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1.
Masumi?Ujiie?MikoshibaEmail author Satoshi?Kanisawa Yukihiro?Matsuhisa Shigeko?Togashi 《Contributions to Mineralogy and Petrology》2004,146(4):433-449
The Orikabe Plutonic Complex, northeast Japan, is a zoned pluton and one of the Cretaceous intrusions in the Circum-Pacific area. In the Main body, K-rich calc-alkaline rocks composed of marginal gabbro and a large amount of monzodiorite–quartz monzonite–monzogranite are intruded successively by innermost calc-alkaline rocks of granodiorite. The gabbro and monzodiorite–monzogranite have a continuous chemical variation, while the granodiorite has lower concentrations of K, Rb, Y, Zr, Nb and F at the same SiO2 content. The gabbro and monzodiorite–quartz monzonite have a Rb-Sr whole-rock age of 119±12 Ma with an initial 87Sr/86Sr ratio of 0.70392±0.00007. The initial 87Sr/86Sr ratio of the innermost granodiorite is estimated to be about 0.7042. The 18O values of fresh rocks range from +6.7 to +8.3, indicating a positive correlation with SiO2 contents. The K-rich calc-alkaline rocks were derived through fractional crystallization from a mafic parental magma with a slightly high 18O value, implying a major contribution of a sub-arc mantle at a continental margin. Trace element modeling indicates that the source could have been a fertile lherzolite enriched in LILE and depleted in HFSE. The innermost granodiorite was the differentiation product of a distinct parental magma, suggesting the involvement of a small amount of crustal component in the source and partial melting under a more hydrous condition.Editorial responsibility: J. Hoefs 相似文献
2.
Bago River is an important river in Myanmar. Although shorter than other rivers, it has its own river system, and people along
the river rely heavily on it for their daily lives. The upper part of the watershed has changed rapidly from closed forest
to open forest land in the 1990s. Since the recent degradation of the forest environment, annual flooding has become worse
during the rainy season in Bago City. This paper aims at determining soil conservation prioritization of watershed based on
soil loss due to erosion and morphometric analysis in the Bago Watershed by integrating remote sensing and geographic information
system (GIS) techniques. In this study, soil erosion of the Bago watershed was determined using the Universal Soil Loss Equation.
Such factormaps as rainfall, soil erodibility, slope length gradient, and crop management were compiled as input parameters
for the modeling; and the soil loss from 26 sub-watersheds were estimated. Then, the soil erosion maps of the Bago watershed
for 2005 were developed. The resulting Soil Loss Tolerance Map could be utilized in developing watershed management planning,
forestry management planning, etc. 相似文献
3.
A nonlinear numerical model based on depth averaged equations and a relevant physical model have been investigated for the deformation of the water wave propagating over a submerged parabolic obstacle in the presence of uniform current. Physical and numerical modeling for wave with both following and opposing currents are done to explore the wave evolutions during passage over the submerged obstacle. A third-order Stokes dispersion relation is utilized in some cases in the computation. Separated flow zone is taken into consideration by two empirical equations obtained from the physical model testing done by the authors. Verification and validation of the numerical model by other published theoretical and experimental data are presented. 相似文献
4.
5.
Shigeko Haruyama 《GeoJournal》1993,31(4):327-334
The author has investigated the micro-geomorphology of the area flooded by the Chao Phraya river, in the central plain of Thailand. The hydrological condition of the Chao Phraya river which occurs throughout most of this plain has changed considerably over the last five decades due to the construction of artificial structures, such as embankments, multi-purpose dams, storing reservoirs, barrages, irrigation ditches and drainage canals. This report describes a recent transformation in flooding in the plain.The geomorphological units in the central plain of Thailand are classified as follows: 3 types of fans, higher and lower natural levees, 3 types of back marshes, 4 types of deltas, higher and lower mud spits and lagoons, tidal flats and former river courses. The geomorphological units correspond with flood conditions. The most serious flood damage to this point has occurred in deep back marshes and lagoons. The depth of the back marshes is greater than 3 m, and in some cases as much as 6 m. The depth of flood waters ranges from 50 cm to 1 m, and the period of submergence of the lagoonal area is more than 3 months. 相似文献
6.
