Kusatsu-Shirane Volcano is one of the most active volcanoes in Japan. The summit of the volcano comprises three young pyroclastic cones: the Motoshirane Pyroclastic Cone Group (MPCG), which erupted on January , , with almost no eruptive precursors; the Ainomine Pyroclastic Cone, of unknown age; and the Shirane Pyroclastic Cone Group (SPCG), which is the site of numerous historical phreatic eruptions. In this study, we present the results of an investigation of the stratigraphy and eruption history of the MPCG. The MPCG consists of overlapping pyroclastic cones including, from south to north, Motoshirane-nishi, the Older and Younger Motoshirane, Kagamiike, and Kagamiike-kita. The stratigraphic relationships and geochemical characteristics of the erupted material suggest that construction of most of these cones involved initial lava flow and subsequent cone-forming stages. Four lava flows, the Daimyozawa, Ishizu, Sessho, and Furikozawa lavas, form the bases of the Motoshirane-nishi, Older Motoshirane, Kagamiike, and Kagamiike-kita cones, respectively. The subsequent cone-forming stages included Vulcanian and phreatomagmatic eruptions. Products of the Kagamiike and Kagamiike-kita eruptions can be correlated with the ca. cal yr BP L Volcanic Sand (Hayakawa and Yui, ), which lies at the eastern foot of the volcano, and the juvenile jointed block-rich horizon (after ca. cal yr BP) on the southern flank of the Kagamiike cone, respectively. In summary, the MPCG eruption sites shifted from south (the Motoshirane-nishi cone) to north (the Kagamiike-kita cone), and magmatic eruptions continued until just after ca. cal yr BP. Petrological analyses of the erupted material suggest that the MPCG eruptions were fed by a mixture of dacitic magma from the long-lived crustal magma chamber, and repeatedly recharged mafic magmas with different compositions for each pyroclastic cone.
Three-dimensional-computed tomography (3D-CT) cholangiography is a 3D shaded surface display image of the biliary tract obtained by using helical CT after intravenous cholangiography or cholangiography per percutaneous transhepatic cholangio-drainage tube. We investigated whether 3D-CT cholangiography could provide a useful image, for preoperative examination in laparoscopic cholecystectomy. Sixty-five patients with biliary diseases were examined by 3D-CT cholangiography. Helical scanning was performed on a Proceed Accell (GE Medical Systems, Waukesha, WI, USA). Three-dimensional images were created using an independent workstation. A clear image of the common bile duct was obtained for all patients (100%) by 3D-CT cholangiography. The gallbladder was well visualized in 54 (93%) and the cystic duct was shown to be opacified in 55 (95%) of the 58 patients with a gallbladder. Thirty-one patients were diagnosed as having gallstones by 3D-CT cholangiography (sensitivity. 72.1%; specificity, 100%; accuracy, 79.3%), while 43 were diagnosed as having cholecystolithiasis by ultrasonography. The advantages of 3D-CT cholangiography were a low level of invasiveness, easily obtained images compared to those obtained with endoscopic retrograde cholangiography (ERC), good opacification, and provision of a three-dimensional understanding of the biliary system, especially of the cystic duct. When combined with ultrasonography and routine liver function tests, 3D-CT cholangiography was considered very useful for obtaining information before laparoscopic cholecystectomy. It allowed the omission of ERC in many patients who were considered to have no common bile duct stone, by employment of 3D-CT cholangiography.
Tyatya Volcano, situated in Kunashir Island at the southwestern end of Kuril Islands, is a large composite stratovolcano and one of the most active volcanoes in the Kuril arc. The volcanic edifice can be divided into the old and the young ones, which are composed of rocks of distinct magma types, low‐ and medium‐K series, respectively. The young volcano has a summit caldera with a central cone. Recent eruptions have occurred at the central cone and at the flank vents of the young volcano. We found several distal ash layers at the volcano and identified their ages and sources, that is, tephras of ad 1856, ad 1739, ad 1694 and ca 1 Ka derived from three volcanoes of Hokkaido, Japan, and caad 969 from Baitoushan Volcano of China/North Korea. These could provide good time markers to reveal the eruptive history of the central cone, which had continued intermittently with Strombolian eruptions and lava flow effusions since before 1 Ka. Relatively explosive eruptions have occurred three times at the cone during the past 1000 years. We revealed that, topographically, the youngest lava flows from the cone are covered not by the tephra of ad 1739 but by that of ad 1856. This evidence, together with a report of dense smoke rising from the summit in ad 1812, suggests that the latest major eruption with lava effusion from the central cone occurred in this year. In 1973, after a long period of dormancy, short‐lived phreatomagmatic eruptions began to occur from fissure vents at the northern flank of the young volcano. This was followed by large eruptions of Strombolian to sub‐Plinian types occurring from several craters at the southern flank. The 1973 activity is evaluated as Volcanic Explosivity Index = 4 (approximately 0.2 km3), the largest eruption during the 20th century in the southwestern Kuril arc. The rocks of the central cone are strongly porphyritic basalt and basaltic andesite, whereas the 1973 scoria is aphyric basalt, suggesting that magma feeding systems are definitely different between the summit and flank eruptions.
A combined study of major ions, δ18O, δD, 13C, 87Sr/86Sr isotopes, X-ray diffraction, scanning electron microscopy, and electron probe microanalyses on springs and spring mineral precipitates along the Cameroon Volcanic Line (CVL) was undertaken to understand water chemistry, and infer the type and origin of the precipitates. The waters are of evaporated Na+K-Cl and non-evaporated Ca+Mg-HCO3 types, with the more mineralized (electrical conductivity-EC of 13130 μS/cm) Lobe spring inferred to result from interaction of circulating 49°C waters with magmatic volatiles of the active Mt. Cameroon. Water mineralization in the other springs follows the order: Sabga A > Sabga B> Bambui B > Bambui A > Nyos Cave. But for the Nyos Cave spring, all other springs contain fluoride (up to 0.5-35.6 mg/l above WHO potable water upper limit). The Sabga spring contains arsenic (up to 1.3 mg/l above the WHO limits). The springs show low fractionation temperatures in the range of 19-43 ᵒC. The Lobe and Sabga A springs are precipitating dolomite (CaMg(CO3)2), while the Nyos Cave, Bambui A, Bambui B and Sabga B springs precipitate trona ((Na3H(CO3)2.H2O). Our data suggest a marine provenance for the carbonates, and point to a volcanic input for the Lobe, Nyos, Sabga A, and Bambui A springs. The latter springs are therefore proposed as proxies for monitoring volcanic activity for hazard mitigation along the CVL. Revision Notes to Editor and reviewers Click here to download Revision Notes: NOTE TO EDITOR AND REVIEWERS.docx RESPONSE TO EDITOR AND REVIEWERS L. 28: contained = contains : Corrected on line 28 L. 55-56: Order references in chronological order (also L. 84 and check throughout the MS) : References have been ordered chronologically in the entire MS.
A dropstone-bearing, Middle Permian to Early Triassic peri-glacial sedimentary unit was first discovered from the Khangai-Khentei Belt in Mongolia, Central Asian Orogenic Belt. The unit, Urmegtei Formation, is assumed to cover the early Carboniferous Khangai-Khentei accretionary complex, and is an upward-fining sequence, consisting of conglomerates, sandstones, and varved sandstone and mudstone beds with granite dropstones in ascending order. The formation was cut by a felsic dike, and was deformed and metamorphosed together with the felsic dike. An undeformed porphyritic granite batholith finally cut all the deformed and metamorphosed rocks. LA-ICP-MS, U-Pb zircon dating has revealed the following 206 Pb/ 238
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