Hydrogen and oxygen isotope studies of metamorphic fluid-rock interactions in the Dabie Mountains

Hydrogen and oxygen isotope studies were carried out on mineral separates from high to ultrahigh pressure metamorphic rocks at Huangzhen and Shuanghe in the eastern Dabie Mountains, East China. The δ¹⁸O values of eclogites cover a wide range of −5‰ to+9‰, but the δD values of micas fall within a narrow range of −85% to −70‰. Both equilibrium and disequilibrium oxygen isotope fractionations were observed between quartz and the other minerals, with reversed fractionations between omphacite and garnet in some eclogite samples. The δ¹⁸ O values of −5‰ to −1‰ for some of the eclogites represent the oxygen isotope compositions of their protoliths which underwent meteoric water-rock interaction prior to plate subduction. The preservation of oxygen isotope heterogeneity in the eclogites implies a channelized flow of fluids during progressive metamorphism caused by rapid subduction. Retrograde metamorphism has caused oxygen and hydrogen isotope disequilibria between some of the minerals, but the fluid for retrograde reactions was internally buffered in the stable isotope compositions. Project supported by the Chinese Ministry of Science and Technology (Grant No. 95-Pre-39), the National Natural Science Foundation of China (Grant Nos. 49794042, 49473173 and 49453003) and the Chinese Academy of Sciences (Grant No. KZ951-A1-401-5)     

华东地区中强地震序列特征研究

通过系统分析１９７０年以来华东地区ＭＳ５．０以上中强震序列,结合华东地区域特征,根据最大地震与次大震震级差,将地震序列划发为弧立型、接近孤立型主余型,主余型和震群型４类。用０．５、１天、２天、３天、５天和７天等几个时段的余震样本来研究序列类型的早期判断,结果较为满意,尝试用一种新的方法分析余震持续时间,认为某区域有一个地震活动背影景值,当余震衰减这到个背景值时,则余震活动基本结束,用此方法总结了华     

用水氡最大变化率法对强震时间作中短期预报

介绍了水氡变化率的物理含义以及变化率动态图象的生成方法,强震前在动态图象上存在着变化率≥０．０６高值异常区,异常区中心的最大变化率随时间有规律地演化,且与发震时间有着良好的统计关系。据此提出４个时间预测指标。检验性预测结果表明,预测的发震时间段长短大多数为２至６个月,可满足强震的中短期预报尺度的需要。     

肝豆状核变性的影像学诊断

目的为了解肝豆状核变性的影像学表现。明确病变范围及程度。明确病变范围及程度。方法采用普通Ｘ线摄片,ＭＲＩ或ＣＴ对颅脑进行扫描。结果Ｘ线表现为四肢骨远端、椎体、骨盆、腕关节、指间关节等均可受累,表现形式为骨质脱下,软化、碎裂、称疏和骨质增生,ＣＴ表现为铮双侧对称性豆状核及周转低密度病主烃及其它脑组织萎缩等表现：ＭＲＩ表现为豆状核、丘脑、尾状核及齿状核在Ｔ２加权图像上呈对称异常高信号。在Ｔ１加权图像上     

Geochemistry and origin of elements in some UK coals

Twenty-four UK coals ranging in rank with 4.6%–37.6% volatile matter were analysed for 46 major and trace elements. The samples were obtained from the UK Coal Bank and are representative of the major UK coal fields. The major element distributions are interpreted in terms of the mineralogical variations—quartz and kaolinite are largely responsible for the Si and Al, carbonates for Ca and Mg and pyrite for Fe. Also exerting an influence in some samples are siderite, Al-phosphate minerals and illite. Based on statistical relationships with the major elements, Rb, Cr, Th, Ce, Zr, Y, Ga, La, Ta, Nb and V are thought to be mainly present in the clay minerals, and As, Mo, Sb, Tl, Se and Bi and Pb are probably present in pyrite. Strontium and Ba are concentrated in a restricted number of samples related to the phosphate minerals. Germanium is the only element for which a major organic association can be demonstrated. Elements with an indirect association with the organic matter are Na, Cl, and Br in porefluids and possibly Te. The ash content is controlled mainly by the detrital input and the trace elements related to the ash content are therefore those elements associated with the clay minerals. Variations with rank would appear to be mainly related to the moisture content (porefluids). The trace elements associated with the quartz and clay minerals are thought to be dominantly detrital in origin. The non-detrital elements, essentially those contained in pyrite, are thought to have been incorporated in the depositional environment from waters with enhanced salinities through seawater ingress, hence there are positive relationships between S and trace element concentrations.     

