Viscoelastic behaviour and temporal fractal properties of lherzolite and marble: possible extrapolation from experimental results to the geological time-scale   总被引：1，自引：0，他引：1  

Yusuke Kawada  Hiroyuki Nagahama 《地学学报》2004,16(3):128-132

The viscoelastic relaxation behaviour of lherzolite and marble and their temporal fractal properties are studied. Based on the high‐temperature viscoelastic behaviour for these rock types derived from the time–temperature superposition principle, the relaxation function for the viscoelastic behaviour of lherzolite and marble can be expressed as a flow law from a power‐law function of temperature‐reduced time given by normalizing the various temperature behaviours, with a non‐integer exponent. The relaxation function is thus time‐scale invariant, i.e. there is a temporal fractal property to the temperature‐reduced time. Their rheological behaviour over geological time‐scales at low temperature can be extrapolated from the experimental high‐temperature behaviour based on the temporal fractal property. Our derived flow law satisfies not only transient behaviour but also steady‐state behaviour.  相似文献   

Source mechanisms of deep and intermediate-depth low-frequency earthquakes beneath Iwate volcano, northeastern Japan   总被引：2，自引：0，他引：2  

Haruhisa Nakamichi  Hiroyuki Hamaguchi  Satoru Tanaka  Sadato Ueki  Takeshi Nishimura  Akira Hasegawa 《Geophysical Journal International》2003,154(3):811-828

  相似文献   

Evidence of Microbial Activity in the Formation of Manganese Wads at the Asahidake Hot Spring in Hokkaido, Japan     

Naoki Mita  Hiroyuki Miura 《Resource Geology》2003,53(3):233-238

Abstract. Mt. Asahidake is an active volcano, with more than 90 active wells, in the Daisetsu volcanic group located in central Hokkaido, Japan. Wells along the Yukomanbetsu-sawa River showed high manganese concentrations and associated manganese deposits. These deposits consist of manganese oxides, and the concentration of iron is very low except for one sample collected from the upper reach of the river. Most of the wet samples showed basal diffraction characteristic of todorokite (9.6 Å). Cultivation tests showed that microorganisms were responsible for the oxidation of dissolved Mn²⁺ in the Asahidake hot spring. The dissolved Mn²⁺ concentration in the sterilized hot spring water was unchanged after four days, whereas the Mn²⁺ concentration in the sterilized hot spring water with a small amount of fresh manganese wad was decreased to zero after three days, and manganese oxide formed. This result implies that the activity of microorganism oxidizes dissolved Mn²⁺ and forms manganese oxide at the Asahidake manganese deposits. In addition to Komanoyu hot spring and Yunotaki Falls, this is the third report of microbial activity forming considerable deposits of manganese oxides in hot spring waters.  相似文献   

Relationships between Volcanism, Hydrothermal Alteration and Epithermal Gold-Silver Mineralization in the Muka Mine Area in the Kitami Metallogenic Province, Hokkaido, Japan     

