Intergranular trace elements in mantle xenoliths from Russian Far East: Example for mantle metasomatism by hydrous melt

Based on both major and trace element chemistry, the occurrence of the intergranular component in mantle-derived xenoliths from far eastern Russia has been constrained. Whole-rock trace element measurements of one xenolith show apparent negative anomalies in Ce, Th, and high field strength elements on normalized trace element patterns. The trace element pattern of the whole rock differs from those of constituent minerals, indicating that the anomalies in the whole rock are attributable to the presence of an intergranular component. That assumption was confirmed using in situ analysis of trace elements in the intergranular substance and melt inclusion using laser ablation inductively coupled plasma–mass spectrometry. Both the intergranular component and the melt inclusions have identical trace element patterns, which mean that these materials are a cognate metasomatizing agent. The anomalies are regarded as mantle metasomatism related to an aqueous fluid. Hydrous minerals were observed on the wall of the melt inclusions using micro-Raman spectroscopy, indicating that the melt inclusions contained a large amount of water. Thus, this study reveals a trace element composition of a hydrous metasomatizing agent in the mantle.     

地球自转对强震震中附近中小地震的影响

论述2008年5月12日四川汶川Ms8.0地震和2010年4月14日青海玉树Ms7.1地震前震中附近中小地震和地球自转季节性变化的关系,介绍1970年以来中国大陆其他14例M≥7.0地震震例.研究发现,在强震前几年时间内,震中附近地区的中小地震有偏向发生于地球自转速率季节性变化加速或者减速某一阶段的现象.该结果对深入认识地震与地球自转之间的关系具有一定启示意义,对地震预测具有一定指导意义.     

Depositional ramps: asymmetrical distribution structure in the Ata pyroclastic flow deposit,Japan

The asymmetrical distribution of the welded Ata large-scale pyroclastic flow deposit in Southern Kyushu, Japan was identified. This distribution pattern was defined as depositional ramps. Depositional ramps can be identified in valleys wider than 1 km and become smaller-scale with increasing distance from the source. Upslope directions of depositional ramps are generally radially away from the source caldera, suggesting that the structure was formed by the flow of pyroclastic material radially away from the source. The original depositional surface was reconstructed based on field mapping and density measurements of the pyroclastic flow deposit. Depositional ramps having a dip angle of more than 9° were reconstructed on the vent-facing slopes of the topography underlying the valley-filling deposits in the area within 10 km of the caldera rim. Such a dip angle is much larger than previously described dip angles. The size and gradient of the depositional ramps decreases with increasing distance from the source. Depositional ramps are recognized commonly in densely welded pyroclastic flow deposits. A high emplacement temperature is required to form the depositional ramps. This suggests that the pyroclastic flow was transported as a dense, fluidized layer to minimize heat loss.     

First Report of Sapphirine+Quartz Assemblage from Southern India: Implications for Ultrahigh-temperature Metamorphism

We report here for the first time, the occurrence of sapphirine+quartz assemblage in textural equilibrium from quartzo-feldspathic and pelitic granulites from southern India. The sapphirine-bearing rocks occur as layered gneisses associated with pink granite within massive charnockite in Rajapalaiyam area in the southern part of Madurai Block. Sapphirine occurs in three associations: (i) fine-grained subhedral mineral associated with quartz enclosed in garnet, (ii) intergrowth with Al-rich orthopyroxene (up to 9.7 wt.% Al₂O₃), and (iii) in symplectitic intergrowth with orthopyroxene (Al₂O₃= 5.9–6.7 wt.%) and cordierite surrounding garnet. The sapphirine in association with quartz is slightly magnesian (X_Mg = 0.79–0.80) and low in Si content (1.55–1.56 pfu) as compared with those associated with orthopyroxene and cordierite (X_Mg= 0.77–0.79, Si = 1.59–1.63 pfu). The sapphirine+quartz assemblage suggests that the granulites underwent T>1050 °C peak metamorphism. Cores of porphyroblastic orthopyroxene in the sapphirine-bearing rocks shows high-Al₂O₃ content of up to 9.7 wt.%, suggesting T = 1040–1060°C and P = 8 kbar. FMAS reaction of sapphirine+quartz→garnet+sillimanite+cordierite indicates a cooling from sapphirine+quartz stability field after the peak ultrahigh-temperature metamorphism. Slightly lower temperature estimates from ternary feldspar and sapphirine-spinel geothermometers (T = 950–1000°C) also support a post-peak isobaric cooling. Corona textures of orthopyroxene+cordierite (±sapphirine), orthopyroxene+sapphirine, and cordierite+spinel around garnet suggest subsequent decompression. The sapphirine-quartz association and related textures reported in this study have important bearing on the ultrahigh-temperature metamorphism and exhumation history of the Madurai Block as well as on the tectonic evolution of the continental deep crust in southern India.     

