U–Pb zircon ages of the Nakanogawa Group in the Hidaka Belt,northern Japan: Implications for its provenance and the protolith of the Hidaka metamorphic rocks          下载免费PDF全文

Futoshi Nanayama  Yutaka Takahashi  Toru Yamasaki  Mitsuru Nakagawa  Hideki Iwano  Tohru Danhara  Takafumi Hirata 《Island Arc》2018,27(2)

Zircon U–Pb ages of two acidic tuff and two turbidite sandstone samples from the Nakanogawa Group, Hidaka Belt, were measured to estimate its depositional age and the development of the Hokkaido Central Belt, northeast Japan. In the northern unit, homogeneous zircons from pelagic acidic tuff from a basal horizon dated to 58–57 Ma, zircons from sandstone from the upper part of the unit dated to 56–54 Ma, and zircons from acidic tuff from the uppermost part dated to 60–56 Ma and 69–63 Ma. Both of the tuff U–Pb ages are significantly older than the youngest radiolarian fossil age (66–48 Ma). Therefore, the maximum depositional age of the turbidite facies in the northern unit is 58 Ma and the younger age limit, estimated from the fossil age, is 48 Ma. In the southern unit, homogeneous zircons from turbidite sandstone dated to 58–57 Ma. Thus the depositional age of this turbidite facies was interpreted to be 66–56 Ma from the fossil age, probably close to 57 Ma. Most of the zircon U–Pb ages from the Nakanogawa Group are younger than 80 Ma, with a major peak at 60 Ma. This result implies that around Hokkaido volcanic activity occurred mainly after 80 Ma. Older zircon ages (120–80 Ma, 180–140 Ma, 340–220 Ma, 1.9 Ga, 2.2 Ga, and 2.7 Ga) give information about the provenance of other rocks in the Hidaka Belt. It is inferred that the Nakanogawa Group comprises protoliths of the upper sequence of the Hidaka Metamorphic Zone, which therefore has the same depositional age as the Nakanogawa Group (66–48 Ma). The depositional ages of the lower sequence of the Hidaka Metamorphic Zone and the Nakanogawa Group are probably the same.  相似文献   

The last deglacial history of Lützow‐Holm Bay,East Antarctica     

Masako Yamane  Yusuke Yokoyama  Hideki Miura  Hideaki Maemoku  Shogo Iwasaki  Hiroyuki Matsuzaki 《第四纪科学杂志》2011,26(1):3-6

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Characteristics of observed turbulent mixing across the Antarctic Slope Front at 140°E, East Antarctica     

Daisuke Hirano  Yujiro Kitade  Hideki Nagashima  Masaji Matsuyama 《Journal of Oceanography》2010,66(1):95-104

The strength of mixing due to turbulence in the Antarctic Slope Front (ASF) region was investigated using CTD (conductivity-temperature-depth profilers) observations and direct measurements of turbulence conducted off Adélie Land, East Antarctica along 140°E from the 12th–14th February, 2005. The strongest horizontal gradient of the ASF was located below 300 m depth near the 1000 m isobath. The turbulent measurements revealed that the energy dissipation rate frequently exceeded 10^?8 Wkg^?1 on the continental shelf and upper slope regions. Turbulent diffusivities near the shelf break were higher than 10^?3 m²s^?1. Near the ASF the average turbulent heat flux was 5.7 Wm^?2 and 1.1 Wm^?2 across the temperature minimum layer to 250 m and from 300 to 600 m, respectively. The distribution of the high dissipation rate was consistently explained by the characteristic curve of the M2 internal wave emanating from the shelf break and continental slope. The water mass observed in the ASF below 300 m in the continental slope comprised Modified Circumpolar Deep Water and low salinity Shelf Water originating from either the upper layer of the Adélie Depression or the Adélie Bank, and produced by boundary mixing near the shelf break.  相似文献   

Non-metamorphosed autochthonous Kuncha-Naudanda-Heklang Formations and their differences from those of the Kuncha nappe: A multichronological approach     

Wataru Kobayashi  Harutaka Sakai  Hideki Iwano  Tohru Danhara  Takafumi Hirata 《Island Arc》2021,30(1):e12396

Non-metamorphosed, autochthonous Lesser Himalayan sediments (LHS), which are correlated to the Kuncha and Naudanda Formations, were found in a narrow belt between the Main Boundary Thrust and the Lesser Himalayan Thrust at the base of the Kuncha nappe in southeastern Nepal. The autochthonous Naudanda Formation is comprised of cross-bedded and rippled orthoquartzite and yielded a maximum depositional age of 1795.1 Ma ±5.1 Ma using detrital zircons. Low-grade metamorphosed quartzite in the Kuncha nappe yielded a maximum depositional age of 1867.4 Ma ±3.4 Ma, although it is totally recrystallized. These ages and age distribution patterns of detrital zircon grains indicate that the meta-quartzite of the nappe is originally Naudanda Formation. A zircon fission-track age of the autochthonous Naudanda Formation shows partially annealed age of 864 Ma ±56 Ma, in contrast, that of the Kuncha nappe shows a totally annealed age of 11.9 Ma ±1.6 Ma. These results suggest that the autochthonous LHS have never undergone metamorphism during the Himalayan orogeny. We also discovered a non-metamorphosed Heklang Formation that rests on the Naudanda Formation, and designated it as a sub-type section on the basis of detailed lithostratigraphic study. It is characterized by black and light green slate with dolerite sills and ill-sorted quartzose sandstone, and correlated to the metamorphosed Dandagaon Phyllites in the Kathmandu area. Non-metamorphosed autochthonous formations distributed to the south of the nappe front suggest that they escaped from thermal metamorphism by hot nappe.  相似文献   

