Changes

Divergent plate boundary displays the phenomenon of sea-floor spreading. Mid-Oceanic Ridge (MOR) is the place where magma from below the Earth emerges and crystallizes as oceanic crust. The spreading of the sea-floor causes decompression, triggering partial melting of the source rock. Generation of oceanic crust in MOR enables it to be the youngest crust making up the Earth. No oceanic crust is found to be older than Jurassic.

Divergent plate boundary displays the phenomenon of sea-floor spreading. Mid-Oceanic Ridge (MOR) is the place where magma from below the Earth emerges and crystallizes as oceanic crust. The spreading of the sea-floor causes decompression, triggering partial melting of the source rock. Generation of oceanic crust in MOR enables it to be the youngest crust making up the Earth. No oceanic crust is found to be older than Jurassic.

Due to interaction with seawater, magma crystallizes as pillow lava with basalt composition. Oceanic crust is not homogenous structurally. Keary and Vine (1994) divides oceanic crust into three layers. Layer 1, the uppermost part, consists of sedimentary cover varying from pelagic sediments, limestone, clays, and chert. Consolidated sediment and extrusive igneous materials form the Layer 2. Layer 3 gives plutonic foundation with gabbroic composition and consists of serpentinized materials.

Due to interaction with seawater, magma crystallizes as pillow lava with basalt composition. Oceanic crust is not homogenous structurally. Keary and Vine<ref name=KV>Keary, Philip and Vine, Frederick J. 1994. Geoscience Texts: Global Tectonics. Oxford: Blackwell Scientific Publications.</ref> divides oceanic crust into three layers. Layer 1, the uppermost part, consists of sedimentary cover varying from pelagic sediments, limestone, clays, and chert. Consolidated sediment and extrusive igneous materials form the Layer 2. Layer 3 gives plutonic foundation with gabbroic composition and consists of serpentinized materials.

Continental crust is found ranging in age from Hadean to recent. The thickness of this crust ranges from 35 – 40 km and 38 km on average. Continental crust is composed of two layers: upper and lower continental crust. Kearey and Vine (1990) stated that upper continental crust is composed of granodiorite and diorite composition. Lower continental crust requires seismic observations since the rock is not exposed on the surface. Seismic velocity, ranging from 6,5 – 7,6 km s-1, represents that rocks are more felsic than basalt constructing the lower continental crust. Roberts and Bally (2012) states that granulite or pyroxene granulite forms lower continental crust.

Continental crust is found ranging in age from Hadean to recent. The thickness of this crust ranges from 35 – 40 km and 38 km on average. Continental crust is composed of two layers: upper and lower continental crust. Kearey and Vine<ref name=KV /> stated that upper continental crust is composed of granodiorite and diorite composition. Lower continental crust requires seismic observations since the rock is not exposed on the surface. Seismic velocity, ranging from 6,5 – 7,6 km s-1, represents that rocks are more felsic than basalt constructing the lower continental crust. Roberts and Bally (2012) states that granulite or pyroxene granulite forms lower continental crust.

==Principles of Subduction Zone==  

==Principles of Subduction Zone==  

===Zonation of Deformation===

===Zonation of Deformation===

Subduction produces areas of different deformation mechanism. Different mechanisms lead to different potential of earthquake. Keary and Vine (1994) constructs cross-section of subduction zone consisting three zonations of deformation: a, b, and c. This classification is based on deformation mechanism and materials involved.

Subduction produces areas of different deformation mechanism. Different mechanisms lead to different potential of earthquake. Keary and Vine<ref name=KV /> constructs cross-section of subduction zone consisting three zonations of deformation: a, b, and c. This classification is based on deformation mechanism and materials involved.

Zone ‘a’ represents plastic deformation of oceanic crust plunging into the trench. Flexural bending of oceanic crust creates topographic bulge, causing regional positive gravity anomaly of +500 gu. Zone ‘b’ is the contact of oceanic and continental crust. Compressive forces are built in the overriding crust and extensional regime develops landward on continental crust. As the plate descending to zone ‘c’, the interaction with asthenosphere produces deformation due to unbending of the slab. This mechanism leads to internal deformation of oceanic crust.

