Statistical analyses and modeling approaches to hydrodynamic characteristics in alluvial aquifer

This study is aimed at quantifying the difference in aquifer's response to recharge between some different locations in a fan aquifer and a delta aquifer for a preliminary study of revealing mechanisms of water transport in alluvial aquifer. The aquifer's response to recharge is statistically quantified with the two viewpoints: (1) timing and volume of recharge and (2) time length of aquifer's holding water. For the first point, a statistical model that links precipitation and groundwater level is introduced, and its parameters are identified using correlation analysis. Our results show that the recharge rate at the toe is higher than that at the apex and at the delta. For the second point, the concept of ‘memory effect’ of aquifer is adopted and quantified using the autocorrelation and spectral analyses. Our results show that the memory effect is longer at the toe of fan than at the apex, and thus, a temporary increase of water level has about five times as long‐term influence on subsequent water levels at the toe of the fan as at the apex. This study demonstrates that the statistical analyses and modeling of hydrological data are useful for characterizing aquifer's hydrodynamics. Copyright © 2012 John Wiley & Sons, Ltd.     

Olivine-spinifex basalt from the Tamba Belt, southwest Japan: Evidence for Fe- and high field strength element-rich ultramafic volcanism in Permian Ocean

Abstract   Permian basalt showing typical spinifex texture with >10 cm-long olivine pseudomorphs was discovered from the Jurassic Tamba accretionary complex in southwest Japan. The spinifex basalt occurs as a river boulder accompanied by many ferropicritic boulders in a Permian chert-greenstone unit. Groundmass of this rock is holocrystalline, suggesting a thick lava or sill for its provenance. Minor kaersutite in the groundmass indicates a hydrous magma. The spinifex basalt, in common with the associated ferropicritic rocks, is characterized by high high field strength element (HFSE) contents (e.g. Nb = 62 ppm and Zr = 254 ppm) and high-HFSE ratios (Al₂O₃/TiO₂ = 3.9, Nb/Zr = 0.24 and Zr/Y = 6.4) unlike typical komatiites. The spinifex basalt and ferropicrite might represent the upper fractionated melt and the lower olivine-rich cumulate, respectively, of a single ultramafic sill (or lava) as reported from the early Proterozoic Pechenga Series in Kola Peninsula. Their parental magma might have been produced by hydrous melting of a mantle plume that was dosed with Fe- and HFSE-rich garnet pyroxenite. The spinifex basalt is an evidence for the Pechenga-type ferropicritic volcanism taken place in a Permian oceanic plateau, which accreted to the Asian continental margin as greenstone slices in Jurassic time.     

双壳类软体动物的水产遗传学研究进展

双壳类是水产养殖业中非常重要的养殖贝类,在世界范围其产量日益增长。作者综述了近年来双壳类遗传学研究进展,包括遗传变异、数量遗传、选种育种、杂交育种、染色体及分子遗传学等领域的最新研究进展。     

Effects of cyclonic mesoscale eddies on the marine ecosystem in the Kuroshio Extension region using an eddy-resolving coupled physical-biological model

Effects of mesoscale eddies on the marine ecosystem in the Kuroshio Extension (KE) region are investigated using an eddy-resolving coupled physical-biological model. The model captures the seasonal and intra-seasonal variability of chlorophyll distribution associated with the mesoscale eddies, front variability, Kuroshio meanders, and upwelling. The model also reproduces the observed interannual variability of sea surface height anomaly (SSHA) in the KE region along a zonal band of 32–34°N from 2002 to 2006. The distribution of high surface chlorophyll corresponds to low SSHA. Cyclonic eddies are found to detach from the KE jet near 150°E and 158°E and propagate westward. The westward propagating cyclonic eddies lift the nutrient-rich thermocline into the euphotic zone and maintain high levels of chlorophyll in summer. In the subsurface layer, the pattern in chlorophyll is influenced by both lateral and vertical advection. In winter, convection inside the eddy entrains high levels of nutrients into the mixed layer, increasing production, and resulting in high chlorophyll concentration throughout the surface mixed layer. There is significant interannual variability in both the cyclonic eddy activity and the surface phytoplankton bloom south of the KE jet, although whether or not there is a causal link is unclear.     

Petrological and Geochemical Characteristics of Intrusive Rocks Related to Porphyry Copper Mineralization and the Implications for the Genesis of Deposits in the Namosi area, Viti Levu, Republic of the Fiji Islands

