Regions where this process occurs are known as subduction zones. Role of h2o in subductionzone magmatism department of. For the vast majority of cases the same conclusions will apply. Anisotropic viscosity changes subduction zone thermal. Control of subduction rate on tongakermadec arc magmatism. The products of this first episode of postcollisional volcanism in western anatolia were subalkaline in character, with rocks ranging in composition from basalt, basaltic andesite, and andesite to dacite. Thermal impact of magmatism in subduction zones core. Cordillera show similar features including double volcanic zones and barkarc. Arcs are consequences of subduction zone processes preserved in the overlying crust, geological evidence of deformation and chemical recycling caused by subduction. The presence of magmatism and intermediatedepth 70300 km deep seismicity at subduction zones is at first sight surprising. Earth, sio2rich arc magmas that ultimately form the continental crust are a consequence of. 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. Pdf continuous plate subduction marked by the rise of. Subduction zones are also distinct from arctrench complexes.
Subduction zones are major sites of volcanism on the earth. 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. Thermal impact of magmatism in subduction zones by david w. Relations between subduction parameters and magmatism.
Imaging subduction, magmatism and continental rifting 34. Pdf download subduction zone magmatism frontiers in earth. A global subduction zone compilation is presented showing that flat slabs preferentially occur at old. 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. Here, the pacific plate is being subducted underneath the north american plate and the rate of subduction changes from west to east from 7. Physical model of source region of subduction zone volcanics. 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 gravity into the mantle.
Crustal modification during subductionzone magmatism. This paper discusses the role of h 2o in magmageneration processes at subduction zones. In this study, we focus on the geochemical evolution of subduction related arc felsic rocks. Matsukage e,2, yingwei fei b, and shigeaki ono a,f. Therefore, the lownbth is commonly considered as a distinct. Dehydrationmelting of oceanic crusts during returning to the mantle in subduction zones are related to origin of arc lavas. 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, 61 route 9w, palisades ny 10964, usa. Pdf slab melting versus slab dehydration in subduction. These results are consistent with many examples of presentday subduction zones, in which phases of actively spreading backarc correspond to a gap or a decrease of the arc volcanic activity. Outstandingquestionson the distribution of magmatism in the north islandinclude. 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. Island arc magmatism arc magmatism university at buffalo.
Not all arcs are truly island arcs, but the description. In this paper, we examine the effect of anisotropic viscosity on the thermal structure of subduction zone mantle wedges and quantify its importance relative to other thermal and rheological factors. All books are in clear copy here, and all files are secure so dont worry about it. Magmatism occurs in the volcanic arc and the backarc basin. But there is no concensus about the temperature distribution through the subducted crust, or within the overlying mantle wedge. Water and magma generation at subduction zones springerlink. The subduction initiation in the intraoceanic lithosphere and the initial. Relation of flat subduction to magmatism and deformation. Abundant observations of seismic anisotropy in subduction zones attest that the material in the mantle wedge has a strong fabric and therefore should be mechanically anisotropic.
Rates of subduction are typically in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per. Subduction zones are where sediments, oceanic crust, and mantle lithosphere return to and reequilibrate with earths mantle. The arc igneous rocks are commonly depleted in high field strength elements e. The thermal structure of subduction zones changes in both time and space at different depths. Slab melting versus slab dehydration in subductionzone magmatism kenji mibe a,b,c,1, t atsuhiko kawamoto d, kyoko n. Chemical geodynamics of mafic magmatism above subduction. To understand these evolutionary processes, we need to understand the physical and chemical consequences of all. Soil and earth sciences group, iae, massey university, palmerston. The evolution of the subduction zone magmatism on the. Arc magmas are assumed to be the products of chemical reactions of their source materials, which are governed by the slab and mantle conditions.
