The first carbonatite dyke at Bayan Obo is well exposed on the surface for a length and width of approximately 60 m and 1.1-1.5 m, respectively. Along its strike, the fenitized H1 （Qs） and H2 （Cs） quartzite is rep...The first carbonatite dyke at Bayan Obo is well exposed on the surface for a length and width of approximately 60 m and 1.1-1.5 m, respectively. Along its strike, the fenitized H1 （Qs） and H2 （Cs） quartzite is replaced by Na-amphiboles, aegirines, and alkali-feldspars, intermittently stretching as far away as 800 m in length. Based on petrographical characteristics, the dyke＇s fenitized wall rocks are divisible into different zones： （1） outer, （2） middle, and （3） inner. The outer zone is 5-17 m from the NW margin of the dyke. The middle zone is located at 3.5-5 m from the NW margin of the dyke. The inner contact zone is located between direct contact with the dyke and 3.5 m from the dyke. In the outer zone, upon visual examination, no evidence of outcrop fenitization was found and the major elemental rock composition is nearly identical to the unaltered H1 and H2 lithologies. In the thin sections, however, small amounts of Na-amphibole and phlogopite are present. Despite relatively poor development throughout the 5 m of fenitization, the wall rocks have retained at least a small geochemical signature comparable to the original sedimentary protolith. The fenites occurring in the inner zone exhibit distinct variations, not only for the sharp contact at the outcrop scale, but also for variations in major, rare earth elements （REE）, and trace elements and Sm-Nd isotope composition. The wall rocks within 3.5 m have undergone strong fenitization, inheriting the geochemical signature derived from the carbonatite dyke. Fenitization in the middle zone was not as strong, at least compared to the inner zone, but was stronger than the outer zone. Compared to some trace elements and REEs, the major elements are relatively immobile during fenitization. The Sm-Nd isotope data for the carbonatite dyke and the adjacent fenitized wall rocks, where the Sm and Nd originate solely from the dyke, plots as a six-point isochron with an age of 1308~56 Ma. This age is identical to that of ore-bearing dolomite carbonatite and the related ore-forming events, indicating that there may be a petrogenetic link between the two. Based on Sr and Nd isotope compositional data, the first carbonatite dyke may be derived from an enriched mantle.展开更多
在昆柳龙多端混合直流输电工程背景下,为研究多端混合直流输电系统交流侧的故障响应特性,建立了基于数字信号处理(digital signal processing,DSP)的多端混合直流输电系统的机电暂态模型。在此基础上,对多端混合直流输电系统各端交流侧...在昆柳龙多端混合直流输电工程背景下,为研究多端混合直流输电系统交流侧的故障响应特性,建立了基于数字信号处理(digital signal processing,DSP)的多端混合直流输电系统的机电暂态模型。在此基础上,对多端混合直流输电系统各端交流侧进行三相接地故障(交流侧电压降至0)仿真,得到了不同情况下的系统交流侧故障响应特性,并将结果与PSCAD(power systems computer aided design)的仿真结果进行对比,发现两者主要电气量的波形基本一致,验证了该模型的准确性,为本工程后续仿真计算的研究工作提供了基础条件和技术参考。展开更多
基金financially supported by the National Nature Science Foundation of China (grant No. 41372081)
文摘The first carbonatite dyke at Bayan Obo is well exposed on the surface for a length and width of approximately 60 m and 1.1-1.5 m, respectively. Along its strike, the fenitized H1 （Qs） and H2 （Cs） quartzite is replaced by Na-amphiboles, aegirines, and alkali-feldspars, intermittently stretching as far away as 800 m in length. Based on petrographical characteristics, the dyke＇s fenitized wall rocks are divisible into different zones： （1） outer, （2） middle, and （3） inner. The outer zone is 5-17 m from the NW margin of the dyke. The middle zone is located at 3.5-5 m from the NW margin of the dyke. The inner contact zone is located between direct contact with the dyke and 3.5 m from the dyke. In the outer zone, upon visual examination, no evidence of outcrop fenitization was found and the major elemental rock composition is nearly identical to the unaltered H1 and H2 lithologies. In the thin sections, however, small amounts of Na-amphibole and phlogopite are present. Despite relatively poor development throughout the 5 m of fenitization, the wall rocks have retained at least a small geochemical signature comparable to the original sedimentary protolith. The fenites occurring in the inner zone exhibit distinct variations, not only for the sharp contact at the outcrop scale, but also for variations in major, rare earth elements （REE）, and trace elements and Sm-Nd isotope composition. The wall rocks within 3.5 m have undergone strong fenitization, inheriting the geochemical signature derived from the carbonatite dyke. Fenitization in the middle zone was not as strong, at least compared to the inner zone, but was stronger than the outer zone. Compared to some trace elements and REEs, the major elements are relatively immobile during fenitization. The Sm-Nd isotope data for the carbonatite dyke and the adjacent fenitized wall rocks, where the Sm and Nd originate solely from the dyke, plots as a six-point isochron with an age of 1308~56 Ma. This age is identical to that of ore-bearing dolomite carbonatite and the related ore-forming events, indicating that there may be a petrogenetic link between the two. Based on Sr and Nd isotope compositional data, the first carbonatite dyke may be derived from an enriched mantle.
文摘在昆柳龙多端混合直流输电工程背景下,为研究多端混合直流输电系统交流侧的故障响应特性,建立了基于数字信号处理(digital signal processing,DSP)的多端混合直流输电系统的机电暂态模型。在此基础上,对多端混合直流输电系统各端交流侧进行三相接地故障(交流侧电压降至0)仿真,得到了不同情况下的系统交流侧故障响应特性,并将结果与PSCAD(power systems computer aided design)的仿真结果进行对比,发现两者主要电气量的波形基本一致,验证了该模型的准确性,为本工程后续仿真计算的研究工作提供了基础条件和技术参考。
