Alteration of rock by volcanic gas in Japan     

Iwaji Iwasaki  Mitsuei Hirayama  Takashi Katsura  Takejiro Ozawa  Jyoyo Ossaka  Masaakira Kamada  Hatao Matsumoto 《Bulletin of Volcanology》1964,27(1):65-78

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Nature of volcanic gases and volcanic eruption     

Iwaji Iwasaki  Takejiro Ozawa  Minoru Yoshida  Takashi Katsura  Bunji Iwasaki  Masaakira Kamada 《Bulletin of Volcanology》1963,26(1):73-81

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Phase relations of pumpellyite-actinolite facies metabasites in the Sanbagawa metamorphic belt in central Shikoku, Japan     

Takashi Nakajima 《Lithos》1982,15(4):267-280

Sanbagawa metabasites metamorphosed at conditions near the upper limit of the pumpellytic-actinolite facies were examined in terms of phase equilibria in the five component system Al₂O₃---Fe₂O₃---CaO---MgO---FeO. The Fe³⁺ content of epidote measured as X^Ep_Fe (=Fe/(Fe + Al) of epidote) in the assemblage epidote-chlorite-actinolite-pumpellyite decreases gradually towards the higher-grade, pumpellyite-free areas. The progressive change in X_Fe^Ep can be detected within one metabasite bed 200 meters thick near the upper limit of the pumpellyite-actinolite facies. The Mg---Fe²⁺ substitution, as expressed by variation of Fe/(Fe + Mg) in chlorite (0.40–0.55) has little effect on the Fe³⁺ + Al) ratios of epidote and pumpellyite in the above-mentioned assemblage. The lowet X_Fe^Ep in the pumpellite-bearing assemblage is 0.15 and hence the upper limit of the pumpellyite-actinolite facies is defined by the appearance of an epidote-chlorite-actinolite assemblage with X^Ep_Fc = C.15  相似文献   

Indicators of critical point behavior prior to rock failure inferred from pre-failure damage   总被引：4，自引：0，他引：4  

Xinglin Lei  Takashi Satoh   《Tectonophysics》2007,431(1-4):97

To investigate possible indicators of critical point behavior prior to rock failure, the statistical properties of pre-failure damage were analyzed based on acoustic emission events (AE) recorded during the catastrophic fracture of typical rock samples under differential compression. AEs were monitored using a high-speed 32-channel waveform recording system. Time-dependent statistics, including the energy release rate, b-value of the magnitude–frequency distribution, fractal dimension and spatial correlation length (SCL) of the AE hypocenters were calculated for each data set. Each parameter is a function of the time-to-failure and thus can be treated as an indicator of the critical point. It is clear that the pre-failure damage evolution prior to catastrophic failures in several common rock-types is generally characterized by: 1) accelerated energy release, 2) a decrease in fractal dimension and SCL with a subsequent precursory increase, and 3) a decrease in b-value from  1.5 to  0.5 for hard rocks, and from  1.1 to  0.8 for soft rocks such S–C cataclasite. However, each parameter also reveals more complicated temporal evolution due to either the heterogeneity of the rock mass or the micro-mechanics of shear fracturing. This confirms the potential importance of integrated analysis of two or more parameters for successfully predicting the critical point. The decreasing b-value and increasing energy release may prove meaningful for intermediate-term prediction, while the precursory increase in fractal dimension and SCL may facilitate short-term prediction.  相似文献   

Vertical heat transfer based on direct microstructure measurements in the ice-free Pacific-side Arctic Ocean: the role and impact of the Pacific water intrusion     

Yusuke Kawaguchi  Takashi Kikuchi  Ryuichiro Inoue 《Journal of Oceanography》2014,70(4):343-353

This study quantifies diapycnal mixing and vertical heat transfer in the Pacific side of the Arctic Ocean, where sea-ice cover has disappeared between July and September in the last few decades. We conducted microstructure measurements in the open water region around the Canada Basin from late summer to fall in 2009 and 2010 using R/V Mirai. In the study domain, the dissipation rate of turbulent kinetic energy, ε, is typically as low level as O(10^?10) W kg^?1, resulting in vertical heat diffusivity of O(10^?7) m² s^?1, which is close to the molecular diffusivity of heat, suggesting comparatively little predominance of mechanical turbulent mixing. An exception is the case at the Barrow Canyon, where the strong baroclinic throughflow generates substantial vertical mixing, producing ε > O(10^?7) W kg^?1, because of the shear flow instability. Meanwhile, in the confluence region, where the warm/salty Pacific water and the cold/fresh Arctic basin water encounter, the micro-temperature profiles revealed a localized enhancement in vertical diffusivity of heat, reaching O(10^?5) m² s^?1 or greater. In this region, an intrusion of warm Pacific water creates a horizontally interleaved structure, where the double-diffusive mixing facilitates vertical heat transfer between the intruding Pacific water and the surrounding basin waters.  相似文献   

Petrology and shock history of the first depleted-like poikilitic shergottite Asuka 12325     

Atsushi Takenouchi  Akira Yamaguchi  Takashi Mikouchi  Richard Greenwood  Sojiro Yamazaki 《Meteoritics & planetary science》2023,58(10):1406-1428

