Study on the manganese nodule V. Thermal studies of the iron-manganese phase     

Akihiko Okada  Tadayuki Minakuchi  Makoto Shima 《Journal of Oceanography》1972,28(2):39-47

The thermal phase transformation of the iron-manganese phase of the Pacific Ocean manganese nodules were studied by the differential thermal and X-ray diffraction methods. X-ray powder patterns of the heated samples at the temperature of 600°C to 1000°C show the occurrence of hematite, bixbyite and cubic and tetragonal (Fe, Mn)₃O₄. Bixbyite produced by the heat treatment of the iron-manganese phase gives an abnormal X-ray pattern in comparison with the standard sample of bixbyite. Cubic (Fe, Mn)₃O₄ is produced not only by the reaction of bixbyite with hematite over 900°C, but also at the lower temperature, such as 600°C. While, tetragonal (Fe, Mn)₃O₄ is a reaction product of cubic (Fe, Mn)₃O₄ with bixbyite over 900°C in the case of manganese rich nodules. The species and quantities of the products after the heat treatment are assumed to be mostly influenced by the relative contents of iron and manganese in the manganese nodule.  相似文献   

A hydraulic experiment on tidal exchange     

Makoto Kashiwai 《Journal of Oceanography》1985,41(1):11-24

Tidal exchange through a narrow entrance channel was studied experimentally with the use of a simplified hydraulic model. The inflowing water mass, visualized with dye solution, exhibits the shape of a starting plume with a starting vortex pair at its head. Because of their periodical formation by the tide, these are called the tidal plume and tidal vortex pair. The axis of the tidal plume deflects and undulates with a period 2 to 9 times that of the tide. Together with this undulation, the vortex pair becomes asymmetric. A circulating flow is formed in the bay which affects the shape of the inflowing and outflowing water masses. A part of the inflowing water mass flows out during the subsequent ebb, and this outflowing portion can be divided into two parts. One is the water remaining in the entrance channel at high water which flows out during the first half of the subsequent ebb and the other is the water flowing round the bay in the circulating flow during flood that flows out during the latter half of the subsequent ebb. Both contribute to the exchange ratio, but we can estimate an upper limit for the exchange ratio by neglecting the latter outflow. This neglected portion is considered in the concept of the age composition of outflowing water. The age composition of the bay water shows the existence of intermittent effluence superposed on a trend in the age composition that is similar to that of the well-mixed case. From the analysis of a model consisting of a number of mixing tanks connected in series with a recycle flow, it is concluded that this intermittent effluence occurs in the case of weak mixing due to the effect of circulating flow in the bay but is negligible in the case of strong mixing.  相似文献   

Sequence stratigraphic evolution of the syn-rift Early Cretaceous sediments,West Beni Suef Basin,the Western Desert of Egypt with remarks on its hydrocarbon accumulations     

Amer A. Shehata  Farouk M. El Fawal  Makoto Ito  Mohammed H. Abdel Aal  Mohammad A. Sarhan 《Arabian Journal of Geosciences》2018,11(12):331

The Beni Suef Basin is a petroliferous rift basin straddling the River Nile containing a thick Mesozoic–Paleogene succession. The Kharita Formation is formed in the syn-rift phase of the basin formation and is subdivided into the Lower and Upper Kharita members. These two members are regarded as two third-order depositional sequences (DSQ-1 and DSQ-2). The lowstand systems tract (LST-1) of the DSQ-1 is represented by thick amalgamated sandstone bodies deposited by active braided channels. Mid-Albian tectonic subsidence led to a short-lived marine invasion which produced coastal marine and inner-shelf facies belts during an ensuing transgressive systems tract (TST-1). At the end of the mid-Albian, a phase of tectonic uplift gradually rose the continent creating a fall in relative sea level, resulting in deposition of shallow marine and estuarine facies belts during a highstand systems tract (HST-1). During the Late Albian, a new phase of land-rejuvenation commenced, with a prolonged phase of fluvial depositional. Fluvial deposits consisted of belts of amalgamated, vertically aggraded sandstones interpreted as braided and moderately sinuous channels, in the lower part of the Upper Kharita Member lowstand stage (LST-2). The continuous basin filling, coupled with significant lowering in the surrounding highlands changed the drainage regime into a wide belt of meandering river depositing the transgressive stage (TST-2). The history of the Kharita Formation finalized with a Cenomanian marine transgressive phase. Economically, the TST-1 and HST-1 play a significant role as source rocks for hydrocarbon accumulations, whereas LST-2 act as good reservoir rocks in the Early Cretaceous in the Basin.  相似文献   

Estimation of groundwater flow from temperature monitoring in a borehole heat exchanger during a thermal response test     

Mayumi Yoshioka  Shinichi Takakura  Youhei Uchida 《Hydrogeology Journal》2018,26(3):853-867

