Hiroshi Kitagawa - Academia.edu (original) (raw)
Papers by Hiroshi Kitagawa
Bilateral Heterogeneity in an Upwelling Mantle via Double Subduction of Oceanic Lithosphere
Journal of Geophysical Research: Solid Earth
Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have bee... more Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have been proposed to explain the mantle upwelling and volcanism in this region; collision of the Indian and Eurasian continents or subduction of the Pacific or Indo-Australian oceanic lithosphere. To place constraints on the origin of the intraplate volcanism in SE Asia, new geochronological and geochemical data for Cenozoic basalts in Vietnam are presented. Based largely on Sr-Nd-Pb isotope systematics, it was found that the sources of basalts from Central and Southern Vietnam are chemically distinct forming a sharp boundary at 13.5°N. The basalts north of the boundary show isotopic features similar to Enriched Mantle type 2 (EM2) ocean island basalts. Whereas the basalts south of the boundary show isotopic features similar to Enriched Mantle type 1 (EM1) ocean island basalts. The EM1 and EM2 basalts display positive Sr anomalies and elevated Pb/Ce and Th/La ratios, respectively. Such features suggest the origins of the sources through recycling of deeply-subducted crustal lithologies. Furthermore, subduction of dense oceanic lithosphere can induce a convecting cell in the upper mantle. Therefore, we suggest that the chemically different basalts from the Central and South of Vietnam represent the surface expression of melting in different convecting cells, one is driven by subduction of the Pacific plate and the other by subduction of the Indo-Australian plate.
Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials
Journal of Analytical Atomic Spectrometry, 2003
We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elem... more We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic CaAlMgHF solution system using two different methods: at <70 °C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205 °C using a TFE ...
琉球大学理学部紀要, Mar 1, 2004
Major and trace element concentrations and Sr and Nd isotopic ratios are presented for volcanic r... more Major and trace element concentrations and Sr and Nd isotopic ratios are presented for volcanic rocks from the Uegusukudake Formation (v3-2 Ma) in Kume-jima, central Ryukyu Arc, in order to understand the origin of varieties of erupted magmas. The Uegusukudake Formation is mainly composed of lavas and pyroclastic rocks with subordinate dikes. Volcanic rocks collected from lavas and dikes are grouped into four types based on their petrological characteristics: (1) picrite basalt (PB); (2) aphyric, tholeiitic basalt and basaltic andesite (A-TH); (3) porphyritic, tholeiitic basaltic andesite (P-TH); and (4) porphyritic, calc-alkaline basaltic andesite and andesite (CA), in ascending order. The PB sample is isotopically distinct in having significantly low 87Sr/MSr (0.7035) and high l<3Nd/'"Nd (0.51290) compared with the other three types. The A-TH, P-TH, and CA types have similar isotopic compositions (87Sr/MSr=0.7045-0.7054, 143Nd/l44Nd=0.51270-0.51284) and show rather coherent incompatible trace element patterns. These results suggest that the three types of magmas were derived from a similar source material, distinctive from the source of the PB magma. A slight difference in isotopic and trace element ratios (La/Sm and La/Yb) among the three types can be attributed to the different degree of contributions of crustal assimilation. Geochemical variations within the A-TH type rocks can be explained by fractional crystallization, and the variation of the CA type is considered to have resulted from internal hybridization within a single magma reservoir. For the variation of the P-TH type, plagioclase accumulation is inferred to have played a dominant role.
New K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data are presented fo... more New K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data are presented for Oligocene to recent mafic volcanic rocks from the Ethiopian Plateau, the Main Ethiopian Rift (MER), and the Afar depression. Chronological and geochemical data from this study are combined with previously published datasets to reveal secular variations in magmatism throughout the entire Ethiopian volcanic region. The mafic lavas in these regions show variability in terms of silica-saturation (i.e. alkaline and sub-alkaline series) and extent of differentiation (mafic through intermediate to felsic). The P-T conditions of melting, estimated using the least differentiated basalts, reveal a secular decrease in the mantle potential temperature, from when the flood basalt magmas erupted (up to 1600 degrees C) to the time of the rift-related magmatism (<1500 degrees C). Variations in the Sr-Nd-Pb isotopic compositions of the mafic lavas can account for the involvement of multiple end-memb...
