Two types of gabbroic xenoliths from rhyolite dominated Niijima volcano, northern part of Izu-Bonin arc: petrological and geochemical constraints

We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths) in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899–955°C) and pressures (3.6–5.9 kbar) than the B-type gabbro (687–824°C and 0.8–3.6 kbar). These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic) magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano

Chlamydia trachomatis infection in early neonatal period

BACKGROUND: The clinical characteristics of Chlamydia trachomatis respiratory tract infections in Japanese neonates were investigated. METHODS: Clinical, laboratory and microbiological characteristics of five infants with pneumonia due to C. trachomatis in early neonatal period were analyzed. RESULTS: Only C. trachomatis was identified in 4 infants. Both C. trachomatis and cytomegalovirus was identified in one. Wheezing, tachypnea and cyanosis were common in infants. Mothers of five infants had negative chlamydial EIAs at 20 weeks of gestation. CONCLUSIONS: We identified five cases of C. trachomatis respiratory tract infections in early neonatal period with the possibility of intrauterine infection. Targeted screening, early diagnosis, and effective treatment of perinatal and neonatal chlamydial infections seems to be necessar

銅同位体を用いた海底自然銅鉱床の形成機構に関する研究

科学研究費助成事業 研究成果報告書：若手研究(B)2014-2015課題番号 : 2680027

銅同位体を用いた海底熱水鉱床の形成機構に関する研究

科学研究費助成事業 研究成果報告書：基盤研究(C)2019-2021課題番号 : 19K0398

Hydrothermal native copper in ocean island alkali basalt from the Mineoka belt, Boso Peninsula, Japan

Native copper grains are found in aphyric amygdaloidal basalt of early Miocene age (ca. 20 Ma) in the southern Mineoka belt of Boso Peninsula, central Japan. The native copper was precipitated in the amygdules or veins along with calcite and analcime. The temperature of precipitation and salinity of the fluids related to the native copper are approximately 133° to 183°C and 0.9 to 3.9 wt % as estimated by fluid inclusions trapped in the calcite containing grains of the native copper. The native copper is interpreted as related to low-temperature, reducing, alkaline hydrothermal fluids. A sulfur-poor environment is inferred by the lack of sulfur-bearing minerals. The host rock of the Mineoka native copper is alkali basalt of oceanic island affinity. Native copper is well known to occur in mid-ocean ridge, island arc, oceanic island tholeiitic basalts, and continental tholeiitic basalt, but this is the first detailed description of an occurrence in ocean island alkali basalt

Two types of gabbroic xenoliths from rhyolite dominated Niijima volcano, northern part of Izu-Bonin arc: petrological and geochemical constraints

We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths) in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899–955°C) and pressures (3.6–5.9 kbar) than the B-type gabbro (687–824°C and 0.8–3.6 kbar). These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic) magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano