Stable carbon isotopes of alkane gases from the Xujiahe coal measures and implication for gas-source correlation in the Sichuan Basin,SW China

The Upper Triassic Xujiahe Formation in the Sichuan Basin, SW China consists of a series of coal measures. The first, third and fifth members of this formation are dominated by gas prone dark mudstones and coals. The mudstones contain Type II and III kerogens with average organic carbon contents around 1.96%. These source rocks are mature in the central Sichuan and highly mature in the western Sichuan Basin, characterized by gas generation with subordinate amounts of light oil or condensate oils. The source rocks are intercalated with the sandstone dominated second, fourth and sixth members of the Xujiahe Formation, thus leading to three separate self contained petroleum systems in the region. The proven gas reserves in the Xujiahe Formation are only less than that of the Triassic Feixianguan Formation and the Xujiahe Formation has the second largest gas field (Guang’an gas field) in the basin. Gases derived from the Xujiahe Formation coals generally show a normal stable carbon isotopic trend for C₁–C₄ n-alkanes, with the highest δ¹³C₂ values among the nine gas pay zones in the basin (?20.7‰ to ?28.3‰), and δ¹³C₁ values as low as ?43.0‰ in the central Sichuan. Gas accumulations with an oil leg have also been found in the eastern and southern Sichuan where the thickness of the Xujiahe Formation is significantly reduced. Gases in these accumulations tend to show low δ¹³C₂ values (?30.0‰ to ?36.3‰), characteristic of oil prone source rocks.     

Study on vertical distribution and activity factor of P forms in sediments of three urban shallow lakes in People’s Republic of China

The vertical variation of P forms in sediments of urban shallow lakes in China, Xuanwu Lake, Daming Lake and Mochou Lake, were sequentially extracted and measured with the method of SEDEX. The results indicated the TP content in the sediment profiles ranged from 371.94 to 777.25 mg kg⁻¹ for Xuanwu Lake, 1,308.14 to 4,632.63 mg kg⁻¹ for Daming Lake, and 995.49 to 1,860.71 mg kg⁻¹ for Mochou Lake. The results of sequential extraction showed that Ca-P and Fe-P were the main fractions. Meanwhile, the proportions of Bio-P to TP were 35.24% for Xuanwu Lake, 29.57% Daming lake, and 25.26%, for Mochou Lake, indicating a high potential of P releasing. The content of Bio-P was significantly and positively correlated with TP (r = 0.978, P < 0.01). Lake hydrations conditions played an important role in the distribution and contents of Bio-P and TP. In the region with macrophytes, the contents of TP and Bio-P were relatively low. Physicochemical properties of sediments were significantly related to the fraction distribution and P contents, and might play an important role in controlling P activity and mobility. Moreover, Fe showed an evident influence on P fraction and the ratio Fe/P might be good indicator to the contents and composition of active P in sediments.     

团簇同位素的基本原理与地质应用*

团簇同位素指的是含有2个及2个以上的重同位素结合在一起形成的同位素体。团簇同位素的数值定义为同位素体的相对丰度偏离随机分布状态的程度。测量该相对丰度较低的同位素体需要高精度的质谱仪,难点在于利用同位素组成已知的参考气体和不同同位素组成的加热气体,以获得绝对参考体系下的数值。团簇同位素体的相对丰度非常低,但是具有非常独特的物理和化学性质。比如碳酸盐矿物中¹³C¹⁸O¹⁶O的丰度对温度具有敏感性,而与矿物的全岩同位素以及矿物形成时期的流体性质无关,因此可以利用测量的碳酸盐团簇同位素来获得矿物的生长温度,再利用矿物的氧同位素(δ¹⁸O),根据传统的氧同位素温度计原理,可以进一步获得矿物的生长流体(水)的氧同位素。目前,团簇同位素温度计已经在古气候(温度)重建、古高度恢复、碳酸盐岩的成岩作用以及甲烷的成因分析等方面得到了广泛应用。评估深埋高温过程引起的C-O化学键重置对碳酸盐团簇同位素的影响、测试仪器产生对团簇同位素的非线性误差校正、以及其他丰度更低的团簇同位素体或大分子的团簇同位素的测量,是下一步的研究方向。     

The clustering properties of Luminous Red Galaxies

By cluster analysis, we study the clustering properties of Luminous Red Galaxies (LRGs) and compare them with those of Main galaxies. We find that the clustering properties of Luminous Red Galaxies is different from those of Main galaxies, and that LRGs cluster mainly in form of close double and multiple galaxies, galaxy groups. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

China's Lunar Exploration Program: Present and future

China launched its first lunar probe, Chang’E-1, at 6:05 p.m. (10:05 GMT), October 24, 2007. Chang’E-1 blasted off on a Long March 3A carrier rocket from the No. 3 launch tower in the Xichang Satellite Launch Center of southwestern Sichuan Province. China National Space Administration performed the lunar orbit injection maneuver for Chang’E-1 at 11:25 a.m. on November 5, 2007 (China Standard Time). Chang’E-1 was injected into the lunar orbit after the maneuver, and will begin to explore the moon in the following 1 year. It is the first step into its ambitious three-phase moon mission, marking a new milestone in the Chinese space exploration history.     

