Arafura slab subduction occurred at an intraoceanic subduction zone that ended 3025 ma ago, when the australian continental edge was still km to the south. Of course, with special conditions, for example, initiation of subduction or ridge subduction, the details of the derived thermal field will differ somewhat. Most of these terranes added during the mesozoic and cenozoic, during which time the continental margin was extended by as much as 800km. Highresolution seismic tomography has revealed prominent lowvelocity lowv and highattenuation lowq zones that exist in the crust and uppermost mantle just beneath active arc volcanoes and extend to 400 km depth in the mantle wedge. Regions where this process occurs are known as subduction zones. Lateral accretion at subduction zones has played a major role in the growth and evolution of the circum pacific margins. Rapid subduction initiation and magmatism in the western. Pdf volatiles in subduction zone magmatism researchgate. Deciphering mantle and crustal signatures in subduction zone.
Cordillera show similar features including double volcanic zones and barkarc. Dehydration of slab crust causes hydration of the mantle, which undergoes partial melting as amphibole a and phlogopite b dehydrate. Pdf the volatile cycle at subduction zones is key to the petrogenesis, transport, storage and eruption of arc magmas. Subduction zone metamorphism szm and behaviors of chemical elements in response to this process are important for both arc magmatism and mantle compositional heterogeneity. Left with the subducted crust and mantle wedge the trace element and isotopic data suggest that both contribute to arc magmatism. Water is a key ingredient in the generation of magmas in subduction zones. Numerous lines of evidence indicate that water derived from. 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. Krawczynski1,3 1department of earth, atmospheric and planetary sciences, massachusetts institute of. Dec 26, 2006 the origin of volcanic rocks and their primary magmas in subduction zones, including island arcs, is an important problem in igneous petrology. A product of subduction is the output of volatiles as volcanic gases. But there is no concensus about the temperature distribution through the subducted crust, or within the overlying mantle wedge. This has in part been spurred by the extremely tangible hazards imposed by subduction, particularly in the form of earthquakes and tsunamis and arc volcanism.
Multistage, multisource process dehydration of the slab provides the lil. Concern regarding these hazards is heightened by the tendency of convergent margins to be heavily populated coastal regions. Subduction zone magmatism frontiers in earth sciences. Pdf subduction initiation and forearc magmatism as. Magmatism occurs in the volcanic arc and the backarc basin. Vent belt in this continuous reach of the northsouth arc is about 40 km wide, east. 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.
Grove tl, till cb, krawczynski mj 2012 the role of h 2 o in subduction zone magmatism. The sinking of cold lithosphere into the mantle is thought by many authors to be the most important source of energy for plates driving forces. At least 23 separate vents are discernible in this southwestward view from low on the southern slope of south sister. Quaternary magmatism in the cascadesgeologic perspectives by wes hildreth 2007 distributed arc volcanoes in the cascades of central oregon. Subduction zones are major sites of volcanism on the earth. Volatiles in subduction zone magmatism geological society, london. If it available for your country it will shown as book reader and user fully subscribe will benefit by having full access to all. Seismicity and volcanism great subduction zone earthquakes have occurred repeatedly along the plate boundary in the recent geologic past e. Therefore it need a free signup process to obtain the book. Suprasubduction magmatism in the moretown terrane, a.
Hydration of oceanic crust begins at midocean ridges through hight and. Ocean crust reaching a subduction zone is relatively cold and wet petrogenesis of arc magmas subduction zone magmatism is a paradox. Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. Subduction zone magmatism yashiyuki tatsumi, stephen eggins. The role of hydraulic fractures and intermediatedepth. Similarly, measurements of geothermal heat flow in sw oregon and ne japan are higher than predicted by. The current model for subduction zone magmatism is that water released from the subducting slab enters the relatively warm mantle wedge, leading to a reduction in melting temperature and. Arc magmatism, subductionzone arthquakes, and other subductionzone processes such as crustmantle. Cold things are brittle and break making earthquakes, hot things bend and flow no earthquakes shallow 250 km subduction zone earthquakes have different causes. Interpreting even modern island arcs is complicated due to structural complexity and a wide variety of magma sources and magmatic manifestations, whereas. Oct 23, 2018 recycling of oceanic lithosphere through subduction is a fundamental process governing plate tectonics, continental collision, and arc magmatism cloos, 1993. Subduction zone, oceanic trench area marginal to a continent in which, according to the theory of plate tectonics, older and denser seafloor underthrusts the continental mass, dragging downward into the earths upper mantle the accumulated trench sediments.
