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Andesites

The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform

Yoshiyuki Tatsumi – 1st expert on this subject based on the ideXlab platform

  • Operation of subduction factory and production of andesite
    Journal of Mineralogical and Petrological Sciences, 2006
    Co-Authors: Yoshiyuki Tatsumi, Toshiro Takahashi

    Abstract:

    The subduction factory processes raw materials such as oceanic sediments and basaltic crust, selectively extracts particular subduction components and manufactures magmas, their solidified materials and continental crust as products. The waste materials from the factory, such as chemically modified oceanic materials and delaminated mafic arc lower crust are transported down to the deep mantle modified their compositions and ultimately recycled as mantle plumes. Andesite composes the bulk continental crust and therefore is the major product in the subduction factory. Two types of Andesites, calk-alkalic and tholeiitic series, are commonly recognized in a single arc volcano. We propose a new mechanism for production of these two magma series on the basis of data obtained by Sr isotopic micro-analyses of plagioclase in volcanic rocks from Zao Volcano, NE Japan. Tholeiitic magmas having constant and enriched isotopic signatures are produced by anatexis of the preexisting mafic lower crust, whereas calc-alkalic magmas, having compositions similar to the bulk continental crust, are products of mixing a mantle-derived, hence isotopically depleted, basaltic magma and crust-derived felsic tholeiites.

  • high mg Andesites in the setouchi volcanic belt southwestern japan analogy to archean magmatism and continental crust formation
    Annual Review of Earth and Planetary Sciences, 2006
    Co-Authors: Yoshiyuki Tatsumi

    Abstract:

    AbstractThe occurrence of unusual high-Mg andesite (HMA) characterizes the Setouchi volcanic belt in SW Japan, which was activated at 13.7±1.0 Ma by subduction of the young and hot Shikoku Basin lithosphere into the high-temperature upper mantle. This tectonic setting may be analogous to the thermal regime during Archean times, which suggests more ubiquitous production of HMA. A plausible process that can comprehensively account for the petrological and geochemical characteristics of Setouchi HMAs involves partial melting of subducting lithosphere, subsequent melt-mantle interactions, and final equilibration with the upper-most mantle. HMAs and more differentiated Andesites, which are coined sanukitoids, are distinct in that they are phenocryst-poor (<10%), compact, and nearly anhydrous, despite HMA magmas originally containing ∼7 wt% H2O, and commonly form composite lava flows. One mechanism for explaining these features is formation of a mostly solidified HMA pluton, remelting of the HMA pluton by intru...

  • The subduction factory: How it operates in the evolving Earth
    GSA Today, 2005
    Co-Authors: Yoshiyuki Tatsumi

    Abstract:

    The subduction factory processes raw materials such as oceanic sediments and oceanic crust and manufactures magmas and continental crust as products. Aqueous fluids, which are extracted from oceanic raw materials via dehydration reactions during subduction, dissolve particular elements and overprint such elements onto the mantle wedge to generate chemically distinct arc basalt magmas. The production of calc-alkalic Andesites typifies magmatism in subduction zones. One of the principal mechanisms of modern-day, calc-alkalic andesite production is thought to be mixing of two end-member magmas, a mantle-derived basaltic magma and an arc crust-derived felsic magma. This process may also have contributed greatly to continental crust formation, as the bulk continental crust possesses compositions similar to calc-alkalic Andesites. If so, then the mafic melting residue after extraction of felsic melts should be removed and delaminated from the initial basaltic arc crust in order to form “andesitic” crust compositions. The waste materials from the factory, such as chemically modified oceanic materials and delaminated mafic lower crust materials, are transported down to the deep mantle and recycled as mantle plumes. The subduction factory has played a central role in the evolution of the solid Earth through creating continental crust and deep mantle geochemical reservoirs.

