Magmatic arc footprints the presentday exposure area, or footprint, of an eroded. The importance of subduction zones, which are major sites of earthquakes, mountain building, and basaltandesiterhyolite volcanism, was nicely presented by stern rev geophys 40. An alternative approach to understanding subduction magmatism, one that is largely independent of observations of arc lavas, is through the petrologic and geochemical study of mafic and ultramafic xenoliths from modern subduction systems. A lullin magmatism between 640 and 580 ma clearly separates windermere events from those associated with the formation of the paleozoic passive margin. An andean type of calc alkaline magmatism is represented by the batholith due to the subduction of the neo tethyan oceanic crust beneath the eurasian plate. Anisotropic viscosity changes subduction zone thermal structure einat lev department of earth, atmospheric and planetary sciences, massachusetts institute of technology, 77 massachusetts avenue, cambridge, massachusetts 029, usa now at lamont. Of the many variables that can affect the isotherms in subduction zone systems, the main ones are. The reduction in the overlying pressure enables mantle melting a process called decompression melting. The transition from subductionrelated to intraplate neogene. A subduction zone is a region of the earths crust where one tectonic plate moves under another tectonic plate. This paper highlights the subduction related magmatism of the tethyan oceanic crust under western edge of the burmese plate on the basis of major and ree geochemistry in the lohit batholith. Subduction zones are major sites of volcanism on the earth. Rapid subduction initiation and magmatism in the western. Relative proportions of quaternary volcanic locality b ba a dr talasea, papua 9 23 55 9 4 little sitkin, aleutians 0 78 4 18 0 mt.
Building a linkage between the various approaches is needed, because the degree and depth of dehydration of the subduction plates strongly dependent on the thermal structure of subduction zones van keken et al. Subduction related magmatism peter ulmerandvolkmartrommsdorff. Synopsis of cenozoic to recent forearc magmatism, alaska to oregon paleogene forearc magmatism forms a complex spatial and temporal pattern within the forearc areas of alaska, british columbia, washington, and oregon fig. Control of subduction rate on tongakermadec arc magmatism. Pdf download subduction zone magmatism frontiers in earth sciences read full ebook. Dehydration d takes place in mature arcs with old lithosphere slab melting m occurs in. Pdf volatiles in subduction zone magmatism researchgate. Subduction zones are critical to the dynamics of the earth because they represent the essential driving force behind the movement of plates. Numerous models for subduction zone metamorphism and dehydration have been developed e. The puzzling subduction arc magmatism of new guinea contains geochemical subduction. Roles of subducted pelagic and terrigenous sediments in early jurassic mafic magmatism in ne china. The volatile cycle at subduction zones is key to the petrogenesis, transport, storage and eruption of arc magmas. Multistage, multisource process dehydration of the slab provides the lil.
Arc magmas account for more than 20% of terrestrially produced magmas and are produced by the dehydration of minerals. As a result, the primary characteristics of crustmantle interactions and the formation of arc magmatism in continental subduction zones have been preserved. Morbnormalized spider diagrams for selected island arc basalts. Most of these terranes added during the mesozoic and cenozoic, during which time the continental margin was extended by as much as 800km. Composition more diverse and silicicbasalt generally occurs in subordinate quantities. Serpentinestability to mantle depthsand subductionrelated. Pdf water is a key ingredient in the generation of magmas in subduction zones. We begin by discussing constraints on the pressuretemperature pt conditions in the mantle wedge. H2o in magmageneration processes at subduction zones. Magma production rates for intraoceanic arcs introduction most magmatism observed on earth is located at midocean ridges and above subduction zones3. Implications for primitive subduction magmatism in an island arc g. Lecture 5 oib arc print 2008 woods hole oceanographic. Petrogenesis of arc magmas subduction zone magmatism is a paradox. Dehydration of slab crust causes hydration of the mantle violet, which undergoes partial melting as amphibole a and phlogopite b dehydrate.
At midocean ridges, oceanic plates diverge and the earths mantle moves upward. Volatiles in subduction zone magmatism esc publications. Rates of subduction are typically measured in centimeters per year. Water is a key ingredient in the generation of magmas in subduction zones. Subduction zones, magmatism, and the breakup of pangea.
Fluids play a critical role in subduction zones and arc magmatism. Lecture 25 subduction related magmatism monday, may 2nd 2005 subduction related magmatism zactivity along arcuate volcanic chains along subduction zones zdistinctly different from the mainly basaltic provinces studied thus far. However, it has been challenging to test these models in either modern or ancient subduction zones because the production of water is dif. Slab melting versus slab dehydration in subductionzone.
The magmatic progression produced during the initiation of the izuboninmarianas subduction zone took place rapidly over 1 million years, but it has been unclear why. Interpreting even modern island arcs is complicated due to structural complexity and a wide variety of magma sources and magmatic manifestations, whereas. Pdf the volatile cycle at subduction zones is key to the petrogenesis, transport, storage and eruption of arc magmas. Cretaceous ultrapotassic magmatism from the savavardar. Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to high gravitational potential energy into the mantle.