Journal of Petrology, 2005
Mechanisms of fractional crystallization with simultaneous crustal assimilation (AFC) are examine... more Mechanisms of fractional crystallization with simultaneous crustal assimilation (AFC) are examined for the Kutsugata and Tanetomi lavas, an alkali basalt-dacite suite erupted sequentially from Rishiri Volcano, northern Japan. The major element variations within the suite can be explained by boundary layer fractionation; that is, mixing of a magma in the main part of the magma body with a fractionated interstitial melt transported from the mushy boundary layer at the floor. Systematic variations in SiO 2 correlate with variations in the Pb, Sr and Nd isotopic compositions of the lavas. The geochemical variations of the lavas are explained by a constant and relatively low ratio of assimilated mass to crystallized mass ('r value'). In the magma chamber in which the Kutsugata and Tanetomi magmas evolved, a strong thermal gradient was present and it is suggested that the marginal part of the reservoir was completely solidified. The assimilant was transported by crack flow from the partially fused floor crust to the partially crystallized floor mush zone through fractures in the solidified margin, formed mainly by thermal stresses resulting from cooling of the solidified margin and heating of the crust. The crustal melt was then mixed with the fractionated interstitial melt in the mushy zone, and the mixed melt was further transported by compositional convection to the main magma, causing its geochemical evolution to be characteristic of AFC. The volume flux of the assimilant from the crust to the magma chamber is suggested to have decreased progressively with time (proportional to t À1/2), and was about 3 Â 10 À2 m/year at t ¼ 10 years and 1 Â 10 À2 m/year at t ¼ 100 years. It has been commonly considered that the heat balance between magmas and the surrounding crust controls the coupling of assimilation and fractional crystallization processes (i.e. absolute value of r). However, it is inferred from this study that the ratio of assimilated mass to crystallized mass can be controlled by the transport process of the assimilant from the crust to magma chambers.
Journal of Petrology, 2008
We present major and trace element concentrations and Sr^NdĤ f^Pb isotope data for the c. 13^2 Ma... more We present major and trace element concentrations and Sr^NdĤ f^Pb isotope data for the c. 13^2 Ma Tertiary lavas from eastern Iceland. Our new geochemical results, together with published geological, geochronological, geochemical and geophysical data, are used to evaluate temporal changes in mantle sources contributing to the Tertiary Icelandic magmatism and the relative roles of these sources in magma productivity. The trace element and radiogenic isotopic compositions clearly distinguish three distinct end-member components in the Tertiary magmatism. Temporal variations in lava geochemistry can be attributed to changes in the relative contributions of these three end-member components to the erupted magmas and correlated with temporal variations in magma productivity. The extrusion of lavas with geochemically and isotopically enriched compositions was particularly pronounced at $13^12 and 8^7 Ma, coincident in time with higher magma productivity. However, the geochemical characteristics of the lavas are different during these two periods: the 13^12 Ma lavas have more radiogenic 176 Hf/ 177 Hf and less radiogenic 206 Pb/ 204 Pb than those erupted from 8 to 7 Ma. The eruption of relatively depleted lavas, at around 10 Ma and younger than 6Á5 Ma, is coincident with lower magma productivity. The correlation between the composition and productivity of the Tertiary lavas from eastern Iceland is probably due to periodic changes in the involvement of the enriched end-member component, followed by a gradation to periods dominated by the signature of the depleted end-member component and lower magma productivity, at an approximate frequency of 5 Myr.
Journal of Geophysical Research Solid Earth, 2021
Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have bee... more Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have been proposed to explain the mantle upwelling and volcanism in this region; collision of the Indian and Eurasian continents or subduction of the Pacific or Indo-Australian oceanic lithosphere. To place constraints on the origin of the intraplate volcanism in SE Asia, new geochronological and geochemical data for Cenozoic basalts in Vietnam are presented. Based largely on Sr-Nd-Pb isotope systematics, it was found that the sources of basalts from Central and Southern Vietnam are chemically distinct forming a sharp boundary at 13.5°N. The basalts north of the boundary show isotopic features similar to Enriched Mantle type 2 (EM2) ocean island basalts. Whereas the basalts south of the boundary show isotopic features similar to Enriched Mantle type 1 (EM1) ocean island basalts. The EM1 and EM2 basalts display positive Sr anomalies and elevated Pb/Ce and Th/La ratios, respectively. Such features suggest the origins of the sources through recycling of deeply-subducted crustal lithologies. Furthermore, subduction of dense oceanic lithosphere can induce a convecting cell in the upper mantle. Therefore, we suggest that the chemically different basalts from the Central and South of Vietnam represent the surface expression of melting in different convecting cells, one is driven by subduction of the Pacific plate and the other by subduction of the Indo-Australian plate.
Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials
J. Anal. At. Spectrom., 2003
We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elem... more We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic Ca–Al–Mg–HF solution system using two different methods: at <70 °C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205 °C using a TFE Teflon® bomb (denoted as the bomb method). Full recovery of HFSE into the supernatant HF solution was not achieved in cases where fluorite (CaF2) forms in the precipitate in both methods and sellaite (MgF2) forms in the ultrasonic method. In order to suppress fluorite precipitation, an ‘Al-addition method’ was developed in which Al solution is added to the sample before decomposition to change the matrix solution to a composition in which no fluorite forms. Using the Al-addition method, HFSE concentrations of Ca-rich materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) by an isotope dilution method for Zr and Hf and by a calibration curve method for Nb and Ta. Furthermore, we foun...
Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials
J. Anal. At. Spectrom., 2003
We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elem... more We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic Ca–Al–Mg–HF solution system using two different methods: at <70 °C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205 °C using a TFE Teflon® bomb (denoted as the bomb method). Full recovery of HFSE into the supernatant HF solution was not achieved in cases where fluorite (CaF2) forms in the precipitate in both methods and sellaite (MgF2) forms in the ultrasonic method. In order to suppress fluorite precipitation, an ‘Al-addition method’ was developed in which Al solution is added to the sample before decomposition to change the matrix solution to a composition in which no fluorite forms. Using the Al-addition method, HFSE concentrations of Ca-rich materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) by an isotope dilution method for Zr and Hf and by a calibration curve method for Nb and Ta. Furthermore, we foun...
Bilateral Heterogeneity in an Upwelling Mantle via Double Subduction of Oceanic Lithosphere
Journal of Geophysical Research: Solid Earth
Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have bee... more Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have been proposed to explain the mantle upwelling and volcanism in this region; collision of the Indian and Eurasian continents or subduction of the Pacific or Indo-Australian oceanic lithosphere. To place constraints on the origin of the intraplate volcanism in SE Asia, new geochronological and geochemical data for Cenozoic basalts in Vietnam are presented. Based largely on Sr-Nd-Pb isotope systematics, it was found that the sources of basalts from Central and Southern Vietnam are chemically distinct forming a sharp boundary at 13.5°N. The basalts north of the boundary show isotopic features similar to Enriched Mantle type 2 (EM2) ocean island basalts. Whereas the basalts south of the boundary show isotopic features similar to Enriched Mantle type 1 (EM1) ocean island basalts. The EM1 and EM2 basalts display positive Sr anomalies and elevated Pb/Ce and Th/La ratios, respectively. Such features suggest the origins of the sources through recycling of deeply-subducted crustal lithologies. Furthermore, subduction of dense oceanic lithosphere can induce a convecting cell in the upper mantle. Therefore, we suggest that the chemically different basalts from the Central and South of Vietnam represent the surface expression of melting in different convecting cells, one is driven by subduction of the Pacific plate and the other by subduction of the Indo-Australian plate.
Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials
Journal of Analytical Atomic Spectrometry, 2003
We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elem... more We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic CaAlMgHF solution system using two different methods: at <70 °C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205 °C using a TFE ...