Most of these terranes added during the mesozoic and cenozoic, during which time the continental margin was extended by as much as 800km. Recycling of oceanic lithosphere through subduction is a fundamental process governing plate tectonics, continental collision, and arc magmatism cloos, 1993. The factors that influence arc magmatism include compositions of the subducting slabs, mantle wedge and subduction rates. Composition more diverse and silicicbasalt generally occurs in subordinate quantities. Subduction zone magmatism frontiers in earth sciences. Thus, changes in backarc activity and mantle flow pattern can be responsible for changes in magmatic composition and the amount of magmatism at the arc. However, distinguishing these factors remains difficult and highly debated. Subducted, detached, and torn slabs beneath the greater. New insights from melt inclusions in highmg basalts from central mexico. Petrogenesis of arc magmas subduction zone magmatism is a paradox. This site is like a library, you could find million book here by using search box in the header.
Subduction zone magmatism yashiyuki tatsumi, stephen. The san plate is composed of oceanic lithosphere that forms from the east side of the east scotia ridge esr, a backarc spreading center that sets the western boundary of the plate. The role of hydraulic fractures and intermediatedepth. The characteristic chemistry of arc magmas is the result of subduction zone geodynamics. Rapid subduction initiation and magmatism in the western. Timing and nature of postcollisional volcanism in western. The production rate and composition of magmas are controlled by the thermal structure of subduction zones. Pdf control of subduction zone age and size on flat slab. Rapid lateral changes in subduction style occur in the central north island of new zealand, with backarc spreading in the taupo volcanic zone in the north, and compression of the backarc wanganui basininthesouth. Pdf volatiles in subduction zone magmatism researchgate. More than 200 terranes have been recognized in the cordillera in western north america.
Pdf the volatile cycle at subduction zones is key to the petrogenesis. These crustal signatures are commonly represented not only by enrichment in large ion lithophile elements lile. The greater caucasus mountains are located between the black and caspian seas. Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. The thermal effect of magmatism evolves to a steady state over a period of about 50 myr. Potential earthquake sources are often obscure in such intracontinental regions, due to their distance from plate. 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. To the east, the plate is bounded by the south sandwich trench formed by the subduction of the south american plate beneath the south sandwich plate pearce et al. Lateral accretion at subduction zones has played a major role in the growth and evolution of the circum pacific margins.
Neoarchean suprasubduction zone magmatism in the sonakhan. 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. Application of the subduction zone infancy model to the late jurassic ophiolites of california provides a framework in which to understand the rapid formation of oceanic crust with strong arc affinities between the younger sierran magmatic arc and the franciscan subduction complex, provides a mechanism for the formation and subsidence of the. Modeling chemical geodynamics of subduction zones using. Enter your mobile number or email address below and well send you a link to download the free kindle app. Volcanism is the surface expression of magmatism magmatism is one of the main processes responsible for mountain formation. A metasomatized lithospheric mantle control on the. 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. N2 water is a key ingredient in the generation of magmas in subduction zones. Transition of subductionrelated magmatism from slab. Then you can start reading kindle books on your smartphone, tablet, or computer no kindle device required. Magmatism in subduction zones builds continental crust and causes most of earths subaerial volcanism. Pdf download subduction zone magmatism frontiers in earth sciences read full ebook. The occurrence of lower basalt sequence followed by iat and boninite.
Laramide the laramide phase of the sevierlaramide orogeny is limited to the time duration 75. Excess density of the mantle lithosphere in subduction zones provides most of the power needed to move the plates while. Delamination and delamination magmatism rice earth science. In this regard, the trace element and radiogenic isotope composition of subduction zone magmas is primarily. Of course, with special conditions, for example, initiation of subduction or ridge subduction, the details of the derived thermal field will differ somewhat. Dehydration d takes place in mature arcs with old lithosphere slab melting m occurs in. Subduction zones are interior expressions of earths 55,000 km of convergent plate margins and are the geodynamic system that builds island arcs. Quaternary plate tectonics collided with the southern margin of middle earth which generated a large subduction zone. The aleutian subduction zone is a 2500 milelong convergence boundary between the north american plate and the pacific plate, that extends from the alaska range to the kamchatka peninsula. Subducting rate is related to the total mass of inputs and controls. 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.
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