挡土结构古典内力计算方法的讨论

根据软土地区大量基坑支护的经验,对目前挡土结构古典内力计算常用的平衡法（悬臂结构）、等值梁法（单支撑结构）和弹性抗力法的计算结果进行了分析与比较,指出了古典内力计算方法的适用性。     

贻贝超氧化物歧化酶的分离纯化和部分性质

采用热变性－硫酸铵分级沉淀－Ｓｅｐｈａｄｅｘ Ｇ－１００和ＤＥ５２柱层析的方法从贻贝中分离纯化铜锌超氧化物歧化酶,并对其部分性质进行分析鉴定。结果该酶的比活力为９４５３．３Ｕ／ｍｇ（ｐｒｏｔｅｉｎ）,提纯倍数为６０９．９,对ＫＣＮ和Ｈ２Ｏ敏感,Ｔ氏液和ＳＤＳ对酶活性没影响,对热较稳定。     

胶东乳山金矿区原生晕地球化学特征及深部成矿预测

英格庄金矿以相对富As、Co、Ni而三甲和铜锡山金矿则以相对富Cu、Pb、Zn、Ag为特征.聚类分析显示,英格庄金矿具Bi+Hg、As+Sb+Co与Pb+Zn组合,三甲金矿具Bi+Hg+As+Sb+Co、Pb+Zn与Ag+Cu+Au组合,而铜锡山金矿则显示Bi+Hg+Sb+Pb+Ag、Cu+Au+Zn+As及Mo+Ni组合.结合Ni、Co、Mo与Ag、Hg、As、Sb等的相关特征,认为上述三个金矿均有成矿头尾晕叠加现象.Au、Ag、Cu、Pb、Zn、As、Sb、Bi、Hg、Mo等元素垂向变化规律显示,英格庄金矿在-200m标高以下、三甲金矿在-500m标高以下尚有成矿富集段存在.其中,所确定的英格庄金矿的靶位在16勘探线附近,三甲金矿的靶位则在16～20勘探线间.     

Velocity structure in the South Yellow Sea basin based on first-arrival tomography of wide-angle seismic data and its geological implications

The South Yellow Sea basin is filled with Mesozoic–Cenozoic continental sediments overlying pre-Palaeozoic and Mesozoic–Palaeozoic marine sediments. Conventional multi-channel seismic data cannot describe the velocity structure of the marine residual basin in detail, leading to the lack of a deeper understanding of the distribution and lithology owing to strong energy shielding on the top interface of marine sediments. In this study, we present seismic tomography data from ocean bottom seismogra...     

Comparative assessment of nitrogen fixation rate by 15N2 tracer assays in the South China Sea

Nitrogen fixation is one of the most important sources of new nitrogen in the ocean and thus profoundly affects the nitrogen and carbon biogeochemical processes. The distribution, controlling factors, and flux of N₂ fixation in the global ocean remain uncertain, partly because of the lack of methodological uniformity. The 15N₂ tracer assay (the original bubble method → the 15N₂-enriched seawater method → the modified bubble method) is the mainstream method for field measurements of N₂ fixation rates (NFRs), among which the original bubble method is the most frequently used. However, accumulating evidence has suggested an underestimation of NFRs when using this method. To improve the availability of previous data, we compared NFRs measured by three 15N₂ tracer assays in the South China Sea. Our results indicate that the relationship between NFRs measured by the original bubble method and the 15N₂-enriched seawater method varies obviously with area and season, which may be influenced by incubation time, diazotrophic composition, and environmental factors. In comparison, the relationship between NFRs measured by the original bubble method and the modified bubble method is more stable, indicating that the N₂ fixation rates based on the original bubble methods may be underestimated by approximately 50%. Based on this result, we revised the flux of N₂ fixation in the South China Sea to 40 mmol/(m2·a). Our results improve the availability and comparability of literature NFR data in the South China Sea. The comparison of the 15N₂ tracer assay for NFRs measurements on a larger scale is urgently necessary over the global ocean for a more robust understanding of the role of N₂ fixation in the marine nitrogen cycle.