Twenty years of subduction zone science geological society of. The evolution of the subduction zone magmatism on the. Tracing subduction zone processes with magnesium isotopes. A key step in representing corner flow in a column model is to introduce a spatially variable, volumetric heating term. Pdf download subduction zone magmatism frontiers in earth sciences read online. Subduction zone magmatism depths to 2900km overview. With continued westward motion, the overriding continent began to deform internally during an event which lasted broadly 30 ma. Previous studies have thrown some light on the geology and geochemistry of the lohit batholith 46, 47, 40, 15, 16.
At 120 ma, the nearly continuous subduction zone that had existed along the southern margin of pangea since at least 200 ma began to break apart with the subduction of the pacificaluk spreading center along eastern australia and northern new zealand. Transition from subduction related to intraplate neogene magmatism 3 duction along eastern greece strabo trench, which is possibly generating a tear zone slab window between the hellenic and cyprus segments of the slab toward the north. Doherty earth observatory, columbia university, 61 route 9w, palisades. Relation of flat subduction to magmatism and deformation in.
Jul 30, 2019 the continuous subduction that dominates at the modern convergent plate boundaries, is characterized by longlived recycling of oceanic plate into the mantle along the subduction zone 7,9,10. One view of the geochemistry of subductionrelated magmatic arcs. At shallow levels in subduction zones subduction zones helped nucleate and grow the continents, they fertilize and lubricate the earths interior, they are the site of most subaerial volcanism and many major earthquakes, and they yield a large fraction of the earths precious metals. Magmatism occurs in the subduction zone as the oceanic crust is subducted underneath the continental crust. Seawater is subducted along with the crust and lowers the melting point of the rocks as well as changing the chemistry. As a result of this subduction, arc magmatism has generated the gondor orogenic belt, mountains of shadow, and the. Jan 01, 2018 the mantle flow in subduction zones is far from onedimensional. Using the normalization and ordering scheme of sun and mcdonough 1989 with increasing compatibility to the right.
Introduction subduction zones, where the oceanic plates sink into the mantle, have been factories since plate tectonics began on earth fig. A metasomatized lithospheric mantle control on the. Such studies are relatively rare because subduction related xenoliths are. The production rate and composition of magmas are controlled by the thermal structure of subduction zones. There is a longstanding debate about whether the fluids released from a subducting slab are aqueous fluid, hydrous silicate melt, supercritical fluid scf, or a combination of these 2, 4, 8 12. Magmatism occurs in the volcanic arc and the backarc basin. Ocean crust reaching a subduction zone is relatively cold and. Volcanic gases in arcs are rich in h 2o, chlorine, bromine and iodine compared to gases at rift and ocean island settings, which directly re. Depths of the second critical endpoints and their bearing on the subduction zone magmatism. Rates of subduction are typically measured in centimeters per year, with the average rate of convergence being. Post subduction magmatism in the mid crust is exemplified by a number of small alkalienriched intrusions, such as sron garbh, scotland 9 and the mordor complex, australia 30.
Subduction zones, island arcs and active continental margins. At a particular depth shown by the yellow dotted line in the figure above complete. Magmatism in subduction zones builds continental crust and causes most of earths subaerial volcanism. The development of such tear faults is consistent with proposed kinematic reconstructions, in which different rates of subduction rollback affected different parts of the subduction zone. Pdf download subduction zone magmatism frontiers in earth. While the model focuses on the detailed form of each slab from their trenches through the seismogenic zone, where it combines data sets from active. How do spatial variations in subduction zone inputs affect seismicity and magmatism. Two contrasting ways of granite formation and implications for crustal growth. As one crustal plate sinks or is pushed beneath another, hot magma is produced and the resultant magma flux is fundamental to both the thermal evolution and chemical differentiation of the mantle and the earth itself. During this timespan, deformation migrated eastward into the continent with time, in concert with the eastward migration of subduction related magmatism. Ocean crust reaching a subduction zone is relatively cold and wet petrogenesis of arc magmas subduction zone magmatism is a paradox. Of course, with special conditions, for example, initiation of subduction or ridge subduction, the details of the derived thermal field will differ somewhat. More than 200 terranes have been recognized in the cordillera in western north america. Continuous plate subduction marked by the rise of alkali.
An examination of table 1 documents that nearprimary arc magmas are sometimes basaltic in. The goal is to provide an updated view of melting from the bottom of the mantle wedge to the top of the crust of the overlying plate. Seismic tomography results show gaps within the subducting lithosphere, which are interpreted as deep 100500 km subvertical tear faults. The hazelton arc axis migrated rapidly south of the skeena arch ca 178175 ma. Kelemenb,1 a department of geological sciences, university of south carolina, 701 sumter st. An examination of table 1 documents that nearprimary arc magmas are. Island arc magmatism arc magmatism university at buffalo. Relations between subduction parameters and magmatism. Garnet growth as a proxy for progressive subduction zone. Anisotropic viscosity changes subduction zone thermal. Water plays an important role in subduction zone magmatism because it can reduce the melting temperature of rocks in subduction zones and hence can generate magmas 1 7. The production of calcalkalic andesites typifies magmatism in subduction zones. Aug 14, 2018 we define the subduction zone as extending from the trench axis to the magmatic front, where petroleum systems may develop within forearc andor trenchslope basins and are directly influenced by subductionrelated heat flow, deformation, and magmatism. Temporal control of subduction magmatism in the eastern trans.
