Neural Network-Based Estimation of Principal Metal Contents in the Hokuroku District,Northern Japan,for Exploring Kuroko-Type Deposits   总被引：7，自引：0，他引：7  

Koike  Katsuaki  Matsuda  Setsuro  Suzuki  Toru  Ohmi  Michito 《Natural Resources Research》2002,11(2):135-156

The Hokuroku district, extending over 40 × 40 km² in northern Japan, is known to be dominated by kuroko-type massive sulfide deposits that have a genetic relation to submarine volcanic activity. The deposits are hosted in a specific stratigraphic zone of Miocene volcanic rocks. Because kuroko-type deposits are under exploration in several countries, it is important to integrate the geologic and geochemical data that have been accumulated in the Hokuroku district to characterize the distribution of deposits and produce a map of mineral potential. Thus, we collected data on multiple chemical components from 1917 rock cores at 143 drillhole sites and concentrated on components with relatively large amounts of data, which are SiO₂, Al₂O₃, and Fe₂O₃ as major elements and Cu, Pb, and Zn as trace elements. Although frequencies of these data can be approximated by normal or lognormal distributions, spatial correlation structures cannot be extracted from the semivariograms of each component nor from the cross-semivariograms between two components of the major or minor elements. To handle such complexity, a spatial method of modeling content distribution, SLANS, is developed by applying a feedforward neural network. The principle of SLANS is to train a network repeatedly to recognize the relation between the data value and the location and lithology of a sample point. One-hundred outputs for each element are obtained by changing the numbers of neurons in a middle layer from 1 to 10 and sample data used for training from 3 to 12, and finally one output is selected based on the estimation precision of the network which is restricted near the target point. After constructing a geologic distribution model from the geological column classified into 25 rock codes, three-dimensional distributions of Cu, Pb, and Zn contents are estimated over the study area. The content models are considered to be valid because high-content zones are located on the known mine sites and the margins of ancient volcanoes or calderas. Some zones are distributed along strikes of major deep-seated fractures in the district.  相似文献   

Influence of the east-west component of the interplanetary magnetic field on the intensity of the auroral electrojet     

Kazuyuki Hakamada  Takao Aoki  Takashi Murayama 《Planetary and Space Science》1980,28(1):29-39

Analysis of interplanetary data has been made to evaluate the influence of the Biny component of the IMF on the magnitude of the AL index, especially with reference to the contribution of B_y in the reconnection process between the IMF and geomagnetic fields in the dayside part of the magnetosphere. The results of the analysis showed that the effect of Biny on AL is predominantly of a different type from that expected by the current theory of reconnection, and the B_y effect of the latter type was found to be much less significant in magnitude than the theory predicts. The discrepancy may be resolved if the region where the reconnection takes place has an elongated shape.  相似文献   

Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles     

C. Kaito  Y. Ojima  K. Kamitsuji  O. Kido  Y. Kimura  H. Suzuki  T. Sato  T. Nakada  Y. Saito  C. Koike 《Meteoritics & planetary science》2003,38(1):49-57

Abstract— Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain‐grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg₂Si polyhedral grains were obtained in a Mg grain‐rich atmosphere. Mg₂SiO₄ polyhedral grains were obtained in a SiO grain‐rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.  相似文献   

Properties of simulated cosmic matters after gamma-ray and neutron irradiation     

K. Koike  M. Nakagawa  H. Chihara  M. Okada  T. Awata  J. Takada 《Planetary and Space Science》2006,54(4):325-330

Interstellar and circumstellar matter is known to be strongly irradiated by cosmic radiation and several types of cosmic ray particles. The effects of irradiation on simulated interstellar and circumstellar matter such as CaCO₃, MgCO₃, SiO₂ and Al₂O₃ are investigated. Especially, thermoluminescence (TL) spectra after γ-ray and neutron irradiation are compared carefully. It is shown that the thermoluminescence after neutron irradiation appears significantly in the wavelength of blue region. On the reflectance in infrared region, the irradiation effect appears scarcely.  相似文献   

Low-temperature single crystal reflection spectra of forsterite     

H. Suto  H. Sogawa  S. Tachibana  C. Koike  H. Karoji  A. Tsuchiyama  H. Chihara  K. Mizutani  J. Akedo  K. Ogiso  T. Fukui  S. Ohara 《Monthly notices of the Royal Astronomical Society》2006,370(4):1599-1606

The infrared reflectivities of crystalline forsterite (Mg₂SiO₄) were measured for the temperature range 295–50 K for each crystal axis, between wavenumber 5000 and 100 cm⁻¹. The reflection spectra show clear dependence of temperature; most of the bands become more intense, sharper and their peak positions shift to higher wavenumber with decreasing temperature. Reflection spectra were fitted with dispersion formula of damped oscillator model of the dielectric constants and the oscillator parameters in the model were derived. The absorption spectra of forsterite particle are calculated with the derived dielectric constants to show that the forsterite features are good thermal indicator for cold temperature range below 295 K.  相似文献   

An upper limit on the mass of a primordial star due to the formation of an H ii region: the effect of ionizing radiation force     

Kazuyuki Omukai  Shu-ichiro Inutsuka 《Monthly notices of the Royal Astronomical Society》2002,332(1):59-64