Asuka (A) 12325 is the first poikilitic shergottite having a depleted pattern in light rare earth elements (REE). Compared with known poikilitic shergottites, A 12325 has smaller but more abundant pyroxene oikocrysts with remarkable Fe-rich pigeonite rims, indicating that A 12325 cooled relatively faster at a shallower part of the crust. The redox condition (logfO₂ = IW + 0.6-IW + 1.7) and Fe-rich chemical compositions of each mineral in A 12325 are close to enriched shergottites. The intermediate shergottites could not form by a simple mixing between parent magmas of A 12325 and enriched shergottites. Although A 12325 contains various high-pressure minerals such as majorite and ringwoodite, plagioclase is only partly maskelynitized. Therefore, the maximum shock pressure may be within 17–22 GPa. Thermal conduction and ringwoodite growth calculation around a shock vein revealed that the shock dwell time of A 12325 is at least 40 ms. The weaker shock pressure and longer shock dwell time in A 12325 may be attained by an impact event similar to those of nakhlites and Northwest Africa (NWA) 8159. Such a weak shock ejection event may be as common on Mars as a severe shock event recorded in shergottites. Alteration of sulfide observed in A 12325 may imply the presence of magmatic fluid in its reservoir on Mars. A 12325 expands a chemical variety of Martian rocks and has a unique shock history among poikilitic shergottites while A 12325 also implies that poikilitic shergottites are common rocks on Mars regardless of their sources.  相似文献   

Editorial Appreciation     

John Leibacher  Takashi Sakurai  Lidia van Driel-Gesztelyi 《Solar physics》2014,289(5):1455-1456

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An overview of decadal climate predictability in a multi-model ensemble by climate model MIROC   总被引：1，自引：1，他引：0  

Yoshimitsu Chikamoto  Masahide Kimoto  Masayoshi Ishii  Takashi Mochizuki  Takashi T. Sakamoto  Hiroaki Tatebe  Yoshiki Komuro  Masahiro Watanabe  Toru Nozawa  Hideo Shiogama  Masato Mori  Sayaka Yasunaka  Yukiko Imada 《Climate Dynamics》2013,40(5-6):1201-1222

Decadal climate predictability is examined in hindcast experiments by a multi-model ensemble using three versions of the coupled atmosphere-ocean model MIROC. In these hindcast experiments, initial conditions are obtained from an anomaly assimilation procedure using the observed oceanic temperature and salinity with prescribed natural and anthropogenic forcings on the basis of the historical data and future emission scenarios in the Intergovernmental Panel of Climate Change. Results of the multi-model ensemble in our hindcast experiments show that predictability of surface air temperature (SAT) anomalies on decadal timescales mostly originates from externally forced variability. Although the predictable component of internally generated variability has considerably smaller SAT variance than that of externally forced variability, ocean subsurface temperature variability has predictive skills over almost a decade, particularly in the North Pacific and the North Atlantic where dominant signals associated with Pacific decadal oscillation (PDO) and the Atlantic multidecadal oscillation (AMO) are observed. Initialization enhances the predictive skills of AMO and PDO indices and slightly improves those of global mean temperature anomalies. Improvement of these predictive skills in the multi-model ensemble is higher than that in a single-model ensemble.  相似文献   

Spinel inclusions in olivine and plagioclase crystals in a layered gabbro: a marker and a tracer for primary phenocrysts in a differentiating magma reservoir     

Takashi?HoshideEmail author  Masaaki?Obata 《Contributions to Mineralogy and Petrology》2014,168(2):1049

The problem of whether cumulate rocks were formed by crystal settling or by in situ crystallization after magma emplacement is an important issue concerning the mechanisms of magmatic differentiation. However, it is hard to distinguish these two processes for plutonic rocks because the primary texture and chemical composition have generally been modified by postcumulus processes. To contribute this problem, we studied the distribution and compositions of Cr-spinel inclusions hosted in olivine and plagioclase in the Murotomisaki Gabbroic Intrusion (MGI), SW Japan. It is shown that the olivine-hosted inclusions are restricted to specific horizons where accumulation of olivine phenocrysts is thought to have occurred and that the compositional variations of the Cr-spinel are explained by a secondary compositional modification that probably took place after the magma emplacement. It is also shown that the Cr-spinel inclusions in a chilled margin have suffered the least compositional modification and nearly retains the primary composition. Those in the interior of the intrusion, on the contrary, have been significantly modified by re-equilibration with residual melt driven by cation diffusions through the host phases. Those in plagioclase have been less modified. It is shown that all the spinel inclusions had primarily the same and common composition at the time of magma emplacement. This implies that all the inclusion-bearing crystals, olivine and plagioclase, represent primary phenocrysts that had already existed in the emplaced magma. In this way, spinel inclusion in the MGI may be regarded to be a useful petrographic “marker” for identifying intratelluric phenocrysts and also as a “tracer” to trace the motion of the primary phenocrysts after the magma emplacement.  相似文献   

ISRM Suggested Methods for Determining the Creep Characteristics of Rock   总被引：4，自引：2，他引：2  

Ömer Aydan  Takashi Ito  Ugur Özbay  M. Kwasniewski  K. Shariar  T. Okuno  A. Özgenoğlu  D. F. Malan  T. Okada 《Rock Mechanics and Rock Engineering》2014,47(1):275-290

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