Changes

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.

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.<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.

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.