Arc-parallel extension in preparation of the rotation of southwest Japan: Tectonostratigraphy and structures of the Lower Miocene Ichishi Group     

Hideki Kinoshita  Atsushi Yamaji 《Island Arc》2021,30(1):e12418

Opening of the Japan Sea back arc basin was accompanied by extensional tectonics in the drifting southwest Japan arc. Various trends of Early Miocene grabens in the arc suggest multi-directional rifting, which necessarily involved strike-slip components of some of basin-margin faults. However, such components are not well understood. In this work we conducted a field survey in the Early Miocene Ichishi basin on the northern side of the Median Tectonic Line, central southwest Japan. We found that the basin was a compound of grabens that were formed along normal and sinistral strike-slip faults, the latter of which had northeast–southwest trends. The block faulting in this phase produced basement highs between sub-basins, which were filled with the lower part of the Ichishi Group. We found a low-angle angular unconformity at a middle horizon in the group, with which we define the upper and lower part of the group. The upper part onlapped both the basement highs and the lower part. It means that the transtensional basin formation ceased sometime between 18 and 17.5 Ma in the Ichishi area. The Ichishi basin turned subsequently into a sag basin subsided due to normal faulting probably along the Nunobiki-sanchi-toen fault zone. The transtension and the basin sag were driven by ENE–WSW extensional stress. This arc-parallel extension produced grabens various areas including Ichishi in the Early Miocene. The extensional deformation was eventually localized to the deep rift along the Fossa Magna to make the lithosphere under southwest Japan decoupled from that under northeast Japan. The decoupling allowed the rapid rotation of southwest Japan from ~17.5 Ma. The cluster of those grabens around the Ise bay probably determined the southeastern margin of the Kinki triangle.  相似文献   

Sources and Exchange of Particulate Organic Matter in an Estuarine Mangrove Ecosystem of Xuan Thuy National Park, Vietnam     

Nguyen Tai Tue  Tran Dang Quy  Hideki Hamaoka  Mai Trong Nhuan  Koji Omori 《Estuaries and Coasts》2012,35(4):1060-1068

The spatio-temporal variations in stable isotope signatures (??¹³C and ??¹⁵N) and C/N ratios of particulate organic matter (POM), and physicochemical parameters in a creek water column were examined in an estuarine mangrove ecosystem of Xuan Thuy National Park, Vietnam. The objective was to examine the factors influencing creek water properties, and the sources and exchange of POM in this important mangrove ecosystem. The diel and seasonal variations in water temperature, flow velocity, pH, dissolved oxygen, and salinity demonstrated that tidal level, season, and biological factors affected the creek water properties. Mangroves had relatively low ??¹⁵N and very low ??¹³C values, with respective average values of 1.5?±?0.9?? and ?28.1?±?1.4??. The low mangrove leaf ??¹⁵N indicated minor anthropogenic nitrogen loading to the mangrove forests. A significant positive correlation between POM?C??¹³C and salinity along the axis of Ba Lat Estuary, Red River, indicated that marine phytoplankton (??¹³C value, ?21.4?±?0.5??) was the predominant source of POM at the estuary mouth. Based on the co-variation of ??¹³C and C/N ratios, marine phytoplankton and mangrove detritus were predominant in POM of major creeks and small creeks, respectively. During the diurnal tidal cycle, the dynamics of POM were affected by sources of organic matter, tidal energy, and seasonal factors. The contribution of mangrove detritus to POM reached a maximum at the low tide and was enhanced during the rainy season, whereas marine phytoplankton contribution was highest at high tide.  相似文献   

Comparison of different methods for estimating soil surface evaporation in a bare field   总被引：2，自引：1，他引：1  

Haofang Yan  Chuan Zhang  Hiroki Oue  Hideki Sugimoto 《Meteorology and Atmospheric Physics》2012,118(3-4):143-149

In this paper, three methods for estimating soil evaporation in a bare field were evaluated: evaporation ratio method (k ratio), complementary relationship and bulk equation. Micro-lysimeters were used to measure the actual evaporation for validation of the three methods. For the k ratio method, pan evaporation was used as the reference evaporation instead of the value obtained from the Penman–Monteith equation. This result is important for areas where meteorological data are unavailable. The results showed that, for daytime evaporation, the k ratio and bulk equation produced a good fit with the observation data, while the complementary relationship generated a larger deviation from the measured data. We recommend that the k ratio method and bulk equation could be used to calculate daytime soil evaporation with high accuracy when soil water content and pan evaporation data or meteorological data are available, while the complementary relationship could be used for a rough estimation when pan evaporation is available. All the methods could be applied to calculate cumulative evaporation.  相似文献   

