Fe-Ni and Mn-Cr isotopic systems in sulfides from unequilibrated enstatite chondrites

In situ measurements of ⁶⁰Fe-⁶⁰Ni and ⁵³Mn-⁵³Cr isotopic systems with an ion microprobe have been carried out for sulfide assemblages from unequilibrated enstatite chondrites (UECs). Evidence for the initial presence of ⁶⁰Fe has been observed in nine sulfide inclusions from three UECs: ALHA77295, MAC88136, and Qingzhen. The inferred initial (⁶⁰Fe/⁵⁶Fe) [(⁶⁰Fe/⁵⁶Fe)₀] ratios show a large variation range, from ∼2 × 10⁻⁷ to ∼2 × 10⁻⁶. The sulfide inclusions with high Fe/Ni ratios yield (⁶⁰Fe/⁵⁶Fe)₀ ratios of ∼(2-7) × 10⁻⁷, similar to most of the (⁶⁰Fe/⁵⁶Fe)₀ values of troilite and pyroxene observed in unequilibrated ordinary chondrites (UOCs). Inclusions with high inferred (⁶⁰Fe/⁵⁶Fe)₀ ratios (∼1-2 × 10⁻⁶) have low Fe/Ni ratios and the magnitude of the ⁶⁰Ni excesses is similar in two MAC88136 assemblages in spite of a difference of a factor of two in their Fe/Ni ratios. The inferred high (⁶⁰Fe/⁵⁶Fe)₀ ratios were probably the result of Fe-Ni re-distribution in the sulfides during later alteration processes.The ⁵³Mn-⁵³Cr system was measured in five of the sulfide assemblages that were examined for their ⁶⁰Fe-⁶⁰Ni systematics. The ⁵³Mn-⁵³Cr isochrons yielded variable initial (⁵³Mn/⁵⁵Mn) [(⁵³Mn/⁵⁵Mn)₀] ratios from ∼(2-7) × 10⁻⁷. There is no obvious correlation between the (⁶⁰Fe/⁵⁶Fe)₀ and (⁵³Mn/⁵⁵Mn)₀ ratios. The variable ⁵³Mn-⁵³Cr isochrons probably also indicate later disturbance to the isotopic systems in these sulfides. Even though no chronological information can be extracted from the ⁶⁰Fe-⁶⁰Ni and ⁵³Mn-⁵³Cr systems in these UEC sulfides, our results indicate that ⁶⁰Fe was present in the enstatite chondrite formation region of the early Solar System.     

Instability characteristics of the East Asian Monsoon recorded by high-resolution loess sections from the last interglacial (MIS5)

The selection of high-resolution loess sections is needed in order to determine the climatic variability of the East Asian Monsoon during the last interglacial. Two sequences of S1 on the eastern and west-ern sides of the Liupan Mountain were both composed of five paleosol layers and four loess layers,indicating that there were five strong summer monsoon events and four strong winter monsoon events in MIS5. This corresponds with other records of the East Asian Monsoon,along with NGRIP and the North Atlantic records,implying that the climate of the Northern Hemisphere was very instable during the last interglacial. Two layers of paleosols and one layer of loess had developed during MIS5a and MIS5c. Compared with MIS5e,the climate in MIS5a and MIS5c fluctuated more intensively on a millen-nial scale,whereas the climate was relatively stable in MIS5e.     

Ternary geochemical-tracing system in natural gas accumulation

The establishment of geochemical-tracing system of gas generation and accumulation is helpful to re-elucidating the gas migration and accumulation in time and space. To deduce the complex process of gas accumulation, a ternary geochemical-tracing system is set up, according to stable isotope inheritance of source rocks, kinetic fractionation of stable isotopes, time-accumulating effect of noble gas isotopes, mantle-derived volatile inheritance, and organic molecule inheritance of light hydrocarbons and thermally kinetic fractionation in their generation, in combination with the previous achievements of gas geochemistry and geochemical parameters of gas-source correlation. There are tight interactions for the geochemical parameters with much information about parent inheritance and special biomarkers, in which they are confirmed each other, reciprocally associated and preferentially used for the requirement so that we can use these geochemical parameters to effectively demonstrate the sources of natural gas, sedimentary environments and thermal evolution of source rocks, migration and accumulation of natural gas, and rearrangement of natural gas reservoirs. It is necessary for the ternary geochemical-tracing system to predict the formation of high efficient gas reservoir and their distribution in time and space.     

梁山雷电灾害及农村防雷对策的初步分析

利用1961—2000年梁山雷电天气资料,对梁山雷电年、日变化特征进行分析,总结了梁山近40年雷电及其灾害的特征,并提出了相应的农村防雷对策。     

空间直角坐标和大地坐标的转换

目前国内在空间直角坐标和大地坐标转换公式使用问题上 ,还明显缺乏必要的统一性。针对这个问题 ,本文作者在全面分析和比较国内外现有各种转换方法的基础上 ,重点推荐和介绍根据 Bowring研究思路导出的转换公式 ,这组公式既简单又具有很高的计算精度 ,能够满足各个部门的使用要求     

中国石炭纪生物礁造礁群落演化

中国石炭纪造礁群落是弗拉斯期—法门期生物绝灭事件后新兴起的。该群落在早期演化过程中经历了形成、发展、完善和衰落的过程,构成一个群落演化旋回。晚期又开始新一轮的旋回,群落的二分性十分显著。显然,石炭纪造礁群落代表一个不连续的演化过程。     

萝北井水位年动态变化研究

详细讨论了萝北井的年动态变化趋势,并分析了其成因机制。结果表明萝北井各年动态变化曲线出现的Ｗ形异常与地下构造活动无关,主要是由于农田用水引起。     

Two dimensional transient fundamental solution due to suddenly applied load in a half-space

A transient Green function due to suddenly applied line loads in an isotropic and homogeneous half-space is reported in this paper. The derivation of the half-space Green function in the Laplace and the Fourier transform spaces is first reviewed. Following an explicit inversion of the Fourier transform, the inverse Laplace transform is implemented along the contour integral on the p-complex plane in an integral form. The half-space Green function consists of full-space Green functions and a singularity-free complementary term. It can be easily incorporated into current transient boundary elements using the transient full-space Green function. Combined with finite elements, the half-space Green function can be used in a hybrid procedure to solve transient half-space problems without discretization of the free surface. Numerical results are presented to illustrate transient wave propagation in a half-space.     

储层裂缝特征测井解释方法综述

为了更好地研究裂缝性砂砾岩储层和其它裂缝性储层裂缝的测井解释问题,综述了目前在裂缝性储层裂缝测井解释中主要采用的常规评价、人工神经网络和斯通利波３类方法在识别裂缝带和定量计算储层裂缝参数两个方面的应用原理和研究现状,并指出了今后的一些研究方向。     

Spatial Disparity of Slope Farmland and Food Security in Three Gorges Area

As an important measure of ecoenvironmental construction, the process of de-farming in slope farmland is being undertaken gradually in the whole China. Meanwhile, the problem of reducing in food yield in de-farming areas can not be neglected any more. It is especially the case in areas with concentrated slope farmland and inconvenient transportation. In this paper, we analyze the causes of hidden troubles in food security, and the spatial relationship between farmland and slope farmland in the reservoir area of Three Gorges, and unveil the spatial disparity of contradictions between food supply and demand. Finally, combining the accessibility of areas, three different spatial types of food security, food security area, food alert area, and food crisis area, are divided.