Subduction polarity reversal: Difference between revisions

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'''Subduction polarity reversal''' is a geologic process in which two converging plates switch roles: The over-lying plate becomes the down-going plate, and vice versa. There are two basic units which make up a [[Subduction|subduction zone]]. This consists of an overriding plate and the subduction plate.<ref name=":142">{{Cite book|url=http://www.springer.com/gp/book/9783540885573|title=Arc-Continent Collision {{!}} Dennis Brown {{!}} Springer}}</ref> Two plates move towards each other due to [[Tectonics|tectonic forces]].<ref name=":142" /> The overriding plate will be on the top of subducting plate.<ref name=":142" /> This type of tectonic interaction is commonly found in many [[Plate tectonics|plate boundaries]].<ref name=":142" />

However, some Geologists propose that the roles of the overriding plate and subducting plate do not remain the same infinitely.<ref name=":113">{{Cite journal|last=Chemenda|first=A. I.|last2=Yang|first2=R. -K.|last3=Stephan|first3=J. -F.|last4=Konstantinovskaya|first4=E. A.|last5=Ivanov|first5=G. M.|date=2001-04-10|title=New results from physical modelling of arc–continent collision in Taiwan: evolutionary model|url=http://www.sciencedirect.com/science/article/pii/S0040195100002730|journal=Tectonophysics|volume=333|issue=1–2|pages=159–178|doi=10.1016/S0040-1951(00)00273-0}}</ref> Their roles will swap, which means the plate originally subducting beneath will become the overriding plate.<ref name=":113" /> This phenomenon is called '''subduction switch''',<ref>Willett, S. D., & Beaumont, C. (1994). Subduction of Asian lithospheric mantle beneath Tibet inferred from models of continental collision. ''Nature'', ''369''(6482), 642-645642–645.</ref> '''the flipping of subduction polarity'''<ref name=":132222">{{Cite journal|last=Teng|first=Louis S.|last2=Lee|first2=C. T.|last3=Tsai|first3=Y. B.|last4=Hsiao|first4=Li-Yuan|date=2000-02-01|title=Slab breakoff as a mechanism for flipping of subduction polarity in Taiwan|url=http://geology.gsapubs.org/content/28/2/155|journal=Geology|language=en|volume=28|issue=2|pages=155–158|doi=10.1130/0091-7613(2000)282.0.CO;2|issn=0091-7613}}</ref> or '''subduction polarity reversal'''.<ref name=":113" />

Examples of subduction systems with subduction polarity reversal are:

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The initial setting of the simulated [[Subduction|subduction zone]] model is confined by two pistons. The piston connected to the overriding plate is locked, while the piston linking to subducting plate is subjected to a constant rate of compression.<ref name=":113" /> More importantly, there is a relatively thin [[Volcanic arc|magmatic arc]] and pre-existing fault dipping towards the subducting plate at the overriding plate.<ref name=":113" /> The detachment of the pre-existing fault occurs when buoyant [[continental margin]] is in contact with the overriding plate.<ref name=":113" /> It is because the buoyant margin resists [[subduction]] and significantly increases the [[Friction|frictional force]] in the contact region.<ref name=":113" /> The subduction then stops. Subsequently, the new subducting slab develops at an overriding plate with the continuous compression.<ref name=":113" /> The new developing slab eventually penetrates and breaks the old slab.<ref name=":113" /> A new subduction is developed with an opposite direction of the previous one.<ref name=":113" />

