Erratum to: Crystal growth during dike injection of MOR basaltic melts: evidence from preservation of local Sr disequilibria in plagioclase     

Georg F. Zellmer  Kenneth H. Rubin  Peter Dulski  Yoshiyuki Iizuka  Steven L. Goldstein  Michael R. Perfit 《Contributions to Mineralogy and Petrology》2011,161(1):175-176

Profiles of a total of 23 plagioclase crystals erupted within the 1982–1991 and 1993 flows of the Coaxial segment of the Juan de Fuca ridge, the 1996 flow of the North Gorda ridge, and from the Western Volcanic Zone of the ultra-slow spreading Gakkel Ridge, have been studied for variations in major and trace element concentrations. We derive equilibration times for the relatively rapidly diffusing Sr in mid-ocean ridge basalt (MORB) plagioclase crystals of the order of months to a few years in each case. All crystals preserve diffusive disequilibria of strontium and barium. Crystal residence times at MORB magmatic temperatures are thus significantly shorter, of the order of days to a few months at most, precluding prolonged crystal storage in axial magma chambers and instead pointing to rapid crystal growth (up to ~10⁻⁸ cm s⁻¹) and cooling (up to ~1°C h⁻¹) shortly prior to eruption of these samples. Growth of these crystals is therefore inferred to occur almost entirely within oceanic layer 2 during dike injection. Crystals that grew at lower crustal levels or earlier in the differentiation sequence appear to have been excluded from the erupted magmas, as might occur if most of the gabbroic rocks in oceanic layer 3 formed an interlocking crystal framework, with viscosities that are too high to carry earlier formed crystals with the melt. The vertical extent of eruptible, crystal-poor melt lenses within the gabbroic zone is constrained to ~1 m or less by considering the width of local equilibrium growth zones, equilibration times, and crystal settling velocities. This lengthscale is consistent with field evidence from ophiolites. Finally, crystal aggregates within the Gakkel ridge sample studied here are the result of synneusis within the propagating dike during melt ascent.  相似文献   

日本南海弧前西端之下俯冲的九州—帕劳海岭的地震构造意义     

J.-O.Park  T.Hori  Y.Kaneda  张洁 《世界地震译丛》2011,(2)

作为菲律宾海板块残余岛弧的九州—帕劳海岭正沿着日本南海海槽的最西端俯冲于欧亚板块之下。沿走向布设的地震反射剖面显示出沿弧前增生楔前缘俯冲的九州—帕劳海岭70km宽的构造影像。地磁异常特征、海底地形特征、广角折射数据和陆地地貌证据等使得我们能够将俯冲海岭在弧前的延伸段一直追踪至九州岛的东部。正在俯冲的九州—帕劳海岭携带有大量冗余物质,可能具有相对较大浮力,因此在深部俯冲时与上覆板块的碰撞具有较大的抗性。有鉴于此,我们推测在俯冲海岭和上覆板块基底的接触区之间存在局部大应力构造。此局部大应力区人们已标出有历史冲断层型中等级别地震(6~7级)。当九州—帕劳海岭俯冲至深部时,漂浮的俯冲海岭其两侧的翼部更容易被撕裂而形成板块破裂。我们认为,俯冲的九州—帕劳海岭在深部不仅起到地震凹凸体的作用,而且产生板块破裂作为地震障碍体抑制邻近的日向段巨大逆冲地震的破裂传播。  相似文献   

Introduction to ocean floor networks and their scientific application     

Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):177-180

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New buoy observation system for tsunami and crustal deformation     

Narumi Takahashi  Yasuhisa Ishihara  Hiroshi Ochi  Tatsuya Fukuda  Jun’ichiro Tahara  Yosaku Maeda  Motoyuki Kido  Yusaku Ohta  Katsuhiko Mutoh  Gosei Hashimoto  Satoshi Kogure  Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):243-253

We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication.  相似文献   

Tectonic stacking of back-arc formations in the Thelichi section (Indus valley) of the Kohistan arc,northern Pakistan     

Hiroshi Yamamoto  Hafiz Ur Rehman  Yoshiyuki Kaneko  Allah Bakhsh Kausar 《Journal of Asian Earth Sciences》2011,40(2):417-426

