RHEOLOGICAL HETEROGENEITY AND THE DEEP TREMOR SOURCE IN SUBDUCTION ZONES

10.1130/abs/2017am-299672 ◽

2017 ◽

Cited By ~ 1

Author(s):

Whitney M. Behr ◽

◽

Alissa Kotowski ◽

Kyle Ashley

Keyword(s):

Subduction Zones ◽

Rheological Heterogeneity

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HOW MANY M9 EARTHQUAKES ARE POSSIBLE? INTERSEISMIC COUPLING AND RUPTURE PATCH MAGNITUDES ALONG 15 OF THE WORLD’S SUBDUCTION ZONES

10.1130/abs/2017am-297658 ◽

2017 ◽

Author(s):

Shannon E. Graham ◽

◽

John P. Loveless ◽

Brendan J. Meade ◽

...

Keyword(s):

Subduction Zones ◽

Interseismic Coupling

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METAMORPHIC DEHYDRATION FROM OCEANIC CRUST PROVIDES FLUID SOURCES FOR DEEP SLOW SLIP AND TREMOR IN SUBDUCTION ZONES

10.1130/abs/2020am-357702 ◽

2020 ◽

Author(s):

Cailey Condit ◽

◽

Victor Guevara ◽

Jonathan R. Delph ◽

Melodie French

Keyword(s):

Oceanic Crust ◽

Subduction Zones ◽

Slow Slip ◽

Fluid Sources ◽

Metamorphic Dehydration

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Os isotopic composition of western Aleutian adakites: Implications for the Re/Os of oceanic crust processed through hot subduction zones

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2020.10.009 ◽

2021 ◽

Vol 292 ◽

pp. 452-467

Author(s):

Rachel Bezard ◽

Simon Turner ◽

Bruce Schaefer ◽

Gene Yogodzinski ◽

Kaj Hoernle

Keyword(s):

Isotopic Composition ◽

Oceanic Crust ◽

Subduction Zones

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The role of sulphur on the melting of Ca-poor sediment and on trace element transfer in subduction zones: an experimental investigation

Journal of Petrology ◽

10.1093/petrology/egab005 ◽

2021 ◽

Author(s):

Anne-Aziliz Pelleter ◽

Gaëlle Prouteau ◽

Bruno Scaillet

Keyword(s):

Trace Element ◽

Partial Melting ◽

Subduction Zones ◽

Sediment Flux ◽

Arc Magmas ◽

Trace Element Contents ◽

The Stability ◽

Element Transfer ◽

High Sediment

Abstract We performed phase equilibrium experiments on a natural Ca-poor pelite at 3 GPa, 750-1000 °C, under moderately oxidizing conditions, simulating the partial melting of such lithologies in subduction zones. Experiments investigated the effect of sulphur addition on phase equilibria and compositions, with S contents of up to ∼ 2.2 wt. %. Run products were characterized for their major and trace element contents, in order to shed light on the role of sulphur on the trace element patterns of melts produced by partial melting of oceanic Ca-poor sediments. Results show that sulphur addition leads to the replacement of phengite by biotite along with the progressive consumption of garnet, which is replaced by an orthopyroxene-kyanite assemblage at the highest sulphur content investigated. All Fe-Mg silicate phases produced with sulphur, including melt, have higher MgO/(MgO+FeO) ratios (relative to S-free/poor conditions), owing to Fe being primarily locked up by sulphide in the investigated redox range. Secular infiltration of the mantle wedge by such MgO and K2O-rich melts may have contributed to the Mg and K-rich character of the modern continental crust. Addition of sulphur does not affect significantly the stability of the main accessory phases controlling the behaviour of trace elements (monazite, rutile and zircon), although our results suggest that monazite solubility is sensitive to S content at the conditions investigated. The low temperature (∼ 800 °C) S-bearing and Ca-poor sediment sourced slab melts show Th and La abundances, Th/La systematics and HFSE signatures in agreement with the characteristics of sediment-rich arc magmas. Because high S contents diminish phengite and garnet stabilities, S-rich and Ca-poor sediment sourced slab melts have higher contents of Rb, B, Li (to a lesser extent), and HREE. The highest ratios of La/Yb are observed in sulphur-poor runs (with a high proportion of garnet, which retains HREE) and beyond the monazite out curve (which retains LREE). Sulphides appear to be relatively Pb-poor and impart high Pb/Ce ratio to coexisting melts, even at high S content. Overall, our results show that Phanerozoic arc magmas from high sediment flux margins owe their geochemical signature to the subduction of terrigenous, sometimes S-rich, sediments. In contrast, subduction of such lithologies during Archean appears unlikely or unrecorded.

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