In the Namosi district, of Viti Levu Island, Republic of the Fiji Islands, we conducted chemical analysis on intrusive rocks and attempted to clarify the relationship between petrological characteristics and mineralization. Samples were collected from the Waisoi copper deposit, Waivaka corridor, Waisomo, Wailutelevu and Wainabama Southwest localities. The intrusive rocks in the district show the overall characteristics of calc-alkaline magnetite series. Using the normative composition diagram for granite classification, most of the intrusive rocks plot in the tonalite, granodiorite, quartz monzodiorite and quartz diorite fields. Rare earth element (REE) analysis revealed that at Waisoi the intrusive rocks tend towards an Eu positive anomaly, whereas most of those at Waisomo tend to have a negative anomaly. The (Ce_cn/Yb_cn)/Yb_cn ratio shows that the intrusive rocks in the Namosi district may be derived from a mantle origin magma possibly contaminated by crustal materials. Waisoi rocks have less contamination with continental crust and show higher gold content compared to those of the Waivaka corridor. The observed differences between Waisoi and Waivaka corridor in the Cu/Au ratio might also be caused by varying amounts of contamination by crustal materials. There is no clear correlation between the La/Yb ratio and K–Ar ages, however, the La/Yb ratio of the Waivaka corridor rocks has a wide range, suggesting a variable amount of crustal contamination of the magma from 7 to 5 Ma. The less crustal contamination and generation of relatively high silica contents under relatively oxidized conditions in the Waisoi magmas is correlated with Au-rich porphyry copper mineralization and in contrast more crustal contamination produced Au-poor porphyry copper mineralization at the Waivaka Corridor in the Namosi district.     

A Proposed Method to Estimate In Situ Dissolved Gas Concentrations in Gas‐Saturated Groundwater

Gas‐saturated groundwater forms bubbles when brought to atmospheric pressure, preventing precise determination of its in situ dissolved gas concentrations. To overcome this problem, a modeling approach called the atmospheric sampling method is suggested here to recover the in situ dissolved gas concentrations of groundwater collected ex situ under atmospheric conditions at the Horonobe Underground Research Laboratory, Japan. The results from this method were compared with results measured at the same locations using two special techniques, the sealed sampler and pre‐evacuated vial methods, that have been developed to collect groundwater under its in situ conditions. In gas‐saturated groundwater cases, dissolved methane and inorganic carbon concentrations derived using the atmospheric sampling method were mostly within ±4 and ±10%, respectively, of values from the sealed sampler and pre‐evacuated vial methods. In gas‐unsaturated groundwater, however, the atmospheric sampling method overestimated the in situ dissolved methane concentrations, because the groundwater pressure at which bubbles appear (P_critical) was overestimated. The atmospheric sampling method is recommended for use where gas‐saturated groundwater can be collected only ex situ under atmospheric conditions.     

Podiform chromitites in the lherzolite-dominant mantle section of the Isabela ophiolite, the Philippines

Abstract The Isabela ophiolite, the Philippines, is characterized by a lherzolite‐dominant mantle section, which was probably formed beneath a slow‐spreading mid‐ocean ridge. Several podiform chromitites occur in the mantle section and grade into harzburgite to lherzolite. The chromitites show massive, nodular, layered and disseminated textures. Clinopyroxene (±orthopyroxene/amphibole) inclusions within chromian spinel (chromite hereafter) are commonly found in the massive‐type chromitites. Large chromitites are found in relatively depleted harzburgite hosts having high‐Cr? (Cr/(Cr + Al) atomic ratio = ～0.5) chromite. Light rare earth element (LREE) contents of clinopyroxenes in harzburgites near the chromitites are higher than those in lherzolite with low‐Cr? chromite, whereas heavy REE (HREE) contents of clinopyroxenes are lower in harzburgite than in lherzolite. The harzburgite near the chromitites is not a residual peridotite after simple melt extraction from lherzolite but is formed by open‐system melting (partial melting associated with influx of primitive basaltic melt of deeper origin). Clinopyroxene inclusions within chromite in chromitites exhibit convex‐shaped REE patterns with low HREE and high LREE (+Sr) abundances compared to the host peridotites. The chromitites were formed from a hybridized melt enriched with Cr, Si and incompatible elements (Na, LREE, Sr and H₂O). The melt was produced by mixing of secondary melts after melt–rock interaction and the primitive basaltic melts in large melt conduits, probably coupled with a zone‐refining effect. The Cr? of chromites in the chromitites ranges from 0.65 to 0.75 and is similar to those of arc‐related magmas. The upper mantle section of the Isabela ophiolite was initially formed beneath a slow‐spreading mid‐ocean ridge, later introduced by arc‐related magmatisms in response to a switch in tectonic setting during its obduction at a convergent margin.     

Modal selection in oscillator model equations with two-mode nonresonant coupling

We present a revised criterion for the double-mode pulsation in oscillator model equations with two-mode nonresonant coupling. By applying the criterion, we demonstrate that there are four cases, namely, mode 0-only, mode 1-only, either-or, and double-mode ones on limiting amplitude space. We also show that models with evolutionary masses are preferable for double-mode pulsations. Moreover, we study numerically modal selection properties of the oscillator model equations corresponding to various limiting amplitudes. The results show the suggested criterion to be useful for prediction of modal selection properties. Some examples of the phase-locking behaviour are also shown.     

Application of distinct element analysis to three simple block models aimed at practical application to toppling failure of fissured rock slopes

To examine the accuracy and the chracteristics of the Distinct Element Method (DEM) which has non-deformable elements, the results simulated by the DEM were compared to the results of experiments and/or theories for three simple block models of a pillar, a mass and a toppling model. Consequently, it was elucidated that the DEM is a good numerical method which can be effectively applied to toppling failure of real fissured rock slopes.