To estimate the groundwater flow around a borehole heat exchanger (BHE), thermal properties of geological core samples were measured and a thermal response test (TRT) was performed in the Tsukuba upland, Japan. The thermal properties were measured at 57 points along a 50-m-long geological core, consisting predominantly of sand, silt, and clay, drilled near the BHE. In this TRT, the vertical temperature in the BHE was also monitored during and after the test. Results for the thermal properties of the core samples and from the monitoring indicated that groundwater flow enhanced thermal transfers, especially at shallow depths. The groundwater velocities around the BHE were estimated using a two-dimensional numerical model with monitoring data on temperature changes. According to the results, the estimated groundwater velocity was generally consistent with hydrogeological data from previous studies, except for the data collected at shallow depths consisting of a clay layer. The reasons for this discrepancy at shallow depths were predicted to be preferential flow and the occurrence of vertical flow through the BHE grout, induced by the hydrogeological conditions.  相似文献   

Hybridization of a Shallow 'I-type' Granitoid Pluton and its Host Migmatite by Magma-Chamber Wall Collapse: the Tokuwa Pluton, Central Japan   总被引：1，自引：0，他引：1  

Saito  Satoshi; Arima  Makoto; Nakajima  Takashi 《Journal of Petrology》2007,48(1):79-111

The Miocene Tokuwa pluton of ‘I-type’ granitoidaffinity was emplaced discordantly into a Cretaceous to Paleogeneaccretionary complex and induced a contact aureole in whichvarious thermally metamorphosed rocks were developed, includinghornfels, metatexite, diatexite and cordierite-bearing tonalite(Crd-tonalite) of ‘S-type’ granite affinity. Thethermally metamorphosed rocks show low-pressure reaction texturesculminating in partial melting. Peak P–T conditions of3 kbar at 780°C are estimated on the basis of the TWQ thermobarometerfor the garnet-bearing rocks. The rocks in the contact aureoleexhibit a gradual transition from hornfels, through metatexiteand diatexite to Crd-tonalite. The Sr-isotopic composition atthe time of Tokuwa pluton emplacement at 12 Ma decreases systematicallyfrom metatexite (0·7100–0·7112) throughdiatexite (0·7078–0·7094) to Crd-tonalite(0·7067–0·7068); this trend is interpretedin terms of mixing between the Tokuwa magma and the aureolemigmatites. The field relationships, geochemical data, and isotopicdata collectively suggest that the emplacement of the Tokuwapluton triggered partial melting of the surrounding metasedimentaryrocks. Subsequent hybridization of the Tokuwa magma with themetatexite in variable proportions produced the Crd-tonaliteand diatexite. The hybridization was caused by invasion of theTokuwa magma into the migmatite zone, accompanied by gravitationalcollapse of the previously crystallized wall of the magma chamber.The data presented demonstrate that even a relatively low-temperature,shallow, ‘I-type’ granitoid pluton can induce contactanatexis and hybrid ‘S-type’ granitoid formationat the intrusive contact. KEY WORDS: contact metamorphism; hybridization; magma–host-rock interaction; migmatite; ‘S-type’ granitoid  相似文献   

U–Pb dating of detrital zircon from Permian successions of the South Kitakami Belt,Northeast Japan: Clues to the paleogeography of the belt     

Yuxiao Li  Makoto Takeuchi 《Island Arc》2022,31(1):e12435

The South Kitakami Belt in the northeast Japan is unique in presence of a thick Paleozoic–Mesozoic sedimentary rocks. The Permian sedimentary succession in the Maiya area of this belt is divided into the Nishikori, Tenjinnoki, and Toyoma formations, in ascending stratigraphic order. The Tenjinnoki Formation includes the Yamazaki Conglomerate Member containing granitic clasts. We performed U–Pb dating for detrital zircon of one sample of tuffaceous sandstone from the Nishikori Formation, six samples of sandstone from the Tenjinnoki and Toyoma formations, and five granitic clasts from the Yamazaki Conglomerate using laser ablation-inductively coupled plasma-mass spectrometry. Our dating results show that the tuffaceous sandstone sample has two age peaks at 287 and 301 Ma for the Nishikori Formation, three age peaks at 320–300, 290, and 270 Ma for the Tenjinnoki and Toyoma Formation, and ages of 311, 300, and 270 Ma from granitic clasts of the Yamazaki Conglomerate. In addition, older ages of 452–435 and 380 Ma were obtained from some zircon grains of the sandstone and granitic clasts. Our results suggest igneous activity in these periods. The South Kitakami Belt's origin with respect to continental blocks has been discussed in regard of the margin of North China Block or South China Block. Based on the stratigraphic ages and timing of igneous activity, we conclude that during the Permian the South Kitakami Belt was located at the margin of the South Central Asian Orogenic Belt, near the Solonker-Xra Moron-Changchun suture and the North China Block in East Asia.  相似文献   