The Elura Zn-Pb-Ag deposit, situated 43 km NNW of Cobar, western New South Wales, is hosted by the C.S.A. Siltstone, a distal turbidite sequence. Deep weathering has given rise to a bleached quartz-muscovite-kaolinite rock to a depth of approximately 80 m. Weathered bedrock is mantled by a thin (0.3–2 m) layer of soil and transported overburden which contains thin layers of maghemite-bearing gravels. Outcrop in the area is extremely poor with the insignificant gossan subcrop covered by 0.2 m of soil. The water table is presently at a depth of about 80 m. Groundwater is saline with up to 2.5% total dissolved solids.Oxidation of the orebody has resulted in the formation of a gossan and ferruginization of wall rocks. Elements associated with ore and retained at high concentration in the gossan are Ag, As, Ba, Cu, Hg, Mo, Pb, Sb, (Se) and Sn; much of the Zn has been leached whilst Cd and Tl are below the detection limits. Silver, Cu and Hg have been partially leached and concentrated in the supergene zone. Ferruginous wall rock contains substantial amounts of Pb, As and Ba but other element contents are substantially lower than in the gossan.Secondary dispersion from the Elura orebody is largely restricted to an interpreted paleodrainage channel SW of the orebody and has occurred in two distinct periods. Mobile elements, particularly Zn, leached during gossan formation, occur in anomalous concentrations at or near the water table. More recently, the less mobile elements Pb, As, Bi, Hg and Sb have been leached from mechanically transported fragments of ferruginized wall rock and gossan by the saline groundwaters and occur as anomalies up to 150 m from the gossan in near-surface bedrock. Copper and Zn form broad low-contrast anomalies whilst Sn is retained within the gossan.Iron-rich bands, 50–1200 mm in thickness, which are common in the weathered zone about the Elura orebody, were formed by precipitation from groundwater passing along bedding planes, shears, fractures and cracks. They have higher As, Bi, Co, Cu, Mn, Ni, Zn, lower values of Ba and Sr, and similar Pb, Sb and Sn contents to the weathered siltstones. Iron may be derived from Fe-rich carbonates in the siltstones and be redeposited as goethite and minor hematite. These Fe-rich bands have trapped target and pathfinder elements which are believed to be from primary haloes rather than from the orebody or gossan.A two-stage mechanism for the formation of some secondary minerals within the weathered zone has been confirmed by stable light isotope studies. These studies have also shown that fractionation of S isotopes is minimal during gossan formation, and that a S isotopic halo in weathered bedrock may be used as an exploration tool. 相似文献
7.
Smail Mostefaoui Noriko T. Kita Shigeko Togashi Shogo Tachibana Hiroko Nagahara Yuichi Morishita 《Meteoritics & planetary science》2002,37(3):421-438
Abstract— We performed a systematic high‐precision secondary ion mass spectrometry 26Al‐26Mg isotopic study for 11 ferromagnesian chondrules from the highly unequilibrated ordinary chondrite Bishunpur (LL3.1). The chondrules are porphyritic and contain various amounts of olivine and pyroxene and interstitial plagioclase and/or glass. The chemical compositions of the chondrules vary from FeO‐poor to FeO‐rich. Eight chondrules show resolvable 26Mg excesses with a maximum δ26Mg of ?1% in two chondrules. The initial 26Al/27Al ratios inferred for these chondrules range between (2.28 ± 0.73) × 10?5 to (0.45 ± 0.21) × 10?5. Assuming a homogeneous distribution of Al isotopes in the early solar system, this range corresponds to ages relative to CAIs between 0.7 ± 0.2 Ma and 2.4+0.7?0.4 Ma. The inferred total span of the chondrule formation ages is at least 1 Ma, which is too long to form chondrules by the X‐wind. The initial 26Al/27Al ratios of the chondrules are found to correlate with the proportion of olivine to pyroxene suggesting that olivine‐rich chondrules formed earlier than pyroxene‐rich chondrules. Though we do not have a completely satisfactory explanation of this correlation we tentatively interpret it as a result of evaporative loss of Si from earlier generations of chondrules followed by addition of Si to the precursors of later generation chondrules. 相似文献
8.