Ali Polat – 2nd expert on this subject based on the ideXlab platform

  • a ca 2 1 ga andean type margin built on metasomatized lithosphere in the northern yangtze craton china evidence from high mg basalts and Andesites
    Precambrian Research, 2017
    Co-Authors: Songbai Peng, Ali Polat, Timothy M Kusky, Hao Deng, Tuoyu Wu

    Abstract:

    Abstract We report for the first time the presence of a suite of Paleoproterozoic (2.12 Ga) metamorphosed high-Mg basalts and Andesites in the Huangling dome, northern Yangtze craton, China, which provide new insights into crustal growth processes in the craton during the Paleoproterozoic era. The high-Mg basalts and Andesites are mineralogically and texturally amphibolites and quartz-bearing amphibolites, respectively, and occur as deformed layers within the metasedimentary rocks of the Shuiyuesi Group in the northern Huangling dome. We present new field and petrographic observations, zircon U-Pb ages, in situ zircon Hf isotope and whole-rock major and trace element and Nd isotope data, to assess the petrogenetic origin and geodynamic setting of these high-Mg rocks. The igneous zircons from the Andesites yield a weighted age of ca. 2.12 Ga that is interpreted to be the formation age of the magmatic protolith. The basalts are characterized by moderate SiO2 (49 wt.%), low TiO2 (0.63–0.65 wt.%), high MgO (13.7–14.6 wt.%) and high Mg-numbers (58–59). The Andesites have 53–60 wt.% SiO2, 0.45–0.50 wt.% TiO2 and 6.6–9.5 wt.% MgO contents, yielding high Mg-numbers (63–76). Both the basalts and Andesites are enriched in LILE and LREE, but depleted in Nb, Ta, and HREE. Zircons in the Andesites have eHf (t) values between −0.2 and +3.3 and corresponding Hf isotopic model age (TDM1) of 2.4 Ga, reflecting various degrees of crustal input. They have negative eNd (t) values, ranging from −4.4 to −2.7. Geochemical characteristics of the basalts and Andesites indicate that they are equivalent to high-Mg basalts and Andesites, respectively, occurring in Phanerozoic suprasubduction zones. The Nd and Hf isotope compositions of the high-Mg rocks suggest that they were derived from partial melting of subarc lithospheric mantle above a subducting oceanic slab. The formation age and general geochemical characteristics of the high-Mg rocks reveal the presence of a Paleoproterozoic (2.1–2.2 Ga) Andean-type continental margin developed on metasomatized lithospheric mantle in the northern Huangling dome. The geochemical and geochronological data presented in this study provide important insights into Paleoproterozoic evolution of the Yangtze craton.

  • nd isotope systematics of 2 7 ga adakites magnesian Andesites and arc basalts superior province evidence for shallow crustal recycling at archean subduction zones
    Earth and Planetary Science Letters, 2002
    Co-Authors: Ali Polat, Robert Kerrich

    Abstract:

    Abstract An association of adakite, magnesian andesite (MA), and Nb-enriched basalt (NEB) volcanic flows, which erupted within ‘normal’ intra-oceanic arc tholeiitic to calc-alkaline basalts, has recently been documented in ∼2.7 Ga Wawa greenstone belts. Large, positive initial ϵNd values (+1.95 to +2.45) of the adakites signify that their basaltic precursors, with a short crustal residence, were derived from a long-term depleted mantle source. It is likely that the adakites represent the melts of subducted late Archean oceanic crust. Initial ϵNd values in the MA (+0.14 to +1.68), Nb-enriched basalts and Andesites (NEBA) (+1.11 to +2.05), and ‘normal’ intra-oceanic arc tholeiitic to calc-alkaline basalts and Andesites (+1.44 to +2.44) overlap with, but extend to lower values than, the adakites. Large, tightly clustered ϵNd values of the adakites, together with Th/Ce and Ce/Yb systematics of the arc basalts that rule out sediment melting, place the enriched source in the sub-arc mantle. Accordingly, isotopic data for the MA, NEBA, and ‘normal’ arc basalts can be explained by melting of an isotopically heterogeneous sub-arc mantle that had been variably enriched by recycling of continental material into the shallow mantle in late Archean subduction zones up to 200 Ma prior to the 2.7 Ga arc. If the late Archean Wawa adakites, MA, and basalts were generated by similar geodynamic processes as their counterparts in Cenozoic arcs, involving subduction of young and/or hot ocean lithosphere, then it is likely that late Archean oceanic crust, and arc crust, were also created and destroyed by modern plate tectonic-like geodynamic processes. This study suggests that crustal recycling through subduction zone processes played an important role for the generation of heterogeneity in the Archean upper mantle. In addition, the results of this study indicate that the Nd-isotope compositions of Archean arc- and plume-derived volcanic rocks are not very distinct, whereas Phanerozoic plumes and intra-oceanic arcs tend to have different Nd-isotopic compositions.

  • magnesian Andesites nb enriched basalt Andesites and adakites from late archean 2 7 ga wawa greenstone belts superior province canada implications for late archean subduction zone petrogenetic processes
    Contributions to Mineralogy and Petrology, 2001
    Co-Authors: Ali Polat, Robert Kerrich

    Abstract:

    Magnesian Andesites (MA) occur with ‘normal’ tholeiitic to calc-alkaline basalt-andesite suites in four greenstone belts of the 2.7 Ga Wawa subprovince, Canada. Collectively, the magnesian Andesites span ranges of SiO2=56–64 wt%, Mg-number=0.64–0.50, with Cr and Ni contents of 531–106 and 230–21 ppm, respectively. Relative to ‘normal’ Andesites, the magnesian Andesites form distinct trends on variation diagrams, with relatively high Th and LREE contents, uniform Yb over a range of MgO, more fractionated HREE, and lower Nb/Thpm and Nb/Lapm ratios. Niobium-enriched basalts and Andesites (NEBA; Nb=7–16 ppm), and an Al-enriched rhyolite (adakite) suite are associated in space and time with the magnesian Andesites. Nb-enriched basalts and Andesites are characterized by high TiO2, P2O5, Th, and Zr contents, variably high Zr/Hf (36–44) ratios, and more fractionated HREE (Gd/Ybcn=1.3–4.1) compared to the ‘normal’ tholeiitic to calc-alkaline basalt-andesite suites. The adakite suite has the high Al (Al2O3=16–18 wt%), high La/Ybcn (21–43), and low Yb (0.4–1.2 ppm) of Archean tonalite-trondhjemite-granodiorite (TTG) suites and Cenozoic adakites, indicative of liquids derived mainly from slab melting. The basalt-andesite suites are not characterized by normal tholeiitic or calc-alkaline fractionation trends of major or trace elements. Rather, compositional trends can be accounted for by some combination of fractional crystallization and variable degrees of metasomatism of the source of basalt and/or Andesites by adakitic liquids. The occurrence of magnesian Andesites, Nb-enriched basalts/Andesites, and adakites has been described from certain Phanerozoic arcs featuring shallow subduction of young and/or hot oceanic lithosphere. Adakites likely represent slab melts, magnesian Andesites the product of hybridization of adakite liquids with mantle peridotite, and Nb-enriched basalts/Andesites melts of the residue from hybridization. Geological similarities between the late-Archean Wawa greenstone belts and certain Cenozoic transpressional orogens with the MA-NEBA-adakite association suggest that subduction of young, hot oceanic lithosphere may have played an important role in the production of this arc-related association in the late Archean.

Robert Kerrich – 3rd expert on this subject based on the ideXlab platform

  • nd isotope systematics of 2 7 ga adakites magnesian Andesites and arc basalts superior province evidence for shallow crustal recycling at archean subduction zones
    Earth and Planetary Science Letters, 2002
    Co-Authors: Ali Polat, Robert Kerrich

    Abstract:

    Abstract An association of adakite, magnesian andesite (MA), and Nb-enriched basalt (NEB) volcanic flows, which erupted within ‘normal’ intra-oceanic arc tholeiitic to calc-alkaline basalts, has recently been documented in ∼2.7 Ga Wawa greenstone belts. Large, positive initial ϵNd values (+1.95 to +2.45) of the adakites signify that their basaltic precursors, with a short crustal residence, were derived from a long-term depleted mantle source. It is likely that the adakites represent the melts of subducted late Archean oceanic crust. Initial ϵNd values in the MA (+0.14 to +1.68), Nb-enriched basalts and Andesites (NEBA) (+1.11 to +2.05), and ‘normal’ intra-oceanic arc tholeiitic to calc-alkaline basalts and Andesites (+1.44 to +2.44) overlap with, but extend to lower values than, the adakites. Large, tightly clustered ϵNd values of the adakites, together with Th/Ce and Ce/Yb systematics of the arc basalts that rule out sediment melting, place the enriched source in the sub-arc mantle. Accordingly, isotopic data for the MA, NEBA, and ‘normal’ arc basalts can be explained by melting of an isotopically heterogeneous sub-arc mantle that had been variably enriched by recycling of continental material into the shallow mantle in late Archean subduction zones up to 200 Ma prior to the 2.7 Ga arc. If the late Archean Wawa adakites, MA, and basalts were generated by similar geodynamic processes as their counterparts in Cenozoic arcs, involving subduction of young and/or hot ocean lithosphere, then it is likely that late Archean oceanic crust, and arc crust, were also created and destroyed by modern plate tectonic-like geodynamic processes. This study suggests that crustal recycling through subduction zone processes played an important role for the generation of heterogeneity in the Archean upper mantle. In addition, the results of this study indicate that the Nd-isotope compositions of Archean arc- and plume-derived volcanic rocks are not very distinct, whereas Phanerozoic plumes and intra-oceanic arcs tend to have different Nd-isotopic compositions.

  • magnesian Andesites nb enriched basalt Andesites and adakites from late archean 2 7 ga wawa greenstone belts superior province canada implications for late archean subduction zone petrogenetic processes
    Contributions to Mineralogy and Petrology, 2001
    Co-Authors: Ali Polat, Robert Kerrich

    Abstract:

    Magnesian Andesites (MA) occur with ‘normal’ tholeiitic to calc-alkaline basalt-andesite suites in four greenstone belts of the 2.7 Ga Wawa subprovince, Canada. Collectively, the magnesian Andesites span ranges of SiO2=56–64 wt%, Mg-number=0.64–0.50, with Cr and Ni contents of 531–106 and 230–21 ppm, respectively. Relative to ‘normal’ Andesites, the magnesian Andesites form distinct trends on variation diagrams, with relatively high Th and LREE contents, uniform Yb over a range of MgO, more fractionated HREE, and lower Nb/Thpm and Nb/Lapm ratios. Niobium-enriched basalts and Andesites (NEBA; Nb=7–16 ppm), and an Al-enriched rhyolite (adakite) suite are associated in space and time with the magnesian Andesites. Nb-enriched basalts and Andesites are characterized by high TiO2, P2O5, Th, and Zr contents, variably high Zr/Hf (36–44) ratios, and more fractionated HREE (Gd/Ybcn=1.3–4.1) compared to the ‘normal’ tholeiitic to calc-alkaline basalt-andesite suites. The adakite suite has the high Al (Al2O3=16–18 wt%), high La/Ybcn (21–43), and low Yb (0.4–1.2 ppm) of Archean tonalite-trondhjemite-granodiorite (TTG) suites and Cenozoic adakites, indicative of liquids derived mainly from slab melting. The basalt-andesite suites are not characterized by normal tholeiitic or calc-alkaline fractionation trends of major or trace elements. Rather, compositional trends can be accounted for by some combination of fractional crystallization and variable degrees of metasomatism of the source of basalt and/or Andesites by adakitic liquids. The occurrence of magnesian Andesites, Nb-enriched basalts/Andesites, and adakites has been described from certain Phanerozoic arcs featuring shallow subduction of young and/or hot oceanic lithosphere. Adakites likely represent slab melts, magnesian Andesites the product of hybridization of adakite liquids with mantle peridotite, and Nb-enriched basalts/Andesites melts of the residue from hybridization. Geological similarities between the late-Archean Wawa greenstone belts and certain Cenozoic transpressional orogens with the MA-NEBA-adakite association suggest that subduction of young, hot oceanic lithosphere may have played an important role in the production of this arc-related association in the late Archean.