We investigate analytically the formation of an H  ii region in the accreting envelope of a newborn star. Special care is taken to examine the role of ionizing radiation force. This effect modifies velocity and density distributions, and thereby affects the expansion of the H  ii region. As a result, the upper limit of the stellar mass imposed by the growth of an H  ii region around a forming star is increased by a larger factor than the previous estimate. In particular, for a star forming out of metal-free gas, this mechanism does not impose a firm upper limit on its mass.  相似文献   

一个基于模拟退火法的陆面数据同化算法   总被引：15，自引：3，他引：15  

李新  小池俊雄  程国栋 《地球科学进展》2003,18(4):632-636

陆面数据同化系统是近年来兴起的新领域。我们发展了一个实验型的陆面数据同化方案,它使用一种启发式优化算法——模拟退火法极小化目标泛函。与变分法和Kalman滤波方法比较,这一算法具有独立于目标泛函的优点,可处理模型和观测算子的非线性和不连续性。使用GAME—Tibet实验中的土壤水分观测值进行单点数值实验,成功地将土壤水分观测同化到陆面过程模型SiB2中。结果表明,与不进行同化相比,土壤水分的估计值有较大改善。  相似文献   

Polarity Reversal Time of the Magnetic Dipole Component of the Sun in Solar Cycle 24     

Kazuyuki Hakamada 《Solar physics》2013,283(2):247-252

The Sun’s general magnetic field has shown polarity reversal three times during the last three solar cycles. We attempt to estimate the upcoming polarity reversal time of the solar magnetic dipole by using the coronal field model and synoptic data of the photospheric magnetic field. The scalar magnetic potential of the coronal magnetic field is expanded into a spherical harmonic series. The long-term variations of the dipole component ( $g^{0}_{1}$ ) calculated from the data of National Solar Observatory/Kitt Peak and Wilcox Solar Observatory are compared with each other. It is found that the two $g^{0}_{1}$ values show a similar tendency and an approximately linear increase between the Carrington rotation periods CR 2070 and CR 2118. The next polarity reversal is estimated by linear extrapolation to be between CR 2132.2 (December 2012) and CR2134.8 (March 2013).  相似文献   

Identifying groundwater arsenic contamination mechanisms in relation to arsenic concentrations in water and host rocks   总被引：1，自引：1，他引：0  

Irwan Iskandar  Katsuaki Koike  Purnama Sendjaja 《Environmental Earth Sciences》2012,65(7):2015-2026

Leaching and oxidation of high arsenic (As) host rocks tend to be induced by circulation of deep geothermal waters, which increase As concentration in shallow groundwater. The purpose of this study is to identify the mechanism of groundwater As contamination in relation to leaching and oxidation along the border between the South Minahasa and Bolaang Mongondow districts, North Sulawesi, Indonesia. This region contains Miocene sedimentary rock-hosted disseminated gold deposits associated with hydrothermal alteration in a fault zone. Abnormally high As concentrations were observed in hot and cold springs and in surrounding shallow groundwater for a total mineralization area of 8 × 10 km². Two methods were adopted in this study: (1) microscopic and spectroscopic analyses of rock samples for mineral identification and (2) geostatistics for spatial modeling of As concentrations in groundwater. Jarosite was identified as the chief fill mineral in rock defects (cracks and pores). The presence of this mineral may indicate release of As into the environment, as can occur as an alteration product derived from oxidation and leaching of pyrite, As-rich pyrite or sulfide minerals by geothermal waters. Moreover, As concentrations in groundwater were estimated using geostatistics for spatial modeling. The co-kriging map identified local anomalies in groundwater As concentrations over the permissible limit (10 ppb). Such anomalies did not appear through ordinary kriging. Integration of the results indicates that As contamination in shallow groundwater probably is controlled by heterogeneous distributions of jarosite and variations in intensity and extent of hydrothermal activities.  相似文献   

Existence of multiple units with different accretionary and metamorphic ages in the Sanbagawa Belt,Sakuma–Tenryu area,central Japan     

Yukiyasu Tsutsumi  Atsushi Miyashita  Kenji Horie  Kazuyuki Shiraishi 《Island Arc》2012,21(4):317-326

U–Pb ages of detrital zircons and white mica K–Ar ages are obtained from two psammitic schists from the western and eastern units of the Sanbagawa Metamorphic Belt located in the Sakuma–Tenryu area. The detrital zircons in the sample from the western unit (T1) show an age cluster around 95 Ma, and the youngest age in the detrital zircons is 94.0 ± 0.6 Ma. The detrital zircons in the sample from the eastern unit (T5) show a main age cluster in the Late Cretaceous with some older ages, and the youngest age in the detrital zircons is 72.8 ± 0.9 Ma. The youngest zircon ages restrict the older limit of the depositional ages of each sample. White mica K–Ar ages of T1 and T5 are 69.8 ± 1.5 Ma and 56.1 ± 1.2 Ma, respectively, which indicate the age of exhumation and restrict the younger limit on the depositional age of each sample. The results show that the western and eastern units were different in their depositional and exhumation ages, suggesting the episodic subduction and exhumation of the Sanbagawa Belt in the Sakuma–Tenryu area. These results also suggest simultaneous existence of subduction and exhumation paths of metamorphic rocks in the high‐P/T Sanbagawa Metamorphic Belt.  相似文献