Hydrostatic pressure tests for the permeability - formation factor relation on crystalline rocks from the KTB drilling project

Transport properties (permeability and electrical conductivity) have been measured at different hydrostatic pressure runs on 7 crystalline rocks (gneisses and amphibolites) sampled from the KTB drilling project. The decrease of permeability by pressure are compared with the pressure-dependent data of the electrical conductivity (formation factor) resulting from complex impedance measurements. According to the equivalent-channel model (ECM), there exists a linear relationship between these parameters by representing both properties on logarithmic scales. The results show that it is possible to extrapolate high-pressure permeability from low-pressure (< 60 MPa) permeability data by using the pressure-dependent electrical conductivity (up to 300 MPa).     

Influence of oxygen partial pressure on the Mg/Fe distribution in olivines

The dependence of Mg/Fe ordering on oxygen partial pressure in natural olivine crystals of volcanic origin has been studied by X-ray diffraction. Two natural crystals with 10% and 12% fayalite have been investigated and the atomic positions, anisotropic temperature factors, extinction coefficients and site occupancies have been refined, reaching R-values of 2.2%. After subjecting the crystals to oxygen partial pressures of 10^?16 bar and 10^?21 bar the crystals were studied again. In total six crystals were studied and the distribution coefficients K _D determined. The natural untreated crystals had K _D=1.09 and 1.06, e.g., a slight preference of Fe in (M1). p(O₂) of 10^?16 bar increased the ordering of Fe in (M1) to K _D=1.2, while p(O₂)=10^?21 bar reversed K _D to 0.8 with ordering of Fe in (M2). These experiments suggest that Mg/Fe ordering in olivines is primarily determined by the prevailing oxygen partial pressure.     

Impacts of climate change on the hydro-climatology of the upper Ishikari river basin,Japan

Evidence for climate change impacts on the hydro-climatology of Japan is plentiful. The objective of the present study was to evaluate the impacts of possible future climate change scenarios on the hydro-climatology of the upper Ishikari River basin, Hokkaido, Japan. The Soil and Water Assessment Tool was set up, calibrated, and validated for the hydrological modeling of the study area. The Statistical DownScaling Model version 4.2 was used to downscale the large-scale Hadley Centre Climate Model 3 Global Circulation Model A2 and B2 scenarios data into finer scale resolution. After model calibration and testing of the downscaling procedure, the SDSM-downscaled climate outputs were used as an input to run the calibrated SWAT model for the three future periods: 2030s (2020–2039), 2060s (2050–2069), and 2090s (2080–2099). The period 1981–2000 was taken as the baseline period against which comparison was made. Results showed that the average annual maximum temperature might increase by 1.80 and 2.01, 3.41 and 3.12, and 5.69 and 3.76 °C, the average annual minimum temperature might increase by 1.41 and 1.49, 2.60 and 2.34, and 4.20 and 2.93 °C, and the average annual precipitation might decrease by 5.78 and 8.08, 10.18 and 12.89, and 17.92 and 11.23% in 2030s, 2060s, and 2090s for A2a and B2a emission scenarios, respectively. The annual mean streamflow may increase for the all three future periods except the 2090s under the A2a scenario. Among them, the largest increase is possibly observed in the 2030s for A2a scenario, up to approximately 7.56%. Uncertainties were found within the GCM, the downscaling method, and the hydrological model itself, which were probably enlarged because only one single GCM (HaDCM3) was used in this study.     

Pressure induced phase transition in Mg2GeO4 as determined by frequency dependent complex electrical resistivity measurements

The phase transition of Mg₂GeO₄ from the olivine structure (α-phase) to the spinel structure (γ-phase) was determined by complex electrical resistivity measurements in the frequency range 10 Hz up to 100 kHz. The stability fields of the α- and the γ-phase were confirmed up to 2.05 GPa in the temperature range 845° C–1400° C. Based on volume resistivity data, a decrease of about a factor of 5 was found at the α-γ phase transition. Activation energies of electrical conduction E _a at 1.05 GPa and 2.05 GPa were calculated using the volume resistivities (?) and the relaxation times (τ). The values range from 1.98 eV up to 2.78 eV. The relative dielectric permeability increases with increasing temperature. This is is due to crystal defects and charge transport mechanisms.     

