Trace Elements Characteristics of Black Shales from the Ediacaran Doushantuo Formation, Hubei Province, South China： Implications for Redox and Open vs. Restricted Basin Conditions

In the present study, we carried out trace element analyses of black shales of the Edia- caran Doushantou Formation from two sections （Jiulongwan, Baiguoyuan） in Hubei Province, South China. Mo-U characteristics of black shales from the two sections and compiled Mo-U data of Dou- shantuo black shales from sections of a variety of sedimentary facies described the temporal/spatial variability in the redox conditions of paleo-seawater during deposition of the Donshantuo Formation. Changes in Mo-U patterns of the Doushantuo Member II （DST2） shales of open marine environments are consistent with a shift from a predominately oxic to a predominately anoxic ocean during their deposition. Mo-U patterns of the DST2 black shales from intra-shelf sections reflect basin restriction may have happened in the intra-shelf basin and are compatible with the redox-stratified model of the intra-shelf basin. Mo-U patterns of black shales of the Doushantuo Member IV （DST4） reveal that the shales from intra-shelf sections have more pronounced Mo enrichment and more significant enrich- ment of Mo over U than the slope shales, indicating the operation of a Mn particulate shuttle in the intra-shelf basin. High Mo/TOC ratios of the DST4 at the intra-shelf sections, in combination with similar Mo-TOC patterns of the DST4 from both intra-shelf and slope sections, indicate the intra- shelf basin was well connected to the open ocean during deposition of the DST4.

砂-凹凸棒土竖向隔离墙材料的压缩及渗透特性试验研究（英文）

目的:压缩性和渗透性是垃圾填埋场竖向隔离墙材料的2个重要指标。本文旨在探讨不同凹凸棒土添加量对砂-凹凸棒土隔离墙材料压缩性和渗透性的影响,并在Kozeny-Carman方程的框架下建立经验公式来预测砂-凹凸棒土隔离墙材料的渗透系数。创新点:1.系统全面地研究了不同凹凸棒土添加量对砂-凹凸棒土隔离墙材料压缩性和渗透性的影响;2.建立经验公式,预测砂-凹凸棒土隔离墙材料的渗透系数。方法:1.通过固结试验和刚性壁渗透试验,得出不同凹凸棒土添加量对砂-凹凸棒土隔离墙材料压缩性和渗透性的影响(图3和4,表1);2.通过公式推导,建立经验公式来预测砂-凹凸棒土隔离墙材料的渗透系数(公式(3)和(4))。结论:1.压缩指数(Cc)和回弹指数(Cs)均随回填料中凹凸棒土含量(Ap)的增加而增大,且Cc和Cs与Ap均有很好的线性关系:Cc=0.0062Ap+0.0161(r2=0.9914),Cs=0.0009Ap-0.0058(r2=0.9888)。2.用Casagrande和Taylor方法计算的固结系数(Cv)值均随回填料中凹凸棒土含量的增加而降低。3.利用太沙基固结理论计算的回填料渗透系数(ktheory)随回填料中凹凸棒土含量的增加而降低;在有效固结压力σ′<100 k Pa的情况下,只有凹凸棒土含量Ap≥30%,ktheory才会低于10-9 m/s;用刚性壁渗透试验测得的渗透系数kf与ktheory有相同的变化特征。4.基于试验数据提出了2种预测砂-凹凸棒土回填料渗透系数的方法,其中方法 2更好;由于这些方法都是经验公式,所以它们能否应用于原位场地或其它类型回填料仍需进一步的研究。