基于独居石标样Trebilcock的激光剥蚀等离子体质谱微区原位U-Th-Pb同位素定年方法

独居石是重要的U-Th-Pb同位素地质年代矿物计之一.设计小束斑剥蚀条件下的16组交叉实验,对独居石标样Trebilcock开展了原位LA-ICP-MS分析(剥蚀直径13μm和20μm,激光剥蚀频率5 Hz和3 Hz,能量密度约3,4,5和6 mJ·cm-2).结果显示,剥蚀束斑直径20μm、频率3 Hz、能量密度约3 mJ·cm-2和束斑直径为13μm、频率3 Hz、能量密度约5 mJ·cm-2,206Pb/238U和208Pb/232Th分馏指数FI(Fractional Index)较低,U-Th-Pb同位素年龄结果与TIMS(Thermal Ionization Mass Spectrometry)年龄(272±4 Ma)偏差仅为0.05%和0.14%,相应的箱线图方盒对称性好且面积最小.随后对广东广宁黑云母花岗岩样品17GN-01中独居石进行了U-Th-Pb年龄分析,得到208Pb/232Th加权平均年龄为256.8±0.8 Ma,与锆石206Pb/238U加权平均年龄250.7±1.6 Ma基本一致,表明建立的实验方法可行.     

低维磁性拓扑绝缘体与拓扑半金属

磁性与拓扑性之间复杂的相互作用引起了越来越多的关注.磁性拓扑材料展示了多种新奇的物理效应,有望应用于未来低功耗高速自旋电子学器件.本文从量子霍尔效应出发,回顾了磁性拓扑材料,包括陈绝缘体、反铁磁拓扑绝缘体、磁性外尔半金属及其他磁性拓扑态等在理论与实验上的进展,并详细介绍了我们课题组最近几年在磁性拓扑材料方面的理论工作....     

Paleoceanographic records in the sedimentary cores from the middle Okinawa Trough

Two gravity piston cores (Cores 155 and 180) involved in this study were collected from the middle Okinawa Trough. Stratigraphy of the two cores was divided and classified based on the features of planktonic foraminifera oxygen isotope changes together with depositional sequence,millennium-scale climatic event comparison, carbonate cycles and AMS^14C dating. Some paleoclimatic information contained in sediments of these cores was extracted to discuss the paleoclimatic change rules and the short-time scale events presented in interglacial period. Analysis on the variation of oxygen isotope values in stage two shows that the middle part of the Okinawa Trough may have been affected by fresh water from the Yellow River and the Yangtze River during the Last Glacial Maximum (LGM). The oxygen isotope value oscillating ranges of the cores have verified that the marginal sea has an amplifying effect on climate changes.The δ^13C of benthic foraminifera Uvigerina was lighter in the glacial period than that in the interglacial period, which indicates that the Paleo-Kuroshio‘s main stream moved eastward and its influence area decreased. According to the temperature difference during the “YD” period existing in Core 180 and other data, we can reach the conclusion that the climatic changes in the middle Okinawa Trough area were controlled by global climatic changes, but some regional factors had also considerable influence on the climatechanges. Some results in this paper support Fairbanks‘s point that the “YD” event was a brief stagnation of sea level rising during the global warming up procession. Moreover,the falling of sea level in the glacial period weakened the exchange between the bottom water of the Okinawa Trough and the deep water of the northwestern Pacific Ocean and resulted in low oxygen state of bottom water in this area.These procedures are the reasons for carbonate cycle in the Okinawa Trough area being consistent with the “Atlantic type”carbonate cycle.     

拖拉机发生故障有“信号”

<正>拖拉机出现故障前往往会表现出特有的外观现象,这也可称作"信号"。这些"信号"一般都具有可听、可闻、可见、可触摸或可测量的性质,概括起来有以下6种:(1)作用反常。拖拉机技术状态和性能出现异常情况,如发动机启动困难,拖拉机制动失效,主离合器打滑,发电机不发电,以及拖拉机牵引力过小等。     

英台断陷深层天然气成因分析及气源对比

松辽盆地南部深层天然气资源丰富,但其烃类气既存在有机成因气(包括油型气和煤型气),亦存在无机成因,还存在混合成因,在同位素序列上常表现为部分倒转和完全倒转。为了明确英台断陷天然气的成因及来源,根据烃源岩的地化指标、天然气组分、碳同位素以及轻烃指纹对研究区的天然气成因类型加以分析,并进行气源对比。研究表明,英台断陷烃类气为凝析油伴生气和煤型气的混合,其中南部洼槽天然气主要来自于沙河子组,而北部则来自于营城组。通过判定天然气成因的类型和识别气源方向,有利于加深对英台断陷深层天然气成藏条件和成藏模式的认识,从而为研究天然气藏的分布规律,以及下一步的天然气勘探指引方向。     

同位素技术测试地下水流速流向的原理及应用

介绍了利用同位素方法测试水文地质参数(主要是地下水的流速、流向)的基本原理，并结合广东省某研究区的实际测试成果进行了分析，指出在今后类似测试中需注意的4个问题：完善测试钻孔的结构和成井工艺，特别是过滤器的结构；含水层水力坡度的精确测定；测试井孔的代表性和经济合理性；测试数据的解释必须具有扎实的地质和水文地质知识。