An Integrated Study on Physical Properties of a KTB Gneiss Sample and Marble from Portugal: Pressure Dependence of the Permeability and Frequency Dependence of the Complex Electrical Impedance

— Pressure-induced variations in pore geometry were studied on dry- and fluid- saturated samples by means of electrical impedance spectroscopy and permeability measurements. Hydrostatic pressures (up to 120 MPa) and uniaxial pressures (up to failure) were applied. Hydrostatic pressures reduce the aspect ratio of cracks and thus cause a decrease of permeability and electrical bulk conductivity. The opposite was observed in uniaxial pressure experiments where new cracks were formed and consequently permeability and electrical conductivity were increased. More specific informations of these generated observations were derived from the interpretation of the frequency dispersion of the complex electrical conductivity. This least-squares-refinement considers electrochemical interactions between the fluid pore electrolyte and the inner surface of the sample, thus providing informations on the pore geometry and pressure-induced variations. Consequently changes in aspect ratio, size and geometry of the pore system can be detected by means of impedance spectroscopy.     

New heat flow data from the immediate vicinity of the Kola super-deep borehole: Vertical variation in heat flow confirmed and attributed to advection

We present new heat flow values and other geothermal data in the upper crystalline crust in the immediate vicinity of the 12.4-km deep Kola super-deep borehole, NW Russia. Our results show a systematic vertical increase in geothermal gradient and heat flow density as deep as we could measure (1.6 km). Our results confirm earlier results on vertical heat flow trends of in the uppermost part of the Kola super-deep hole, and imply that the thermal regime is not in steady-state conductive conditions. In an area of 3-km × 5-km measurements were performed in 1–2-km deep boreholes surrounding the Kola super-deep hole and on core samples from these holes. Temperature logs are available from 36 holes. Core data exists from 23 boreholes with a total length of 11.5 km at a vertical resolution of 10 m. We carried out a very detailed study on thermal conductivity with regard to anisotropy, inhomogeneity and temperature dependence. Tensor components of thermal conductivity were determined on 1375 core samples from 21 boreholes in 3400 measurements. Additionally, we measured specific heat capacity, heat generation rate, density, porosity, and permeability on selected subsets of core samples. Heat flow from 19 boreholes varies between 31 and 45 mW m⁻² with an average value of 38 mW m⁻². In most boreholes the vertical heat flow profiles show a considerable variation with depth. This is consistent with observations in the upper part of the Kola super-deep borehole. We conclude that this variation is not caused by technical operations but reflects a natural process. It is considered to be due to a combination of advective, structural and paleoclimatic effects. Preliminary 3-D numerical modeling of heat and flow in the study area provides an indication of relative contributions of each of these factors: advective heat transfer turns out to have a major influence on the vertical variation of heat flow, although transient changes in surface temperature may also cause a significant variation. Heterogeneity of the rocks in the study area is less important.     

Anomalous atmospheric events leading to Kyushu’s flash floods,July 11–14, 2012

During July 11–14, 2012, deadly floods and landslides triggered by a series of unprecedented heavy rains hit Kyushu, Japan, causing at least 32 deaths and around 400,000 evacuations. We focus on synoptic anomalies identified after inspecting rainfall patterns and documenting the conditions associated with this tragic event using data combined from the Global Rainfall Map in Near Real Time data, the NCEP/NCAR Reanalysis dataset, and the global forecast system. Rainfall maps indicated that there were many heavy rains in Kyushu in these days and this disaster was associated with the pattern of forecasts and standardized anomalies. A weather trough with positive height anomalies appeared, the center of which moved to the north of Japan over this period, which might cause wind anomalies and whereby lots of water vapor were transported to Kyushu area with up to 90 m s^?1, and high values of precipitable water formed with up to 60 mm. These results suggest that a larger-scale pattern is conducive for heavy rainfall and the anomalies put the pattern in context as to the potential for an extreme rainfall event, which can provide insights and methods for predicting extreme events’ or something similar.