地震震相分析与测量的进展

地震震相分析是地震学研究中最基本、也是最基础的工作。本文就震相分析与测量方面的一些重要进展进行了概述,主要包括初动到时和极性的测量,震相中其他参数的测量,以及其他震相的识别与测量等。本文还着重介绍了《IASPEI标准地震震相表》,该震相表的完成与公布是地震震相分析工作的重要进展。     

地震快报目录自动网上发布软件QCAT的开发与应用

地震快报目录是国家数字地震台网分中心数据服务的重要组成部分之一,为了能够更好地提供服务,我们使用Perl语言,开发了地震快报目录自动网上发布软件QCAT。本文分析了QCAT软件开发的应用需求,阐明了软件的设计思路,描述了软件的功能和结构,并对QCAT软件的各个模块进行了详细介绍,最终对应用QCAT之后,用户访问快报目录的方法做了说明。     

国家数字地震台网产出资料的分析与说明

介绍了2001年以来地震台站的资料分析情况和国家数字地震台网分中心的资料产出情况,通过分析表明,由于宽频带数字地震资料具有频带宽、动态范围大等特点,2003年利用数字地震台网资料分析地震的数量比传统的模拟记录提高30％～40％。     

Quantifying the carbon source of pedogenic calcite veins in weathered limestone: implications for the terrestrial carbon cycle

The continent is the second largest carbon sink on Earth’s surface. With the diversification of vascular land plants in the late Paleozoic, terrestrial organic carbon burial is represented by massive coal formation, while the development of soil profiles would account for both organic and inorganic carbon burial. As compared with soil organic carbon, inorganic carbon burial, collectively known as the soil carbonate, would have a greater impact on the long-term carbon cycle. Soil carbonate would have multiple carbon sources, including dissolution of host calcareous rocks, dissolved inorganic carbon from freshwater, and oxidation of organic matter, but the host calcareous rock dissolution would not cause atmospheric CO₂ drawdown. Thus, to evaluate the potential effect of soil carbonate formation on the atmospheric pCO₂ level, different carbon sources of soil carbonate should be quantitatively differentiated. In this study, we analyzed the carbon and magnesium isotopes of pedogenic calcite veins developed in a heavily weathered outcrop, consisting of limestone of the early Paleogene Guanzhuang Group in North China. Based on the C and Mg isotope data, we developed a numerical model to quantify the carbon source of calcite veins. The modeling results indicate that 4–37 wt% of carbon in these calcite veins was derived from atmospheric CO₂. The low contribution from atmospheric CO₂ might be attributed to the host limestone that might have diluted the atmospheric CO₂ sink. Nevertheless, taking this value into consideration, it is estimated that soil carbonate formation would lower 1 ppm atmospheric CO₂ within 2000 years, i.e., soil carbonate alone would sequester all atmospheric CO₂ within 1 million years. Finally, our study suggests the C–Mg isotope system might be a better tool in quantifying the carbon source of soil carbonate.

     

Response of Aeolian Flux to Soil Particle Properties and Airflow Turbulence Fluctuation

The process of aeolian flux in wild areas is usually unstable due to turbulent fluctuation of airflow. The physical parameters of wind and aeolian flux have strong pulsation characteristics and are even intermittent. Since the classical aeolian flux equations derived from steady sediment transport processes do not take into account the physical parameters such as soil particle properties and airflow turbulence characteristics, they cannot accurately predict the process of sediment transport driven by turbulent wind. Based on the analysis of the variables contained in the classical aeolian flux equations and their effects on the aeolian flux, the soil particle properties and the airflow turbulent fluctuation which influence unsteady sediment transport process, and the delayed response of the unsteady sediment transport process to airflow turbulent fluctuation, then the steady and unsteady sediment transports were defined. Strictly, there is no steady sediment transport process in nature, but the sediment transport process in a short period of time can be roughly considered to be a steady sediment transport process as the fluctuation of sediment transport is very little. Thus, the unsteady sediment transport process in a long-term series can be regarded as series of steady sediment transport processes on an "appropriate time scale" (Δt). The construction principles, variables in unsteady aeolian flux equation, and establishing unsteady aeolian flux equation of the way which is the method of determining each variable by controlling the conditional experiments were put forward. Finally, the foreseeable key issues in the process of establishing the unsteady aeolian flux equation were discussed.