Hiroyuki MAEDA 《Resource Geology》1998,48(3):197-208

Abstract: Neogene magmatism in the Muka mine area in the Kitami metallogenic province was characterized on the basis of K-Ar age data by felsic–to–mafic terrestrial extrusive and intrusive volcanism from Late Miocene to Early Pliocene. The geology of the Muka mine area comprises the Upper Cretaceous-Paleocene Yubetsu Group, consisting primarily of sandstone and shale; Upper Miocene Ikutahara Formation, consisting of clastic and felsic volcaniclastic rocks and Kane-hana Lava (rhyolite) of 7. 5 Ma; Upper Miocene Yahagi Formation, consisting of clastics, felsic volcaniclastics and rhyolite lavas; Late Miocene andesite and rhyolite dikes (Chidanosawa Rhyolite of 7. 2 Ma and Hon-Mukagawa Andesite of 6. 6 Ma); Lower Pliocene Hakugindai Lava (basalt: 4. 0 Ma); and Quaternary System. The volcanism consists of earlier Late Miocene felsic extrusive activity during the sedimentation of the Ikutahara Formation, later Late Miocene felsic extrusive and intrusive activities during the sedimentation of the Yahagi Formation and intermediate intrusive activity after the sedimentation of the Yahagi Formation and Early Pliocene mafic extrusive activity. The Muka gold-silver ore deposit occurs primarily in the felsic volcaniclastic rocks and Kanehana Lava of the Ikutahara Formation and in Hon-Mukagawa Andesite. These wall–rocks, the clastic rocks of the Ikutahara Formation and the clastic and felsic volcaniclastic rocks of the Yahagi Formation were affected to various extents by hydrothermal alteration. The hydrother-mal alteration can be divided into two stages (early and late) based on the modes of occurrence and mineral assemblages. Early hydrothermal alteration is characterized by regional and vein-related alterations associated with epithermal gold-silver mineralization in a near-neutral hydrothermal system. Regional alteration can be subdivided into a zeolite zone (mordenite+adularia±heulandite–clinoptilolite series mineral±smectite±quartz°Cristobalite±opal–CT) and a smectite zone (smec–tite±quartz±opal–CT). Vein-related alteration can be subdivided into a K-feldspar zone (quartz+adularia±illite±interstratified illite/smectite±pyrite), an illite zone (quartz+illite°Chlorite±interstratified illite/smectite±smectite±pyrite) and an interstratified illite/smectite zone (quartz+interstratified illite/smectite±smectite±pyrite). The adularization age of 6. 8 Ma in the K-feldspar zone that developed in Kanehana Lava hosting ore veins coincides well with the epithermal gold-silver mineralization age of 6. 6 Ma. Late hydrothermal alteration is characterized by a kaolinite zone (kaolinite±dickite±alunite±quartz°Cristobalite± tridymite±pyrite) in an acid hydrothermal system, and cuts early alteration zones such as the K-feldspar zone. Other modes of occurrence of acid alteration are a 7Å halloysite-kaolinite vein in the hydrothermal explosion breccia dike and smectite–kaoli–nite veins along joint planes of Kanehana Lava. The style of the gold-silver deposit associated with early near-neutral hydrothermal alteration is a low-sulfidation epithermal type. The low-sulfidation epithermal gold-silver mineralization of 6. 6 Ma in the vicinity of the Muka ore deposit was essentially accompanied by felsic volcanic activity during the sedimentation of the Yahagi Formation, and was closely related both temporally and spatially to the felsic intrusive activity of Chidanosawa Rhyolite of 7. 2 Ma. The related hydrother-mal activity of the gold-silver mineralization took place at intervals of approximately 0. 4–0. 6 Ma after the volcanic activity related to the mineralization.  相似文献   

Construction of a genomic DNA library with a TA vector and its application in cloning of the phytoene synthase gene from the cyanobacteriumSpirulina platensis M-135   总被引：1，自引：0，他引：1  

许鹭芬 《中国海洋湖沼学报》1998,16(1):17-20

INTRODUCTIONThesignalproaningschemeofmostpnsentsonarsyStasuChaseChosounder,fishfinder,etc.,deteCtsthesignaIsaanrdingt0theamPlitudethasholdafterthefilter.However,inacomplicatalandfrequenhychangingunderotCfacousticalchanne,thesta-bilityandreiabilityofthiskindofsonarsySteIndroeshamlyasanysySthenoisewhleadt0anindedion.AmplitudefaderesultingfromstrongsignalfluCtuationcauseslossofdata.InsomesyStetnS,suchasndnelocatingsonar,highrangingamCyisneded,soasinglededionschernecann0tadapttoit.Resul…  相似文献   

Fine S wave velocity structure beneath Iwate volcano, northeastern Japan, as derived from receiver functions and travel times     

Haruhisa Nakamichi  Satoru Tanaka  Hiroyuki Hamaguchi 《Journal of Volcanology and Geothermal Research》2002,116(3-4)

