The Murotomisaki Gabbroic Complex is a sill like layered intrusion of up to 220 m in thickness and is located at Cape Muroto, Kochi Prefecture, Japan. There are several olivine rich zones within the intrusion, which may have been formed through accumulation of olivine crystals. However, up to now it has not been clear as to whether all of the olivine rich zones formed in this way. To clarify this, we reinvestigated the layered structure by collecting a consistent data set of modal composition, crystal size, and crystal number density of olivine from throughout the intrusion. It was found out that nearly all of the olivine crystals, in terms of crystal numbers, occur in the basal olivine rich zone (within 40 m of the base of the intrusion), and the average value of the crystal number density of olivine throughout the entire intrusion coincides with the crystal number density of olivine in the outermost parts of the lower and upper chilled margins. Hence, we conclude that most primary olivine phenocrysts within the magma settled under the influence of gravity and accumulated to form the basal olivine rich zone. The crystal number density of olivine within the mid level zones (40 100 m from the base of the intrusion) is much less than the initial values, as indicated by values recorded in the chilled margins. It is proved that the increase of the olivine mode within this zone is attributed not to the crystal accumulation of olivine but to the increase of the crystal size of olivine, i.e., the crystal growth. In this way, considering the mode, crystal size, and crystal number density of olivine throughout the intrusion, the olivine rich zones within the intrusion can be classified, in terms of their origin, as either crystal accumulation zone (AC zone) or crystal growth zone (GR zone). The growth of olivine crystals in the GR zone was apparently accompanied by an increase in MgO, FeO, and MnO concentrations to levels well above initial (i.e., the chilled marginal) values. This enrichment suggests that crystal growth occurred within a chemically open system in the sense that the increase in MgO content within the GR zone arose from material transfer between the boundary layer (the GR zone) and the overlying magma.

On June 29, 2015, a small phreatic eruption occurred in the most intensively steaming area of Hakone volcano, Japan. A previous magnetotelluric survey for the whole volcano revealed that the eruption center area (ECA) was located near the apex of a bell-shaped conductive body (resistivity < 10 Ωm) beneath the volcano. We performed local, high-resolution magnetotelluric surveys focusing on the ECA before and after the eruption. The results from these, combined with our geological analysis of samples obtained from a steam well (500 m deep) in the ECA, revealed that the conductive body contained smectite. Beneath the ECA, however, the conductive body intercalated a very local resistive body located at a depth of approximately 150 m. This resistive body is considered a vapor pocket. For the 2 months prior to eruption, a highly localized uplift of the ECA had been observed via satellite InSAR. The calculated depth of the inflation source was coincident with that of the vapor pocket, implying that enhanced vapor flux during the precursory unrest increased the porosity and vapor content in the vapor pocket. In fact, our magnetotelluric survey indicated that the vapor pocket became inflated after the eruption. The layer overlaying the vapor pocket was characterized by the formation of various altered minerals, and mineral precipitation within the veins and cracks in the layer was considered to have formed a self-sealing zone. From the mineral assemblage, we conclude that the product of the 2015 eruption originated from the self-sealing zone. The 2015 eruption is thus considered a rupture of the vapor pocket only 150 m below the surface. Even though the eruption appeared to have been triggered by the formation of a considerably deeper crack, as implied by the ground deformation, no geothermal fluid or rocks from significantly deeper than 150 m were erupted.

The Murotomisaki Gabbro is a sill like layered igneous complex that contains several layers of olivine enrichment. In our previous paper (Hoshide et al, 2006), we have identified two zones of olivine enrichment: 'the crystal accumulation zone (AC zone)', formed by gravity settling and accumulation of olivine crystals, and 'the crystal growth zone (GR zone)', in which increase of modal olivine was caused by crystal growth of olivine and not by crystal accumulation.Based on whole rock compositional data, we have found that the AC zone rocks define a linear compositional trend (termed as 'AC trend') which is consistent with the crystal settling and accumulation hypothesis. However the GR zone data define another linear trend with a slope different from that of the AC trend. Moreover, the compositions of the coarse gabbros and the upper olivine gabbros that occur above the GR zone and an anorthosite vein from the GR zone roughly lie on the same trend, but on the opposite side of the GR zone composition, defining the 'GR trend' as a whole. Some anorthositic veins and wavy pegmatitic veins have plume like structures, suggesting that these veins are remnant of crystal mushes that have been mobilized and ascended diapirically during magmatic differentiation.Considering the observed compositional relationships and the mode of occurrences of the anorthosite and wavy pegmatitic veins, we conclude that the segregation and separation of anorthositic material out of semi solidified crystallization boundary layers was responsible for the formation of the GR zone and the GR trend. Phase equilibrium calculations reveal that the hypothetical anorthosite material was a mixture of fractionated melt and plagioclase crystals that precipitated from the melt. The GR zone represents a residue from the separation of anorthositic crystal mushes and the coarse gabbros and the upper olivine gabbro parts represent mixtures of the crystal mush and the initial melt.

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or physical sensing devices. On-off switching of solid-state luminescence intensity have been achieved by adsorption and desorption of guest molecules or thermal stimuli. However, there has been few reports on the switching of luminescence mode. Here, we report the regulation of luminescence mode of organic salts of anthracene-2,6-disulfonic acid (ADS) with sec-butylamine by external stimuli. The organic salts yielded inclusion crystals with 1,4-dioxane, 1,4-thioxane or benzene. Whereas emission spectra of inclusion crystal with 1,4-thioxane or benzene have vibrational structure, that of inclusion crystal with 1,4-dioxane are broad and redshifted by 20 nm. This indicate that the latter exhibited excimerlike emission derived from the large π/ π overlap of the anthracene moieties. Powder X-ray diffraction (PXRD) analyses indicated that the inclusion crystals with 1,4-dioxane showed supramolecular isomerization by chemical and physical stimuli. When the inclusion crystal with 1,4-dioxane was heated until 473 K, 1,4-dioxane was released completely from the crystal. The emission spectrum of the resulting crystal was similar to inclusion crystal with 1,4-thioxane or benzene. PXRD pattern and emission spectra suggest the rearrangement of ADS. By the exposure of the crystal to 1,4-dioxan, the PXRD peak shifted to the longer distance. After cooling of the crystal until 253 K, the peak in PXRD pattern and emission spectrum became similar to that of original crystal. These date confirm that the inclusion crystal with 1,4-dioxane changes the emission mode from monomer emission to excimer-like one through the reversible structure transition by external stimuli.