阿塔卡马海沟表层水颗粒有机碳与微生物群落呼吸作用的时空变化研究

海沟是全球大洋体系的重要组成部分。研究这一极端环境的生物地球化学循环过程有助于我们进一步理解海洋的物质循环。前期研究发现,海沟表层水体的初级生产力(NPP)对海沟沉积物埋藏的有机碳性质具有重要影响,但是,颗粒有机碳(POC)在沉降过程中被微生物呼吸和降解的过程尚不清楚。因此,本研究利用2018年春"太阳号"阿塔卡马海沟(Atacama Trench)国际联合航次SO261所采集的表层水样品,测试其中POC浓度、C/N、δ¹³C、δ¹⁵N等参数,并结合0.2—0.8、0.8—3.0、>3.0μm三种粒径微生物群落呼吸(microbial community respiration,MCR)速率测试,探究其日变化模式及不同站位的空间变化模式,进而衡量微生物对POC的呼吸降解作用。结果表明,该海域表层水中对POC降解占主导作用的微生物类群粒径为0.8—3.0μm;24 h时间序列实验表明MCR随时间呈现"M"型曲线的双峰变化模式,且和C/N、δ¹³C、δ¹⁵N等参数变化趋势吻合,表明同一站位的呼吸速...     

Trees, lateral shrinkage and building damage

This article presents the study conducted and the actions taken to stabilise the foundations of 25 low-rise (two/three-storey) buildings in Alcázar de San Juan (Ciudad Real, central Spain). Owing to the immediate attention required, it was decided that the study would focus on procuring a synthetic model that would be able to provide a satisfactory explanation for the tendency of the movements, overlooking the detailed model of each building. This analysis pointed out that the mobilisation was probably due to both the shrinkage caused by the existing trees during the dry-growing seasons, and to the loss of lateral confinement caused by the excavation of a service trench adjacent to the footings of the buildings. In keeping with this mechanism, stabilization was carried out by transplanting the trees growing near the damaged buildings and installing a line of piles to provide lateral support to the footings. The evolution of the damage was therefore stopped.     

马里亚纳南部弧内坡橄榄岩中的角闪石成分对于弧下地幔交代流体的指示

马里亚纳弧前的橄榄岩被认为是SSZ型蛇绿岩的现代等同物,记录了弧下地幔与俯冲流体的交代反应,其中的角闪石被认为是俯冲流体交代的产物.电子探针的数据表明角闪石主要包括透闪石和镁闪石两种,其中前者具有低的钠含量,后者则具有明显高的钠、铝含量,但Mg#较低.角闪石的组成反映了俯冲流体具有高硅、钙、铝、钠等元素的特征.形成成分...     

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THE APPLICATION OF IMAGE-BASED MODELING IN PALEOEARTHQUAKE TRENCH STUDY

The geological structure exposed by paleoearthquake trenches is the key material to the right cognition of fault activity and paleoearthquake. However, paleoearthquake trenching inevitably destroys active tectonic geomorphic evidence and trench exposures are usually difficult to reserve. The conventional process of recording the delicate geological information, manually constructing photomosaics by image-editing software, is time-consuming and produces undesirable artificial distortions. Herein, we explored the process of constructing trench orthophotomosaics and the 3D image model using the Image-based Modeling technology and applied it to the Liutiaohe trench across the Tianqiaogou-Huangyangchuan Fault, Gansu Province. Based on the 3D image modeling and orthophotomosaic, we firstly constructed the control points and scale bars on cleaned trench walls and collected photos of all sections of the trench with a digital camera in the field, and then reconstructed the 3D model of the trench through the Agisoft PhotoScan, an efficient image-based modeling software, and finally yielded the 3D image model of the trench and othophotomasaics of the trench exposures. The results show that the automated workflow can produce seamless, sub-millimeter-level high-resolution photomosaics more quickly, with precision in the centimeter range, and the 3D image model is of great help to identify strata and geological structures in trenches with much lower capital and labor costs and low expertise levels compared with LiDAR, meanwhile, the 3D archive benefits the share and communication and even allows future reinterpreting the site using new insights.     