In this paper, we provide examples of both active and ancient arcs in order to understand magmatism and its changes in volume over time in subduction systems. Subduction zone metamorphism szm and behaviors of chemical elements in response to this process are important for both arc magmatism and mantle compositional heterogeneity. This paper reports new geochemical data for submarine volcanic pumice sampled from two volcanoes sm. All books are in clear copy here, and all files are secure so dont worry about it. Role of h2o in subductionzone magmatism department of. Subduction zones and their hydrocarbon systems geosphere. Professor fangzhen teng department of earth and space sciences subduction and recycling of oceanic plates change the chemical composition of mantle and affect its physical properties, thereby modulating earths dynamics. Relation of flat subduction to magmatism and deformation. Quaternary plate tectonics collided with the southern margin of middle earth which generated a large subduction zone. Previous work published in jarrard 1986 focuses on the relationships between 26 subduction parameters for 39 modern subduction zones. The link between mantle flow and magmatism in subduction zones. A new perspective on subduction zone magmatism tetsu kogisoa.
Arcrelated volcanic and intrusive activity ceased north of the arch, replaced by regional subsidence and. Relation of flat subduction to magmatism and deformation in the western usa eugene humphreys department of geological sciences, university of oregon, eugene, oregon, usa abstract flat subduction of the farallon plate beneath western usa during the laramide orogeny was caused by the combined effects of oceanic plateau subduction and unusually great. Oceanic materials such as pelagic and ter rigenous sediments, altered and fresh basaltic oceanic crust, and mantle lithosphere enter. Physical model of source region of subduction zone volcanics. The general mechanism of water weakening and volcanism produced by smallscale convection could also be applied at a larger scale to the anorogenic igneous activity of the circummediterranean region lustrino and wilson, 2007, where large areas of mantle transition zone might have been hydrated by the mediterranean subduction zones nolet and. The link between mantle flow and magmatism in subduction. Temporal control of subduction magmatism in the eastern transmexican volcanic belt. Tracing subduction zone processes with magnesium isotopes yan hu chair of the supervisory committee. Lateral accretion at subduction zones has played a major role in the growth and evolution of the circum pacific margins. Regions where this process occurs are known as subduction zones. Magmatism is dominantly mafic during the initial phase of crustal thinning during cryogenian time.
A unifying theme of the sz4d initiative is the integration of observational data sets and models across three spatial dimensions and time. This cold subduction was associated with a subhorizontal benioff zone identi. The continuous subduction collision history of the aegean. The role of h 2o in subduction zone magmatism arizona state. Krawczynski1,3 1department of earth, atmospheric and planetary sciences, massachusetts institute of. Winter, chapter 16 island arc magmatism activity along arcuate volcanic island chains along subduction zones distinctly different from the mainly basaltic provinces composition more diverse and silicic basalt generally occurs in subordinate quantities more explosive than the quiescent basalts. Straub3 1soil and earth sciences group, iae, massey university, palmerston north 4442, new zealand 2department of earth sciences, university of cambridge, downing street, cambridge cb2 3eq, uk 3lamont doherty earth observatory of columbia university. Moreover, magmatism initiated by subduction is responsible for the creation of continental crust through a series of complex processes. Most andesites occur in subduction zone settings table 161.
Dehydration of slab crust causes hydration of the mantle, which undergoes partial melting as amphibole a and phlogopite b dehydrate. Sublithospheric smallscale convectiona mechanism for. Trace elements in clinopyroxenes from aleutian xenoliths. Cordillera show similar features including double volcanic zones and barkarc. As a result of this subduction, arc magmatism has generated the gondor orogenic belt, mountains of shadow, and the island arc chain that stretches out into the western ocean. In most of the earths present normaltype subduction zones, basaltic magmas are considered to be generated by the melting of mantle wedge peridotite by the addition of aqueous fluid released from the subducting slab 1, 3 7. Fisher, 2009 bbva foundation frontiers of knowledge in basic sciences. Thermal impact of magmatism in subduction zones sciencedirect. Kinematics of slab tear faults during subduction segmentation. Volatiles control the flux of slab components into the mantle wedge, are responsible for melt generation through lowering the solidi of mantle materials, and influence the crystallizing phase assemblages in the overriding crust. Pdf roles of subducted pelagic and terrigenous sediments. Subduction zones are also our planets largest recycling system. Mantle sources, slab contributions, and crustal contamination. Subduction zone magmatism frontiers in earth sciences.
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