琉球大学理学部紀要, Mar 1, 2004
Major and trace element concentrations and Sr and Nd isotopic ratios are presented for volcanic r... more Major and trace element concentrations and Sr and Nd isotopic ratios are presented for volcanic rocks from the Uegusukudake Formation (v3-2 Ma) in Kume-jima, central Ryukyu Arc, in order to understand the origin of varieties of erupted magmas. The Uegusukudake Formation is mainly composed of lavas and pyroclastic rocks with subordinate dikes. Volcanic rocks collected from lavas and dikes are grouped into four types based on their petrological characteristics: (1) picrite basalt (PB); (2) aphyric, tholeiitic basalt and basaltic andesite (A-TH); (3) porphyritic, tholeiitic basaltic andesite (P-TH); and (4) porphyritic, calc-alkaline basaltic andesite and andesite (CA), in ascending order. The PB sample is isotopically distinct in having significantly low 87Sr/MSr (0.7035) and high l<3Nd/'"Nd (0.51290) compared with the other three types. The A-TH, P-TH, and CA types have similar isotopic compositions (87Sr/MSr=0.7045-0.7054, 143Nd/l44Nd=0.51270-0.51284) and show rather coherent incompatible trace element patterns. These results suggest that the three types of magmas were derived from a similar source material, distinctive from the source of the PB magma. A slight difference in isotopic and trace element ratios (La/Sm and La/Yb) among the three types can be attributed to the different degree of contributions of crustal assimilation. Geochemical variations within the A-TH type rocks can be explained by fractional crystallization, and the variation of the CA type is considered to have resulted from internal hybridization within a single magma reservoir. For the variation of the P-TH type, plagioclase accumulation is inferred to have played a dominant role.
New K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data are presented fo... more New K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data are presented for Oligocene to recent mafic volcanic rocks from the Ethiopian Plateau, the Main Ethiopian Rift (MER), and the Afar depression. Chronological and geochemical data from this study are combined with previously published datasets to reveal secular variations in magmatism throughout the entire Ethiopian volcanic region. The mafic lavas in these regions show variability in terms of silica-saturation (i.e. alkaline and sub-alkaline series) and extent of differentiation (mafic through intermediate to felsic). The P-T conditions of melting, estimated using the least differentiated basalts, reveal a secular decrease in the mantle potential temperature, from when the flood basalt magmas erupted (up to 1600 degrees C) to the time of the rift-related magmatism (<1500 degrees C). Variations in the Sr-Nd-Pb isotopic compositions of the mafic lavas can account for the involvement of multiple end-memb...
Journal of Petrology, 2005
Mechanisms of fractional crystallization with simultaneous crustal assimilation (AFC) are examine... more Mechanisms of fractional crystallization with simultaneous crustal assimilation (AFC) are examined for the Kutsugata and Tanetomi lavas, an alkali basalt-dacite suite erupted sequentially from Rishiri Volcano, northern Japan. The major element variations within the suite can be explained by boundary layer fractionation; that is, mixing of a magma in the main part of the magma body with a fractionated interstitial melt transported from the mushy boundary layer at the floor. Systematic variations in SiO 2 correlate with variations in the Pb, Sr and Nd isotopic compositions of the lavas. The geochemical variations of the lavas are explained by a constant and relatively low ratio of assimilated mass to crystallized mass ('r value'). In the magma chamber in which the Kutsugata and Tanetomi magmas evolved, a strong thermal gradient was present and it is suggested that the marginal part of the reservoir was completely solidified. The assimilant was transported by crack flow from the partially fused floor crust to the partially crystallized floor mush zone through fractures in the solidified margin, formed mainly by thermal stresses resulting from cooling of the solidified margin and heating of the crust. The crustal melt was then mixed with the fractionated interstitial melt in the mushy zone, and the mixed melt was further transported by compositional convection to the main magma, causing its geochemical evolution to be characteristic of AFC. The volume flux of the assimilant from the crust to the magma chamber is suggested to have decreased progressively with time (proportional to t À1/2), and was about 3 Â 10 À2 m/year at t ¼ 10 years and 1 Â 10 À2 m/year at t ¼ 100 years. It has been commonly considered that the heat balance between magmas and the surrounding crust controls the coupling of assimilation and fractional crystallization processes (i.e. absolute value of r). However, it is inferred from this study that the ratio of assimilated mass to crystallized mass can be controlled by the transport process of the assimilant from the crust to magma chambers.