雅浦海沟南缘铁锰结核矿物与地球化学特征及其成因研究

本文采用X射线衍射、全岩地球化学和电子探针等测试方法,对雅浦海沟南部附近海域获得的铁锰结核样品进行了显微构造、矿物和地球化学分析,并探讨了其成因。结果表明:铁锰结核的显微构造主要包括平行纹层构造、柱状构造、叠层状构造和同心环状构造;显微构造和探针结果显示铁锰结核在生长初期处于底部海洋动力比较强烈的环境,后期生长环境逐渐趋于稳定;铁锰结核的矿物组分以水羟锰矿、钠水锰矿、石英和钙十字石为主;样品中Fe、Mn元素含量较高且含量比较接近,Cu、Co、Ni和REE相对富集,REE分布模式整体比较平缓并都出现较强的Ce正异常和重稀土元素亏损现象;文中两块铁锰结核都为水成成因,成矿物质主要来自同期的海水沉淀,同时也受一定海底火山物质和陆源风尘物质的影响。     

武汉绕城公路东北段主要工程地质问题研究

为了给项目的设计和施工提供科学依据，对武汉绕城公路东北段软土、膨胀土、砂土地震液化、岩溶、深路堑、高填路基、筑路材料等潜在的地质灾害进行了详细评价，通过采用工程地质测绘及钻探、触探、物探、试验分析等多种勘探、测试手段，对沿线的各种工程地及其危害表现形式进行计算分析，预测施工过程及工程建成后可能出现的岩土工程问题，提出了相应的施工方法，对同类工程的建设具有指导意义。     

LATE QUATERNARY PALEOEARTHQUAKES ON THE MIDDLE SEGMENT OF THE LIJIANG-XIAOJINHE FAULT,SOUTHEASTERN TIBET

More attention has been paid to the late Quaternary activity of the boundary fault of the Sichuan-Yunnan block in eastern Tibet. The Lijiang-Xiaojinhe Fault (LXF) locates along the boundary of the northwest Sichuan and central Yunnan sub-blocks in the Sichuan-Yunnan block. Clear displaced landforms show that the fault has undergone strong late-Quaternary activity. However there is no surface-rupturing earthquake occurring on the LXF in the historical record. The LXF crosses the city of Lijiang, one of the most important tourist cities in Southwest China. The rupture behavior on this fault remains unclear and it is hard to assess its seismic hazard in the future. In this study, on the base of the interpretation of high-resolution satellite imagery, we chose the middle segment of the LXF and dug three trenches at Muzhuda, Hongxing, and Gantangzi sites to constrain the ages of paleoearthquakes combined with radiocarbon dating and OxCal modeling. The Muzhuda trench shows that at least three events occurred on the middle segment of the LXF at 7 940~6 540a BP, 4 740~4 050a BP and 1 830~420a BP, respectively. The Hongxing trench indicates that the LXF underwent two events at 5 120~3 200a BP and 2 100~1 220a BP. The Gantangzi trench reveals at least three paleoearthquakes at 44 980~17 660a BP, 7 210~3 810a BP and 2 540~1 540a BP, respectively. The events in the Gantangzi trench might be incomplete because of stratigraphic gap. These three trenches indicate that three events occurred on the middle segment of the LXF in the Holocene at 7 940~7 210a BP, 4 740~4 050a BP and 1 830~1 540a BP, respectively. Large earthquakes on the middle segment of the LXF appear to fit the quasi-periodic model with the mean recurrence interval of~3 000a and the estimated magnitude 7.5. Given the strong late-Quaternary activity of the middle segment of the LXF and a long elapsed time, we propose that the middle segment of the LXF might have a high seismic hazard potential in the near future.     

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沟槽内海底管道的水动力特性研究

基于水力模型实验，引入相对沟形系数αｒ，获得了以αｒ为表征的相对水动力系数与ＫＣ数的关系；对于浅沟而言，这种关系较有规律性。根据所设计沟形的αｒ值和所选定的ＫＣ值，应用本文结果，可以方便地判断其力折减程度和掩护效果