Risk evaluation and warning threshold of unstable slope using tilting sensor array     

Wang  Lin  Seko  Ichiro  Fukuhara  Makoto  Towhata  Ikuo  Uchimura  Taro  Tao  Shangning 《Natural Hazards》2022,114(1):127-156

Slope monitoring and early warning systems are a promising approach toward mitigating landslide-induced disasters. Many large-scale sediment disasters result in the destruction of infrastructure and loss of human life. The mitigation of vulnerability to slope and landslide hazards will benefit significantly from early warning alerts. The authors have been developing monitoring technology that uses a micro-electro-mechanical systems tilt sensor array that detects the precursory movement of vulnerable slopes and informs the issuance of emergency caution and warning alerts. In this regard, the determination of alarm thresholds is very important. Although previous studies have investigated the recording of threshold values by an extensometer which installation of an extensometer at appropriate sites is also difficult. The authors prefer tilt sensors and have proposed a novel threshold for the tilt angle, which was validated in this study. This threshold has an interesting similarity to previously reported viscous models. Additionally, multi-point monitoring has recently emerged and allows for many sensors to be deployed at vulnerable slopes without disregarding the slope’s precursory local behavior. With this new technology, the detailed spatial and temporal variation of the behavior of vulnerable slopes can be determined as the displacement proceeds toward failure.

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Large-scale hydraulic conductivity distribution in an unconfined carbonate aquifer using the ocean tidal propagation     

Yang  Heejun  Tawara  Yasuhiro  Shimada  Jun  Kagabu  Makoto  Okumura  Azusa 《Hydrogeology Journal》2021,29(6):2091-2105

The hydraulic conductivity of an unconfined carbonate aquifer at the uplifted atoll of Minami-Daito, Japan, was evaluated by a combination of cross-spectral analysis, analytical solution, and density-dependent groundwater modeling based on observed groundwater levels in 15 wells and at sea level. The island area was divided into 10 subregions based on island morphology and on inland propagation of ocean tides. The hydraulic conductivity was obtained for each subregion using analytical solutions based on phase lags of M₂ constituents of ocean tides at each well by assuming two aquifer thicknesses (300 and 1,800 m) and two effective porosities (0.1 and 0.3). The density-dependent groundwater model evaluated the hydraulic conductivity of the subregions by reproducing observed groundwater levels. The hydraulic conductivity in the subregions was estimated as 3.46?×?10^?3 to 6.35?×?10^?2 m/s for aquifer thickness of 300 m and effective porosity of 0.1, and as 1.73?×?10^?3 to 3.17?×?10^?2 m/s for aquifer thickness of 1,800 m and the effective porosity of 0.3. It was higher in southern and northern areas, and higher in interior lowland than in the western and eastern areas. Fissures and dolomite distributions on the island control differences of the omnidirectional ocean tidal propagation and cause these differences in hydraulic conductivity. The method used for this study may also be applicable to other small islands that have few or no data for hydraulic conductivity.

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Clogging mechanisms and preventive measures in artificial recharge systems          下载免费PDF全文

Shahbaz Akhtar M  Nakashima Yoshitaka  Nishigaki Makoto 《地下水科学与工程》2021,9(3):181-201

Groundwater which occurs in fractured rock or porous aquifers or other geological weak zones such as faults and fractures is usually extracted via boreholes, hand wells or other sources such as springs.Water scarcity has become a severe problem due to many factors, such as an alarming increase in population and per capita water consumption, over exploitation of groundwater resources and abrupt global climatic change along with its related eco-environmental geological problems. In such situation, application of artificial recharge systems(e.g. surface recharge basin and deep injection well systems) can help to effectively manage and augment the unitization of groundwater resources. However, the clogging problem,which may be caused by a complex interdependent mechanisms of physical, chemical and biological has been a challenge for the efficacy and the implementation of recharge facilities. Clogging can reduce the permeability, recharge rate and longevity of recharge facilities and increase the operational and maintenance costs. Major influencing factors associated with the occurrence of clogging include the chemical composition of groundwater(both the recharge water and native groundwater), aquifer medium and microbial diversity, together with other environmental factors such as temperature, pressure, total dissolved solids, total soluble salts, pH, Eh, nutrients, gases, carbonates and others; these factors ultimately increase the piezometric head but reduce the permeability and infiltration rates of porous/seepage media.Pretreatment of recharge water can minimize the potential clogging. In the case of clogged wells,rehabilitation methods need to be deployed. In the meantime, there is an urgent needs to understand the basic causes and developmental processes/mechanisms of clogging in order to mitigate this problem. This paper reviews the major clogging mechanisms and their possible preventive measures and redevelopments in artificial recharge systems.  相似文献   

New developments of performance-based design codes and practice,honouring Prof. Yusuke Honjo     

Makoto Suzuki  Masahiro Shirato 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(3)

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