Zone ‘a’ represents plastic deformation of oceanic crust plunging into the trench. Flexural bending of oceanic crust creates topographic bulge, causing regional positive gravity anomaly of +500 gu. Zone ‘b’ is the contact of oceanic and continental crust. Compressive forces are built in the overriding crust and extensional regime develops landward on continental crust. As the plate descending to zone ‘c’, the interaction with asthenosphere produces deformation due to unbending of the slab. This mechanism leads to internal deformation of oceanic crust.

===Types of Subduction Zone===

===Types of Subduction Zone===

Subduction zone induces various surface manifestation and tectonic implications. Subduction zone is divided in two groups according to Jolivet and Nataf (2001): Chilean Type and Mariana Type. The division of subduction zone is based on density of oceanic crust and dip of plunging plate. Chilean Type has younger oceanic crust, gentle dip of plunging plate, strong mechanical coupling implying to strong earthquake, and cordilleran type compressive deformation. On the other hand, Mariana Type has older oceanic crust, steep dip of plunging plate, weak mechanical coupling implying to weak earthquake, and extensional type of deformation of the upper plate.

Subduction zone induces various surface manifestation and tectonic implications. Subduction zone is divided in two groups according to Jolivet and Nataf:<ref name=JL2001>Jolivet, Laurent, and Nataf, Henri-Claude. 2001. Geodynamics. Dunod: A. A. Balkema.</ref> Chilean Type and Mariana Type. The division of subduction zone is based on density of oceanic crust and dip of plunging plate. Chilean Type has younger oceanic crust, gentle dip of plunging plate, strong mechanical coupling implying to strong earthquake, and cordilleran type compressive deformation. On the other hand, Mariana Type has older oceanic crust, steep dip of plunging plate, weak mechanical coupling implying to weak earthquake, and extensional type of deformation of the upper plate.

==Structural Features of Subduction Zone==  

==Structural Features of Subduction Zone==  

====Backarc Basin====

====Backarc Basin====

Backarc basin forms landward of the volcanic arc. Mechanisms for backarc basin have been proposed by several authors. Karig (1971) in Keary and Vine (1994) stated that the formation of backarc basin is influenced by extensional tectonic regime produced by subduction zone and igneous processes. Basaltic mantle diapirs also contribute to the extension of the plate and increasing heat flow. However, Packham and Falvey (1971) proposed that magma upwelling in backarc basin is passive, generated as a result of extensional regime of the plate. Tamaki (1985) in Keary and Vine (1971) stated that the initial rifting of backarc basin takes place at the island arc. The dip of subduction zone controls the nature of rifting. Single rifts form within narrow volcanic zone with steeply dipping Benioff zone. On the other hand, multirift system forms in wider zone with shallow angle of subduction. Another concept of backarc basin formation comes from Chase (1978) and Fein & Jurdy (1986). Regional extension of overriding plate comes from roll-back of the trench. Roll-back occurs when the trench migrates seaward and the oceanic crust retreating. This process produces trench suction force.

Backarc basin forms landward of the volcanic arc. Mechanisms for backarc basin have been proposed by several authors. Karig (1971) in Keary and Vine<ref name=KV /> stated that the formation of backarc basin is influenced by extensional tectonic regime produced by subduction zone and igneous processes. Basaltic mantle diapirs also contribute to the extension of the plate and increasing heat flow. However, Packham and Falvey (1971) proposed that magma upwelling in backarc basin is passive, generated as a result of extensional regime of the plate. Tamaki (1985) in Keary and Vine<ref name=KV /> stated that the initial rifting of backarc basin takes place at the island arc. The dip of subduction zone controls the nature of rifting. Single rifts form within narrow volcanic zone with steeply dipping Benioff zone. On the other hand, multirift system forms in wider zone with shallow angle of subduction. Another concept of backarc basin formation comes from Chase (1978) and Fein & Jurdy (1986). Regional extension of overriding plate comes from roll-back of the trench. Roll-back occurs when the trench migrates seaward and the oceanic crust retreating. This process produces trench suction force.

