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Mass Transfer and Chemical Interactions in Subduction Zones.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Mass Transfer and Chemical Interactions in Subduction Zones./
Author:	Codillo, Emmanuel Avila.
Description:	1 online resource (408 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-02, Section: B.
Contained By:	Dissertations Abstracts International85-02B.
Subject:	Plate tectonics. -
Online resource:	click for full text (PQDT)
ISBN:	9798380097048

Mass Transfer and Chemical Interactions in Subduction Zones.
Codillo, Emmanuel Avila.

Mass Transfer and Chemical Interactions in Subduction Zones. - 1 online resource (408 pages)

Source: Dissertations Abstracts International, Volume: 85-02, Section: B.

Thesis (Ph.D.)--Massachusetts Institute of Technology, 2023.

Includes bibliographical references

Subduction zones are important sites of material recycling on Earth, with volatiles playing key roles in mass transfer processes and magma formation. This thesis investigates outstanding questions associated with a continuum of interrelated processes that occur as oceanic plates descend in subduction zones by integrating petrological and geochemical constraints from exhumed high-pressure rocks and erupted arc magmas, high pressure-temperature laboratory experiments, and thermodynamic calculations. Chapters 2 and 3 investigate the fluid-mediated reactions between mafic and ultramafic rocks at conditions relevant to the slab-mantle interface and show that Mg-metasomatism of mafic rocks to form chlorite-rich assemblages is favored and is likely more pervasive in subduction zones than in oceanic settings. Contrary to common belief, talc is unlikely to form in high abundance in ultramafic rocks metasomatized by Si-rich slab-derived fluids. This means that talc-rich assemblages formed via Si-metasomatism along the slab-mantle interface are less likely to be playing prominent roles in volatile transport, in facilitating slow-slip events, and in controlling the decoupling-coupling transition of the plate interface. Chapter 4 experimentally investigates the phase equilibria, melting, and density evolution of melange rocks that formed by mixing and fluid-rock interactions. Results show that melting of melanges is unlikely to occur along slab-tops at pressures ≤ 2.5 GPa. Accordingly, diapirism into the hotter mantle wedge would be required to initiate melting. The density contrast between melanges and the overlying mantle would allow for buoyancy-driven diapirism at relatively low pressures and melting could subsequently occur in the hotter mantle wedge during ascent. However, diapir buoyancy may be limited at higher pressures due to the formation of abundant garnet especially in melange rocks with peraluminous composition. Chapter 5 experimentally investigates the compositions of melts and mineral residues from melting of a mantle wedge hybridized with small amounts of melange rocks to simulate an end-member scenario where solid melange diapirs dynamically interact with the mantle wedge. Results from laboratory experiments show that melting of a melange-hybridized mantle wedge can produce melts that display compositional characteristics similar to arc magmas. Finally, Chapter 6 presents new interpretations on the evolution of slab-to-mantle transfer mechanisms from subduction initiation to arc maturity. Analyses of published magma compositions from global arcs reveal that melting of melange plays an increasingly important role in magma formation as slab-tops cool and arcs mature over time. This trend is attributed to the deepening of the decoupled plate interface during subduction where melange zones can form more extensively and contribute to the melting process more significantly. Taken together, this thesis highlights (i) the dynamic connection between mechanical mixing of different lithologies and fluid-rock interactions along the slab-mantle interface, (ii) how these processes modify the petrophysical and geochemical properties of subducted materials, and (iii) how these processes collectively influence the mechanisms of slab-to-mantle transfer, elemental cycles, and the formation of arc magmas worldwide.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798380097048Subjects--Topical Terms:

782857
Plate tectonics.
Index Terms--Genre/Form:

554714
Electronic books.

Mass Transfer and Chemical Interactions in Subduction Zones.
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504 $a Includes bibliographical references
520 $a Subduction zones are important sites of material recycling on Earth, with volatiles playing key roles in mass transfer processes and magma formation. This thesis investigates outstanding questions associated with a continuum of interrelated processes that occur as oceanic plates descend in subduction zones by integrating petrological and geochemical constraints from exhumed high-pressure rocks and erupted arc magmas, high pressure-temperature laboratory experiments, and thermodynamic calculations. Chapters 2 and 3 investigate the fluid-mediated reactions between mafic and ultramafic rocks at conditions relevant to the slab-mantle interface and show that Mg-metasomatism of mafic rocks to form chlorite-rich assemblages is favored and is likely more pervasive in subduction zones than in oceanic settings. Contrary to common belief, talc is unlikely to form in high abundance in ultramafic rocks metasomatized by Si-rich slab-derived fluids. This means that talc-rich assemblages formed via Si-metasomatism along the slab-mantle interface are less likely to be playing prominent roles in volatile transport, in facilitating slow-slip events, and in controlling the decoupling-coupling transition of the plate interface. Chapter 4 experimentally investigates the phase equilibria, melting, and density evolution of melange rocks that formed by mixing and fluid-rock interactions. Results show that melting of melanges is unlikely to occur along slab-tops at pressures ≤ 2.5 GPa. Accordingly, diapirism into the hotter mantle wedge would be required to initiate melting. The density contrast between melanges and the overlying mantle would allow for buoyancy-driven diapirism at relatively low pressures and melting could subsequently occur in the hotter mantle wedge during ascent. However, diapir buoyancy may be limited at higher pressures due to the formation of abundant garnet especially in melange rocks with peraluminous composition. Chapter 5 experimentally investigates the compositions of melts and mineral residues from melting of a mantle wedge hybridized with small amounts of melange rocks to simulate an end-member scenario where solid melange diapirs dynamically interact with the mantle wedge. Results from laboratory experiments show that melting of a melange-hybridized mantle wedge can produce melts that display compositional characteristics similar to arc magmas. Finally, Chapter 6 presents new interpretations on the evolution of slab-to-mantle transfer mechanisms from subduction initiation to arc maturity. Analyses of published magma compositions from global arcs reveal that melting of melange plays an increasingly important role in magma formation as slab-tops cool and arcs mature over time. This trend is attributed to the deepening of the decoupled plate interface during subduction where melange zones can form more extensively and contribute to the melting process more significantly. Taken together, this thesis highlights (i) the dynamic connection between mechanical mixing of different lithologies and fluid-rock interactions along the slab-mantle interface, (ii) how these processes modify the petrophysical and geochemical properties of subducted materials, and (iii) how these processes collectively influence the mechanisms of slab-to-mantle transfer, elemental cycles, and the formation of arc magmas worldwide.
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650 4 $a Geochemistry. $3 648291
650 4 $a Sediments. $3 1465441
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650 4 $a Lithosphere. $3 1020959
650 4 $a Rocks. $3 866903
650 4 $a Rheology. $3 644023
650 4 $a Trace elements. $3 1178656
650 4 $a Petrology. $3 783490
650 4 $a Seawater. $3 784687
650 4 $a Isotopes. $3 885739
650 4 $a Earthquakes. $3 677160
650 4 $a Geology. $3 670379
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