Metamorphosed volcanic and sedimentary rocks of the Jaglot Group are exposed along the west bank of the Indus River near Thelichi. The structural bottom unit, the Thelichi Formation, is composed of metavolcaniclastic, metavolcanic, metapelitic, and metacalcareous rocks. Bedding planes of the Thelichi Formation trend E–W or NW–SE and dip steeply to the N. The middle unit, Gashu-Confluence Volcanics, is composed of metavolcaniclastic, metavolcanic, and metacalcareous rocks. Bedding planes trend NW–SE and dip moderately to the N. The top unit, the Gilgit Formation, is composed of interlayered metapsammitic and metapelitic rocks. Graded bedding, cross-bedding, and pillow structures are preserved in these metamorphic rocks of the Jaglot Group. Those indicate clastic sedimentary and volcanic origins. There is no major repetition of layers due to folding (so-called “the Jaglot syncline”) as is evidenced by the consistent northward younging of the beds. The three lithological units constitute a north-dipping tectonic stack. The tectonic stack was provably caused by the northward subduction of the back-arc basin under the Asian margin and subsequent collision between the Asia and the Kohistan (the closure of back-arc basin).  相似文献   

Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method   总被引：1，自引：0，他引：1  

Masahito Ueyama  Ken Hamotani  Wataru Nishimura  Yoshiyuki Takahashi  Nobuko Saigusa  Reiko Ide 《Theoretical and Applied Climatology》2012,109(3-4):461-472

We measured the methane flux of a forest canopy throughout a year using a relaxed eddy accumulation (REA) method. This sampling system was carefully validated against heat and CO₂ fluxes measured by the eddy covariance method. Although the sampling system was robust, there were large uncertainties in the measured methane fluxes because of the limited precision of the methane gas analyzer. Based on the spectral characteristics of signals from the methane analyzer and the diurnal variations in the standard deviation of the vertical wind velocity, we found the daytime and nighttime precision of half-hourly methane flux measurements to be approximately 1.2 and 0.7?μg?CH₄?m^?2?s^?1, respectively. Additional uncertainties caused by the dilution effect were estimated to affect the accuracy by as much as 0.21?μg?CH₄?m^?2?s^?1 on a half-hourly basis. Diurnal and seasonal variations were observed in the measured fluxes. The biological emission from plant leaves was not observed in our studies, and thus could be negligible at the canopy-scale exchange. The annual methane sink was 835?±?175?mg?CH₄?m^?2?year^?1 (8.35?kg?CH₄?ha^?1?year^?1), which was comparable to the flux range of 379–2,478?mg?CH₄?m^?2?year^?1 previously measured in other Japanese forest soils. This study indicated that the REA method could be a promising technique to measure canopy scale methane fluxes over forests, but further improvement of precision of the analyzer will be required.  相似文献   

Crust-mantle interaction during the tectono-thermal reactivation of the North China Craton: constraints from SHRIMP zircon U–Pb chronology and geochemistry of Mesozoic plutons from western Shandong     

Yi?Gang?XuEmail author  Xiao-Long?Huang  Jin-Long?Ma  Yan-Bin?Wang  Yoshiyuki?Iizuka  Ji-Feng?Xu  Qiang?Wang  Xiang-Yang?Wu 《Contributions to Mineralogy and Petrology》2004,147(6):750-767

Chronological, geochemical and Sr–Nd–Pb isotopic analyses have been carried out on the Mesozoic plutons in western Shandong with the aim of characterizing crustal–mantle evolution during the tectono-thermal reactivation of the craton. Detailed SHRIMP zircon U–Pb dating reveals two main periods of Mesozoic activity with contrasting compositions. The older magmatic pulse is manifested by monzonites and monzodiorites from Tongshi for which zircon rims yield a concordant age of 177±4 Ma and the cores have a discordant age of ca. 2.5 Ga. Low MgO and Cr, high Na₂O contents and especially their isotopic compositions (⁸⁷Sr/⁸⁶Sr < 0.7042, ²⁰⁶Pb/²⁰⁴Pb < 16.8 and _Nd ~ –12) are consistent with derivation from late Archean–Paleoproterozoic lower crust. Relatively high HREE contents in these Jurassic plutons indicate a garnet-free source (<32 km), in contrast to the garnet-bearing source (>40 km) of the late Mesozoic high Sr and low Y granitoids from the same region. Distinctively different depths of crustal melting suggest dynamic thickening of the crust by magmatic underplating during the Jurassic and Cretaceous. The younger dioritic plutons from Laiwu and Yinan were emplaced at 132–126 Ma and show relatively high MgO and Cr contents and large isotopic variability. They were likely derived from enriched lithospheric mantle source and were subjected to crustal contamination during magma evolution. Early Cretaceous mantle melting is coeval with the widespread late Yanshanian granitic magmatism in North China. Early Cretaceous time may correspond to a critical period when a temperature increase due to lithospheric thinning allowed the intersection of the local geotherm and the wet peridotite solidus. While some mantle-derived magmas were erupted, most were trapped at variable crustal depths, triggering large-scale concomitant melting of the crust. Lithospheric thinning must have continued until the late Cretaceous because of the change in the source of mafic magmas from lithospheric to asthenospheric at that time. It is proposed that removal of the lithospheric keel beneath the North China craton may have been initiated as early as the Jurassic, but with the most intense period in the Cretaceous between 130–75 Ma. Such a relatively long timescale (~100 Ma) emphasizes the role of thermomechanical erosion by convective mantle in lithospheric thinning beneath this region.  相似文献   