Journal of Petrology, 2008
We present major and trace element concentrations and Sr^NdĤ f^Pb isotope data for the c. 13^2 Ma... more We present major and trace element concentrations and Sr^NdĤ f^Pb isotope data for the c. 13^2 Ma Tertiary lavas from eastern Iceland. Our new geochemical results, together with published geological, geochronological, geochemical and geophysical data, are used to evaluate temporal changes in mantle sources contributing to the Tertiary Icelandic magmatism and the relative roles of these sources in magma productivity. The trace element and radiogenic isotopic compositions clearly distinguish three distinct end-member components in the Tertiary magmatism. Temporal variations in lava geochemistry can be attributed to changes in the relative contributions of these three end-member components to the erupted magmas and correlated with temporal variations in magma productivity. The extrusion of lavas with geochemically and isotopically enriched compositions was particularly pronounced at $13^12 and 8^7 Ma, coincident in time with higher magma productivity. However, the geochemical characteristics of the lavas are different during these two periods: the 13^12 Ma lavas have more radiogenic 176 Hf/ 177 Hf and less radiogenic 206 Pb/ 204 Pb than those erupted from 8 to 7 Ma. The eruption of relatively depleted lavas, at around 10 Ma and younger than 6Á5 Ma, is coincident with lower magma productivity. The correlation between the composition and productivity of the Tertiary lavas from eastern Iceland is probably due to periodic changes in the involvement of the enriched end-member component, followed by a gradation to periods dominated by the signature of the depleted end-member component and lower magma productivity, at an approximate frequency of 5 Myr.
Journal of Geophysical Research Solid Earth, 2021
Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have bee... more Vietnam is a major field of Cenozoic volcanism in Southeast Asia. Two contrasting models have been proposed to explain the mantle upwelling and volcanism in this region; collision of the Indian and Eurasian continents or subduction of the Pacific or Indo-Australian oceanic lithosphere. To place constraints on the origin of the intraplate volcanism in SE Asia, new geochronological and geochemical data for Cenozoic basalts in Vietnam are presented. Based largely on Sr-Nd-Pb isotope systematics, it was found that the sources of basalts from Central and Southern Vietnam are chemically distinct forming a sharp boundary at 13.5°N. The basalts north of the boundary show isotopic features similar to Enriched Mantle type 2 (EM2) ocean island basalts. Whereas the basalts south of the boundary show isotopic features similar to Enriched Mantle type 1 (EM1) ocean island basalts. The EM1 and EM2 basalts display positive Sr anomalies and elevated Pb/Ce and Th/La ratios, respectively. Such features suggest the origins of the sources through recycling of deeply-subducted crustal lithologies. Furthermore, subduction of dense oceanic lithosphere can induce a convecting cell in the upper mantle. Therefore, we suggest that the chemically different basalts from the Central and South of Vietnam represent the surface expression of melting in different convecting cells, one is driven by subduction of the Pacific plate and the other by subduction of the Indo-Australian plate.
Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials
J. Anal. At. Spectrom., 2003
We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elem... more We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic Ca–Al–Mg–HF solution system using two different methods: at <70 °C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205 °C using a TFE Teflon® bomb (denoted as the bomb method). Full recovery of HFSE into the supernatant HF solution was not achieved in cases where fluorite (CaF2) forms in the precipitate in both methods and sellaite (MgF2) forms in the ultrasonic method. In order to suppress fluorite precipitation, an ‘Al-addition method’ was developed in which Al solution is added to the sample before decomposition to change the matrix solution to a composition in which no fluorite forms. Using the Al-addition method, HFSE concentrations of Ca-rich materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) by an isotope dilution method for Zr and Hf and by a calibration curve method for Nb and Ta. Furthermore, we foun...
Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials
J. Anal. At. Spectrom., 2003
We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elem... more We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic Ca–Al–Mg–HF solution system using two different methods: at <70 °C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205 °C using a TFE Teflon® bomb (denoted as the bomb method). Full recovery of HFSE into the supernatant HF solution was not achieved in cases where fluorite (CaF2) forms in the precipitate in both methods and sellaite (MgF2) forms in the ultrasonic method. In order to suppress fluorite precipitation, an ‘Al-addition method’ was developed in which Al solution is added to the sample before decomposition to change the matrix solution to a composition in which no fluorite forms. Using the Al-addition method, HFSE concentrations of Ca-rich materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) by an isotope dilution method for Zr and Hf and by a calibration curve method for Nb and Ta. Furthermore, we foun...