香山群辉绿岩地球化学特征及其构造背景

现有地质资料分析,把发育于香山群第三亚群辉绿岩时代下限定为早古生代。辉绿岩主元素以高钠、镁,低钾、钛为特征。稀土总量(∑REE)较低,轻、重稀土分馏作用不明显;基本不显示Eu异常,球粒陨石标准化配分曲线具有平缓的特征。与原始地幔相比,微量元素值约是原始地幔标准值的2~10倍,大离子亲石元素(LILE)相对亏损,高场强元素(HFSE)分布平坦且不分异;N-MORB标准化蛛网图上,呈现大离子亲石元素(LILE)富集特征。地球化学特征表明:辉绿岩属于大洋拉斑玄武岩系列,显示了伸展作用的构造背景。另外,结合岩石学、沉积背景和同构造期岩套特征分析,再次验证了在中晚寒武世,阿拉善地块南缘与鄂尔多斯地块西南缘具离散型大陆边缘性质。     

中国太湖五里湖内不同凤眼莲密度圈闭内的沉降率

The dynamic model of physical-biological engineering for purifying water quality in Lake Taihu needs the parameter of sedimentation rate (SR). Especially, it is seldom reported how SR is influenced by interactions between algae and aquatic plant. So 6 enclosures with each area of 5×5 m² were constructed in Wulihu with 2 m depth, a small hypereutrophic bay of Taihu Lake, China. Enclosures, in which the original water quality was the same as that in surrounding lake, were input Eichhomia crassipes at various original densities from 0-6 kg·m^-2 on August 9, 1996. SR had been measured separately at depths of 0.6, 1.2f 1.8 m in each enclosure during 20 days. Main results were as follows:1) SR average in enclosures (17.3g·m^-2 d^-1) was as much as about 1/14 that in the surrounding lake; 2) The deeper was it, the higher rate was it in each enclosure, generally; 3) SR cures versus original densities of Eichhomia crassipes (ODE) in enclosures had the ship of "V" at different depths; SR minimuma were observed in the enclosure with original meso-density of Eichhomia crassipes (EMESO, 4kg·m^-2), the average of SR minimuma was about 8.55 g ·m^-2 d^-1) SR in enclosures with original hypo-density (EHYPO, 0-3kg·m^-2) were mainly negative related with water temperature and light intensity;while those with original hyperdensity (EHYPR, 5-6kg·m^-2) were mainly negative related with transparency (SD) instead.These SR-distribution characteristics may be explained by interactions between dead algae and relics of Eichhomia crassipes.     

强震下水闸结构抗震性能分析

强震下的水闸结构抗震性能尚待深入研究,结合实际工程案例,运用UC-WCOMD有限元分析软件建立精细化的水闸计算模型,并分别采用Pushover法和时程分析法讨论水闸在强震作用下的抗震性能,结果表明:结合抗震设防目标,采用Pushover分析法评估水闸的抗侧能力,并采用弹塑性时程分析方法进行强震下的抗震性能校核,是值得推荐的研究方法。     

Petrology and mineralogy of volcanic glass in meteorite Northwest Africa 11801: Implications for their petrogenesis

The study of lunar magma evolution holds significant importance within the scientific community due to its relevance in understanding the Moon's thermal and geological history. However, the intricate task of unraveling the history of early volcanic activity on the Moon is hindered by the high flux of impactors, which have substantially changed the morphology of pristine volcanic constructs. In this study, we focus on a unique volcanic glass found in the lunar meteorite Northwest Africa 11801. This kind of volcanic glass is bead-like in shape and compositionally similar to the Apollo-14 and Apollo-17 very low-Ti glass. Our research approach involves conducting a comprehensive analysis of the petrology and mineralogy of the volcanic glass, coupled with multiple thermodynamic modeling techniques. Through the investigation, we aim to shed light on the petrological characteristics and evolutionary history of the glass. The results indicate that the primitive magma of the glass was created at 1398–1436°C and 8.3–11.9 kbar (166–238 km) from an olivine+orthopyroxene mantle source region. Then, the magma ascended toward the surface along a non-adiabatic path with an ascent rate of ~40 m s⁻¹ or 0.2 MPa s⁻¹. During the magma ascent, only olivine crystallized and the onset of magma eruption occurred at ~1320–1343°C. Finally, the glass cooled rapidly on the lunar surface with a cooling rate ranging between 20 and 200 K min⁻¹. Considerable evidence from petrology, mineralogy, cooling rate, and the eruption rate of the glass beads strongly supports the occurrence of ancient explosive volcanism on the Moon.