Dissolved Al, In, and Ce in the eastern Indian Ocean and the Southeast Asian Seas in comparison with the radionuclides Pb and Po     

Hajime Obata  Yoshiyuki Nozaki  Yoshiyuki Yamamoto 《Geochimica et cosmochimica acta》2004,68(5):1035-1048

To carry out comparative geochemical investigation of refractory and reactive metals in different oceanic settings covering different θ-S characteristics, productivity, dissolved oxygen profiles, water and sediment discharge, etc., we have determined the vertical profiles of dissolved (<0.04 μm) Al, In and Ce, as well as ²¹⁰Pb and ²¹⁰Po in the eastern Indian Ocean (from 40°S in the Southern Ocean to 8°N in the Bay of Bengal) and the Southeast Asian Seas. In the Antarctic Circumpolar Region, the concentrations of these refractory metals are very low, presumably due to very low the atmospheric input and intensified scavenging. Resemblance in the vertical profiles of these metals is often seen in some other stations. However, there are also significant differences among their distributions, for example, in the magnitude of surface enrichment caused by the external input from eolian and fluvial-coastal sources. Comparison of Al distributions in surface waters with those of atmospherically derived ²¹⁰Pb suggests the relative importance of eolian input over fluvial-coastal sources. Fluvial and coastal input appears to be insignificant for dissolved In, but may be important for Ce. The mean residence time of Al in the surface mixed layer was estimated to be ∼2 years which is similar to that of ²¹⁰Pb.In the intermediate and deep waters, the concentrations of each element vary with depth and location. The range of variation is in the order of Al>Ce>In, depending upon particle reactivity. Although dissolved Al decreases along the water trajectory by particle scavenging, variations of dissolved In and Ce are relatively small which may be due to less scavenging for both elements. Compared with significantly high (>4 pM) dissolved Ce throughout the water column in the Bay of Bengal, dissolved Al concentration remains low, suggesting that it has higher affinity to particles and hence is scavenged by sinking particulate matter. This is consistent with the observation that the dissolved Al in the Antarctic Intermediate Water (AAIW) decreases from 4 to 6 nM in the 30°S Perth Basin to <0.7 nM in the 10°S West Australia Basin along its trajectory. Using the chlorofluorocarbons (CFCs) ventilation age of AAIW (Fine, 1993), the mean residence time of Al in the intermediate and deep waters in the eastern Indian Ocean is estimated to be <17 yr, approximately the same as that of ²¹⁰Pb (10-15 yr). In the semiclosed basins of Southeast Asia, the distributions of Al, In and Ce are also very unique. In the South China Sea, there is a strong sediment source for dissolved In and Ce during the deepwater passage through the Luzon Strait.  相似文献   

3-D finite-element modelling of deformation and stress associated with faulting: effect of inhomogeneous crustal structures   总被引：2，自引：0，他引：2  

S. Zhao  R. D. Müller  Y. Takahashi  Y. Kaneda 《Geophysical Journal International》2004,157(2):629-644

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Geologic and geochemical features of the volatile-rich ore fluid and its tracing and dating in the Xuebaoding Beryl-Scheelite Vein Deposit, China   总被引：7，自引：0，他引：7  

曹志敏  郑建斌  李佑国  任建国  徐仕进  王汝成  T.Shoji  H.KANEDA  S.KABAYASHI 《中国科学D辑(英文版)》2002,45(8):719-729

Laser Raman spectrochemical analysis on single inclusion reveals that multi-phase fluid inclusions exist in the Xuebaoding Beryl-Scheelite Vein Deposit. Besides the solid daughter mineral, there are vapor CO₂, liquid CO₂, water-deficient CO₂ and salt water solution from its center to the border. A close study on the fluid inclusion components and carbon, oxygen, helium and argon isotope tracing and dating suggests that the volatile-rich ore fluid might derive from postmagmatic fluid and rare element enrichment is the result of the mixture of the plutonic alkali granite with crustal material.  相似文献