A genetic algorithm inversion of receiver functions derived from a dense seismic network around Iwate volcano, northeastern Japan, provides the fine S wave velocity structure of the crust and uppermost mantle. Since receiver functions are insensitive to an absolute velocity, travel times of P and S waves propagating vertically from earthquakes in the subducting slab beneath the volcano are involved in the inversion. The distribution of velocity perturbations in relation to the hypocenters of the low-frequency (LF) earthquakes helps our understanding of deep magmatism beneath Iwate volcano. A high-velocity region (dV_S/V_S=10%) exists around the volcano at depths of 2–15 km, with the bottom depth decreasing to 11 km beneath the volcano’s summit. Just beneath the thinning high-velocity region, a low-velocity region (dV_S/V_S=−10%) exists at depths of 11–20 km. Intermediate-depth LF (ILF) events are distributed vertically in the high-velocity region down to the top of the low-velocity region. This distribution suggests that a magma reservoir situated in the low-velocity region supplies magma to a narrow conduit that is detectable by the hypocenters of LF earthquakes. Another broad low-velocity region (dV_S/V_S=−5 to −10%) occurs at depths of 17–35 km. Additional clusters of deep LF (DLF) events exist at depths of 32–37 km in the broad low-velocity zone. The DLF and ILF events are the manifestations of magma movement near the Moho discontinuity and in the conduit just beneath the volcano, respectively.  相似文献   

Victoria Carbonate-Base Metal Gold Deposit and Its Significance in the Mankayan Mineral District, Luzon, Philippines   总被引：1，自引：0，他引：1  

Fernando G. Sajona    Eiji Izawa  Yoshinobu Motomura    Akira Imai    Hiroyuki Sakakibara  Koichiro Watanabe 《Resource Geology》2002,52(4):315-328

Abstract. The Victoria gold deposit is a low-sulfidation style epithermal carbonate-base metal gold deposit discovered in 1995 in the Mankayan mineral district, northern Luzon, Philippines. It occurs just south of a high-sulfidation copper-gold orebody (Lepanto enargite deposit) and a porphyry copper-gold orebody (Far Southeast (FSE) deposit). Radiometric dating of the Victoria mineralization yields ages from 1.6 to 1.1 Ma, similar to ages of the Lepanto enargite deposit. Mineralogical, geochemical, fluid inclusion and sulfur isotope studies suggest that the Victoria deposit is not directly related to the late stage of hydrothermal activity that produced the FSE porphyry copper-gold and the Lepanto enargite deposits. The hydrothermal fluids from which Victoria was formed appear to have been derived from the south, and not from the FSE intrusive center to the northeast. This would suggest a regional south to north hydrothermal gradient, consistent with the similar flow within the FSE porphyry-Lepanto enargite system. On a district scale, structures similar to those of the Victoria deposit in trend and nature would be highly prospective, especially if they occur north of identified plutons and volcanic centers.  相似文献   

Fluctuations of snow accumulation in the Antarctic and sea level pressure in the Southern Hemisphere in the last 100 years     

Hiroyuki Enomoto 《Climatic change》1991,18(1):67-87

This paper summarizes the long-term fluctuations of snow accumulation in the Antarctic and analyzes its correlation with the sea level pressure (SLP) in the middle latitude (40°–50° S) of the Southern Hemisphere. Stratigraphic data which were compiled from studies on ice cores and snow-pits at eight stations in the Antarctic were used in the present study. It was found that the data concerning fluctuations in snow accumulation for East Antarctica showed correlations, whereas no such correlation was observed for the data from West Antarctica.This study shows possible relationships between snow accumulation in the Antarctic and SLP in the middle latitudes. The fluctuations of accumulation at South Pole, Dome C, Wilkes and South Ice Point show correlations with SLP over a large area in the 40°–50° S latitudinal zone. For the long-term fluctuations of SLP in the 40°–50 ° S latitudinal zone, a zonal fluctuation with wave number zero structure and a longitudinal variation of SLP anomalies due to their out-of-phase-fluctuation between the Pacific and the Indian Oceans were observed. The temporal scales for these fluctuations were found to be in the order of 20–30 years and 40–60 years, respectively. The influences of these two modes on the behaviour of snow accumulation in the Antarctic is also discussed.Now at Kitami Institute of Technology, Kitami, Hokkaido, Japan.  相似文献   

Radiometric ages of Alpine metamorphic rocks in the western and central Alps   总被引：1，自引：0，他引：1  

Hiroyuki  Takeshita Tetsumaru  Itaya 《Island Arc》1993,2(4):193-212

Abstract The chronological characteristics of Alpine metamorphic rocks are described and Alpine metamorphic events are reinterpreted on the basis of chronological data for the western and central Alps from 1960 to 1992. Metamorphic rocks of the Lepontine, Gran San Bernardo, Piemonte, Internal Crystalline Massifs and Sesia-Lanzo mostly date Alpine metamorphic events, but some (along with granitoids and gneisses from the Helvetic and Southern Alps) result from the Variscan, Caledonian or older events and thus predate the Alpine events. Radiometric age data from the Lepontine area show systematic age relations: U-Pb monazite (23-29 Ma), Rb-Sr muscovite (15–40 Ma) and biotite (15–30 Ma), K-Ar biotite (10-30 Ma), muscovite (15–25 Ma) and hornblende (25-35 Ma), and FT zircon (10-20 Ma) and apatite (5-15 Ma), which can be explained by the different closure temperatures of the isotopic systems. A 121 Ma U-Pb zircon age for a coesite-bearing whiteschist (metaquartzite) from the Dora-Maira represents the peak of ultra-high pressure metamorphism. Coesite-free eclogites and blueschists related to ultra-high pressure rocks in the Penninic crystalline massifs yield an ⁴⁰Ar-³⁹Ar plateau age of about 100 Ma for phengites, interpreted as the cooling age. From about 50 Ma, eclogites and glaucophane schists have also been reported from the Piemonte ophiolites and calcschists, suggesting the existence of a second high P/T metamorphic event. Alpine rocks therefore record three major metamorphic events: (i) ultra-high and related high P/T metamorphism in the early Cretaceous, which is well preserved in continental material such as the Sesia-Lanzo and the Penninic Internal Crystalline Massifs; (ii) a second high P/T metamorphic event in the Eocene, which is recognized in the ophiolites and calcschists of the Mesozoic Tethys; and (iii) medium P/T metamorphism, in which both types of high P/T metamorphic rocks were variably reset by Oligocene thermal events. Due to the mixture of minerals formed in the three metamorphic events, there is a possibility that almost all geochronological data reported from the Alpine metamorphic belt show mixed ages. Early Cretaceous subduction of a Tethyan mid-ocean ridge and Eocene continental collision triggered off the exhumation of the high pressure rocks.  相似文献   

White mica K-Ar ages of blueschist-facies rocks from the Piemonte 'calc-schists' of the western Italian Alps     

Hiroyuki  Takeshita  Hisamichi  Shimoya Tetsumaru  Itaya 《Island Arc》1994,3(3):151-162

Abstract Fifty calc-schists have been systematically collected from the Piemonte zone of the western Italian Alps and examined in terms of petrology, X-ray powder diffractometer (XRD) analysis of carbonaceous materials, and K-Ar ages of white mica separates. The petrological study and XRD analysis of carbonaceous materials have shown that calc-schists have suffered blueschist-facies metamorphism in the subduction zone of the convergent margin between the Apulian (African) continental and Tethyan oceanic plates. The metamorphic sequence is divided into three mineral zones based on increasing metamorphic temperature: chlorite (lower than 300°C), chloritoid, and rutile (higher than 450°C). The chlorite zone has dispersed ages of white mica separates, ranging from 115 to 44 Ma, whereas the rutile zone has a comparatively uniform age distribution from 60 to 40 Ma. The chloritoid zone has an intermediate age variation. The large variation in the chlorite zone is attributed to mixing of variable amounts of detrital mica derived from older high temperature metamorphic rocks in the separates, which have not been completely reset during Alpine metamorphism. The uniform age (average ca 50 Ma) in the rutile zone is the cooling age of blueschist-facies calc-schists, which have been episodically exhumed at the collision event of the European and Apulian continents in the Paleocene-Eocene.  相似文献