Island arc magmatism arc magmatism university at buffalo. Volcanism is the surface expression of magmatism magmatism is one of the main processes responsible for mountain formation. 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. Zone 1 zone 2 zone 3,4 550 ma moretown fm gondwanan a sequence of sketches showing the tectonic evolution of the new england appalachians from coish 2010, modi. Typical thermal model for a subduction zone isotherms will be higher i. For the vast majority of cases the same conclusions will apply. Subduction initiation and forearc magmatism as recorded in suprasubduction zone ophiolites. A metasomatized lithospheric mantle control on the. The subduction zone, accordingly, is the antithesis of the midoceanic ridge. Monks judging our slides composition of the subducting plate slab dehydration pattern thermal structure of the subduction zone mantle wedge dynamics mantle source melt migration thickness and composition of the overriding plate overriding plate stress regime. Thermal impact of magmatism in subduction zones sciencedirect. Subduction zones, magmatism, and the breakup of pangea. The mantle flow in subduction zones is far from onedimensional.
A key step in representing corner flow in a column model is to introduce a spatially variable, volumetric heating term. The production of calcalkalic andesites typifies magmatism in subduction zones. Pdf volatiles in subduction zone magmatism georg f. Seismological structure of subduction zones and its. Calciuminolivine geohygrometer and its application to. Schematic view of volatile recycling and magma generation in subduction zones. Physical model of source region of subduction zone volcanics. Petrological estimates of subarc temperature conditions in both continental and oceanic subduction zones are systematically higher than predicted by thermal models, typically by 200300 k, at depths less than. Laramide the laramide phase of the sevierlaramide orogeny is limited to the time duration 75. Welcome,you are looking at books for reading, the subduction, you will able to read or download in pdf or epub books and notice some of author may have lock the live reading for some of country.
The cascadia subduction zone and related seismicity. More than 200 terranes have been recognized in the cordillera in western north america. 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. Quaternary magmatism in the cascadesgeologic perspectives. Deciphering mantle and crustal signatures in subduction zone magmatism. Subduction is a major process that plays a firstorder role in the dynamics of the earth. Earth, but subduction zone earthquakes are as deep as 670km. Sediment and altered basaltic oceanic crust transport volatiles into subduction.
The volatile cycle at subduction zones is key to the petrogenesis. Thermal and petrologic structure of subduction zones. The role of h 2o in subduction zone magmatism arizona state. Convergent plate margins, subduction zones, and island arcs. Relations between subduction parameters and magmatism. Rates of subduction are typically measured in centimeters per year. There is a great degree of variability observed in the volcano concentration, from zero holocene recently active volcanoes observed in the central chile. The paper represents the descending oceanic crust and the transparency represents the overriding plate. Occurrence of magmatism the most important feature of subduction zone magmatism is the occurrence of magmatism itself, that is, the fact that hot magmas are generated at settings in which the mantle is being cooled by subduction of cold oceanic lithosphere. This process is controlled by plate tectonic variables that ultimately influence the location of the active volcanic arc above subduction zones.
The westdirected force acting on the craton would increase north america absolute velocity and pull north america over the subduction zone, greatly intensifying compression of the western usa in the process odriscoll et al. Water and magma generation at subduction zones springerlink. Relation of flat subduction to magmatism and deformation in. Role of h2o in subductionzone magmatism department of. Cordillera show similar features including double volcanic zones and barkarc extension.
Most andesites occur in subduction zone settings table 161. The evolution of the subduction zone magmatism on the. 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. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of magma or lava. Crustal modification during subductionzone magmatism. The mechanisms allowing for the initiation of new subduction zones are related to either spontaneous or induced subduction and are thought to occur predominantly within weaknesses in oceanic lithosphere such as transform faults and. Studies of volcanic rocks in the japanese island arc began in the late 19th century and greatly advanced during the earlymiddle 20th century, based mainly on the petrological characters of volcanic rocks. Earth, sio2rich arc magmas that ultimately form the continental crust are a consequence of.
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