Discovery of Late Cretaceous garnet two-pyroxene granulite in the southern Lhasa terrane, Tibet and its tectonic significances

The Lhasa terrane, located between the Bangonghu-Nujiang suture zone and the Indus-Yalung Tsangpo suture zone in the southern Tibetan Plateau, was considered previously as a Precambrian continental block. Mesozoic and Cenozoic tectonic evolution of the Lhasa terrane is closely related to the subduction of the Tethys ocean and the collision between the Indian and European continents; so it is one of the keys to reveal the formation and evolution of the Tibetan plateau. The garnet two-pyroxene granulite which was found at the Nyingtri rock group of the southeastern Lhasa terrene consists of garnet, clinopyroxene, orthopyroxene, labradorite, Ti-rich amphibolite and biotite, with a chemical composition of mafic rock. The metamorphic conditions were estimated to be at T = 747 similar to 834 degrees C and P = 0.90 similar to 1.35GPa, suggesting a formation depth of 45km. The zircon U-Pb dating for the garnet amphibolite and marble associated with the granulite give a metamorphic age of 85 similar to 90Ma. This granulite-facies metamorphic event together with a contemporaneous magmatism demonstrated that the southern Lhasa terrane has undergone an Andean-type orogeny at Late Mesozoic time.

Trace element composition of peridotites from the southern Mariana forearc: Insights into the geochemical effects of serpentinization and/or seafloor weathering

Peridotites from the southern Mariana forearc were sampled on the landward trench slope of the Izu-Bonin-Mariana (IBM) subduction zone by dredging. These mantle wedge peridotites underwent hydration by fluid derived from a dehydrated descending slab, and later interacted with seawater after emplacement at or near the seafloor. This study investigates how these two different rock-fluid interaction processes influenced trace element distribution in the southern Mariana forearc peridotites. We measured trace element concentrations of peridotites from the southern Mariana forearc. The southern Mariana forearc peridotites are characterized by a distinct seawater-like REE pattern with an obvious negative Ce anomaly, and La shows good correlation with other REEs (except Ce). In addition, there is a great enrichment of U, Pb, Sr and Li elements, which show a distinct positive anomaly relative to adjacent elements in the multi-element diagram. For the seawater-like REE pattern, we infer that REEs are mainly influenced by seawater during peridotite-seawater interactions after their emplacement at or near the seafloor, by serpentinization or by marine weathering. Furthermore, the anomalous behavior of Ce, compared with other rare earth elements in these samples, may indicate that they have undergone reactions involving Ce (IV) when the peridotites interacted with seawater. Positive U, Pb, Sr and Li anomalies are inferred to be related to seawater and/or fluids released during dehydration of the subducting slab.

Comparison Between Lurr And State Vector Analysis Before Strong Earthquakes In Southern California Since 1980

There are seven strong earthquakes with M >= 6.5 that occurred in southern California during the period from 1980 to 2005. In this paper, these earthquakes were studied by the LURR (Load/Unload Response Ratio) method and the State Vector method to detect if there are anomalies before them. The results show that LURR anomalies appeared before 6 earthquakes out of 7 and State Vector anomalies appeared before all 7 earthquakes. For the LURR method, the interval between maximum LURR value and the forthcoming earthquake is 1 to 19 months, and the dominant mean interval is about 10.7 months. For the State Vector method, the interval between the maximum modulus of increment State Vector and the forthcoming earthquake is from 3 to 27 months, but the dominant mean interval between the occurrence time of the maximum State Vector anomaly and the forthcoming earthquake is about 4.7 months. The results also show that the minimum valid space window scale for the LURR and the State Vector is a circle with a radius of 100 km and a square of 3 degrees 3 degrees, respectively. These results imply that the State Vector method is more effective for short-term earthquake prediction than the LURR method, however the LURR method is more effective for location prediction than the State Vector method.

小型气驱动式U形振荡水槽

本文介绍气驱动式U形振荡水楷(U形管)的设计特点、流场品质和初步实验结果。在结构设计上采用了理论计算的弯管型线、步进电机带动蝶阀的控制系统和吸气驱动等较先进的技术措施,使得该设备具有流场品质好、结构简单、调节方便等优点,是开展振荡流实验研究的基本设备。

用LDA测量U形水槽内的振荡流

本文介绍LDA用于测量U形水槽内的振荡流。水槽直管段为正方形,弯管段内侧弯面及外侧弯面是专门计算设计的。对于水平直管段、竖管段及弯管段共七个截面,测量了边界层外振荡流速的振幅分布。对于水平直管段上底面及下底面各三个截面,测量了边界层內振荡流速的振幅分布及相位分布。测量结果和无限长槽道的理论计算结果作了比较,二者基本符合。

Spatial and Temporal Variation of LURR and Its Implication for the Tendency of Earthquake Occurrence in Southern California

Based on the theory of LURR and its recent development, spatial and temporal variation of Y/Y-c (value of LURR/critical value of LURR) in the Southern California region during the period from 1980 through March, 2001 was studied. According to the previous study on the fault system and stress field in Southern California, we zoned the Southern California region into 11 parts in each of which the stress field is almost uniform. With the time window of one year, time moving step of three months, space window of a circle region with a radius of 100 km and space moving step of 0.25 degree in latitude and longitude direction, the evolution of Y/Y-c were snapshot. The scanning results show that obvious Y/Y-c anomalies occurred before 5/6 of strong earthquakes considered with a magnitude of 6.5 or greater. The critical regions of Y/Y-c are near the epicenters of the strong earthquakes and the Y/Y-c anomalies occur months to years prior to the earthquakes. The tendency of earthquake occurrence in the California region is briefly discussed on the basis of the examination of Y/Y-c.

基于U形塑料光纤的氧气传感器

报道了一种基于荧光猝灭原理的光纤氧气传感器.采用塑料光纤作为传感和传光元件进行氧气传感,传感头制成U形.以邻菲咯啉钌作为荧光标记物,用溶胶-凝胶法制备敏感材料.采用相移法来实现对荧光寿命的测定.测量了不同弯曲半径传感头对氧气传感的灵敏度,发现当U形光纤的弯曲半径较小时系统的灵敏度较高.对荧光寿命和氧气浓度的关系进行了测量,发现二者呈亚线性关系,提出双荧光体模型解释这一实验现象.

基于U型塑料光纤和邻啡咯啉钌的溶解氧传感器

本文提出了一种基于U型塑料光纤和邻啡咯啉钌的溶解氧传感器。光纤传感头放在样品池中，测量了不同氮氧体积比情况下荧光强度和寿命。研究了邻啡咯啉钌的浓度、传感头的退火时间和U型光纤的弯曲半径对系统灵敏度的影响。我们提出了双层模型来解释实验结果不符合S-V方程的实验现象，并用双层模型分析了弯曲半径对系统灵敏度的影响。通过对溶解氧浓度和荧光寿命亚线性曲线的拟合，我们得出敏感层的厚度和S-V系数分别为0.59和0.61。