Counter-clockwise prograde P–T path in collisional orogeny and water subduction at the Precambrian–Cambrian boundary: The ultrahigh-pressure pelitic schist in the Kokchetav massif,northern Kazakhstan     

Hideki Masago  Soichi Omori  Shigenori Maruyama 《Gondwana Research》2009,15(2):137-150

A prograde pressure–temperature (P–T) path is estimated for pelitic schists from the latest Precambrian Kokchetav ultrahigh-pressure massif, Kazakhstan, using compositional zoning and mineral inclusions in coarse-grained and inclusion-rich garnets. Ti-bearing inclusions are abundant in garnet and display a zonal distribution. Ilmenite occurs in the inner-core, where most of it makes a composite inclusion with rutile, whereas monomineralic rutile occurs in the outer-core to mantle domains. In the rim region both ilmenite and rutile are present, although in small amounts. Application of the ilmenite-garnet thermometer yields a systematic temperature increase towards rim from 500 to 750 °C. The pressure-sensitive reaction: 3 Fe-Ilm (in Ilm) + Ky + 2 Qtz = 3 Rt + Alm (in Grt) yielded pressures of 1.2–1.3 GPa for the outer-core inclusions.A petrogenetic grid in the K₂O–CaO–FeO–MgO–Al₂O₃–SiO₂–H₂O model system was used to estimate the equilibrium compositions of the garnet. The change of the grossular component along the model P–T path expected from the forward modelling is close to the observed compositional profile of the outer-core to rim domains. No constraint is available from thermobarometry in the inner-core; however, the forward modelling of garnet zoning provides information on the early stage of the P–T path during the garnet growth.The estimated P–T path is counter-clockwise in the prograde stage with a steep bend at around 700 °C and 1.2–1.5 GPa. This is similar to the metamorphic P–T gradient of the Kokchetav massif. This result contrasts markedly with the traditional clockwise P–T path in many collisional metamorphic terranes, and is regarded to represent a subduction geotherm at the Precambrian–Cambrian boundary. The P–T path proposed in this study also supports the models for the recovery of the “snowball Earth” from late-Proterozoic glaciation through effect of water in the solid Earth mantle.  相似文献   

Magma discharge variations during the 2011 eruptions of Shinmoe-dake volcano, Japan, revealed by geodetic and satellite observations     

Tomofumi Kozono  Hideki Ueda  Taku Ozawa  Takehiro Koyaguchi  Eisuke Fujita  Akihiko Tomiya  Yujiro J Suzuki 《Bulletin of Volcanology》2013,75(3):1-13

We present precise geodetic and satellite observation-based estimations of the erupted volume and discharge rate of magma during the 2011 eruptions of Kirishima-Shinmoe-dake volcano, Japan. During these events, the type and intensity of eruption drastically changed within a week, with three major sub-Plinian eruptions on January 26 and 27, and a continuous lava extrusion from January 29 to 31. In response to each eruptive event, borehole-type tiltmeters detected deflation of a magma chamber caused by migration of magma to the surface. These measurements enabled us to estimate the geodetic volume change in the magma chamber caused by each eruptive event. Erupted volumes and discharge rates were constrained during lava extrusion using synthetic aperture radar satellite imaging of lava accumulation inside the summit crater. Combining the geodetic volume change and the volume of lava extrusion enabled the determination of the erupted volume and discharge rate during each sub-Plinian event. These precise estimates provide important information about magma storage conditions in magma chambers and eruption column dynamics, and indicate that the Shinmoe-dake eruptions occurred in a critical state between explosive and effusive eruption.  相似文献   

Investigation on the Performance of Pipe Roof Method Adjacent to the Underground Construction     

Ma  Peng  Shimada  Hideki  Sasaoka  Takashi  Hamanaka  Akihiro  Dintwe  Tumelo K. M.  Pan  Donjiang 《Geotechnical and Geological Engineering》2021,39(6):4677-4687

In this paper, the behaviour of the pipe roof method with different pipe roofs disposition schemes including the pipe roof gate system and L-shaped system is discussed in terms of ground settlement reduction in the condition of underground space construction adjacent to the existing structure by using numerical simulation method. Considering the construction sequences of parallel underground tunnels with rectangular cross sections, the appropriate parameters and ground response characteristics of the corresponding pipe roof methods are evaluated by the ground surface displacement. The results indicated that the construction impacts from new buildings can be reduced by the pipe roof method. However, the theoretical performance of pipe roofs is highly dependent on the spacing between two structures. Generally, the L-shaped system is more effective in case of the distance (D) that is less than or equal to 1/2 width of box culvert (R) under the condition of a new structure constructed nearby the existing building. When two structures are constructed simultaneously, the excavation and the construction of structures influence each other reciprocally. The conclusions could provide a reference for the pipe roof method with the application scenario of adjacent building protection.

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