As rifting proceeds in backarc basin, basaltic crust may rise and become the base of the basin. Extensional tectonic regime on overriding plate migrates seaward, generating new backarc basin. Formation of new backarc basin ceases the development of the older one. Time taken for the formation and abandonment of backarc basin requires approximately 20 million years.

As rifting proceeds in backarc basin, basaltic crust may rise and become the base of the basin. Extensional tectonic regime on overriding plate migrates seaward, generating new backarc basin. Formation of new backarc basin ceases the development of the older one. Time taken for the formation and abandonment of backarc basin requires approximately 20 million years.

===Igneous Petrology===

===Igneous Petrology===

====Thermal Structure of Subduction Zone====

====Thermal Structure of Subduction Zone====

Thermal structure of subduction zone encompasses various factors affecting magma generation. Temperature distribution of subducted slab depends on physical properties of the slab, amount of water involved, and kinematics of the plate. Due to its solid phase, oceanic crust needs intensive interaction with heat source to distribute thermal energy through conduction. Keary and Vine (1994) proposed seven factors affecting thermal structure of subducted slab:

Thermal structure of subduction zone encompasses various factors affecting magma generation. Temperature distribution of subducted slab depends on physical properties of the slab, amount of water involved, and kinematics of the plate. Due to its solid phase, oceanic crust needs intensive interaction with heat source to distribute thermal energy through conduction. Keary and Vine<ref name=KV /> proposed seven factors affecting thermal structure of subducted slab:

# The rate of subduction

# The rate of subduction

#* Slow rate of subduction enables heat to widely distributed into the slab.

#* Slow rate of subduction enables heat to widely distributed into the slab.

Volcanic arc above subduction zone is a manifestation of magma generation below the Earth’s surface. Magma generation in subduction zone focuses on the potential sources of partial melting, mechanism of partial melting, and types of magma generated. Magma generated in subduction zone will ascent to the surface as a consequence of buoyancy. Assimilation and fractional crystallization (AFC) will take place, especially in active continental margin.

Volcanic arc above subduction zone is a manifestation of magma generation below the Earth’s surface. Magma generation in subduction zone focuses on the potential sources of partial melting, mechanism of partial melting, and types of magma generated. Magma generated in subduction zone will ascent to the surface as a consequence of buoyancy. Assimilation and fractional crystallization (AFC) will take place, especially in active continental margin.

Potential sources of magma generation are the subducted oceanic crust, mantle wedge, and sea water. Oceanic crust, as previously discussed, consists of terrigenous, carbonate and pelagic sediments, and also sedimentary rock, basalt, and gabbro. Mantle wedge as a part of asthenosphere provides lherzolite and harzburgite. Sea water doesn’t provide silicate materials in magma generation. Otherwise, sea water takes a role in reducing solidus of silicate material. As a result, partial melting can be achieved at lower temperature. Water may reduce the temperature of partial melting about 300oC. Wilson (2007) proposed specific potential sources of partial melting:

Potential sources of magma generation are the subducted oceanic crust, mantle wedge, and sea water. Oceanic crust, as previously discussed, consists of terrigenous, carbonate and pelagic sediments, and also sedimentary rock, basalt, and gabbro. Mantle wedge as a part of asthenosphere provides lherzolite and harzburgite. Sea water doesn’t provide silicate materials in magma generation. Otherwise, sea water takes a role in reducing solidus of silicate material. As a result, partial melting can be achieved at lower temperature. Water may reduce the temperature of partial melting about 300oC. Wilson<ref name=Wilson>Wilson, Majorie. 2007. Igneous Petrogenesis: A Global Tectonic Approach. Dordrecht: Springer.</ref> proposed specific potential sources of partial melting:

* Amphibolite, with or without aqueous fluid

* Amphibolite, with or without aqueous fluid

* Eclogite, with or without aqueous fluid

* Eclogite, with or without aqueous fluid

Magma generation of subduction zone greatly involves dehydration process. Prograde metamorphism occurs as the plate subducting. Increasing pressure and temperature dehydrate OH-bearing minerals, such as hornblende and biotite. Zeolite may prograde to amphibolite facies, then to eclogite facies. Water produced from metamorphism may occur at depth of 80 – 125 km. As water generated, it migrates upward as intergranular fluid. Water supply from subducted slab lowers the solidus of the mantle wedge.

Magma generation of subduction zone greatly involves dehydration process. Prograde metamorphism occurs as the plate subducting. Increasing pressure and temperature dehydrate OH-bearing minerals, such as hornblende and biotite. Zeolite may prograde to amphibolite facies, then to eclogite facies. Water produced from metamorphism may occur at depth of 80 – 125 km. As water generated, it migrates upward as intergranular fluid. Water supply from subducted slab lowers the solidus of the mantle wedge.

Magma generated from mantle wedge in dry condition is basaltic or picritic in composition (Wilson, 2007). The presence of volatiles (H2O and CO2) can produce magma with higher silica content. Andesite can be directly produced from mantle wedge at depth less than 40 km with concentration of H2O of 15 wt. % (Mysen, 1982 and Wyllie, 1982 in Wilson, 2007).

Magma generated from mantle wedge in dry condition is basaltic or picritic in composition.<ref name=Wilson /> The presence of volatiles (H2O and CO2) can produce magma with higher silica content. Andesite can be directly produced from mantle wedge at depth less than 40 km with concentration of H2O of 15 wt. % (Mysen, 1982 and Wyllie, 1982 in Wilson<ref name=Wilson />).

Boron, beryllium, thorium, and lead are possible indicators in determining the mode of flow within mantle wedge. Boron indicates transportation by fluid, while thorium and beryllium are effectively transported by melts.

Boron, beryllium, thorium, and lead are possible indicators in determining the mode of flow within mantle wedge. Boron indicates transportation by fluid, while thorium and beryllium are effectively transported by melts.

Classification of igneous rocks in geochemistry utilizes the alkaline (K2O and Na2O) and silica content of the rock. Classification based on alkaline and silica content divides igneous rock as alkaline and subalkaline rock. Plotting of K2O and Na2O may be conducted in separate graphs. If the plot in K2O graph states the rock is alkaline while in Na2O says the rock is subalkaline, then the rock is classified as transitional. Graph for alkaline and silica content plotting will be given in Fig. 7 and Fig. 8.

Classification of igneous rocks in geochemistry utilizes the alkaline (K2O and Na2O) and silica content of the rock. Classification based on alkaline and silica content divides igneous rock as alkaline and subalkaline rock. Plotting of K2O and Na2O may be conducted in separate graphs. If the plot in K2O graph states the rock is alkaline while in Na2O says the rock is subalkaline, then the rock is classified as transitional. Graph for alkaline and silica content plotting will be given in Fig. 7 and Fig. 8.

Igneous rocks generated in subduction zone generally belong to subalkaline rock. Plotting of K2O and Na2O in Harker diagram produces for classes of subduction magma series: low-K series, calc-alkaline series, high-K series, and shoshonitic series. Potash content in igneous rock is critical because it can represent the degree of contamination of magma. Low-K series is the same as tholeiitic rock. Calc-alkaline magma series have high alumina content. Shoshonitic series represents alkaline rock. Miyashiro (1974) in Wilson (2007) reveals the difference between calc-alkaline magma series with tholeiitic magma through Fe content. Calc- alkaline magma series show decreasing content of FeO in increasing SiO2 content. Otherwise, tholeiitic magma series show enrichment of Fe in early stage of fractionation.