Song Hong (Red River) delta evolution related to millennium-scale Holocene sea-level changes 总被引：2，自引：0，他引：2
Susumu Tanabe Kazuaki Hori Yoshiki Saito Shigeko Haruyama Van Phai Vu Akihisa Kitamura 《Quaternary Science Reviews》2003,22(21-22):2345-2361
The Song Hong (Red River) delta occurs on the northwest coast of the South China Sea. Its evolution in response to Holocene sea-level changes was clarified on the basis of sedimentary facies and 14 radiocarbon dates from the 40 m long Duy Tien core from the delta plain, and using previously reported geological, geomorphological, and archaeological data. The delta prograded into the drowned valley as a result of early Holocene inundation from 9 to 6 cal. kyr BP, as sea-level rise decelerated. The sea-level highstand at +2–3 m from 6 to 4 cal. kyr BP allowed widespread mangrove development on the delta plain and the formation of marine notches in the Ha Long Bay and Ninh Binh areas. During sea-level lowering after 4 cal. kyr BP, the former delta plain emerged as a marine terrace, and the delta changed into the present tide- and wave-influenced delta with accompanying beach ridges. Delta morphology, depositional pattern, and sedimentary facies are closely related to Holocene sea-level changes. In particular, falling sea level at 4 cal. kyr BP had a major impact on the evolution of the Song Hong delta, and is considered to be linked to climate changes. 相似文献
9.
Comparing Loss Estimation with Observed Damage: A Study of the 1999 Kocaeli Earthquake in Turkey 总被引：4，自引：0，他引：4
Robin Spence Julian Bommer Domenico del Re Juliet Bird Nuray Aydinoğlu Shigeko Tabuchi 《Bulletin of Earthquake Engineering》2003,1(1):83-113
Loss estimation from future earthquakes is of growing importance in planning earthquake protection strategies in high-risk
areas. Loss models based on the spectral displacement approach are now widely used because of generally acknowledged deficiencies
in earlier approaches using macroseismic intensity or peak ground-motion parameters. However, there has been to date rather
little earthquake damage data by which the new generation of models can be assessed and which can be used to calibrate the
parameters involved. The availability of several detailed damage surveys carried out following the 1999 Kocaeli earthquake
in Turkey, provides a rare opportunity for such an assessment. In this paper the losses which would be predicted from two
different approaches to loss assessment – one using predicted macroseismic intensity, the other using the spectral displacement
method – are compared with actual observed losses in the Kocaeli event at two different locations where surveys were carried
out. One of these sites was very close to the surface fault rupture (< 3 km distance), the other at a distance of about 4.5 km.
It is shown that the predictive methods available generally overestimated the losses at these distances, and a number of possible
reasons for these discrepancies are considered. The sensitivity of loss estimates to variations in the key parameters governing
the estimation in each case are explored, in particular with respect to modifications in the parameters of the attenuation
relationships and the vulnerability parameters. The implications of these results for estimating future losses are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Undisturbed sediment cores were collected by a modified gravity corer from Funka Bay. The sedimentation rate is determined by both210Pb and pumice chronological methods. The sedimentation rates by210Pb method are concordant with those by pumice methods. The derived rate varies from 0.06 to 0.22 g cm–2 y–1, and an average is 0.09 g cm–2 y–1. 相似文献