Social capital as a shield against anxiety among displaced residents from Fukushima

The March 2011 meltdowns at the Fukushima nuclear power plants in Japan resulted in an increased risk of psychological distress among affected residents. We conducted original surveys of Futaba residents, a town in Fukushima where all of the residents were forced to evacuate from their homes due to radioactive contamination, obtaining 585 responses (a response rate of about 20%). Using this original data set, we investigate the role of social capital in maintaining mental health among the residents. First, we found the level of stress captured by the Kessler index (K6) to be unusually high compared both with people across Japan and with those who were displaced because of the earthquake and/or tsunami (but not the nuclear catastrophe). However, having high levels of social capital—captured by the number of neighbors from Futaba after displacement, participation in volunteer work after displacement, and participation in tea parties after displacement—plays an important role in reducing anxiety and distress among Futaba residents. Finally, we provide concrete recommendations for policy makers and NGOs to increase resilience among affected residents by strengthening social ties.     

Eutrophication-induced changes in Lake Nakaumi,southwest Japan

Lake Nakaumi, southwest Japan, is an enclosed lagoon characterized by polyhaline and halocline conditions. Since the last century, its ecological state has been altered by eutrophication. We used a paleolimnological approach and studied multiple proxies, including chemical compounds, diatoms, foraminifera and molluscs, to infer the eutrophication history of the ecosystem. Eutrophication in Lake Nakaumi was associated with several factors, including increased nutrient loading, input of herbicides, and dike building since the 1920s. The ecological condition of this lake was divided into several stages that reflect the eutrophication process after the 1940s. A catastrophic “regime shift” from a clear state with aquatic vegetation to a turbid one with phytoplankton occurred in the early 1950s. Environmental degradation in the Honjo area, a part of Lake Nakaumi, was attributed primarily to physical changes caused by the construction of an enclosing dike. Eutrophication occurred almost simultaneously with the physical changes to the Honjo area in the 1970s. Until recently, no regime shift was observed in this area, though the core-top sediments show possible symptoms of incipient change.     

Contributions from mafic alkaline magmas to the Bingham porphyry Cu–Au–Mo deposit, Utah, USA

The Bingham porphyry Cu-Au-Mo deposit, Utah, may only be world-class because of substantial contributions of sulfur and metals from mafic alkaline magma to an otherwise unremarkable calc-alkaline system. Volcanic mafic alkaline rocks in the district are enriched in Cr, Ni, and Ba as well as Cu, Au, platinum group elements (PGE), and S. The bulk of the volcanic section that is co-magmatic with ore-related porphyries is dacitic to trachytic in composition, but has inherited the geochemical signature of high Cr, Ni, and Ba from magma mixing with the mafic alkaline rocks. The volcanic section that most closely correlates in time with ore-related porphyries is very heterogeneous containing clasts of scoriaceous latite, latitic, and minette, and flows of melanephelinite, shoshonite, and olivine latite in addition to volumetrically dominant dacite/trachyte. Bingham ore-related porphyries show ample evidence of prior mixing with mafic alkaline magmas. Intrusive porphyries that have not been previously well-studied have several chemical and mineralogical indications of magma mixing. These "mixed" lithologies include the hybrid quartz monzonite porphyry, biotite porphyry, and minette dikes. Even some of the more silicic latite and monzonite porphyries retain high Cr and Ba contents indicative of mixing and contain trace amounts of sapphire (<1 mm). The heterogeneous block and ash flow deposits also contain sapphire and are permissively correlated with the intrusions based on chemical, mineralogical, and isotopic data. Magma mixing calculations suggest about 10% of the monzonitic/latitic ore-related magma may have been derived from mafic alkaline magma similar to the melanephelinite. If the original S content of the mafic magma was about 2,000-4,000 ppm, comparable with similar magmas, then the mafic magma may have been responsible for contributing more than half of the S and a significant portion of the Cu, Au, and PGE in the Bingham deposit.     

基于支持向量机理论的地下水动态遥感监测模型与应用

地下水是我国内陆干旱地区水资源的重要组成部分,也是极为敏感的生态环境因素之一。地下水动态变化影响着绿洲和湿地的演化,以及土地资源的开发。西北地区地下水监测网尚不完善,动态资料相对缺乏。遥感技术可以弥补传统地下水位监测手段的不足。由于降水极少,西北干旱区地表反射率与地下水水位埋深关系极其密切。选用归一化植被指数(NDVI)、地表温度(LST)数据,应用支持向量机回归方法,建立西北干旱地区地下水位遥感监测模型。提取MODIS影像中的NDVI和LST产品上的地表温度和植被指数信息,作为模型的输入,通过合理选择核函数进行支持向量机的回归分析,从而建立地表植被指数、地表温度与地下水位的相关数学模型,并分析了不同核函数所拟合结果。在河西走廊疏勒河流域的研究成果表明,运用MODIS数据开发地下水动态模型反演水位变化是可行的,模型拟合的结果比较符合实际情况,尤其是对于细土平原地下水浅埋地区模型应用效果更为理想。一次多项式核函数适合模拟埋深小于3m浅埋地下水,径向基函数RBF核函数和三次多项式核函数法则更适合模拟较大埋深情况。开发的地下水位遥感监测模型可为西北干旱区水循环研究和流域水资源管理提供技术手段。