Igneous rocks generated in subduction zone generally belong to subalkaline rock. Plotting of K2O and Na2O in Harker diagram produces for classes of subduction magma series: low-K series, calc-alkaline series, high-K series, and shoshonitic series. Potash content in igneous rock is critical because it can represent the degree of contamination of magma. Low-K series is the same as tholeiitic rock. Calc-alkaline magma series have high alumina content. Shoshonitic series represents alkaline rock. Miyashiro (1974) in Wilson<ref name=Wilson /> reveals the difference between calc-alkaline magma series with tholeiitic magma through Fe content. Calc- alkaline magma series show decreasing content of FeO in increasing SiO2 content. Otherwise, tholeiitic magma series show enrichment of Fe in early stage of fractionation.

Tholeiitic rock of subduction zone produces basalt and basaltic andesite. With its mafic composition, tholeiitic rock doesn’t produce explosive materials, such as pyroclastic fall and flow. Amphibole and biotite may be absent due to low volatile content. Another implication lies in geometry of volcano. Because of low viscosity, tholeiitic magma series tend to build shield volcano.

Tholeiitic rock of subduction zone produces basalt and basaltic andesite. With its mafic composition, tholeiitic rock doesn’t produce explosive materials, such as pyroclastic fall and flow. Amphibole and biotite may be absent due to low volatile content. Another implication lies in geometry of volcano. Because of low viscosity, tholeiitic magma series tend to build shield volcano.

Calc-alkaline magma series principally generates two-pyroxene andesite with about 59% SiO2. (Wilson, 2007). Increasing viscosity of magma implies to more explosive eruption and geometry of volcano. Due to explosive eruption, calc-alkaline magma is able to produce pyroclastic materials. In addition, calc- alkaline magma series build stratovolcano geometry.

Calc-alkaline magma series principally generates two-pyroxene andesite with about 59% SiO2.<ref name=Wilson /> Increasing viscosity of magma implies to more explosive eruption and geometry of volcano. Due to explosive eruption, calc-alkaline magma is able to produce pyroclastic materials. In addition, calc- alkaline magma series build stratovolcano geometry.

====Spatial and Temporal Distribution of Island-arc Magma Series====

====Spatial and Temporal Distribution of Island-arc Magma Series====

Geochemistry of igneous rocks in subduction zone is not constant in time and space. The evolution of magma series occurs because of subduction geometry and time. Spatial distribution of magma series builds on K – h relationship proposed by Dickinson (1975) in Wilson (2007). If silica content is hold constant, the amount of K2O (K) will increase as depth of Benioff zone (h) deepening. Therefore, volcano will produce rock of increasing alkalinity as it migrates away from the trench. Reversal of this characteristic also occurs. Relationship of magma series and time is represented with increasing alkalinity as time progresses. Deeper knowledge is required to build a model for temporal distribution as it is currently poorly understood.

Geochemistry of igneous rocks in subduction zone is not constant in time and space. The evolution of magma series occurs because of subduction geometry and time. Spatial distribution of magma series builds on K – h relationship proposed by Dickinson (1975) in Wilson.<ref name=Wilson /> If silica content is hold constant, the amount of K2O (K) will increase as depth of Benioff zone (h) deepening. Therefore, volcano will produce rock of increasing alkalinity as it migrates away from the trench. Reversal of this characteristic also occurs. Relationship of magma series and time is represented with increasing alkalinity as time progresses. Deeper knowledge is required to build a model for temporal distribution as it is currently poorly understood.

====Active Continental Margin====

====Active Continental Margin====

Active continental margin becomes the most complicated site of magma generation of Earth. As discussed in previous section, magma generation begins at the slab and mantle wedge. Partial melting of mantle wedge generates basaltic primitive magma. In island-arc, primitive magma rises to the surface and builds basaltic or andesitic volcano. Igneous processes in island-arc differ with active continental margin in assimilation and fractional crystallization.

Active continental margin becomes the most complicated site of magma generation of Earth. As discussed in previous section, magma generation begins at the slab and mantle wedge. Partial melting of mantle wedge generates basaltic primitive magma. In island-arc, primitive magma rises to the surface and builds basaltic or andesitic volcano. Igneous processes in island-arc differ with active continental margin in assimilation and fractional crystallization.