In reality, the magmatic arc is a relatively weak zone at the overriding plate because it has a thin lithosphere and is further weakened by high heat flow<ref>{{Cite journal|last=Currie|first=Claire A.|last2=Hyndman|first2=Roy D.|date=2006-08-01|title=The thermal structure of subduction zone back arcs|url=http://onlinelibrary.wiley.com/doi/10.1029/2005JB004024/abstract|journal=Journal of Geophysical Research: Solid Earth|language=en|volume=111|issue=B8|pages=B08404|doi=10.1029/2005JB004024|issn=2156-2202}}</ref><ref>{{Cite journal|last=Currie|first=C. A|last2=Wang|first2=K|last3=Hyndman|first3=Roy D|last4=He|first4=Jiangheng|date=2004-06-30|title=The thermal effects of steady-state slab-driven mantle flow above a subducting plate: the Cascadia subduction zone and backarc|url=http://www.sciencedirect.com/science/article/pii/S0012821X04002687|journal=Earth and Planetary Science Letters|volume=223|issue=1–2|pages=35–48|doi=10.1016/j.epsl.2004.04.020}}</ref> and hot fluid.<ref>{{Cite journal|last=Arcay|first=D.|last2=Doin|first2=M.-P.|last3=Tric|first3=E.|last4=Bousquet|first4=R.|last5=de Capitani|first5=C.|date=2006-02-01|title=Overriding plate thinning in subduction zones: Localized convection induced by slab dehydration|url=http://onlinelibrary.wiley.com/doi/10.1029/2005GC001061/abstract|journal=Geochemistry, Geophysics, Geosystems|language=en|volume=7|issue=2|pages=Q02007|doi=10.1029/2005GC001061|issn=1525-2027}}</ref><ref>{{Cite journal|last=Honda|first=Satoru|last2=Yoshida|first2=Takeyoshi|date=2005-01-01|title=Application of the model of small-scale convection under the island arc to the NE Honshu subduction zone|url=http://onlinelibrary.wiley.com/doi/10.1029/2004GC000785/abstract|journal=Geochemistry, Geophysics, Geosystems|language=en|volume=6|issue=1|pages=Q01002|doi=10.1029/2004GC000785|issn=1525-2027}}</ref> Pre-existing faults in this simulation are also common in the magmatic arc.<ref>{{Cite journal|last=Toth|first=John|last2=Gurnis|first2=Michael|date=1998-08-10|title=Dynamics of subduction initiation at preexisting fault zones|url=http://onlinelibrary.wiley.com/doi/10.1029/98JB01076/abstract|journal=Journal of Geophysical Research: Solid Earth|language=en|volume=103|issue=B8|pages=18053–18067|doi=10.1029/98JB01076|issn=2156-2202}}</ref> This experiment is a successful analogy to subduction polarity reversal happening at Kamchatka in early Eocene<ref name=":54" /><ref>{{Cite journal|last=Konstantinovskaia|first=Elena A|date=2000-10-15|title=Geodynamics of an Early Eocene arc–continent collision reconstructed from the Kamchatka Orogenic Belt, NE Russia|url=http://www.sciencedirect.com/science/article/pii/S0040195100001323|journal=Tectonophysics|volume=325|issue=1–2|pages=87–105|doi=10.1016/S0040-1951(00)00132-3}}</ref> and the active example at Taiwan region<ref name=":113" /><ref name=":03" /> as well as at Timor.<ref>Silver, E. A., Reed, D., McCaffrey, R., & Joyodiwiryo, Y. (1983). Back arc thrusting in the eastern Sunda arc, Indonesia- A consequence of arc-continent collision. ''Journal of Geophysical Research'', ''88''(B9), 7429-74487429–7448.</ref><ref>{{Cite journal|last=Snyder|first=D. B.|last2=Prasetyo|first2=H.|last3=Blundell|first3=D. J.|last4=Pigram|first4=C. J.|last5=Barber|first5=A. J.|last6=Richardson|first6=A.|last7=Tjokosaproetro|first7=S.|date=1996-02-01|title=A dual doubly vergent orogen in the Banda Arc continent-arc collision zone as observed on deep seismic reflection profiles|url=http://onlinelibrary.wiley.com/doi/10.1029/95TC02352/abstract|journal=Tectonics|language=en|volume=15|issue=1|pages=34–53|doi=10.1029/95TC02352|issn=1944-9194}}</ref>

[[File:Lithospheric_break-up_model_setup.svg|thumb|444x444px|A. Chemenda's Experiment setup of lithosphere break-up model: White colour indicates the oceanic plate ( Higher density) ; Brown colour indicates the continental plate ( Lower density) ;Green colour shows the pre-exsiting fault ; The plates represented by hydrocarbons floats at the asthenopshere represented by water.|center]][[File:Lithoshperic_break-up.gif|thumb|444x444px|The evolution diagram showing how the subduction reversal initiated by a pre-existing fault at the overriding plate. 1: Compression pushing ; 2: New slab develops with the failure of the fault ; 3: New slab penetrates ; 4: New slab breaks the old slab|center]]