Primitive magma generated from the mantle wedge ascent to the boundary of crust and mantle. Due to density contrast, magma from mantle wedge underplates at the base of crust and experiences melting, assimilation, storage, and homogenization (MASH). Assimilation occurs because the crust is molten and enriching the composition of ascending magma. Winter (2001) defines fractionation as mechanical separation of materials with distinct phases. Simplified explanation of fractional crystallization is represented in Bowen reaction series. Magma will ascent from the base of the crust when faults creating fractures for magma migration. This requirement may occur in thinning area.

Primitive magma generated from the mantle wedge ascent to the boundary of crust and mantle. Due to density contrast, magma from mantle wedge underplates at the base of crust and experiences melting, assimilation, storage, and homogenization (MASH). Assimilation occurs because the crust is molten and enriching the composition of ascending magma. Winter<ref name=Winter>Winter, John D. 2001. An Introduction to Igneous and Metamorphic Petrology. New Jersey: Prentice- Hall Inc.</ref> defines fractionation as mechanical separation of materials with distinct phases. Simplified explanation of fractional crystallization is represented in Bowen reaction series. Magma will ascent from the base of the crust when faults creating fractures for magma migration. This requirement may occur in thinning area.

Assimilation and fractional crystallization of magma in the continents depends on the type of the crust. Continental crust itself is generally divided as upper and lower parts, represented with distinctive composition as previously discussed. With several possibilities of interaction, assimilation and fractional crystallization of magma have different Sr, Nd, Pb, and O isotopic signature. The use of Sr, Nd, and Pb data for interpreting young continental crust may trigger misleading result. Since young continental crust may have slightly different composition with the primitive magma, the data will show that contamination doesn’t occur. Winter (2001) states that assimilation and fractional crystallization in the deep-level generates magma with higher concentrations of K2O, Rb, Cs, Ba, Th, and Light Rare Earth Elements (LREE). Assimilation in active continental margin depends on temperature, composition, and thickness of the crust.

Assimilation and fractional crystallization of magma in the continents depends on the type of the crust. Continental crust itself is generally divided as upper and lower parts, represented with distinctive composition as previously discussed. With several possibilities of interaction, assimilation and fractional crystallization of magma have different Sr, Nd, Pb, and O isotopic signature. The use of Sr, Nd, and Pb data for interpreting young continental crust may trigger misleading result. Since young continental crust may have slightly different composition with the primitive magma, the data will show that contamination doesn’t occur. Winter<ref name=Winter /> states that assimilation and fractional crystallization in the deep-level generates magma with higher concentrations of K2O, Rb, Cs, Ba, Th, and Light Rare Earth Elements (LREE). Assimilation in active continental margin depends on temperature, composition, and thickness of the crust.

===Sedimentary Petrology===

===Sedimentary Petrology===

===Metamorphic Petrology===

===Metamorphic Petrology===

Subduction zone has distinct metamorphic rocks: formation of jadeite and glaucophane of blueschist faceis. Metamorphism in subduction zone is related to dewatering processes in magma generation. Dewatering and higher pressure and temperature induce prograde metamorphism. Keary and Vine (1994) states that surface volcanism is related to the formation of andalusite, high temperature and low pressure mineral.

Subduction zone has distinct metamorphic rocks: formation of jadeite and glaucophane of blueschist faceis. Metamorphism in subduction zone is related to dewatering processes in magma generation. Dewatering and higher pressure and temperature induce prograde metamorphism. Keary and Vine<ref name=KV /> states that surface volcanism is related to the formation of andalusite, high temperature and low pressure mineral.

Miyashiro (1973) in Keary and Vine (1994) states that subduction zone has paired metamorphic belts. An outher high pressure/low temperature on the seaward and low pressure/high temperature belt of similar age associated with the island arc.

Miyashiro (1973) in Keary and Vine<ref name=KV /> states that subduction zone has paired metamorphic belts. An outher high pressure/low temperature on the seaward and low pressure/high temperature belt of similar age associated with the island arc.

<gallery mode=packed heights=200>

<gallery mode=packed heights=200>

File:Subduction Fig-1.png|Fig. 1. Forces in Subduction Zone (Derived and modified from Keary and Vine, 1994)

File:Subduction Fig-1.png|Fig. 1. Forces in Subduction Zone (Derived and modified from Keary and Vine)<ref name=KV />

File:Subduction Fig-2.png|Fig. 2. Zonation of Deformation in Subduction Zone. This figure models the explanation above. (Derived and modified from Keary and Vine, 1994)

File:Subduction Fig-2.png|Fig. 2. Zonation of Deformation in Subduction Zone. This figure models the explanation above. (Derived and modified from Keary and Vine)<ref name=KV />

File:Subduction Fig-3.png|Fig. 3. Types of Subduction Zone (Derived from Jolivet and Nataf, 2001)

File:Subduction Fig-3.png|Fig. 3. Types of Subduction Zone (Derived from Jolivet and Nataf)<ref name=JL2001 />

File:Subduction Fig-4.png|Fig. 4. Structural Features of Subduction Zone (Derived from Nichols, 2009)

File:Subduction Fig-4.png|Fig. 4. Structural Features of Subduction Zone (Derived from Nichols)<ref>Nichols, Gary. 2009. Sedimentology and Stratigraphy Second Edition. West Sussex: John Wiley & Sons Ltd.</reF>

File:Subduction Fig-5.png|Fig. 5. Schematic Model of Island-arc (Derived from Wilson, 2007)

File:Subduction Fig-5.png|Fig. 5. Schematic Model of Island-arc (Derived from Wilson)<ref name=Wilson />

File:Subduction Fig-6.png|Fig. 6. Plot of wt.% K2O versus wt.% SiO2 to Show Major Divisions of Island-arc Volcanic Suites (Derived from Wilson, 2007)

File:Subduction Fig-6.png|Fig. 6. Plot of wt.% K2O versus wt.% SiO2 to Show Major Divisions of Island-arc Volcanic Suites (Derived from Wilson)<ref name=Wilson />

File:Subduction Fig-7.png|Fig. 7. Plot of A = K2O + Na2O, F = FeO + 0,9Fe2O3, and M = MgO to Differentiate between Tholeiitic and Calc-alkaline Magma Series (Derived from Wilson, 2007)

File:Subduction Fig-7.png|Fig. 7. Plot of A = K2O + Na2O, F = FeO + 0,9Fe2O3, and M = MgO to Differentiate between Tholeiitic and Calc-alkaline Magma Series (Derived from Wilson)<ref name=Wilson />

File:Subduction Fig-8.png|Fig. 8. Schematic Model of Subduction Zone in Active Continental Margin (Derived from Winter, 2001)

File:Subduction Fig-8.png|Fig. 8. Schematic Model of Subduction Zone in Active Continental Margin (Derived from Winter)<ref name=Winter />

File:Subduction Fig-9.png|Fig. 9. Classification of Tectonic Settings based on Mineral Composition in Sandstone (Derived from Dickinson et. al. (1983) in Boggs<ref name=Boggs />)

File:Subduction Fig-9.png|Fig. 9. Classification of Tectonic Settings based on Mineral Composition in Sandstone (Derived from Dickinson et. al. (1983) in Boggs<ref name=Boggs />)

</gallery>

</gallery>

==References==

==References==

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{{reflist}}

 

* Plummer, C. C., Carlson, Diane H., and Hammersley, Lisa. 2013. Physical Geology Fourteenth Edition. New York: McGraw-Hill Companies, Inc.

* Plummer, C. C., Carlson, Diane H., and Hammersley, Lisa. 2013. Physical Geology Fourteenth Edition. New York: McGraw-Hill Companies, Inc.